Gear ratio question?

Hi there, I’m new to this forum.

I posted this thread in the Just Conversation section and was advised to post it here instead…

I’m thinking about building a geared unicycle based on a 29" wheel. I only have limited access to a workshop, so I don’t really want to waste time experimenting with gear ratios - I would rather pick one ratio and build it to suite.

I’ve seen the schlumpf hub has a ratio of 1:1.5. I’m thinking I want to aim a little higher than that - maybe around 1:1.75. I am looking at a compound gearing system to do this.

Does anyone have experience with this? What would be a manageable ratio which is still ride-able?

It would be great to have 1:2, but I expect it would be near impossible to ride. Any suggestions or comments are welcome.

Cheers,

Peter

Peter-

Wow. Sorry. I thought you would get more responses here. Maybe everyone’s out riding. I was earlier.

I remember a several years ago riding a Penguin giraffe that Steve DeKoekkoek owned. I think it was geared up 1:2 with a 20" wheel. This would be a 40" equivalent wheel. I think it was not that hard to ride but very difficult to mount. Some years later Abram Clarks made a 20" geared Penguin which a few of us rode. It had a super skinny tire and I think it was 1:2 also. Again, harder to mount than to ride. You might be able to search RSU and find Abram’s giraffe.

Pete Perron (unisk8r) is your man. His Red Menace guni has interchangeable chain rings that allow him to get a whopping 1:1.96 ratio (if I remember correctly).
Do a search for Pete’s posts or “Red Menace” and you should come up with some very inspiring pics and descriptions.

Geoff

What are you trying to accomplish? If you’re trying to make a fast unicycle for controlled conditions (track racing, say), I’d expect 1:2 is totally plausible to ride; in fact, it’s probably not nearly high enough to optimize for speed. I think the eventual hour record uni will be a 700c/29er setup with a 1:2.5 or 1:3 gear ratio.

But it really depends on what you expect to do with the unicycle, and whether it would be shiftable.

Thanks guys for the info on the Red Menace. I’ve just read the entire post (on this forum) and it is indeed an impressive machine! It’s pretty much exactly what I had in mind - right down to the disc brake.

I want to use the unicycle as a commuter and weekend tourer. This is why I prefer the 29" wheel so I can take it easily on the ferry to get to work - I think the 36" wheel would be too cumbersome for commuting. After some recent research, I am thinking I will make a variety of gear sets (at least two) so I can choose the gear depending on the ride.

Pete, if you’re out there? Can you give me some information on the hub you used? Or, if anyone else knows I’d greatly appreciate it?

Peter

Various people have put years of research and a whole heap of money into designing a geared unicycle.

Your choices are “sun and planet” gears inside the hub; or some sort of chain drive system.

In both cases, the problems to address will be:

Weight

Complexity/maintenance

Shifting on the fly

Eliminating “play”. Even a tiny bit of slop between the cranks moving and the wheel starting to turn would be unpleasant to ride.

The fact that the commercially available geared hub is so expensive should tell you something about how difficult the exercise is.

But good luck.

This is my penguin, The Troxelator, that was made from a BMX frame. The gear ratio is 1:1.9 and I could make it higher by shortening the chain and moving it to a different sprocket.(There is are multiple gears on the back hub.)

This was by no means a professional job, so it does feature the “play” mentioned above. It is also uncomfortable and exhausting to ride. A new seat would be a great improvement, but a gel cover makes a big difference. I think one of the reasons it is tiring to ride is that the seat is too low…I guess I’ll raise it.

I figure you could use a normal bike derailer system to change gears. Maybe it’s already been done, but I have not heard of it.

Does that cycle have a freewheel? You need a freewheel to be able to use a derailleur.

It is possible to ride a one-wheeled contraption with a freewheel and a brake, but it’s a lot harder than riding a standard unicycle.

Though this brings to mind the question–could a unibike (modified bicycle with the front wheel removed) be competitive in speed events? The downside is that it’s a lot harder to ride, but the upside is that you could have a full range of bicycle gearing and a freewheel. I have no idea what it would be like to ride a bike in a wheelie for an event like RTL, but it has the potential to be a quantum leap better than the fastest available pure unicycles.

Ah! That’s why it wouldn’t work. Not that I tried it, but The Troxelator originally was going to be a free wheeler(I’m glad it’s not!), but the welding guys de-freewheeled it without me saying anything about it. In fact, I never even talked to the guys; it was my boss who took it in to the shop. :slight_smile:

I think if you wanted to spend more time and money then I did, you could make something fairly comfortable and functional for high speeds, especially if it had some handles.

Can one just “gear up” a giraffe unicycle? If you take a unicycle like one shown below and switch out gears, wouldn’t you get a reasonable higher-speed unicycle?

http://www.unicycle.com/shopping/shopexd.asp?id=1136

or

http://www.unicycle.com/shopping/shopexd.asp?id=747

I have no experience riding a giraffe. Would a 2:1 gear ratio on a 20" wheel be ridable? Someone must have tried this variation–it seems much simpler than the “Red Menace” solution.

Just scroll up to post 2 in this thread. Reading the rest of the thread might also be informative.

I did read up Harper! :slight_smile:

The one just above is a converted bike frame with a bizarre seat and an odd frame. It seems like the giraffe would be a much simpler modification.

Are there any pictures of the unicycles you described? Do they behave like a Coker or are the completely strange to ride?

Yeah, one could just gear up a giraffe, but that’s not what I’m after :slight_smile:

Many people mention “shifting on the fly”, does this literally mean shifting gears while riding? That sounds like a difficult thing to get used to - especially if your making such a large ratio step like going from 1:1 to 1:1.5. Can someone clarify this for me?

I would still like to know a little about the hub Pete used in the Red Menace - anyone?

Peter

BTW - Biggestbtc - I like your Troxelator!

Here is Abram Clark’s gorgeous Penguin with the skinny tire. It looks like 1:2 to me.

AbramsPenguin.jpg

Here’s a dark one of me on Steve DeKoekkoek’s 1:2 geared giraffe and him on BlueShift.

DeKsPenguin.jpg

Here’s a better photo of Steve’s giraffe.

There used to be a guy who posted in this forum, sadly now deceased. He posted as Unibiker, and his posts will still be available on the search function. He rode a “unibike” which was basically the back half of a bicycle with shiftable derailleur gears. The seat and bars were modified and the front forks and wheel were removed. He set himself some speed and distance challenges including aiming to average 15 mph (24 kmh) on a particular route. He proved that it can be done, but I think his machine was less versatile than a conventional unicycle.

On a 28 or 29 is is perfectly possible for a fit rider to average 10mph (16 kmh) or more. A skilled rider can hit 15 mph (24 kmh) on a direct driven 24" with 125mm cranks. The commercially avaliable Schlumpf hub on a 29" or 36" wheel can take you to speeds that would hurt you if you fell off.

Why reinvent the, er…, wheel?

I had (look at the picture) a 1:2.5 geared uni. Jogi is building a 1:1.75 geared uni. The gear is allready ready but it isn´t in a uni until now:) For informations about the technical details you should ask him (his name in the forum is jogi as well) :roll_eyes:

Great pictures guys - the one posted by enaddi is especially interesting… heavy though.

Harper - how do you think that 1:2 set-up would go on a 29" wheel?

Peter

BTW - My posts are being delayed for some reason. Sorry if my messages appear out of order.

Hi Harper,

Thank you for the pictures. It would be fun to try to ride one. I suppose I could go to a Uni convention and see if anyone has one to share. :roll_eyes: