They are wider, much soffter, internal structure is completely redesigned to allow for better load distribution and more contact patch. I can run a softer material but without decreasing range.
On the left, is the V2 Hollow Wheel. On the right is the V3 Hollow Wheel. I made entirely new molds and new structure (color isn't finalized).
I dialed in the negative camber exactly to the material as well for better grip.
I also redesigned the suspension insert to allow it to increase range and grip as well. I'm very excited.
Who is heavy and can beta test!?
Thanks,
Doug
I'm the designer of Hollow Wheels, a mechanical engineer with a background in designing everything from race car engines to sensor-embedded clothing. I've released and manufactured 20+ products and manufactured hundreds of thousands of units. But how did I get to that point? I'll tell you how. Today, I'm sharing an overview on how you can create your own customized wheels for monster grip, super comfort, or personal expression. It's the same process that I used to develop and fine tune the Hollow Wheels.
Hollow Wheels are light, absorbing large impacts and offering high grip with an integrated suspension insert for a customizable ride. It took 3 years and numerous iterations to design them.
Creating your own production ready wheels involves many iterations and user feedback before considering the expensive step of making molds, used to cost $20,000 to $50,000. But you can do it much cheaper, for as little as $300-1,000. Here's a guide on making your own wheels using urethane 80A or softer that lasts and without breaking the bank. If you have this equipment, then cheaper still - about $100 in materials. You'll need:
Additional validation equipment can be explored in future posts. Get cast urethane from www.bjbenterprises.com - the best and easiest to work with.
Steps:
1. Create the solid model of your wheel
2. Design a mold for urethane casting
3. Cast the urethane
4. Pop it out of the mold and ride!
Ask for feedback, make iterations, and repeat the process. Stay tuned for the next post on how to create the actual mold!
By the way, I am having a big Black Friday/Cyber Monday deal. The Hollow Wheels are on sale for as low as $129.99. With a purchase, you'll get a free pulley conversion kit, belts, bearings, and free suspension inserts, which is all worth $90 in value.
Thanks,
Doug
The V2 Hollow Wheel Comfort will be arriving by the 20th of January. The factory is packing the wheels this Tuesday and they will be boarding a shipping boat right before Christmas. We have learned a lot from the shipping experience of the batch 1 and think we will be able to get through the shipping experience as fast as possible without USA customs issues.
Video: https://youtube.com/shorts/1TUWAQ7Nt_U?feature=share
V2 Improvements: I listened to your feedback
Notes: What did not make it yet to production
Hollow Wheel PRO review by City Surfa
Corey has the best cinematography in the electric skateboard scene. He reviewed the Hollow Wheel PRO and said this: 'I give them a 5-star, especially for the comfort.'
Use his discount code 'CitySurfa' to get reduced pricing on anything on the site, except for Hollow Wheel Comfort.
Please let me know if you have any feedback or questions.
Thanks,
Doug
What is happening? Ultimately, there was an issue with the material interaction between the core and the tread.
The core is the white part. The black part is the tread.
In this case, the core is placed inside a mold as a solid, cold part, and the tread is injected into the mold as a hot liquid. This creates melting of the two materials as the hot liquid is injected into each other at high pressure and temperature. There must be certain preparations in order for the core to be clean.
What causes the problem to happen?
If there is inadequate chemical bond, as heat generates the material gets weaker and wants to flex more. The more flex it has, the more that there can be relative movement between core and the tread. When there begins to be the very slightest hint of relative movement, then the core and tread will soon separate.
As this is a first batch production and a new set of challenges arise, there are always things we will continue to improve. At scale, material processes will be better defined and controlled. Its an evolving process.
Can I upgrade to PRO?
The PRO is safe to ride and unaffected as the materials are vastly different and have inherently better chemical adhesion performance. require different injection molding procedure. However, the load capacity (190lbs) on the PRO is less so than the material used in Comfort. The load capacity will increase over time as I gather more data but for now, I am being conservative.
What am I doing to fix the problem?
I am creating a V2 Hollow Wheel. I am doing three main things to improve production efficiency:
Item 1: Material testing and improvements
Current status: Real-world testing & test rig validation testing. Should be complete in 2 weeks.
We have decided to move away from the raw material supplier but source the same type of material from more reputable sources. We know the chemical compound to work very well, but the problem with the original supplier is that they were not able to provide adequate data on the production process related to QA.
We are running new injection tests on 3 different materials using the same molds. Then, we will conduct quick tests to determine if there is an improvement on delamination. If there is, we will be shipping the wheels (8 sets) to our durability testers.
Update: I have received the wheels. The bonding strength with new manufacturing supplier and improved processes have drastically improved.
See video here of a factory worker trying to separate the wheel, pulling apart the wheel but there is excellent bonding and no separation that can be seen.
Youtube short (10sec): https://youtube.com/shorts/8D9TZtChjoA?feature=share
We have only 8 individual wheels so I have sent it to a heavy rider (270lb) and I am running tests on the test rig (see below)
Although, we only have 8 individual wheels, the test rig is able to replicate road conditions accurately. I will be running 8
Item 2: Mold changes to improve performance and production efficiency
Current status: Awaiting results from Item 1. Should commence in about 2 weeks, machining of new parts, which will take 30 days to complete.
After we prove that the new materials from the new material suppliers bond better, I will take the opportunity to incorporate changes to improve the mechanical locking between the core and the tread as well as provide improvements to the wheel.
We are going to stiffen the area around the core. So we will increase the thickness of the tread around the core as well as add more mechanical locking features to make sure that area can handle higher stress and strain.
As far as the fixes are concerned. Here is the new design of the wheel wherein the main goal is to increase the stiffness between the wheel and the core. More material stiffness means less likelihood for delamination.
I will be also improving some things related to:
Customers above a combined weight of 200lbs+ (rider+gear+board), I have three options:
I am highly encouraging people to take option 1 because I know this project will be a success and I cannot do this project without you guys. Know that I am 100% dedicated to seeing this project all the way through and providing the very best product.
If you pick option 1, you’ll get V2 of the Hollow Wheels with improved durability and improved grip performance. The comfort will stay the same, which these are very comfortable to begin with - just ask any Hollow Wheel user what they think.
Please contact me of your decision. If I do not hear back, I will assume you want option 1.
For people under 200 lbs (rider + gear + board),
I will continue to ship. Should anything happen, I will provide you a full refund or new replacement.
Please let me know if you fall into this category.
If you are under the 190lb (board + body weight), then I will upgrade you for free upon request.
Random Reviews of Hollow Wheels that I captured on Social
More reviews here:
Durability Testers Needed:
My go to durability tester is no longer available and cannot put in the time to help ride. I need help from someone that is 220-250lbs. I'm looking for about 3-5 people. I will refund your orders and supply you with wheels to test.
In particular, I am looking for those who rides a lot, carves a lot, and lives in a warm/hot climate where they can put on 100 miles inside each week.
Kindly fill out this Google form to be eligible: https://docs.google.com/forms/d/e/1FAIpQLSdgxLtJK_PeF3KkxTTZWoMxvS1xrs-W6KC0urRnAT3txVXXGg/viewform
Momentum China & New Investment
I have gained a new partner/investor in China that will help with cash injection to help fund the new set of molds for V2. Moreover, I have been working with my partner, Yuan, during the entirety of this project and he has been instrumental in bringing this project to this stage. He has seen the dedication and effort I have put in and wanted to help back the project. He has been responsible for helping manage the factory overseas as well as the material suppliers. Without him, I could not have done it. With his help, he will help me bring the project to new heights.
Closing thoughts
Thank you for your patience. Sorry it is taking so long. If we stick this through, we will make improve the community for the better. I am 100% dedicated to the success of this project.
Feel free to ask me any questions.
Doug
I am preparing everything to start shipping on Friday or on Monday. You'll be seeing tracking numbers come in after 9/29! There is a lot of organization, inspection, and counting to make sure I get the orders out correctly so that is why it is slated for 9/29.
Only a fraction of the wheels and still unpacking and sorting.
ESK8Unity says they are the grippiest street wheels he has tested so far. Check out his video if you haven't already seen it. If you're a grip addict, then I made these wheels for you. If you have an order with the Normal Hollow Wheels and want to upgrade, send me an email at Hello@momentum-boards.com
There has been a lot of requests for the normal Hollow Wheels and those are in production now. They are finished with production in a week or so now
Pre-sale for Regular Hollow Wheels are in production and being completed in a week. Then it goes on a boat to the USA to be arriving in November.
First 15 orders will get 15% off.
Check it out here: https://momentum-boards.com/products/reg
My thoughts on crossing this life milestone: Watching the truck pull up and seeing the pallets get pulled out of the truck was one of the most fulfilling and exciting moments recently. It has been a long journey, spanning somewhere around 3 years and involving many challenges.
This was a crazy journey, one of the hardest and most stressful, but they’re here. I’ve designed and mass manufactured a lot of things (including a V8 and V6 engines, clothing with embedded sensors that can measure human body movement and recreate a real-time, fully motion data quantified 3D avatar on an iPhone) but as an employee or using investor’s capital, but this is the first major project that I funded 100% myself and did nearly everything else myself.
