Remember when SRAM acquired PowerTap and we all scratched our heads as to why, because they already owned Quarq from an earlier acquisition? Well, maybe it’s because they, like us, saw the potential for getting into the indoor bike trainer business. While they may have missed the first wave of frenzied fitness purchases spurred by stay-at-home orders, operations like Zwift, Rouvy, Kinomap and others means the indoor cycling market still has plenty of runway.

But for those of us who still like to ride our own bike inside, they have a very interesting hub concept that disconnects the freehub body so you keep your standard cassette on the bike and just drop it onto the indoor trainer. But first, the bike…

SRAM Training Bike Concept

This recent patent filing from SRAM shows a modular indoor cycling trainer, which we’d guess would get the PowerTap branding over Quarq. Or, at least, use it’s technology to put the power meter into a hub-like unit rather than a crank-based power meter like Quarq.

patent drawings for sram indoor cycling trainer

The patent filing mentions two key differentiators that could set this bike apart from other cycling-brand offerings. First, modular construction that assembles easily and makes it smaller and lighter for shipping. And, it means that parts (like the drive system, electronics, etc.) can be replaced or upgraded in the future.

This also means they could offer an inexpensive, friction-and-weight-based flywheel system that’s driven directly by the cranks, or a belt-driven, electronically controlled resistance unit that’s offset from the crank’s spindle. Either way, they could build “smart”, electromagnetic- or friction-based resistance control into it.

prototype sram indoor bike trainer from PowerTap patent filing drawings

Second is the console screen. While it’s only loosely mentioned, the illustrations show it as an integral part rather than a tray for placing your tablet or phone (but it also mentions options for that).

Assuming they integrate a screen, those two features could differentiate it from standalone indoor cycle trainers from Stages and Wahoo, which lack a screen and are built with a solid, one-piece frame.

patent drawings for sram indoor bike trainer

Modular and swappable seats, handlebars and pedals let multiple riders share the same bike.

If the bike comes in under $1,500 to $1,800, and uses an Android-based or similar platform that allows for 3rd party apps, it could potentially give users the ability run anything from Peloton’s App to Zwift to Rouvy to Kinomap to just spinning and binging Netflix.

What do you think? What other features could they add to make this replace your bike-on-trainer setup?

SRAM Indoor Trainer Hub Decoupler Concept

sram patent for detachable freehub body that uses current cassette on indoor trainer without having to remove it from the bike

Nevermind that trainers are getting more and more expensive, but then you have to add a $50 (at least) cassette to it. And everytime you upgrade your drivetrain? There’s a good chance you’ll need another cassette to go with it. Or maybe you like swapping between your road, gravel, cyclocross and mountain bikes on your trainer…there’s no way you’re going to keep swapping cassettes on and off, right?

sram freehub body decoupler patent for using your same cassette on an indoor trainer

And that’s where this patent from SRAM comes in, using a two-piece system that decouples the freehub body from the hub body, allowing you to keep the cassette on your bike even when you remove the rear wheel. Here’s how it works:

how sram hub decoupler works so you can keep your cassette on your bike when putting it on the indoor trainer

The freehub body is bolted into the frame, just as you would with a normal thru axle, except that you’re bolting just the freehub body portion (with cassette already mounted on it) into the frame.

Then, you place the wheel into the bike and it uses a spring-loaded ratchet wheel to connect the hub body with the freehub body. Then you insert a shortened thru axle just like normal, except this one’s threading into the freehub body rather than the opposite dropout.

sram freehub body decoupler patent for using your same cassette on an indoor trainer

The trainer would be equipped with a matching ratchet wheel as what’s inside the hub shell, so all you’d need to do is pull the wheel out of which ever bike you wanna train on and drop it onto the trainer.

Yes, there are a lot of issues with this…namely the likely limited hub selection and also very likely additional weight. But, from a problem solving standpoint, it’s clever and we’re stoked to see the concept. And even more stoked to see if it goes anywhere!

6 COMMENTS

  1. One of the main issues with the decoupler-patent is that this idea has been patented in numerous ways by many folks before. There’s a lot of prior art, so Sram most likely is using this patent description as a smoke screen for specific tech to be found perhaps in other parts later on.

    Furtheremore, with cassettes nowadays overhanging the spoke flange, the decoupler will not work. A workaround could be to put the flange more towards the center of the wheel, out of the way of a cassette. But that for sure is not beneficial to the strength of the wheel.

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