Was riding today when i thought about this idea for a mountainbike gearbox. It uses a cassette and a gear, but instead of a derailleur the upper gear(middle axle) moves along a splined axle to shift. The power flow would go through the pedal input->cassette->chain->upper gear->belt drive->output axle->output gear. Output axle is attached to emotor.
My goal with this design is to:
make a design that isnt as heavy as the pinion gearboxes,
has the motor connected directly to the rear wheel without a ratchet(the ratchet would be between somehere between the middle axle and the output axle), thereby allowing for regenerative braking or slowing down with the motor reducing brakepad wear on long decents.
Moving the weight to the center
Belt drive to the rear wheel
Fully enclosed to protect from debri and allowing oil bath
Feel free to comment if youve seen a similar solution somewhere else or if you have any thoughts about this
Sorry for the ugly drawing, i dont have my usual technical drawing setup since im not at uni atm.
by Prestigious_Elk4887
16 Comments
Let’s say this is good, i honestly don’t know: it’s a bold move putting it on the internet for big bike to find. Get a patent and give it a rip homie.
more gears = more friction, and I don’t get how this bypasses the wheel spokes. Really strange diagram too, model it in cad and repost.
That’s basically the same design that Honda used for their downhill bike back in the mid 2000’s.
At the timetThere was lots of speculation on how it worked and it just turned out it was a derailer and cassette encased in a box.
Great start! I think the main issue is the limited gear range this would offer- a 1x needs such large cassettes because the high gear is as small as possible, not sure how well that’d package into the BB area. Not an issue for standard gearboxes because each set of gears can have different-sized drive gears, instead of a fixed-size chainring.
I may be wrong here but there may be issues with the shifting action- a normal derailleur only has to shift the leading side of the chain and the rest follows. I worry that if you shift the entire chain allignment, meaning both leading and tailing sides, it either wont shift or will jump off.
Typically, for drivetrains with electric motors, engineers try to locate the motor at the bottom bracket (which is where the pedals are mounted) to reduce unsprung mass. The motors can be fairly heavy, so mounting them directly to the rear axle results in more force applied to the suspension, which transfers into the rest of the bike and the rider. But other than that, ot looks like a neat concept and I commend you for thinking outside the box!
You lost me at motor.
A lot like this: https://www.trinitymtb.com/about
Honestly this isn’t an original idea, check out Honda mtb, and most notably right now check out WRP gearbox. Although you want to include a motor too which is novel. I would say that doing something more like the pinion MGU makes sense when you are running a lot of power thru the system as it’s in an oil bath and will last much longer.
How often do you anticipate having to rebuild this?
Pioneer i beleave is now adding gearboxes 8n theire emtbs,, maybe something like that but then for non emtbs? It removes the derailleur completely which is a component that often gets some hits and can be expensive to replace
How do you get the gears to shift? All gearboxes I know of are constant mesh
From one ME to another: improve your hand sketches. Sketching and taking a picture could have a much better result. It’s one of the best skills you can have early in your career.
You had a good idea to reduce the mass of a gearbox but by the time you add so much stuff to get power to the wheel it’s going to be heavier.
[https://www.cyclingabout.com/homemade-bicycle-gearbox-recycled-parts/](https://www.cyclingabout.com/homemade-bicycle-gearbox-recycled-parts/)
[https://praxiscycles.com/hit/](https://praxiscycles.com/hit/)
[https://www.pinkbike.com/news/shimano-gearbox-in-the-works-files-patents-on-hybrid-roller-chain-sequential-shifting-transmission.html](https://www.pinkbike.com/news/shimano-gearbox-in-the-works-files-patents-on-hybrid-roller-chain-sequential-shifting-transmission.html)
[https://www.cyclingabout.com/inside-the-revolutionary-honda-bicycle-gearboxes/](https://www.cyclingabout.com/inside-the-revolutionary-honda-bicycle-gearboxes/)
Not an exhaustive list, but hopefully some useful insights in these for you. Good luck with your design project.
This is a novel idea but I don’t think it’s a very feasible approach. My perspective as a Mechanical Engineer.
The internal chain and derailleur setup would be very hard on a standard bike chain. The short throw over such a small distance applies a greater bending moment when shifting, resulting in premature failure.
Keeping chain tension will take up a lot of space in an area that is already limited. Most 1x MTBs use a 10-52t cassette. With a standard 1/2in chain pitch, that’s 10.5in (~267mm) of chain slack that has to go somewhere inside the frame.
Placing a cassette down at the bottom bracket greatly reduces your ground clearance and would increase the q-factor. These are bad for technical terrain and terrible for your knees/efficiency.
More complexity may increase weight and decreases reliability. You also decrease efficiency getting power to the ground, which means more reliance on the electric motor just to fight the extra drivetrain drag.
Keep brainstorming and iterating on ideas!
Shimano patented a double-cassette-in-a-box a few years ago, similar to this it uses 2 cassettes positioned oppositely (for a constant-length chain) and has the dinkiest little derailleur mechanism to push the chain. If you don’t plan on selling this it might be fun to take some cues (heheh) straight from their patent
Starter/generators which are generally used for drive and regen are horrifically heavy. My understanding is that if their coils, magnets and stators are scaled down in any meaningful way their efficacy makes them pointless. I would imagine the relatively short bursts of braking n a bike wouldn’t make a significant input to the battery to justify the weight penalty