I had to develop everything from scratch, from all the 3D printed molds, creating all the sales channels, marketing strategies, the website, the videos, the crazy durability testing machine that can simulate 100,000 impacts from pot holes in a matter of minutes, the thousands of hours of durability testing, the head scratching when the wheels broke, the head scratching when trying to figure out a solution to the issues, the $100k that I spent and not knowing if I’ll get a return, dealing with the many haters that I would never finish and that this was a scam and I am a fraud, the endless customer support emails, the 30 blog posts, the many 4 or 5AM nights working with suppliers, the many supplier negotiations, the many pep talks to suppliers to not lose hope and that this was going to finally get past the durability phase, the amazing conversations with so many of you, the endless support from the amazing community, the great people that were willing to risk their board and their skin to test my wheels, and everything else in between.
I never thought that I would have to deal with a global pandemic, a crashing economy, and the most extensive and frustrating global supply chain crisis. But I did it. I emerge from this with more confidence and many new business lessons that will be beneficial to my other companies, and most importantly a group of friends that will be enjoying the thing we all help contribute to - the Hollow Wheels.
Thanks everyone!
Doug
It has been at the port since the 3rd… I live like 20 miles from the port. With any luck, they should be here by this Friday. See below:
We still have some Hollow Wheel PRO wheels unclaimed. The PRO is increasing 25% in price as soon as the wheels hit my warehouse, which is an anticipated Friday. I will provide a blog post with pictures as soon as they do. Customers already that have placed orders will not incur additional cost.
Current customer wanting to upgrade to PRO?
If you're a current customer that wants to upgrade, you can do so for the pre-order discounted rate and pay a difference of $20 - email me at Hello@momentum-boards.com.
Why are PRO more expensive than regular?
The material cost is substantially higher than the regular Hollow Wheels as the material used in the PRO are a similar compound as automotive tire racing compound.
If you're a rider that wants the ultimate in grip, then the PRO is the wheel that you'd prefer over the regular.
Visit his channel. Like and subscribe!
ESK8Unity concluded that these are the grippiest street wheel on the market. It would really stick to the ground. As much as I would push it, it would always keep traction. No matter how much I tried, it just wouldn't break traction.
Why did I launch the PRO at the same time as the regular?
While I was in the R&D phase, I tested and came across the material for the PRO and the regular. The PRO was a more expensive but more grippy version whereas the regular was more balanced between grip and comfort.
The material best suited for regular, unfortunately, had a very long production lead time. Whereas the material best suited for PRO had a short lead time. So I decided I would launch both since the molds are the same but just a simple material change. The PRO did not add to any unnecessary lead time. I am incentivized to launch fast anyway and not wait.
We are out of stock of regular Hollow Wheels and I have kicked off the factory to make more Hollow Wheels (only regular). I will keep the blog updated on the next shipment of Regular Hollow Wheels. Anticipated for early November delivery.
Please let me know if you guys have any questions.
Thanks,
Doug
The factory said the shipping container of wheels got delayed due to inspection at the port in China. They said they are estimating the arrival of the entire batch at my warehouse from 9/9 to 9/16.
It will take us about a week to fulfill.
From the 27th to the 4th, I will not have any internet access so I won't be able to respond to calls or emails. Sorry for any inconvenience this may cause.
Review from ESK8Unit on Pro Hollow Wheels coming on the 5th or so of September!!
I am super excited to have ESK8Unity review my Hollow Wheels Pro. The review is coming shortly and will be posted on Fred's channel: https://www.instagram.com/esk8unity/
I chose Fred (ESK8 Unity) to be the first to review the Hollow Wheels because I think he is an excellent rider and creates quality content; he strives to to provide very unbiased reviews, and thinks a lot about the pro and cons of a product from many different perspectives that may align with a lot of riders. He is also a great guy with great character (he recently gifted probably $1000+ worth of electric skateboard and related equipment to a homeless man).
For now, I only have Hollow Wheels PRO. I will be increasing prices around 9/9-9/16 or whenever the Hollow Wheels arrive at my warehouse. If you want to upgrade now and ensure the lowest prices then contact me at Hello@momentum-boards.com. Prices are increasing by 25%.
Hollow Wheel regular are sold out for the time being and may not be getting more inventory for 3 or more months or so. Still getting more data from the factory.
The Hollow Wheels has been a personal project spanning 2 years and I fought through COVID and the ensuing global supply chain crisis. This has been the result of years of sleepless nights, stressing over every little detail, working day and night, and never ending delays that were out of my control. I'm super grateful to all my early supporters and for all the initial beta testers that were brave enough to try out my hand made wheels.
The Hollow Wheels PRO are designed for riders that want no compromise grip. It's by far the lightest wheel in the category and just about as light as a 85mm Caguama wheel, but grips so hard that in a skid pad my legs literally give out (due to high, sustained load... riding in a circle for 10 minutes at a time is like feels like holding a 140lb squat for 10 minutes) before I can break traction.
I have been seeing a trend in wheels wherein they are constantly getting larger but exceedingly heavier, which has adverse effects on the nimbleness and agility of the board. I began to miss that and so it was my goal to bring back lightness. I think the result is something very special.
I devoted thousands of hours to testing and developing, using as data to guide my decisions to make the grippiest wheel that I could.
Here is an example of a skidpad (pretty much a big circle and riding as fast as possible to yield the lowest lap time possible. Faster lap time = more grip.)
I gave Fred my very first and only production set that I have on hand so he could make a video in time for the Hollow Wheel official launch. All orders will be fulfilled soon as my shipping container full of already almost sold out Hollow Wheels hit USA land!
Shipping container is expected to hit US soil in a couple of weeks last I heard from the supplier!!!!!!
Here are some pictures from Fred's first ride today!
Here are some pictures over the years!
My custom rolling road durability simulator - it can simulate rider weight of 600lbs and subject a wheel to hitting a .5 inch bump at 35mph (AKA over 90,000 bumps in a matter of minutes!)
Countless iterations of wheels. I went through 10-15 (I lost count) iterations of the wheels over the years to increase durability and performance.
The early days of me hand casting wheels and the initial production of the first set of wheels!
]]>The wheels are on the boat and are in route in a shipping container. I'm expecting them in mid August but the tracking doesn't really update very often. In addition, after receiving the wheels, it could take us a week or a couple to finish shipping all the orders due to the sheer volume. Furthermore, I want to inspect every wheel and package to make sure they're dimensionally good since this is the first batch.
I realized that I didn't send pictures of all the fun at the factory before they boarded the boat. Sorry about that.
Suspension inserts:
I really love the color and I hope you to too.
The inserts really make the wheels pop. The inserts will be installed in the wheels (for those that ordered). They're a tight fit but with some will power, you can remove the inserts from the wheels.
Here you can see the metal weights that can be inserted in the suspension inserts so that you can change the inertia and as a result change the coastability. They will change the way the wheel feels and you can adjust it however you like!
Mass Packaging
It's really fulfilling to see all of it come together.
The guy in the purple looks cool.
One of a ton of pallets. Lets goooooooo!
In this first batch, nearly all Hollow Wheels are out of stock. It may be another 4-6 months before I can get another batch to arrive. It requires that I have to upfront significant capital as I have to meet the minimum order quantity for the vendor to start production. If you want to get a set of Hollow Wheels this year, now is your best chance while I have inventory. Prices will also be increasing as soon as I receive notice that the wheels have reached the USA shipping port.
I'll have more content to display in another blog post, but here is a quick comparison between regular and PRO. PRO is $20 more expensive due to higher manufacturing cost - it is imported (high shipping & duty fee), only produced in low volume, and the material is automotive grade (designed specifically for the auto industry which has much higher performance characteristics). It costs me $20 more and so I pass off the cost to you.
Hollow Wheels (regular) was designed for all-around superb comfort and grip while providing minimal range loss.
Tech Specs:
*Compared to 85mm Caguama Wheels
Hollow Wheels PRO was designed for maximum grip. This compound allows for predictable riding-at-the-limit of grip, allowing you to dance around the limit of grip and seamlessly transition into board drifts (if you possess excellent board control skills). Like any high grip tire, it will wear faster than regular Hollow Wheels. The rate of wear is dependent on your weight and riding style.
Tech Specs:
*Compared to 85mm Caguama Wheels
Thanks!
Doug
Cost increases but not to those that have ordered already
I have been trying my best to keep costs low, but manufacturing costs and the weaker US dollar to Chinese conversion have meant that manufacturing costs have increased 50% from when I first started this project and created the initial price point. As a result, I am forced to increase costs of the wheel by 25% to stay competitive. However, I can't justify to myself to increase them till they are very close to becoming in stock.
As such, once the shipment hit the USA customs port, the wheels will increase in price by 25%. After they hit and pass the port of Long Beach, then usually it is about 1 week longer to get them in stock at my warehouse.
