I was thinking as I was wandering along a turf embankment by the sea this afternoon …
… first of all which line I would take if I was riding a unicycle
… secondly what size wheel would be best
… thirdly how to shift-on-the-fly with a “blueshift” type unicycle
Suprisingly enough I managed to answer all 3 questions :
Left, right, over, over, right…
29er (ideally 2 speed).
Replace the tab that normally is anchored to the frame (1.5:1 mode) or rotates freely (1:1 mode) with a standard disc brake rotor. Fit a disc caliper on the frame.
Then you could gradually activate the brake to go smoothly(?) from 1:1 --> 1.5:1 and release it to go back down.
I have discussed this before way back when. I have made small diameter slip clutches (3"-4") and found that it takes a lot of axial force to keep them from slipping. It also has to engage on two sides so the transfer mechanism must be bidirectional. The tab never rotates freely, it is either connected to the hub with a bolt or to the frame with a bolt. Devices like this are generally real-estate hungry. In theory it’s a good idea except for the “gradual” part. There is no gear ratio transition, you’re in one or the other so rapid disconnect-reconnect would be essential.
Presumably, it’s not completely unlike changing gear on a bicycle whilst doing a wheelie. That can be done, although I never learned how. There are differences too, however.
First, let me freely admit that I know nothing about this unicycle except what I have seen and read from these postings. However this is the web, so I won’t let that deter me…
I am guessing that when the tab is disconnected entirely and you pedal, the hub whirls around in the opposite direction and the unicycle doesn’t go anywhere. So this is actually a three speed uni: fast, slow, neutral! Harper let me know if I am way off on this.
I have been mulling over this shift on the fly problem, with gears and chains you always have one of two problems:
freewheeling, unable to provide torque while the chain is moving (typical bike scenario)
locked, both sets of gears are momentarily connected and the shaft won’t turn.
It seems like of these, number 2 would be more tolerable: that you would stop at the top of a hill, shift, then head back down. A very interesting problem.
As Mikefule pointed out, it is similar to shifting while riding a b*ke on one wheel. However, the balance point is way different, and a shifting error would never be a minor incident. A missed gear will cause an instant face plant. I haven’t experienced this yet, but it would be no different than a seized wheel, which I have experienced. You find yourself bouncing along the ground wondering what happened. Additionally, a large gearing change such as that on Blue Shift would be very difficult to compensate for on the fly. My gears are spaced very closely, and shifting is still a very delicate procedure due to the change in the balance envelope and the knowledge that my teeth are only a millisecond away from the pavement.