My dumb question about geared hubs

OK here goes.

Instead of a gearing up from 1:1, why not have it on a larger wheel 1:1 and 1: 0.65?

Would it have good rollover and climbing on a big wheel?

Or perhaps soon someone will come up with a better multi gear solution than the schlumf.

Possibly because of the greater demand for speed. Road riders, commuters and tourists like to cover distance quickly. XC/muni riders like to get to, from or between the tricky sections with a minimum of delay.

Gear a wheel down and all you gain is the ability to climb steeper hills, or to do steeper descents without a brake. On the whole, a larger wheel is less manoeuvrable on tight and twisty stuff and at very low speed.

Therefore, as a general rule, the option to go faster than direct drive would allow is more attractive than the option to go slower.

In a simple epicyclic unicycle hub it is technically more difficult to run in reduced gear mode. I haven’t given much thought to reduced gear operation with compound gearing and don’t even know if it’s possible. Compound gearing, however, is the only way to get increased gear ratios over 2.

The Sturmey Archer 3 speed had one set of sun and planet gears, and a sliding clutch to choose the input and output. That gave you direct drive in 2nd, with (direct plus a third) in 3rd and (direct minus a quarter) in 1st.

Closer ratio hubs were also available, but the “plus a third, minus a quarter” set up was at one time the most popular gearing solution for bicycles in the UK.

Bouin-bouin has been developing a geared hub for a while, though I haven’t heard any news lately. His idea was to do that indeed: a lower gear, a 1:1 and a high gear. With the idea to have it in a 36" wheel.

I tought about using it on my huni-rex: low gear about 31" virtual; direct drive 42"’ virtual; high gear 56". But I cannot find a way to use sprocket on the left side of the hub. Left side hub spins geared while the sprocket on the right goes direct. Do you know if ever existed a geared fixed hub useful for a double chain giraffe or a huni-rex?

the reverse is true in my case: as I practice only muni , I don’t care to go quickly but climbing steep hills with a muni are a nightmare (though I am a pretty good climber with a MTB :o) ! I crave for a reduced speed geared hub.

I’m not sure I fully understand but I did some drawings of a setup which would have 2 gears: 1:1 and then another higher gear with a jackshaft - but i’ve left them at home.

I think a small number of close ratio fixed 3 speed hubs were made, probably back in the 1950s or thereabouts. At one time they had quote an extensive range. I remember when the derailleur “5 speed” was an exciting new idea. Before that, the choice was single speed or Sturmey Archer - at least for ordinary people wanting bikes for normal use.

However, Wikipedia shows that they reintroduced a 3 speed fixed hub in 2009:

<<Three-speed fixed gear hub[edit]
In 2009 Sunrace Sturmey-Archer re-introduced a three-speed fixed gear hub, the S3X.[11] This gives ratios of 100/75/62.5 (i.e. the top gear is direct drive and the others are geared down from it) and the internals are based on the newest five-speed freewheel hub (in the same way as the original fixed ASC was based on the contemporary FC four-speed hub).>>

£193 (193 GBP)

The Sturmey Archer (not a unicycle hub) had the tremendous advantages of being chain-driven and requiring no reverse torque limit. It also didn’t need to have a stout drive shaft running right through the center of the mechanism. This provides a lot of flexibility in the gear connection order.

Although, as you will see upthread, they also made “fixed” versions which did have to cope with torque in both directions. Point is not that the production model would be suitable for a unicycle, but that the concept is theoretically possible.

I’m sure we’re on the same page, Mike. I know that S-A made fixed 3-speed and a fixed 2-speed hubs. I don’t know if they were used widely or if they were successful or mechanically reliable. The freewheeling S-A bicycle hubs were wildly successful and popular. I do know that the backlash exhibited by multi-speed, fixed-gear epicyclic hubs is unacceptable for use on a unicycle whereas it would not even be an inconvenience on a bicycle. I will concede that reduced gear epicyclic hubs for unicycles are theoretically possible but I also know what the engineering gymnastics are that are required to realize it.

I see a few others here would go for a geared down hub.

So how would a 24" with current gearing up be compared to a 36" geared down in various situations?

I would like to see if Schlumpf or someone else can come up with a 3 speed hub with direct, fast and low gearing, the shifting being done by grabbing a lever under the seat instead of clicking the heals.

That would add a lot of potential options for unicycling.

Still under 3D design but no recent progress
It has been presented somewhere in this forum, Greg Harper made some comments at this time. I had long discussion with Florian at Brixen Unicon and he confirmed the right concept

Already know about that but as I said before it has a splined driver only on the right side! My crancks are not connected each other directly. They use 2 chains each per side to drive the hub

They might be hard to find if you haven’t seen them already and don’t know what to search for, but there have been a number of discussions about why they are as they are and what other ways they might be. Certain forum members have argued with great passion for downgearing.


Not an owner of one myself but my Occam’s Razor answer would be that the Schlumpf hub is what it is because that’s what Florian himself wanted when he designed it. It was a labor of love, not an answer to consumer demands.

The search function does not always yield what I seek.

Thank you LargeEddie, my concept was detailed here : If a multi geared hub were available, would that make the 36" wheel obsolete?

@Didier (Bouin-bouin) Since it’s been your goal for all those years (on your signature), and since it looks like you have all the 3D work done (do you?), why don’t you just make a prototype of it to see how it behaves and what must be modified and so on?

Is it because you don’t have the tools to make it, or the budget to make some parts (or all parts) made by a professional, a lack of time or is the 3D work just not complete yet, and in this last case, what are the remaining issues?

About 1/3 of the parts have been designed under CATIA V5 with strong support of Martin Charrier who is less available because preparing is PHD, me too; other points should be OK