Those that have ordered and order until they pass the the Long Beach port (maybe 4-6 weeks from now) will be able to purchase the wheels at the current price. I will be sending a cost increase email then.
The money will go right back into research and development for other variations of Hollow Wheel, supporting operational costs, and to buying more Hollow Wheel inventory.
New Race Compound Wheel: designed for grip and more predictable sliding
I have been quietly developing another compound of the wheel purpose built for racing purposes. On the left is the new compound (looks more like a tire) and the right is the default compound.
Those that want more grip and more control at the limit of the grip, these wheel are for you. These wheels can have a very high limit of grip, but when they break traction, they are very easy to control and hold a slide.
From testing, they are about 20% more grippy than any compound I have tested and wear quicker a little bit quicker in the pursuit of grip. More grip = more wear. The chemical formula is pretty similar to a race tire, which is why I picked it.
I recently finished durability testing of these wheels and they hold up very well, but I am putting a weight limit on these wheels of 99kg (218 lbs) with rider + board weight.
I'll post more data on these wheels as I finalize all the marketing content. I'll dedicate a post for this. The material cost of these wheels are more expensive than the default compound so the price will be higher for these race Hollow Wheels. Those that want these instead will be grandfathered in and receive a discounted upgrade rate.
Moreover, I have been getting as much feedback as I can about these new wheels too. Here is what Jeffery Peralta thinks about them after some testing.
He was also saying this is more for people that know how to control a board, a more professional use case compound.
Video of Jeff Sliding: https://youtube.com/shorts/C1IUqMwlQfo?feature=share
One drawback: Bearing requires more force to insert into the race compound core. I am using a different core compound to get good chemical adhesion between the core and the tread so as to not have the delamination issues. As such, the shrinkage of the core material is a little bit more than the other compound used for the standard compound. As such, the bearing hole is a little tighter. However, I am using one mold for two different compound with different shrinkage rates. It isn't ideal and doesn't pose any durability issues, but something to people to know when considering this.
Thanks so much for your patience and support! Please let me know if you have any other questions!
Doug
Suspension insert mold was completed and we did a first article sample. It's supposed to be red in color, but we just put in black to do the dimensional inspection. There is one dimension that is off and the factory and I are going back and forth on it, but I don't think it will cause a delay for June 20th. The samples are being sent to me in CA so I'll do inspection.
The factory is also starting to work on the thread part of the wheel and dialing in some dimensions as well, but it's looking good so far.
Many of you have been asking for a picture of the Kegel wheel, so here it is below!
Box production is kicking off and so are all the instruction manuals. Those are easy.
This might be just a wheel to some of you, but this has been the most difficult manufacturing experience I have ever been part of. I designed and mass manufactured an 8.8L V8 and a 4.3L V6 engine for Power Solutions International in 4 years as their Chief Engineer and that felt like a cake walk compared to producing something during COVID. I founded a motion tracking fitness startup called Enflux and went thru the silicon valley tech startup journey then raised millions in venture capital for it and that was insane. But this. This was the most challenging project with twists and turns at every single turn. Usually, I would go live in China and produce the product, but obviously I couldn't with COVID, which added so much more time in delays and inefficiency. Dealing with production issues, COVID shut downs, China to USA time difference, using my own capital, and so much more for the past two years has been the most stressful experience but the most fulfilling thing I have done.
If you're still reading and haven't caught up on the last update where I show the entire assembled wheel go here: https://momentum-boards.com/blogs/news/hollow-wheel-manufacturing-update-24-back-in-production
Thanks so much for the support and patience.
Doug
]]>
I'm proud and feeling triumphant. Thanks for all your patience.
Thanks,
Doug
One thing left to do is fixing the core color - they are green. But this is coming.
The not-so-good news is that the factory has been shut down for a week so far because of the recent COVID-19 outbreak, it could take another week to start again. China is seeing a major resurgence of COVID. Let's hope the production team stays safe over there and we can get back to work. My factory is in Shanghai and so this is causing some issues.
https://www.youtube.com/watch?v=aztAae0One4
I will update timeline on when the batch is completed and they board a plane. It will be very soon.
Thanks,
Doug
Here are some quick pictures of production. The wheels are coming off the line and we are dialing in many settings and doing quality inspection as they come off. Things are going well but there have been some minor issues to fix and redo. For first production, it is the small details that can hold up production and cause some small delays, but all of them solvable.
Here are some pictures of the covers:
They will be going to logo printing shortly after the rest of the batch is complete.
We had a color issue on the core in the beginning, which caused a production stop and forced us to redo the covers. In production, this is where you see your quality and manufacturing processes get tested. Sometimes you have some mishaps that require a redo. In this case, there was miscommunication and white pigment was not added to the raw material of the cover core. The cover core raw color is somewhat of a green color. Unfortunately, we had produced all of the covers so we the manufacturer is redoing the batch to correct the color. So this means we need to add an up stream process to make sure color correction is correct before going full speed production. A simple fix, but a little costly. This caused had caused a 2 week delay, but we are currently fixing it now.
The wheel halves are looking really good, but some minor cosmetic issues resultant.
Unfortunately, we ran into the same issues with the wheel halve core where the white color pigment was not added correctly. The factory had produced many of the cores already, so they are in the middle of correcting the color and remolding the cores. Again, a small process change, but still costly and a cause for delay.
Finally, we had another cosmetic issues wherein you can see the injection molding material flow lines. I didn't see that originally because the wheels for testing and validation have always been the raw color, the same greenish kind of color that you see above. During validation, the greenish tint really hid this and so neither the manufacturer or myself saw this. However, when we started to add the black pigment to the tread, the mold flow lines could be seen.
This doesn't pose any functional adversity and it doesn't look quiet as clear when you have the wheel in the face (the camera exposes it more than the naked eye). The wheel circularity isn't impacted, but it is a something that does bug me a little bit. So we are adding more of a textured finish to the mold to reduce the injection molding flow line appearance. The factory is adding the textured surface finish now as we speak.
In this photo above, you can see the wheel in the natural color and it is very difficult or almost impossible to see the mold flow lines. But it can be seen when it is black.
I'll be awaiting new timelines from the manufacturer, but I anticipate production should be complete in the next 30-45 days, then it will board a boat to USA to begin shipping.
I'll post new updates shortly of the logo printing, timelines, and the cosmetic fixes.
Thanks,
Doug
I don't have the completed timeline just yet as there are some behind the scenes things I am still working with the vendors right now, but the information request below is crucial for helping me get that final shipping date (from China that is). Next blog post I will have a very detailed timeline.
I posted this in another email and some of you may have received this message once already, but it is so crucial that I get your information. Thank you to those that already filled out the form. Skip to the section "****" as there are some other interesting things I want to tell you.
Thank you so much for your patience. This has been a long and arduous process, especially being hit with COVID along the way. But, I persevere and don't give up. We are in production right now and I need to confirm some user details as well as collect data to analyze performance metrics on the Hollow Wheel.
I have created a short 2 minute survey to:
First bullet point: I am collecting info such as rider weight and boards so I can better understand field performance. It's just part of engineering where I want to start a dialog with my users to understand how I can better improve the Hollow Wheel. It can also help with durability. As you are well aware, I have been gathering user feedback and durability testing for a very long time now, but now I have a chance to get data at scale so I can continue to create new products for the community.
Second bullet point: I want to make sure I get your order right. In the beginning, I didn't collect enough info about bearing size or ABEC vs. Kegel, so my data is a little spotty. This survey gives me a chance to complete the picture to get your order right the first time.
Here is the user and order survey:https://zks7r4fy7uz.typeform.com/to/dXaRllGK
****
Doug, can you remind me of what is ABEC VS. Kegel?
Kegel has 10 pins. ABEC has 6 spoke.
By the way, ABEC clone or Cloud wheel "Discovery" pulleys directly plug and play into the Hollow Wheel. I made the tolerances super tight. On high torque boards coupled with 220lbs+ riders, you should stick with ABEC pulleys when using these wheels.
Doug, I don't know if I have an 8 or 10mm Bearing. Help?
Take a dollar bill and lay it flat across your current bearing.
This is an 8mm bearing:
This is a 10mm bearing:
New Boxes
I had to make the boxes a little bit small to help save on shipping cost because it is going to be insanely expensive. Here are the pictures of the boxes. You'll notice some wheels in the box. Those were just early samples - only testing fitment inside the box.
Production Progress:
All the material has arrived, is staged, and manufacturers are kicked off. Working out the details and getting all the ducks in the row to execute. It's like organizing an orchestra to work in harmony. Not the most compelling photos but I'll have some really cool ones in a couple of weeks to share.
Suspension inserts
I am behind on these so these will likely ship separately, but I am trying my best to ship at the same time. With the many mold tool changes that I had to do, I had to rethink the suspension insert as I did not want to introduce any durability issues to the wheel.
Here is the original suspension insert juxtaposed to the new design (only 3D printed). I have to pay and make another production tool for it - about a month.
