Request for prototype testers!

Hello all!

My name is David, and I’ve been a member of the club since 2019, although I’ve been a cyclist in the region since about 2013. Unfortunately I haven’t ridden as much as I would have liked this summer - a broken collarbone back in July certainly didn’t help. I’m also an engineer who likes to tinker.

I (along with two of my brothers) have developed what I’m calling a resistive training device that, in a nutshell, makes your cycling harder at lower speeds while road cycling outdoors. You throw the device on, and rather than needing 200W to travel at 30 kph, you now need 250W. The primary use-case would be to allow for cycling with others of different abilities while still getting exactly the workout you want. The way it works is by using high-power magnets to generate eddy currents in an aluminum wheel which creates resistance on the back wheel without needing to make contact with it. For those of you who are familiar with the STAC (now 4iiii) trainer, yes, it is based on the same technology. It sits on your seat tube, and has magnet arms which reach down to the rim. There are silicone strips which protect your paint, so only silicone and rubber bands are in contact with your frame. The device is completely silent, allows for adjustable resistance on the fly, doesn’t impact the ride feel at all, and can be put on/off in seconds.

The idea for the device was sparked by trying to get my partner into cycling and then looking into ebikes for her. After seeing how expensive ebikes were and not wanting to bike at painfully low watts if we both had regular bikes, I thought that rather than speed her up, I should figure out how to slow me down. Thus this project was born.

Here’s an example of it on my bike:

I’m looking for 4-8 people to test out a prototype on a few rides before we finalize our design. There are a few requirements:

  1. Must have a frame that the device is compatible with. We have designed it to work with probably >95% of frames so this shouldn’t be a problem. Here’s a handy guide that shows roughly which styles it’s compatible with. If you’re not sure, and we try to see if it works and it doesn’t, that’s still helpful information for us.

  1. Must have aluminum wheels without a steel bead or pin in the wheels. Here’s a handy guide on how to check if you’re not sure: The wheel can be either rim or disk brake.
  2. You can commit to testing it on 2-4 rides within a week or two of me getting it to you (which should be within a week or two from now).
  3. You’re willing to provide some brief feedback to me on what you liked or didn’t like, and what you think might make it better.
  4. Optional, but helpful: A power meter of some sort on your bike. And then also your willingness to share your ride data with me.

For anyone who is interested, please email me at, let me know below in the comments, or message me.

In appreciation of your contributions, if you like the device after testing and don’t want to return it, you can keep the prototype for $40 (to help cover the costs of the parts), or I can give you a discount for 50% off for the production version if/once we start producing it. We haven’t decided on pricing yet, but it will probably be in the range of $150 - 250.

This has mainly been a fun project over the summer, and I have little idea of what the demand might be for something fairly niche like this (we might only sell like 3 haha), but we’re thinking of doing a kickstarter and we would go ahead with it if we get say 50 or 100+ orders for it.

If anyone has any comments/feedback, I’m super open. Even if it’s critical!

Thanks for your time,


Pretty cool @dwulff ! How much force is applied to the seat tube when you crank up the resistance?

I’d help with the testing but I have my own collarbone fracture healing going on :frowning:


Wouldn’t be a Friday afternoon if I didn’t provide 5 reasons why we need to support this initiative.

And this is how I’m going do it…

1) Tell an old man story from the club’s history to support David.

I’ve known David for a decade. We used to train and race triathlon when we were at UW. He’s ridden on many WCC rides and events and is an all around swell club member. David is half my age so I am continuously slower and jealous of him.

2) Post a vanity race picture from the past.

David and I raced the 2019 KW Classic (Sportif) and we both made the podium on that glorious day.

Chris in 2nd, David in 1st. Your’s truly in 3rd.

3) Make a joke that supports the premise of the post.

You need to target the right person with the greatest motivation to buy the product. I will purchase the first 25 units and insist they are installed on all members of Group 1 on Wednesday night gravel. I am your most highly motivated buyer and will pay for any technology to not get dropped. Consider this my contribution to your secondary “use case” target marketing.

4) Focus attention on the brilliance and initiative of this WCC club member.

Yes, David’s an engineer. But, he happens to hold a PhD in Nanotechnology and Materials Science with a PostDoc. Dude knows advanced materials research. And he’s a cyclist. He’ll take your feedback and probably be able to engineer a quantum-whispering-gallery-mode-terahertz-accelerator to attach to your bike if you want.

Work with him. Tell him what’s important to you.

5) Make Broad Aspirational Parental Statements.

I happen to know a thing or two about innovation in Canada. And the nature of scaling ideas in this country. The economic value it creates at the firm level, as well as for communities, regions and across OECD nations.

It starts with an idea. Usually an unorthodox one. And for a community of visionaries and early adopters to help local inventors and entrepreneaurs work through the specific needs of the marketplace and help barn-build (raise funds and support) to get the MVP tested at the higher TRL levels.

Call to Action: Get involved in Innovation in Real Places.

Waterloo and the WCC specializes in the innovation economy. STAC (mentioned by David above) started in Waterloo Region. Art H. was a WCC member. They sold the company to 4iiii. Which is now based in Calgary and is a world leader in pedal based power meters. All started with an idea similar to David’s and I remember STAC working with WCC in a similar way as David is asking.

You never know where the innovation will go. Or how much Canadian prosperity you will create by helping out. You only know…that you miss every shot you don’t take.

Good luck, David !



I’m sorry about the collarbone! It’s not a fun one to break. I hope your recovery is going well.

