I have 170mm cranks now for MUni but when I get to flat terrain/pavement I want to speed with my 110mm cranks. But changing the cranks in middle of road is so cumbersome and time consuming, with bunch of specific tools needed. Am I the only person with this dilemma? Thanks
That’s why the Schlumpf hub was invented.
Other people use adjustable cranks. Who wants to carry multiple sets of cranks around? The problem is, adjustable cranks are expensive, and may not be very strong.
I don’t like using my Coker for MUni for the same reason; changing the cranks causes wear & tear, both to the axle and to the threads on the cranks. Yup, a pair of adjustables would sure be nice…
Nathan Hoover has some that I think work well for him.
Actually the only extra tool you need to carry is a crank puller, provided you have a crank/pedal tool already. You can use the pedal wrench end of the crank/pedal tool on the crank puller - not a perfect fit but it saves you having to carry another wrench. There’s no way to avoid the extra weight of the spare pair of cranks, however.
I am considering doing this in the upcoming 160km / 100mile Lake Taupo Cycle Challenge - starting on 125mm cranks for the first hilly 100km then changing to 114mm cranks for the reamaining flat 60km.
Nope. I don’t like changing the cranks either, and I’d never consider doing it in the middle of a ride.
There have been some discussions about adjustable crank ideas. One thread is here: Adjustable crank idea. And in particular this post. One of those two designs would make crank changes on the road an easy task. Now someone needs to make the cranks. 
In the past I would change the Coker cranks all the time to match the terrain I was riding, after a couple years of that my hub threads where destroyed. I swapped out to my old KH hub and how I can switch between 170mm and 140mm in less then 5 minutes which I often do when I hit a long uphill. I have thinking about cutting down a set a cranks to 110mm to give me something for the road, so if anyone has a old set of KH cranks laying around PM me.
Although a 6in. crank would remain that length why could’nt a second or third set of 9/16ths holes be drilled and tapped into a crank arm?
It can be done. daVinci Designs makes such a crank.Some people have used the daVinci crank on unicycles. The cranks have pedal holes for 130/150/170.
It would be fantastic if someone made a decent set of adjustable cranks, maybe based on one of the designs in the links above.
Has anyone got any idea of why so much effort has gone into making geared hubs, and so litle into adjustable cranks?
Adjustable cranks have to following pros-
- simplicity- fewer mechanical problems
- fits in with the ‘unicycle ethos’ of ‘doing more, with less’
- once in production, would be much cheaper
- could be easily fitted to any existing unicycle
Certainly, while I would not be interested in aquiring a geared unicycle, i would definitly want to purchase some decent adjustable cranks.
So, why is there so little interest in making them?
This is possible but there is potential to bash your ankles and possibly rip trousers. I have ruined several pairs of trousers by catching the trouser leg end on my kooka cranks and imagine this could be an issue with the above design. (Of course you could just make sure you wear shorts)
U-Turn showed me a set of cranks that had three holes drilled in the cranks, effectively providing three different crank length sizes… with no more effort required than changing a pair of pedals. I suppose these aren’t any good for Muni?
I’d say those daVinci cranks (available through LiveWire too) are most suited for the full range of road and mild off-road riding, though I don’t know that anyone has really pushed them outside those boundaries. I did get a set to Australia with a 36" wheelset, but don’t know what the rider has been able to do with them.
Edit: tuck in your laces! 
The best adjustable cranks I’ve seen are Bronson Silva’s rotational crank. You dialup the lenght you want than screw it down. I don’t have a photo sorry.
But here it is:
Nathan Hoover had a different design of adjustable cranks when he came to NZ for the Moonride. From memory the part of the crank near the axle was a square sleeve inside which the inner adjustable part of the crank slid. They could be adjusted to multiple lengths, but its weak point was that the inner sliding part of the crank was held in place by little set screws which would get shaken loose. At least thats what happened when ridden offroad.
daVinci Adjustable Cranks 170/150/130
I have been enjoying daVinci Adjustable Cranks 170/150/130 for over 6 months now with perfect success. They seem very well made.
I ride them on my Coker, mostly on pavement. Changing effective crank length is easy: use a pedal wrench to remove and reinstall the pedals in a different set of holes. Then adjust seat height and away you go.
I like these cranks. I can hardly wait to install them on my soon-to-arrive LiveWire 36 with Stockton bomber wheel. WooHoo!
?huh
I had the link wrong Ken; nothing to do with the Gecko crank. 
I just visited Tom Miller, who has made custom unicycles for 30 years. I’m sure he would be willing to make adjustable cranks for someone. You can contact Tom at 765-452-2692
Tom has a machine shop in his garage and just finished making a “walking” unicycle. It’s kind of like walking on stilts. He made it the way his customer wanted, but he’s not happy with the design yet.
He’s now working on a very small bicycle for another customer. The size that can fit in your hand.