I had to design and test a whole bunch of different geometries, which you can see some here:
Here are a ton of different iterations. I didn't want to stray away from my original value propositions so I spent a ton of time doing a bunch of different iterations. This configuration was the best for minimal range loss yet still maintaining the ability to drastically change the ride. Adding the weights can be customized to get more "coastability", changing stiffness, or changing grip. Yet, it doesn't affect comfort much still. It's a hard feeling to describe, but I'm very happy with it. I'll post another blog post in a few weeks after I knock out the new tooling and get all the production stuff out of the way.
Thank you to everyone for joining me on this journey.
Doug
]]>Just wanted to post a quick update on production.
Up until now, I have been waiting on material to come in, an agonizing wait for the boat to arrive with raw materials to provide to the injection molding manufacturer to begin production. I didn't really have much updates over the past month and a half, but now I do. Here goes.
As a recap, I am using material made in Germany. The material which I use for the "tread" is only made in Germany. I couldn't find a Chinese based vendor that had the data and quality, so I had to move countries. Not saying there aren't good material suppliers in China, I just couldn't find them myself. This, of course, means that it has to travel to China via boat to be manufactured, then on a boat again to California where we will pick, pack, and ship.
The material which I am using is not a high production item and so the factory didn't have enough inventory. I am ordering over 700kg of material. This payload is not something that I personally can afford to put on a plane, as such, it has to go on a boat. Fortunately, the arrival date is on the 12th according to my German counterparts. Chinese New Year is nearly over and so I will be working closely with the manufacturer to schedule the production.
Summary of what I have done.
Summary of what is next:
Below is an excerpt from last update as nothing really changed.
Timeline:
I have passed this timeline through to my vendors and they have approved of the timeline. I am trying my best to move up several tasks closer in order to save more time.
It's very difficult to estimate sea shipping. In some cases, sea shipping has 6-10 weeks, which this takes most of the time. Hopefully the ports will calm down and it can ship faster (in Pre-pandemic times it usually took 4 weeks).
We are almost to the finish line. Just requires a very close eye and constant communication. I appreciate the patience. You guys are the best.
Please let me know if you have any questions.
Thanks,
Doug
]]>Just wanted to post a quick update on production.
Timeline:
Right now, it is a race against getting the wheels completed before Chinese New Year which typically takes place in the middle of January and ends middle of February; about a month. Chinese New Year is not accounted for in the timeline; basically all of China goes on a national holiday and no one works.
We are currently waiting on material still; we are in a holding pattern till we get that. Our material is imported from Germany. I am using on the best materials that I could find. Currently they are in production of the material and then it has to be sea shipped to China.
In the past, we were air freighting small quantities but for this batch, we are shipping well over 1000lbs and I cannot afford air shipping at that weight.
I have passed this timeline through to my vendors and they have approved of the timeline. I am trying my best to move up several tasks closer in order to save more time.
It's very difficult to estimate sea shipping. In some cases, sea shipping has 6-10 weeks, which this takes most of the time. Hopefully the ports will calm down and it can ship faster (in Pre-pandemic times it usually took 4 weeks).
Logo Printing:
While we are waiting for the material to arrive, we have finished the tooling for the wheels. Note: the wheel used for logo print testing is just a scrap wheel and we were testing, which why there is a huge hole in the middle. The color of the wheel (the polymer) will be black for the first batch. Moreover, the color of the words "Momentum" and "Hollow Wheel" will be white as the wheel tread will be black (it will look like rendering picture below).
The portion of the wheel in which the logo is printed on will not contact the ground so it should last as long as any standard logo printed on most wheels.
The wheel will look like this in production (this is a rendering):
Suspension Inserts
I am still durability testing the suspension inserts to make sure there are no problems with them. This is far easier than the wheel itself. I just wanted to make sure there are no unforeseen issues here. Those that ordered the suspension insert may receive them after the wheels ship; they may be a separate package. The reason they may arrive as a separate package is because the interior of the wheel changed quite a bit and I have to change the molds to accommodate the geometry change. I would estimate that there is a 80% chance that I will get them done in time along with the wheels.
The left wheel is from the very early batches. The right wheel is from the more recent batches. You can see the interior drastically changed.
Here is the picture of the suspension insert:
The left suspension insert (made from a production mold) is for the wheel on the left (picture above). Right suspension insert is a 3D TPU version that I am currently modifying and making sure it won't cause some durability issues. Clearly the old style (left) won't fit in the new wheel (right wheel in picture above) because I had to add the ribbing inside the wheel.
We are almost to the finish line. Just requires a very close eye and constant communication. I appreciate the patience. You guys are the best.
Please let me know if you have any questions.
Thanks,
Doug
]]>Sorry for the delay in the update. I have been busy durability testing. It's going really well. Planning for production now.
Durability issues are fixed as far as I know so far. I'm pretty happy with it. Since the last update, we created 2 more custom compounds; there were two rounds (batches 6 and 7) of material optimization. Batch 6 (shown in Update #17) was the Hollow Wheel made from our first attempt at high temp formulations. While there have been no durability failures and I am confident I fixed the durability issues, the grip was not great. We took this data to optimize and create batch 7 compounds to maintain durability and improve grip.
I have validated that a low melting point and low strength at high temp of the material was the direct cause for the failures that I was seeing.
I was able to simulate a 600lb person (170lbs on one wheel) for hundreds of miles and it went without a hitch with batch 6&7. Also a lot of ride testing with heavy friends. This took a very long time.
Where is the timeline?
I am waiting from the factory to understand the exact timeline. They just had a week long national holiday. Also, there are some global supply chain challenges that we are working around (keep reading). But the silver lining is that I will have one very soon and there isn't much left to do.
I will be back in about a week with a timeline. Sorry. I know. This is very annoying.
Durability
We won't be using urethane for the wheel because with urethane you can't get very high melting points and it breaks down very easily. So I have been focusing on the new rubber compound. Read more below.
At this point, I feel like I have done everything I can do with the resources I have. I am confident in these wheels and I will begin with the initial batch to make sure all the suppliers can work in unison and maintain high standards of quality. I am not saying there will be 100% perfection and 100% of the wheels will be free of defects because that is impossible, but I am comfortable in the design and the materials to begin on the first production batch. If there are, I will replace it and make it right.
There are some global supply chain challenges ahead but this was the biggest step. See below.
Fixing the Grip from Batch 6:
From Batch 6, we increased the melting point of the compounds. Usually when you increase melting point, you end up making the wheel harder and/or you add other chemicals that have different molecular structures. It's hard to predict how it can change grip without a lot of experimentation. This is the case for batch 6 where we started experimenting with a different rubber compound that had a different molecular structure than urethane. Grip isn't usually measured in standard mechanical property tables, so we had to experiment.
How does a wheel generate grip? Here is a little chart that explains it:
In laymen terms, the road is sort of like one giant piece of sand paper. It has a lot of very tiny crevices. To get more grip, the wheel basically needs to latch onto these little crevices. Generally speaking, the softer the rubber or urethane, the more grip it will have - because it can reach into these little crevices. At the same time, if you have a wheel that is softer, then you have more deflection of the structure of the wheel. When you have more deflection (movement), the wheel starts to get hotter. With more heat, you have degradation of the material. After the material gets hot, then it becomes greasy and then your grip degrades. It is a very fine balance in (including but not limited to) how you tune the structure, what temperatures it can endure, and also what material your wheel is made of.
Once I had figured out that the melting point and heat deflection temp was the route cause in my issue, I had to focus on grip testing. So I had to do a lot of skid pad testing (basically driving in a circle as fast as you can and recording your lap time). Actually, it is a half of a skid pad because it is only one circle. With a full skid pad, it would be a figure 8.
For those that don't know what a skid pad is and why it is useful for assessing grip:
Here is a quick video of my half of a skid pad:
Here are some skid pad times (going in a full circle). Compound 2 is part of Batch 7 and an evolution of compound 1. I didn't bother too much with the urethane that we developed with both Batch 6 or 7 because, well, urethane doesn't have the durability that I needed. See the durability section as to why.
How to read the table: The major things are just to take a look at the average time and the standard deviation (STD Dev) time. A wheel with the highest grip will have the lowest time. A very low standard deviation will mean the time is consistent. I have an infrared lap timer that is supposedly accurate to .001s. The new compound 2 is 5.5% faster than Compound 1 and 4.31% faster than a urethane Hollow Wheel. As I am writing this, I really should have tested against a popular urethane wheel so you can see the difference. I'll do that very soon.
Other things left to do:
There are not many things left to do.
The suspension insert molds have to be modified due to me changing the internal geometry back in Update #14 (https://momentum-boards.com/blogs/news/manufacturing-and-shipping-update-14). It is very likely that I will ship the wheels first and those that ordered the suspension inserts will ship those separately. I didn't want to change the suspension geometry till I figured out the reliability issue. Right now, I am trying to get the wheels out as fast as possible.
Next steps in production:
The molding factory is currently very busy producing products for the winter holiday rush, so we are trying to jockey for a production spot at the factory. Still waiting. Here are things that we have to do:
I'll be providing this in a ghantt chart (like I have done in the past updates) in a week. Still awaiting timelines as seen above.