And a great question which requires a bit of math! In a worst case scenario where say it’s providing 434W of resistance when a power cyclist is bombing a hill at 70 kph (which is indeed my rough estimate of the resistance at 70 kph with the device), if all of that force is being applied directly to the back of the seat tube (not really possible with the design, but still a worst case scenario), the force is about 22.4 N, or about 5lbs. (Force = Power/Velocity = 434W/19.4 m/s = 22.4 N). And then that force would be spread across the seat tube with the one (or two) rubber bands. So if you can hold your 15-20 lb bike with one finger from that part of the seat tube (I can’t imagine a bike that couldn’t), your bike should be able to tolerate this device. I did just tested holding my bike from that point with a finger, and it didn’t feel anywhere close to sketchy for the carbon fibre.

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Wow Alain, thank you for the support and the kind words. It’s always been such a pleasure riding (and swimming) together. Your leadership inspires me. And I only made it to the top of that podium through a sneaky sprint at the end after sucking your wheel - these days I’d be happy if I could keep up with you!

The idea is certainly unorthodox, and only time will tell if it gains any traction! If this were able to have a positive impact on the region even in some small way, that would be incredible.


Hey David, it’s been a while since UW but it’s good to see you around and I hope your collarbone isn’t bothering you. To go back to your original inspiration for the device being cycling with your partner, your results may vary but we’ve really enjoyed having a tandem bike. My wife has a Dutch-style bike and tends towards more leisurely or utility biking and has less of a need for speed than I do.

For me it’s a different style of bike to learn the techniques it requires (like threading the needle through rail trail gates with its noodly frame, or navigating climbs that the bike makes more technical like the climb on the trail up from St Jacob’s). It also helps me find rail trails/ multi-use paths less stressful as we’re at a speed closer to what people are prepared for, and we’re already in single-file to pass people.

For her, she doesn’t have to think about shifting, steering, or navigating, and she can put in whatever effort seems appropriate (including full-gas chasing back on to a group during an event) and we stay together. A bonus is that she can look around more and it extends our combined range.

If you wanted to try our tandem we could figure out when and where. @Francqlife does also have one, but I’ll let him tell you what his is named…

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Hey Andrew! Nice to hear from you. I had briefly considered a tandem before, but now I’m thinking more seriously about it after your comments. It does sound like there are some solid advantages to using one. Thanks for the offer to try out yours; if the offer still stands in the spring we might take you up on it!

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Maybe we will get more people on our rec rides if they use this device to slow them down. :joy:

I’m slow enough so I’ll pass on trying this out but I’ll look forward to hearing how it works for the rider(s).


The tricky part with tandems is it does take a bit of time for both sides to get used to it and it is a very different experience for the stoker (the person at the back) than the captain (the person on the front).

I have never been on the back of ours since I’m too big (we have a cannondale t1 jumbo / small) but I think I would struggle not to freak out :slight_smile: Both my son and my wife prefer to ride their own bikes rather than be tied to me. Apparently I ride more aggressively then they are comfortable with although I do try my best to be good! Also I like to ride at a higher cadence and we have to compromise on that too. Welcome to try ours too if you like.

Another option is to just ride a slower bike, I sometimes just ride my gravel bike on the road when the rest of the family ride road bikes. I even rode my fat bike while my son was on his road bike when he was younger but that is a step to far now he is bigger.

Back to the prototype, I recall the Stac trainer was patented (or at least pending). Not sure which part, had a look for the patent but couldn’t find it (I’m sure someone here is better at finding that kind of thing that I!). Now that 4iiii is owned by Specialized something to consider since Specialized are known to be fairly litigious.

I can see the use in this. there was a product a few years ago that had the same idea but it involved a separate wheel

I borrowed Alain’s tandem and they are a lot of fun. I rode Andrew’s around the CX course and it was a fun challenge. My Son loved the tandem, but he would also put the legs on the top tube when he didn’t want to pedal anymore.

My wife uses an ebike and it is like a tandem. They are great but still hard to ride together nicely. Every down hill I would have to coast or ride ride away, I can see this limiting that gap. Now it would make the uphill portions harder when the ebike rider now has an even bigger advantage.

If you don’t find anyone else I’m sure I have wheels and a bike that work, along with power.

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Ok, helpful to have your perspective on a tandem too! And thanks for the offer to try yours as well.

Yes, STAC did have a patent which was assigned to 4iiii, but it seems as though they have abandoned it. Regardless, it is mean for “in-place training” so perhaps my design would be different enough to not infringe anyway. Here it is in case you wanted to take a look. US20180264305A1 - Eddy current cycling resistance apparatus - Google Patents

And helpful to know that Specialized is known to be litigious!

Thanks for bring that other device to my attention. It seems like they aren’t making it anymore, but still good to be aware.

If nothing else, riding a tandem sounds fun!

The nice thing about the design of my device is that the resistance would be quite low at low speeds (e.g. when going up a hill). I estimate that it would only be about 9W at 10 kph. Even so, you could adjust even it lower while you’re riding (probably down to 2-3W easily) by increasing the distance between the magnets and the rim.

And that would be awesome if you’re willing to test it out. I’ll shoot you a message next week about getting one to you. :slight_smile:

Having worked with the guys from STAC and then trying to sell their trainers at Ziggy’s the biggest problem was rim compatibility. Having to educate the customer that not every wheel was compatible was a bit of a pain.

Appreciate the info! Yes this could be one of the biggest challenges, especially as more people move away from aluminum to carbon fibre.