View Full Version : Re: Shifting on the fly PING Harper

August 22nd 03, 01:47 AM

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.

harper - Old dog, no tricks

-Greg Harper


"Are you OK???" - Just about anyone I've ever ridden with

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August 22nd 03, 02:12 AM
Has anyone ever felt what it's like to change gears on a unicycle?

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August 22nd 03, 04:41 PM
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:

1. freewheeling, unable to provide torque while the chain is moving
(typical bike scenario)

2. 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.

Phil (reverse engineer)

schroder - Occaisional Unicycler
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August 22nd 03, 04:47 PM
gerblefranklin wrote:
> *Has anyone ever felt what it's like to change gears on a unicycle? *

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 havenít 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.

unibiker - What is that thing anyway?

Jeff Baker


Favorite comment (from a child) 'You can't do that. That's impossible.'
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