A lot more than the unemployment benefit is currently paying!
As my welding/machining/lathing experience is limited, I would have to pay a machine shop to build them up. Then there’s the cost of the electrics that would be built in. Not cheap for a pair of cranks, but possibly the ultimate distance riding accessory.
STM
Hmm, you lost me at ‘electrics.’
My idea for auto-adjustment was to use a spring that would automatically retract the pedal as progressively less pressure was applied.
I’d be in favor of an initial option that would just be toollessly changeable among a set of standard lengths, maybe in the 100-170mm range.
I reckon that would have to be very heavily damped to make it remotely useful. If it’s just a simple “spring balance” arrangement, then as you pedal the crank would squash under the pressure and shorten at the top of the revolution, do nothing in the middle (where the pressure is at right-angles to the crank) and lengthen at the bottom.
That’s what Al’s “crazy arm cranks” that I linked to earlier were.
I reckon a user-changeable setup (either adjusting crank length or actual gear ratio) is the way to go - automatic systems are never very satisfactory, always using up power to work (which you haven’t got much to spare on a human-powered machine) and not working well anyway when the torque is varying so much over the axle revolution (it would need to be seriously damped to avoid it changing up and down wildly as you pedalled). And with automatically-adjusting crank length you’d need some way to keep both cranks the same length to stop it feeling really odd I’d imagine.
That’s not intended as an attack on your idea, BTW - I’m just “thinking aloud”.
Rob
Good luck with that. I don’t think you realize how a unicycle is contolled; via pressure on the pedals. If you don’t believe me you might want to start with some tensiometer tests of foot pressure on unicycle pedals. It would be interesting to see; I imagine it would be all over the place, even for sustained Coker riding at speed.
Yeah, I had considered that; that’s why I never went farther than “I had an idea” - could be that some sort of shock/hydraulic mechanism would be better suited, or maybe it’s just a bad idea. Wouldn’t be the first time! 
Yeah, it would need to be such that the frequency of any significant change couldn’t be more than about once per revolution, which might well negate any potential auto-adjustment advantage for non-gradual terrain changes.
Don’t worry; it’s been years since it’s been possible to offend me over teh intarwebs. 
Clearly you haven’t seen the new models:
(Credit to Gracie Sorbello)
You get used to it. I’m running an 89mm and a 114mm on my 20" right now.
Obviously no one caught on to the fact that someone stole the prototype to Torkers new cranks to put with their 2010 models.
Actually is this a new KH prototype? I wonder?
Dave Mariner did this test in about 2002 - he made a special pressure sensing pedal. I don’t have the results (they were in some special wacky MS-DOS program he wrote), but I seem to remember what it showed was pretty much a slightly wobbly sine wave for a beginner rider, but much closer to constant pressure for an expert freestyler (it was mounted on a 20" trials and I think the rider was either Leigh or Roger or someone else very good at freestyle). I’d imagine for a good coker rider at constant speed, it’d be very close to constant pressure. Obviously bumps and corners and road stuff mess this up though, meaning that the idea is probably a bad one anyway, but I think the assumption that a rider riding in a straight line uses nearly constant pressure is okay.
Joe
If one had on-the-fly adjustable cranks wouldn’t that require on-the-fly seat height adjustability? Unfortunately those long crank settings require a lower seat meaning that stand up climbing is not a solution to this.
Why?
Do you have one leg shorter than the other?
I asked Leigh about this earlier this evening and it was both her and Rocket that rode the test unicycle with similar evenish pressure for normal riding. It was actually set up to test why Will (Stevens? Can’t remember) kept breaking cranks when doing drops so that DM could see if the pressure was uneven.
STM
Personally I reckon it was because he landed like a sack of bricks, ran silly low pressures, and kept jumping off things about 10 foot high. Not that he wasn’t a really very good rider, just he was perhaps a bit less subtle than most!
I seem to remember DM measuring some ridiculously high amount of force on the cranks from drops, several times the weight of the rider.
Joe
p.s. Spencer, on Sunday, if you have the choice, drive up my road not down, cos we’ll go to Ambergate on the back road.
I don’t care, it’s still awkward.
I put the cranks on my road unicycle at a ninety degree angle to each other for a week or so, and I got used to that, too. Yes, it was extremely awkward. It was actually easier to ride it as a kangaroo uni.
While working in Brussels I spotted this penny-farthing with adjustable cranks!
for sure the design is not adaptable to unis but the need has been there for a long time
PS: I am working this week for a company named UNIWAY! (I am highly qualified for the job :p)
I’m liking the use of the composite pedals but I think the cranks may need a little weight reduction:D
I am not exceptionally mechanically minded, but would it be possible to set the crank arm farthest from the crank to be somehow geared to rotate clockwise in relation to how hard one pedals?
Now that would be fun to ride.
Wow. this is an education… I wonder if folks are actually willing to come up with $200 for disk brakes on their Unis?!
http://www.sjscycles.co.uk/product-Thorn-Thorn-Crank-Shorteners-251.htm/
Fully adjustable from 118mm to 154mm (if fitted to 170mm cranks)
I have only used these for their intended purpose, the Q factor might be too great for a uni.
