Just taking this topic out of another unrelated thread, because I find it intriguing.
The idea of a geared ultimate wheel has been suggested. Like a guni, the wheel would travel further than its circumference with each pedal revolution.
The first substantive debate issue was essentially: how could this be done with planetary gears but without a torque arm on a standard frame (like a Schlumpf/Harper?Bonsch type guni)?
That’s a very good question. One way might be some kind of attachment to the rider’s leg, but this could be a problem during dismounts (whether planned or unplanned).
So must we use a planetary gear arrangement? Or could there be another to accomplish the goal? Anyone?
You could do it with a standard Schlumpf hub… but… you’d need to extend the torque arm to at least the radius of the wheel so that it pushes against the ground for it’s fixed position. To stop it wearing away, you’d probably want to put a roller (or small wheel) on the end though.
It would need to be a lot longer if you plan on doing jumps and stuff though otherwise it’ll spin around when you leave the ground.
But riding a two wheeled geared vehicle kind of takes away from the basic simplicity of an Ultimate Wheel.
Gearing down would seem to be easy (to conceive, anyway). Just sit the externally-toothed axle in an open hub with internal teeth. There’d be more to it than that to be able to transfer torque in other dimensions, but I imagine it would be reasonably workable.
I posted about his in the DAKOROMAN thread. The biggest problem is that you need something to transfer the torque to. I think the best way to do this is to use a torque arm that is as long as possible but shorter than the radius of the wheel with a heavy weight on the end. With a schlumph style hub you could have the weight attached to an extended torque arm. To keep things centered you should probably have a wheel that is sort of shaped like this
[ so the weight can be more central side to side.
It would be even better if you could have the weight inside a hollow wheel to limit the number of exposed parts
The amount of weight and the length of the torque arm would determine how hard you could pedal this thing. for example a 29" UW with a 12" torque arm and 10lb weight would be able to handle 10 foot-pounds of torque before the weight “gerbils” in the wheel effectively turning it into a poorly balanced BC. Higher gearing would produce more torque.
Wow that guy doesn’t give up does he? Saskwatch has an intersting idea, but i think the weight moving would alter the drive too much to balance, it would be a simlar effect to riding with very bendy cranks, pushing hard on the pedals would swing the weight rather than spin the wheel initially.
on leo’s website he had a link about a motorised unicycle where the rider sat inside of the wheel .The effects experienced by that setup can give you an insight into how a rotation inside a rotation works and thereby what would be involved in controlling it,and how the eccentric weighting would be critical to make it work.
Dave, was it you that tried mounting a Schlumpf hub in a penny farthing frame? Anyway, whoever it was found that it wouldn’t work with a few cable ties holding the torque arm to the fork as it snapped the ties. If that’s the kind of force the torque arm can resist, then I’d hate to think how heavy some weights would be to acheive this effect.
Yes it was me, and yes a schlumpf hub can easily snap half a dozen cable ties securing the torque arm.
Employing some slightly ropey science, max torque generated is your weight times crank length, the torque arm has 1.5 times this torque, assume the balance weight is at twice the crank length from the centre, for me the weight would have to be 75kg, more than twice what a man can comfortable lift.
Wouldn’t adding a schlumpf hub (or any hub for that matter) make it …simply not an ultimate wheel? If you did that you would have yourself a GNAUWI, geared not an ultimate wheel. Ultimate Wheels don’t have hubs or cranks right? Either way, I would still want to see someone riding a GNAUWI.
We’re not talking about a central hub & cranks. An UW simply has pedals mounted to it in the right locations. The guwi concept would simply be a multi-part disc wheel, with the same pedal hole locations. Just that there would be an outer ring section (with the rim part) rotating faster than the section to which the pedals are attached, which fits inside the rim portion.
Sorry I have no drawing program to visualize what’s in my head, but it’s basically a 2-piece disc wheel that fits together, with the gears inside.
This should actually be fairly easy to make. I think that using a jack-shaft gearing system would be the best way to gear this thing if it is not to be shiftable.
At them moment I am thinking that using zero Q cranks on a square taper axle might give the most flexibility and ease for DIYers to build their own, but a “disk and doughnut” design could be slimmer, lighter generally better if this was to become a manufactured product.
I will try to draw up some plans and scan them at school some time next week and post them up.
I am liking this, maybe I shouldn’t of dropped out of engineering after-all.
After making a few sketches and looking at some bearing websites it became clear to me that using unicycle cranks and a central 17mm axle to hold most of the bearings would be much cheeper, less complex and probably stronger than the disk and doughnut/disk in disk approach.
In my drawing I have it down to 48mm wide plus cranks (which unfortunately bring the total up to almost 100mm.) We could use slightly smaller 17x38x10mm bearings but I used the unicycling standard 17x40x12 size in the sketches.
I will scan some of my drawings on monday at school.
(1) How much weight do you think it would take so that the hanging jackshaft doesn’t “gerbil” around the central axle?
(2) Assuming the usual profile (thinness) of an ultimate wheel is about the width of the tire at any given point (to minimize the “Q” factor, the distance between the pedals), what could you do to minimize the pedal width?
I originally thought that that if you put 10ft*lb of torque into the main shaft you would need 10lb of weight on a 1ft arm to prevent the garbling on a stationary wheel. I realized this was wrong before I posted it then put it aside and did my homework.
Once I started to work on the problem it became obvious I would need a much lighter weight than I previously thought. The amount or torque applied to the wheel is inverse to the gearing, so a GUWI with a gearing ratio of 1.5:1 would have 67% of the torque go to the wheel and the remaining 33% to the torque arm. A GUWI geared 2:1 would have the torque split 50-50 etc.
So if you built a GUWI with 18 and 22 tooth gears to get a gearing ration of 1.49:1 and are able to put 20lbs more into the front pedal spaced 6” (152mm) from the center you would need a minimum of 3.3lb of weight on a 12” arm.
I hate using the imperial system unless I can make up my own numbers (like 6 and 12”) but I doubt many people would be able to relate to Newton meters like they do to Foot Pounds (or Pound Feet)
To Minimize Q you could have a smaller gearing system, possibly using square cut gears instead of chains and then have the pedals. My original drawing was using almost all pieces that are easily obtainable in the biking/unicycling world. It would take a lot more custom parts and therefore be much more expensive to minimize the Q.
I will post a new sketch with the reduced Q
Edit: square cut gears won’t work due to the twisting force they would put on the hanging arm, a smaller chain system then.
