Truvativ Hammerschmidt planetary gearing

Maybe in the future someone could convince this company to build a geared hub for unicycles? Not that the Schlumpf hubs are bad (they are awesome!), but it’s always better to have an alternative. What do you think?

That’s pretty cool. Cable actuated (I assume), and can probably be adapted to any giraffe unicycle you may already have. :slight_smile:

Modifying it to be a hub drive rather than a chanring replacement might be some pretty major surgery though, which brings us back to the idea of a chain for gearing up the unicycle. This one, however, would allow you to shift on the fly, and not have to switch out parts, or flip the wheel around.

If the chainring was direct drive to the hub body and there was a spindle within a spindle which was attached to the crank, wouldn’t that work ?

and the Hammerschmidt is ISIS

The problem is that it is designed to give output to the back and the side that is facing our hub is stationary and takes control cable.

It would be interesting to combine it with huni-rex like construction, but the price is not test encouraging :wink:

It mightn’t work on a uni, but it sure would be awsome on a SS MTB.

here are some photos


It might work if you could fit a hub body over the bottom bracket (would have to narrow to leave space for frame bearings) then connect the chainring to the hub body via two chains and a jackshaft or some other fixture.

A hub designed around the crank with a single frame leg?

Would be too flimsy wouldn’t it?

How could you reach such a conclusion without even seeing how it’s designed?

Motorcycles have been using single-arm designs, both front and rear, for quite some time now…


Yes they have existed for ~ 15 yrs but not many use single side, esp up front. To get the same stability requires more weight. They first did it to speed wheel changes in endurance races (now they can get the same speed on 2 sided swing arms), also for style purposes.

Having another company would be good and slightly diferent gearing (1:1.6 instead of 1.5). Might b better if u could condense the gears into the hub like Shlumpf, assuming it can be made fixed and still shiftable.

My point exactly. I didn’t literally mean ‘too flimsy’, I meant ‘too flimsy unless beefed up to a stupid degree’.

Another thing I’ve thought of is the fact that the Hammerschmidt has a freewheel in it. One of the reasons why the Schlumpf is so expensive and chunky is due to the fact that it doesn’t freewheel.

Uh, that’s exactly what you typed. If you don’t express your point with words, how else are we to read it?

Ah, now either it’s flimsy or it weighs three tons. I see. Go on with your excellent engineering analysis…

That’s a question, right?

Conclusion? i thought he asked a question?

Now you’ve got him, dissoriented he tries to explain and correct where there’s nothing to explain.

Hmm, what will he do next? Will he use his engineering mind to express his point clearly or summon daylight to make the troll turn to stone?



P.S.: Looks interresting, maybe possible for uni somehow (need to take a closer look and thought at it).

Thanks Byc. I’d be a happy man if there was any sun here nevermind enough to turn someone to stone - damn you english weather.

Some people really have too much time on their hands…

But unwilling to make 125’s.

I’m not saying it can’t be done. Things can often b designed w/o significant cost, weight, or weakness.

Eg more recent single sided motorcycle swing arms (Ducati 996) were able to b designed w/o significant more weight, cost, or loss of riggidity. All the manufactures (Duati & Honda) stopped doing it because dual sided swing arms could then be changed nearly as fast w/ the proper mods and to drop weight. Also those models did most of their races as sprints, so speedy wheel changes weren’t important. So they made the trade off of slightly faster lap times but lower style points and slightly slower rear wheel changes).

When Scott Russell did the Daytona 200 on a Yamaha (two sided swing arm) they had a pit stop that was the fastest of the race. 7.2 siec for two tires and gas when the avg was 10 sec. He won the race.

Oh, wait. I guess that makes me a bit of a hypocrite :o

You didn’t have the luxury of viewing the figures before you replied. The hub is clearly pawl released and free-wheels. It must first be made non-free-wheeling to be used on even a chain-driven uni.

Ben was right on with his original post. The manufacturer would have to be convinced to design a hub for a unicycle. This one won’t do. It does appear that the shift cable comes out on top of the chain guide which is advantageous to one that comes out of the axle. If the shift cable position could be maintained in a redesign, the cable could come straight up one of the frame legs.