Geared Hub

I am designing a prone-suspension bicycle that requires crankarms attached to the axle of a geared hub…something like the attached images of Frank Bonsch’s creations (posted 25-SEP-2007).

Can anyone point to the current state-of-the-art, or a perhaps a gifted machinist who might want to have a go at prototyping such a beast?

Tom Piszkin
Airo-Series, Inc.



You are going to want to look for Schlumpf hubs. They have a 1.5:1 ratio and are shiftable on the fly. They are available with either a square tapered spindle or ISIS.

If it doesn’t have to be brand new there are usually one or two for sale in the trading post. If you want new I am not sure if anyone keeps any stock in the US but there is at least one ISIS version at the canadian UDC store
or you can order direct from Schlumpf

I fell asleep thinking “what on earth could a high end road bike company want with a geared unicycle hub” and I woke up thinking: HIGHER GEAR! FREEWHEEL!

So here is something else you might find interesting:

back to bed

Hey Eric, Thanks for the reply. I’ve looked at the Schulmpf–not ideal.
We are willing to finance an R&D effort to produce what looks like UniFrank (Frank Bonsch) rendered several years ago.

Does anyone know how to contact him directly?


Do you need a freewheel ?

It looks like it’s been a couple years since Frank was active on the forums but have you tried to send him a Private Message through this forum yet? It’s possible it’s still hooked into a current email address. It looks like Frank’s web site was hosted on a provider that no longer serves it. I did find some interesting CAD movies:

In the movie titled “Ansicht1_min.avi” it shows an arm coming off the hub. I’m not sure what the purpose of this is. That design also has sealed bearings on the axle. The 3.8x Sturmey-Archer hub that JR Drift Trikes commissioned (and I’ve pre-ordered) has the fork connecting to it similar to that little arm.

Hey Waaalrus, thanks for the link to these animated illustrations. UniFrank did some pioneering work here. We’re looking to advance this art beyond Schlumpf’s 2-speed hub and apply it to the larger bi-cycle market.


Cool. This sounds pretty much like the inverse of what I proposed in this thread (You: take a unicycle wheel design and lay it down to make a bike, Me: take a bike design and stand it up to make a unicycle). Let me know if you need someone to stress test it by riding the wheel like a unicycle (with full body weight on it) or to demonstrate a wheelie. I would definitely be in the market for such a hub as long as it freewheels.

It would probably be worth it to contact Greg Harper as well. He is harper on the forums. He is usually full of good ideas.

you can also contact “bouin-bouin” on this forum: he has a design for a 2 speeds hub.