Another geared unicycle...

[harper]

Originally posted by billham


All these geared unis... Must ask....
At what speed does a person have to tuck and roll out of a uni crash? How fast can a person run AND how fast can a person's feet go from pedaling to running at full sprint?

I have tucked and rolled from a 20mph dismount with knee pads and a helmet. I was lucky and went down foot, knee, hip, shoulder, hydration pack, helmet, backward somersault. This ended up injury free.

[john_childs]

Originally posted by billham
All these geared unis... Must ask....
At what speed does a person have to tuck and roll out of a uni crash? How fast can a person run AND how fast can a person's feet go from pedaling to running at full sprint?

14 to 15 mph is the max that I can expect to be able to likely run out a UPD and stay on my feet. I've run out a UPD at about that speed and stayed on my feet.

I experienced a Coker UPD at about 17.5 mph and ended up sliding on the ground in a superman position. I had inline skating kneepads and full finger leather cycling gloves on. I was sliding on the gloves and kneepads. No injury to me other than a minor scrape on my forearm from the pavement. I don't have very good instincts to go for a tuck and roll. That's why I ended up in the superman position sliding on the ground. The protective gear did its job.

At 17.5 mph I was able to get one foot on the ground and then the second foot on the ground in an attempt to run it out. But I can't move my legs that fast and the attempt at a run out was futile. One foot, two foot, superman dive (or a tuck and roll if you have the instinct).

One potential problem with the geared unicycles on smaller wheels is that your feet are closer to the ground than with a Coker. With your feet closer to the ground you're not going to have as much time to get your feet into a running position during the first part of the UPD. It will probably be more difficult to run out a UPD on a smaller wheel where your feet are closer to the ground. George's geared uni looks like the pedals are actually a little bit higher than a Coker.

[harper]

Originally posted by Dirtsurfer
Out of curiousity, have you thought about making it a low rider (mounting the cranks below the hub)?

If I look at the frame photo I see four problems with that idea.

1.) It appears that the crank axis to axle axis distance is about 6" or a crank length. For a moderate sized wheel the design would exclude people who don't have that extra 6" of inseam. Actually, 12" of extra inseam going from one design to the other would be required. George has it and wouldn't care, though.

2.) The crank axis would be close to the ground and with a small enough wheel some serious pavement strikes could be made on the pavement with the pedals during a turn.

3.) Hanging the cranks off the bottom eliminates the additional top support strut (the crown) in the frame so it would be more likely to flex.

4.) The chain tensioning mechanisms would suddenly become much more complex.

These problems exist but it doesn't mean that they can't be overcome or some compromises can't be made. You should build one.

[billham]

Originally posted by john_childs
I experienced a Coker UPD at about 17.5 mph and ended up sliding on the ground in a superman position.

After all the quotes and stories about the great JC and unicycles, I would expect that you would literally fly away Superman style. My uni-hero may be mortal.... Oh No! Sorry JC, but you don't get many style points for flying that low to the ground.

The stories from you and Harper are making me think that I might go for another speed attempt on my coker. I've hit 16+ a couple of time but it would be fun to bump that up a little. It will definitely be a full gear attempt if done. Maybe a fall or two won't stop me from going to work the next day.

Bill

[andrew_carter]

Originally posted by Dirtsurfer
Out of curiousity, have you thought about making it a low rider (mounting the cranks below the hub)? Realistically, you won't be doing much offroading, wouldn't lower your center help some? How would changing the pivot at the center of the wheel effect the ride?

Wow, that would be a very odd feeling wouldn't it? When you lean (or loose your balance) forwards, your feet would be sent backwards...very odd.

Originally posted by harper
3.) Hanging the cranks off the bottom eliminates the additional top support strut (the crown) in the frame so it would be more likely to flex.

Couldn't you stick something between (and connected to) the two chain rings to reduce flex?

Andrew

[harper]

Originally posted by andrew_carter
Couldn't you stick something between (and connected to) the two chain rings to reduce flex?

Through the spokes, or around the wheel?

[unisk8r]

Gotta love it, GB! Congrats on another great design!
Add another one to the stable of wild geared wheels!!

[ChangingLINKS.com]

Can I buy one?
How much?

[andrew_carter]

Originally posted by harper
Through the spokes, or around the wheel?

Hahaha, wow I must have been tied this morning!

[Loosemoose]

Having never travelled at anything like 17+ mph on a unicycle I don't really have any idea what I'm talking about, but in theory wouldn't it be possible to do a jumping dismount? Like a triple jumper you plant one foot on the floor at high speed, and use it to spring into the air. This gives you more time to line up the second foot to land on, spring again, and continue until you've reached a safe running speed. You'd probably look stupid, but then you were riding a unicycle a second to two before...

If someone is willing to donate a coker I'd be up for testing out my theory with full scientific data aquisition and a big pillow strapped on my back...

Loose.

[gbarnes]

Thanks for the kind words all.

Regarding the "low-rider" approach. I considered this, but didn't go for it on the first version for the reasons Harper and JF listed. I *did* machine another set of axles, and I hope to tinker with the idea down the road.

I have yet to crash the uni (knock on wood), so I can't say what that's like. I've had my share of hi-speed 36" crashes, usually ending in sliding in the push up position.

Naomi - Ha, that's awesome. What'd you use for a distance reference?

No thanks on production, that's one liability I definitely don't need.

[wobbling bear]

Originally posted by johnfoss

I've never tried a unicycle with the pedals below the wheel axle. That would be different.

how about slightly below and in front? (that is: the axle of the pedals not in the axle of the frame)

please do not howl! I think it will change your way of riding but not *that* much.

bear

[gbarnes]

Yeah, I had sketches of 45 degrees fore and aft. They both look weird, but 45 degrees back might be reasonable (and you gain some clearance).