Some supply chain obstacles that are adding extra time.
I don't know why this had to happen when I'm trying to release the Hollow Wheels but a perfect storm has been created by COVID, natural disasters, radically increased appetite for consumer electronics (fueled by the pandemic), and the brief recession has manifested the following supply chain issues related to:
Mainly the China to USA shipping transit as well as shortage of anything plastic is a major contributor to some of the delays on attaining the timeline.
The obvious question is this: "Doug, why can't you just air ship the wheels?" Reasoning: I would love to but it would bankrupt me.
I priced it out and I unfortunately cannot afford to choose air freight. An equivalent size and weight package sent via sea shipment costing $195 would mean that same package could cost $1000 by air. See reference here: https://www.freightos.com/freight-resources/air-freight-vs-ocean-freight-making-the-decision/
Sea shipping can usually be 4-6 weeks. However, with big shipping time delays, it is looking more like 6 to 8 weeks as I have experienced such in other products I sea ship.
The other bad news facing is very long sea shipment transit times. Ports are backed up. Wall Street Journal says that there are a hundred thousand shipping containers just waiting outside the sea shipping port waiting to be picked up by customs. Customs departments are evidently spending up to 3 days per container. Reported back from the Wall Street Journal: https://www.wsj.com/articles/u-s-ports-see-shipping-logjams-likely-extending-far-into-2022-11630843202
Just so you know I am not making this up...
Rising chemical cost and shortage of raw materials.
Taken from the Boston herald - "The root of the problem has become a familiar one in the 18 months since the pandemic ignited a brief but brutal recession: As the economy sank into near-paralysis, petrochemical producers, like manufacturers of all types, slashed production. So they were caught flat-footed when the unexpected happened: The economy swiftly bounced back, and consumers resumed spending with astonishing speed."
This means all the plastic pellets which makes up for basically everything you're looking and holding is on a shortage too. This adds difficulty when we are getting our materials and we are still waiting to hear back. With this scarce material, the price goes up but that's my problem and not yours.
Reported by the Boston Herald: https://www.bostonherald.com/2021/10/02/from-paints-to-plastics-a-chemical-shortage-ignites-prices/
Believe me, I am working around the clock to get these wheels out. Please do not hesitate to reach out at any time.
Sincerely,
Doug
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This will be a short blog post, but we wanted to keep everyone up to date. We ran through a myriad of material upgrades, increasing the high temperature strength. Through months and months of testing, we are very confident this is the issue.
Here is the new timeline: (use this link to zoom in - https://cdn.shopify.com/s/files/1/0082/2617/7124/files/Timeline_17.png?v=1629135709)
Explaining the timeline: In order to get more orders out faster, I have elected to pulley pursue Task 9 and, for now, omitted, task 8, 9, and 10 because this is the lowest hanging fruit and I think task 9 will get us to the finish line with great results.
We saw delays of getting this material just due to engineering new chemical compositions and the delta variant in Asia has been impacting production of new materials as well as shipping.
We tested completely new formulations of the TPU as well as started to test vastly different materials, working with many engineers from other companies, to help maintain the grip, high temperature resistance, comfort, and mold-ability of the material.
Here are some new photos of the wheel (they look exactly the same, but they're much different):
When you start to test different materials, the shrinkage of other materials are different so the tests can get us close enough. Materials whether polycarbonate, ABS, TPU, and so on and so forth all have different shrinkage rate. In other words, for injection molding, in particular, you are heating up the material to become a liquid, then you inject it into a relatively cold mold. The material cools and then takes shape once again. During this cooling, a material can shrink more and this can introduce warping.
Of course, when you have material that has warped, you need to be over-molding the Soft outer layer of the wheel and so the mold won't be able to seal around the core and avoid "flash". During the molding process, the material is injected into the mold at very high pressures. So then you get a little bit of this flash or spilling of material. So I have to clean up the wheel, but it will still be able to allow me to test the wheel. Just requires a lot of manual labor for me. If this wheel material configuration turns out to be the best, then we have to touch up the mold to compensate for the shrinkage of the new materials so they can seal very well and avoid flash or spilling of the material.
All the molds have been designed for a TPU variant, so the new materials we tested warped a little bit so I'll have to, for instance, remachine the molded wheel so that bearings or the ABEC or KEGEL holes fit, but that will allow me to get an idea if it is a superior material configuration by running tests with controlled variables. That won't take very long for me, maybe a couple of hours, but it will allow me to test many variables for these brand new materials that I think will add a lot of factor of safety in temperature resistance.
I am embarrassed to say that I didn't see this issue.
Initially, we were going to receive 200 sets, but because we added ribs from last time, it meant that injection temperature and pressure increased a lot. The vendor had some Injection molding tuning difficulties and wanted to verify a couple of uncolored wheel samples before running the production.
New shipping timeline:
The issue and solutions have incurred an additional ~9 weeks from the last estimated shipping from the manufacturer. Keep reading and I'll walk you through what solutions/fixes have been completed and what is in progress.
No one wants to ship more than myself. That said, if you do want a refund, I am happy to give you one. I will not give up on this project and I am confident I'll find all the bugs so that this is the very best product that I can make and am really proud of.
If you're having trouble zooming into the timeline, then click here: https://cdn.shopify.com/s/files/1/0082/2617/7124/files/Timeline_16.png?v=1625727132
The problem:
The wheel is overheating and melting in some spots, but only on heavier riders (it seems like 220lbs+) that love to carve for miles on end and on very hot days. Riders that are lighter have not reported any issues so far. Nevertheless, this is a big issue. This is something I didn't quite foresee as much of the testing has been done on the test rig and on riders during winter and spring, but not the summer where temperatures of pavement can reach 140-150F, in some cases.
Add the temperature generated from tire scrubbing during carving and some heat generated from wheel deformation, the wheel can easily reach 170F. The melting point of the current urethane is pretty close to this temperature.
Luckily, there are no core to thread delamination; that issue has not been seen since batch 2.
Solutions/fixes:
There are three solutions, which are designed to cool the wheel, to increase high temperature heat resistance (increase melting point of urethane), and/or to distribute load so as to not generate as much heat in the wheel.
Material Improvement:
The easiest one is to reformulate the material by increasing the melting point. The manufacturer is working on this solution right now. Moreover, I have been working with other vendors, which I have identified two other suppliers, that have materials with a higher melting point temperatures. This will help significantly and be the quickest to implement. See the timeline for next steps. More on the progress in the next update. Currently in the buying stage and reformulation of TPU stage for higher melting point.
Another way to limit the amount of heat which is generated in the wheel is to distribute the load of the wheel more evenly. The negative camber on the wheel definitely increases pressure. For a constant load with a given area (aka contact patch), the contact patch is can be quite small. So the obvious thing to do is to increase the area so that pressure is lower. Lower pressure equates to lower heat generation.
As such, I designed another wheel profile but with less negative camber (but still having negative camber) and removed some mass from the wheel to cool of the area of the wheel that traditionally gets hot (see the picture above for the area which I am referring to... inside edge of the wheel). Then put it on the test rig and also went for a ride to measure the top surface of the wheel. Of course, I didn't cut any production tooling so it is currently impossible to measure the temperature delta using the injection molded TPU material. The next best thing was to test the same hand cast material but compare the surface profiles. So I spent a while doing CAD, creating 3D printed molds, and then molding it. See the picture below. The temperature delta is an average 20F lower on my rides and holding as many variables constant, which is very good news. However, this will require another production mold modification.
As a secondary test, I wanted to put the current wheels on a lathe to cut some other profile geometry to distribute the load so that I can get more data on the impact of heat generation based on the current TPU material. I'll be picking up those machined wheels on Friday (7/9), then riding with my fat friend and measuring temperature deltas. More on that in the next update.
I am sharing this data with the injection mold factory to prepare them for an additional mold change for wheel profile. They'll have a look and share any feedback with me as far as cost, timeline, and any difficulties they see with it (shouldn't be much since it is a simple change).
Cool down the wheel:
Other solution is to cool to the wheel by introducing airflow through the wheel - cooling through convection. Though, I suspect this will not be as effective as the two aforementioned solutions only because the ability of Urethane to reject heat is poor and it will require a significant amount of air flow to reject the heat. Nevertheless, I am experimenting with this solution.
Here is a snippet of what the Mercedes F1 team implemented when they had tire wear issues - they introduced air flow through the wheel.
First, I wanted to see if I could introduce air flow through the wheel, so I started by drilling holes through the wheel.
Then, I packed the wheel with glitter and put grease on the cover to capture any glitter floating out of the wheel. To be sure that this was not just a fluke, I repeated this test 3 times. Moreover, I repeated this test on a wheel with no holes. If glitter fell out of the wheel and stuck to the cover on both wheels (holes and no hole wheel) in every run, then I would know that there is no impact of air flow on the wheel. A side note is that there is a big lip inside the wheel so it is impossible for glitter to just fall out of the wheel and stick to the cover. Coupled with high centrifugal force, the glitter would just want to stick to the inside of the wheel unless there is a big gust of wind trying to blow it outside of the wheel...
Here is a comparison of one wheel with grease on a wheel with no holes (no air flow) and the cover of the wheel with holes, indicating air flow going through the wheel.
The next step on this is to measure how much exact air flow is going through, which is very difficult to do empirically, so I am going to try to estimate through simulation, but I will have to try to estimate air flow. The next best thing is just simply to measure temperature delta of the wheel in real life, which I am still currently doing.
This is a picture of what some proposed holes could look like, but there will be some more optimizations here.
When it comes to temperature, I don't think the Hollow Wheel is the only one that is susceptible to degradation due to high temperature; I think there are others. Other wheels can be seen to have delaminated and after seeing these failures myself, it now is pretty clear to me. That said, I am taking a data driven approach to kill this issue.
Sorry for the delays and just know that I am not going to stop working my butt off to ship this. I am extremely frustrated with myself. This is my top priority. As always, you can reach me via email (the best way to contact me at our support email - Hello@momentum-boards.com, on my website chat, or my personal cell 408-203-6130 (just try not to call after midnight pacific or before 830am).]]>
Quick update: My manufacturer is still organizing the timeline. They have received all the raw materials for the core and thread. They finished machining the revised production mold, as per the last update, and have to run a couple of injection tests first and then dial in the injection mold settings (pressure, temperature, duration of press, etc.) to make sure it is good before the batch run.
This is week 10. The factory said they would let me know this week on the timeline. They have a lot of other jobs so I think they are clearing the queue.
Will send another update later this week, contingent on when they get back to me.
Thanks,
Doug
]]>
Well, correction, they finished the thread tooling, but they are still working on the revision for the suspension inserts, but the most important is the thread tooling, which doesn't need as much validation. But this is a risk factor, but I think low risk.
I got the update from the vendor on the news of the completion of the tooling. I am still awaiting the timeline for production. I was chatting with the injection molding factory and they said they were waiting on the urethane from the material factory. I will be sure to update you all on the timeline here on the next update.
The next step after that is to then wait on shipping as well, which can be painful as shipping from China can take 2 to 4 weeks, depending on how congested air space is. Sea shipping takes closer to 4 weeks whereas air shipping takes closer to 2; however, the price of shipment can be 10 times more expensive than sea shipping. So it depends on how much my wallet can take a hit, but I would obviously like to do air shipping if I can afford it.
After that, then I will perform inspection and testing to make sure the wheels are good. This is a mass scale test to make sure the manufacturer can manufacture at scale. Because producing a couple of wheels to test is one thing, but production of wheels at scale is another challenge. Fingers crossed. We have a good relationship, many people working on this project over in China, and a lot of determination.
Without further ado, here is a picture of the completed tooling. You can see from the pictures of update 12. Here are the new pictures of the tooling with the ribs.
Feel free to ask me any questions!
Thanks,
Doug
We are still in the tooling process as outlined in the timeline below.
The vendor is still machining the revised production molds. There was a 1 week Chinese Labor holiday. I had to finalize some DFM (Design for Manufacturing), they had some questions and had to make a couple of small changes in order to make sure urethane could be injected properly (we also changed a lot of mold lines and other things to get production efficiency and defect rate to be better).
Note: You might have to zoom in
Green represents a completed task and yellow is in progress. The tooling is slated to be completed on the 25th.
They are still in tooling phase and the tooling phase is being completed on the 25th. That is a firm date from the manufacturer. Then they are making the batch, which is about 5-10 business days. Then it ships, but I still have to get a firm date on how long shipping can be. Depending on how expensive it is to air ship, I will air ship, which is about 2 weeks (more if they get stuck in customs). If shipping is insanely expensive for air shipping, then I would have to do boat, which is about 4 weeks. I am pushing for air shipping of course, if I can afford it without going bankrupt.
Thank you for putting your faith in me and I am working hard to get across the finish line.
Cliff Notes: I am feeling confident enough to place the order. I am making a small tool change to strengthen the wheel. I am awaiting a specific timeline and feedback from the manufacturer. See below for details.
Here is a video update for those that want to see more of a behind of the scene look:
In this blog post, I will talk about all the durability testing, small changes to the wheel, and the timeline for production.
I durability tested all the wheels that I had on hand to get as much data to determine if the wheels in the latest configuration are reliable. This means I brought every single wheel that I had to failure to see how they would fail and why and when. Your safety is my ultimate concern.
The bad: I did identify a failure and it is failing on the inside of the wheel during extreme lateral forces (see below to see what "lateral forces" are).
The good: I already came up with a solution and the manufacturer is aware. I tested a bunch of different designs to strengthen the wheel for lateral load conditions and it is much stronger. I hand casted a wheel (see below). The new wheel is a tank even though it is a wheel. Sorry. Bad joke. No failures on the hand casted wheel with lateral load. So far we have 3x the run time over the previous configuration and on the competition. Of course, this is a hand casted wheel and not a production wheel yet, but the production wheel material is better than the hand casted urethane that I use.
The Hollow Wheel stood up against the pot hole test very well, but the lateral test was the true killer. In my durability testing, the Hollow Wheel lasted hundreds of thousands of bumps on the bump test at 30-35mph (See reference section for pot hole testing).
However, when simulating for extended lateral loads of a 600 lb person doing 1G in a corner (what is "G" in a corner? See reference section), the wheel was bending in a certain direction that caused a crack. The reason why I selected 600lbs and 1G corner force is I wanted to get a factor of safety of 2. In other words, there are so many variables in the real-world that I can happen and so I want some extra buffer in case I did not take it into account. I also selected 1G corner force for the same reason. Most standard electric skateboards on urethane won't be able to touch 1G.
That said, this isn't a failure that is very sudden; it doesn't explode. Rather, if you were riding on the wheel, there would be more vibration and you'd probably look to see what the heck is going on. Of course, I am working to completely eliminate this occurrence.
To bench mark the competition, I ran the same lateral test on other wheels to gauge where I was. Here is a picture of another wheel. The main failure here was delamination from the core to the tread.
The new rib design adds 13% more strength to withstand lateral load testing better. Specifically, the ribs help stiffen the wheel against the bending which the wheel has to experience during extreme lateral forces. Here is a simulation we ran. This picture depicts deflection. The yellow zone is where it bends most post ribs. Now it is away from the critical zone.
I tested multiple rib geometries and found this was the most durable and also doesn't adversely impact comfort. It just strengthens the wheel for lateral load conditions.
Here is a picture of the a wheel that I hand casted so I could slap it on the test rig to see if how it performs on the test rig with lateral force loads - if it would out perform the other design. Hint: it does outperform and is now very durable - we have 3x the run time over the previous configuration and on the competition
For those that are not familiar with what "pot hole testing" is, then see this video:
When I say "1G", it refers to the gravitational force equivalent. In other words, when you go through a corner in a car, you can feel a side load on your body. 1G is equivalent to your body weight. In a really fast car, like a Corvette, they can max out at 1G load. Most road cars can only do a maximum of 1G of force in a corner. The race electric skateboards out there maybe could muster 1G in a corner, but most electric skateboards won't come close. Still, I use 1G as a max load for buffer.
Here is a graphical representation of what lateral force is. The driver in this F1 car is experiencing cornering loads of 5G. So this driver is experiencing 5x his body weight in the corner. So if he only weighs 100lbs just standing still, he is experiencing 500lbs of side load through the corner.
Quick update here. Had a delay on the durability testing. One of the motor mounts broke. The mount that drives the wheel for the pot hole testing. I think it had undergone 100,000 impacts or so, but it broke. So I have to wait on steel one. Luckily, someone (Shawn C) from the community had some steel motor mounts and they should be arriving in a couple of days to get me back up and running.
So tearing down and inspecting the test rig added a whole lot of time and set up to test lateral forces. So not all is lost, but it definitely added about 3 days of downtime and extra work. Today, I wasn't able to run the machine because I had to try to fix the test rig. Ugh.
Here is a quick video taken a couple of days ago:
Other news:
Many people are asking if they will be the first to be shipped to in the first 200 set batch, if mass testing goes well. Short answer is: If you're in the first batch, then high chance that you will. If you're in the 2nd batch, then there is a chance.
It is hard to say because I need to inspect these wheels very thoroughly and I will be destructive testing a lot of wheels. The current plan is to destructive test at least 50 sets, minimum. Destructive testing means they will be destroyed either in the testing process or in the after the test inspection (I have to cut them in half and look for signs of failure).
Why 50 sets minimum? It represents a statistically significant sample size wherein the numbers would indicate that it will yield hopefully a low warranty rate and most importantly a hopefully very safe wheel for everyone to ride on.
Why 200 sets in the first place? Well, I would have rather not order that many sets (I would have liked 50 sets) but the manufacturer needs to make some money on this, they can't do low volume, and I need more wheels to test at scale to make sure all our processes and the structure of the wheel is good. 200 is the lowest they could go. They deserve the money and it's the cost of doing business.
Timeline: The completion of the pot hole test due to the motor mount breaking is pushed off by about a week and a half (I said the 6th for completion, but that is pushed off till the 17th because of the repairs). Hopefully the new motor mounts are good. In the meantime, I am making progress on the lateral testing. I am gathering data and trying to make sense of it. The results are OK so far, but I have to think some more before I release my thoughts.
Please let me know if you have any thoughts. If you're getting too impatient (I get it and I am sorry for that), then feel free to get a refund.
Thanks,
Doug
I talked with the manufacturer and they want me to finalize which wheel to go with either the 75A (batch 3, sample A) or the 82A (batch 4, sample B) design, but not both. They also are getting a little tired of all the iteration changes (they just wanna start making money), so the next batch is going to be 200 sets. I hope the 200 sets are the final design bc if they aren’t… well, that is just the cost of doing business, but I have it budgeted.
Currently, I don’t have many wheels (of the best production versions Batch 3, Sample A and Batch 4, Sample B) because each iteration we just made a very small amount of wheels to test. So I have to control the wheels and collect as much data on my instrumentation system *test rig) as possible.
For a recap, here is update #9: https://momentum-boards.com/blogs/news/hollow-wheel-manufacturing-and-shipping-update-9
Timeline:
As the manufacturer wants me to pick one design to do the mass 200 sets order, I have to first finish up the testing on the two candidates:
As outlined in the update #9: Batch 3, Sample A:
Still conducting test rig pothole, radial load, and corning testing. Pothole testing to be completed by Saturday (3/6/21) with testing machine
Corner testing to be completed by 3/12/21 with testing machine
As outlined in the update #9: Batch 4, Sample B:
I asked the manufacturer on the exact timeline of when I say to produce the next batch, how long it would take and waiting for them to get back, but I'll send a small note to you all.
I'll be testing many of the sets to get wide scale durability testing numbers in and also to make sure that the manufacturer can uphold quality.
Basically, the only risks aside from the structure of the wheel is if the manufacturer can produce these reliably, which is what this big batch of 200 wheels is about. If those are good, then I’ll be shipping the extras that I have, then order another batch to ship out. I want to say less than 1 month and definitely less than 2 months. It’s frustrating for me not to be able to give an exact date and I am sorry for that.
]]>I think we are nearly at the finish line. Again, sorry for this embarrassingly long delay. For a recap on why I suck, there were a slew of delays but the longest was getting the injection molding process and materials to work together so that it would not delaminate. Hard to predict and hard to foresee. Also the test rig kept breaking itself, so I had to fix all the weak points. Nevertheless, I put on a lot of miles with the durability test rig and currently waiting on some news about next steps with the vendor. I am feeling cautiously confident about pulling the trigger for the first batch. More on that below.
I am doing a Facebook Live Ask Me Anything event today (3/3) at 730pm to 8pm. Here is the link. Of course, you can ask me anything at any time because you have my personal phone number (4082036130), you have my email (hello@momentum-boards.com), you have my Facebook (https://www.facebook.com/doug.hoang/).
I'll be at my shop and you'll be able to see the Hollow Wheels running on the testing rig. Unfortunately, I can't do it any sooner than that, but if this is something people want me to do again, I can do it again during this weekend.
In this update, I'll be focusing on durability and the science behind it and the next steps
Cliff Notes: Durability is nearly complete. I am waiting on the manufacturer to give me a timeline. The next steps are for me to get the balls to go ahead with a small batch, doing a little bit more testing to make sure quality can be upheld, then hopefully start shipping. My estimate is that it will take them 10-20 days to finish production, then I will make sure all quality processes are in check, then 10-20 days to ship to me. Then, I have to package everything and then ship to you.
Target: The wheel must reach 2,000 miles.
Must avoid failure modes including, but not limited to:
Delamination between core and thread
Any Cracking
Excessive vibration; wheel is imbalanced
Flat spotting of soft TPU
Bearings falling out from core
Excessive bearing noise from bearings
Wheel wear must not be detriment to safe handling, general assembly, or function
Example of past failures:
Tread showing early signs of delamination from Core TPU (Look at Wheel with “C”): https://drive.google.com/file/d/1xWfmPFHTgcBwS3IaCJZvQnW-XHxAi1_R/view?usp=sharing
Simulating Cornering Forces: https://www.youtube.com/watch?v=oFD1YmMNIvY
Temperature: 130F
Mileage: 2,000 to be completed
We simulate at least a 300 lbs rider going over corners for 2,000 miles.
Must not exhibit any of the failure mechanisms shown above
Must test 10 individual wheels that show no failure for the design to pass to production. I am not currently at 10 individual wheels yet (only 4). More on that later.
Pot hole testing: https://www.youtube.com/watch?v=kdMgsfaJH8w
Temperature; 130F
Mileage: 2,000 to be completed
We simulate at least a 300 lbs going over pot holes at 130F for 2,000 miles:
Must test 10 individual wheels that show no failure for the design to pass to production. I am not currently at 10 individual wheels yet (only 4). More on that later.
This is a testing machine that simulates pot hole riding: https://www.youtube.com/watch?v=8H4zavx8XDc
Figure 1: This is my testing machine where the wheels are attached to electric skateboard drivetrain.
Rapid Acceleration and braking repeated
Temperature; 130F
Mileage: 2,000 to be completed
We simulate at least a 300 lbs going over simulating rapid acceleration and braking at 130F for 2,000 miles.
This may be combined with the aforementioned tests above.
Must test 10 individual wheels that show no failure for the design to pass to production
Designed to reduce durability testing time. Designed to simulate forces and temperature from real life.
Pothole impact forces
Cornering forces
Normal Riding forces
The machine has an electric skateboard drive train and has springs to simulate a rider of 500lbs (getting the test rig to rotate that at high speed is another story... Hint: doesn't really roll that well at high speeds).
The wheels and drive train are placed under a drum to simulate road forces. In this configuration, we test normal riding with radial forces placed on the wheel as well as shock testing from a pothole.
The machine can also simulate high load corner forces. In other words, this can simulate when the rider is turning a corner very hard.
The machine also places load on the core to simulate rolling road resistance as well. This is a picture of a motor which acts as a brake for the drum. Bonus points if you can guess what that motor is from.
The pothole testing is an example of a high accelerated life testing. A test is run at 35 mph, which means that the wheel is getting hit about 40 times per second. 35mph is the fastest I can go in this particular test because it turns out hitting a pothole 40 times a second makes it hard to travel much faster with the battery pack that I have (Thanks, Jansen!). This test is run for every 2 minutes and then checked. This means that every 2 minutes, the wheel takes a pothole hit 9,600 times every 2 minutes. The wheel is also heated to 130F. Then there is 2 minutes for inspection for failure. Then repeat till the wheel breaks.
So yes, I am brining the wheel to a point of failure. Now the question is... how do I correlate this to 2,000 miles? This is what is honestly confusing me.
The corner load test is conducted at 50mph for 2 minutes at a time with 2 minutes for checking of failure. The wheel heats to 130F. The common failure to look out for is core delamination (see videos in the first page). I'm still running this test. Testing takes a lot of time.
Batch 1 of Samples: If you recall, this batch was too hard; the tread was too hard.
Testing: A couple of customers had ridden the shit out of this and there weren't any problems with it, but it was too hard, yet still better than a lot of competitor wheels. Though, not as good as the prototypes. I was not satisfied. Back for more iterations.
Because this was a harder wheel, there is less flex so the lack of core/tread delamination did not show it's ugly head.
Batch 2: Went softer on the tread.
Testing: Even higher approval rating, but now there was core delamination (see core delamination videos in first page). This is a risk. Had to change the tooling to eliminate delamination. No chemical adhesion.
Batch 3: Changed core tooling for more mechanical locking and better chemical adhesion. Also went softer on the tread. Changed a bunch of mechanical properties, materials, and injection molding settings.
Sample A: Softer tread and TPU core with new core modification to prevent delamination
Sample B: Softer (same as sample A) tread TPU and different core material with new core modification to prevent delamination
Sample C: Same hardness as batch 2 tread and different core material (same as Sample B in Batch 3) with new core modification with new core modification to prevent delamination
Results:
Sample B and C: Testing showed that core and tread still had delamination but this is because we chose a new material that would have high production efficiency but not great chemical adhesion properties. Originally thinking the new core modifications could make up for it. Didn't pan out.
Sample A: Testing showed this was an insanely comfortable and grippy wheel with no more preliminary delamination from the on going test rig testing. This one has lower production efficiency (higher cost) but excellent chemical adhesion. Might be too soft of tread where durability may be a concern... so commence on going testing (to this day).
Still conducting test rig pothole, radial load, and corning testing. Pothole testing to be completed by Saturday (3/6/21) with testing machine
Corner testing to be completed by 3/12/21 with testing machine
Batch 4 of samples: core material was changed again to improve production efficiency.
Sample A: Same as batch 2 tread with new revised core material to increase production efficiency (less scrap)
Sample B: Softer tread (in the middle between batch 2 and batch 3, sample A with new revised core material to increase production efficiency (less scrap)
Results:
Sample B: performed better than sample A, but slightly worse than Batch 3, sample B on rider comfort and grip
Still conducting test rig pothole, radial load, and corning testing. Pothole testing to be completed by Saturday (3/6/21) with testing machine
Corner testing to be completed by 3/14/21 with testing machine
So far Batch 3, sample A is the lead and durability testing is promising. I wanted to test a total of 10 individual wheels, but only have 4. But the 4 look good. So I am making a really big batch of wheels, which could go out. So this is where I am at. I think Batch 3, sample A is the winner so I am going to make a small bet.
I would be lying if I were not a little bit scared because I don't want to release a bad product and pull a Cloud Wheel, which would pretty much destroy this project. Thoughts?
This is where I am at. Hope to hear good news from the factory by tomorrow night. Sorry for typos.
Thanks for reading!
Doug
Sorry for lack of updates. It's just running. Kinda like watching grass grow violently. Running through all the tests and just making sure it passes. Nothing much to report, which is good news. Quick video of durability testing. This is just one configuration. I also tilt the wheel to simulate cornering forces. Just been running through all the different samples and making sure that they pass the mileage test. So far so good.
Factories start opening up end of this week from Chinese New Year (they take effectively a month off a year for Holiday) so now I can ask them on production timelines. Will update ASAP.
Doug
A lot of the material adhesion problems we have had between the core and the tread was an unforeseen issue. A lot of tweaking and back and forth between 4 teams (urethane supplier, injection molder, myself, my team in China) and shipping between China and US adds up on time. However, we are all taking a data driven approach and working as quickly as possible to bring to market the Hollow Wheel.
The wheels are not shipping till after February due to China having Chinese New year, which is typically about a month long holiday. However, there is a lot of good news in this email. I have had a user approximately 1000 to 1500 miles (he said closer to 1500 miles) on a set (the first sample with the harder urethane) and they look in great condition.
We are now on the 5th iteration and the wheels are better than ever, but just need to make sure they don't break.
Here is a quick recap of what was done in the last update and what I am doing now.
Design of Experiment and Durability Testing
Since the last update on the 31st, we wanted to increase durability of the wheel by improving the bond strength between the core and the urethane. As such, our team decided to try out a couple new iterations of the wheel material break down. We think with the new tooling change (see last update for more info on what was done), we decided to do a design of experiment (DOE). This is a testing method to control variables and change only 1 variable at a time. By changing a few variables, we can then see what works and what doesn't.
With the new tooling update, it has increased the mechanical grip between the core and also added more stiffness in the wheel where it can help prevent core and tread delamination.
Based on the last two batches, we applied that learning to change the injection molding parameters (urethane injection pressure, mold temperature, etc.) to get the best bond strength without drastically increasing injection molding defect rate.
Since the new geometry is now a constant, we decided to use the chemical compound to increase the bond strength. We have three new samples and I am beginning to accelerate the durability testing. Also, finally, we were able to get a durometer for the tread in the 75-80A range, which is in spec to the prototypes.
We have three new samples. We changed the chemical composition
Accelerated Durability Testing
The test rig is up and running and beating the crap out of these wheels. This allows me to put on a lot of miles in a short amount of time. It is running off Arduino and has a program that automates full throttle to 50 mph, then hard braking, then just repeats over and over and over.
Here is the rendering:
Here is the real thing:
Thanks,
Doug
Previous update: www.momentum-boards.com/blogs/news/manufacturing-shipping-update-6
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First, please do not hesitate to email me. I am not using any money from the wheel project to fund the development of the Hollow Wheels. Only the cost to actually make the final wheels. This comes from my own pocket. I have healthy streams of income so don't worry about me going homeless and having to give up. I never give up.
Lots of productive work going on since last update:
This is the timeline of when things will be complete.
We also have Chinese New Year around the corner wherein China takes a break from Jan 15 to Feb 7th or so. So I am racing against the clock to get this done, but don't want to sacrifice anyone's safety. This is important because it can add more delays. Just being honest.
Tooling Change:
We elected to make a tooling change to the core of the wheels. We wanted to make sure there was enough surface area on the core of the wheels to grab on to the soft TPU (the tread). We wanted to both increase mechanical grip between the two compounds as well as provide more surface area for the chemical adhesion (for more on what this is refer to the last update). Sorry for the small, low rest picture. Just need to protect my work from the copy cats as long as I can.
TPU upgrade:
The latest batches have been coming in at 95A and 89A, respectively. All the prototypes have been at 80A, so we're slowly changing the formula to get to that baseline. The wheels are still very comfortable at 89A though. Moreover, we adjusted the formula with more bonding agents so it can get the chemical adhesion that we need.
We're also adjusting the core chemical composition to aid in chemical composition too.
Testing:
I am no plastic injection molding expert, so I hired a third party plastic injection molding consultant. So we have the TPU factory, the Injection molding factory, and a third party consultant working on getting the chemical composition.
Each new sample, we performing more and more tests to make sure we have chemical composition. We were testing in the beginning, but we're just learning more and more and applying these lessons learned to make sure we can minimize downtime. Some additional tests include cutting wheels apart and measuring the amount of force it takes to peel away the soft TPU from the core TPU. Then continue adjusting parameters.
There are a lot of variables including, but not limited to mold temperature, TPU temperature, Core TPU temperature, injection pressure, chemical composition. We just have to control variables and pull one lever, then test. Just using data to make the best decisions.
Not hard. Just takes time and attention to detail. So I'll keep you up to date, but this project is of high priority. We are able to inject a new wheel and test per day, so we have a lot of testing parameters to go through. My estimation is about 2 weeks before the test is complete. Perhaps less. They work 6 days a week and 10+ hours a day. Beasts.
Retail box:
It is looking beautiful, but maybe I'll leave that as a nice surprise when you all get the wheels.
Logo Printing:
No major challenge here as far as I am aware. But you all know how it will look.
Off topic: My room mate got COVID and so I wanted to get tested. Do not take the quick test 80% accurate COVID ($150); it is a waste of money... I thought I would try to save some money since I was feeling fine. Go for the PCR test (supposedly 99% accurate) and spend the extra money - it is $350 w/o insurance ($250 w/ insurance). Anyway, I took the 80% accurate test and it gave me a false positive. Huge mind F**K. I convinced myself that I got sick. Anyway, I took the PCR test and it came back negative.
Thanks,
Doug
Just wanted to give a quick update on the wheels. In the last update (https://momentum-boards.com/blogs/news/shipping-update-4), I said that I would provide an update on the 18th. Sorry, I am a couple days late as I am working on the next steps. First and foremost, thank you all for your support and patience.
I'll cut to the chase. The bond between the core and the thread needs to be stronger. There are signs of delamination between the core and the thread. The problem is that the core and the tread aren't melting together during the injection process; this is to say that the thread is purely relying on a mechanical lock and not a chemical lock (the core and the tread needs to melt together).
Here is a little picture. There is dirt getting trapped between the core and thread. That is not supposed to happen. Since the material is a little clear, I can see some dirt accumulation in the seam (hard to take a picture).
The wheel is undergoing a lot of stress and temperature fluctuation:
As such a strong bond between the core and the thread is essential.
Here is what we are trying to achieve. The red and grey bars represent the two different materials. In our case, it is the core (the hard urethane) and the thread (the soft urethane). The first stage is the molten hot soft urethane is injected into the mold where the core is sitting inside). The molten hot soft urethane transfers heat into the hard urethane and fuses together. Upon cooling, the two urethanes are melted and locked together.
This might sound easier than it is. It can seem like an art more than a science. This is because if inject too hot, then we get a lot of deformation when the material cools down (Basically the wheel isn't too circular). This is called "Shrinkage".
...And it just gets harder to inject and generally control.
Moreover, if we go too cool, then we don't have any chemical adhesion. It just requires a lot of testing and adjustments.
But this is OK. I am not very worried. This is the first wheels off the mold and we just need to adjust mold temperature, injection temperature, injection pressure, and alter the material or introduce some bonding agents.
It's kind of like making pancakes. Sometimes the first pancake needs some work but then the other pancakes after come out a lot better after the first try.
Next steps:
Timeline:
Unfortunately, I don't know the timeline exactly, but hope to know more on Friday after the meeting of a testing game plan. I'll share those details with you all. I hope it isn't much more of a wait. I will be very honest and transparent with you all.
Cross Functional Collaboration targeting success
I have my China team diligently working and regularly working with the factory and conducting quality audits. Then, I have the material supplier company helping provide guidance on bonding and material specification formulation changes. Lastly, I have my plastic injection molding partners working to make this a success. We are all determined to make an amazing product.
Continued testing:
I will continue to do a lot of testing on the wheels to see if I can identify other areas of improvement in parallel. I have given them out to some of my friends to test as well. Also, I have been using the test rig to put more miles on them quickly. Moreover, I have been attending as many ESK8 road course sessions and trying to finish durability and performance testing before shipping.
Test Rig:
Please do not hesitate to reach out or ask any questions. It is getting very close to the finish line.
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