Bob Engelhardt wrote:
....

I captured this pic from a video:
http://home.comcast.net/~bobengelhardt/SlipRoll.png ...

I guess that I was a bit misleading: that's not my roll/roller - it was
a YouTube video that I captured it from cause I liked the crank-and-link
arrangement. I think the video was about making a wheel for something &
the roller was used to make the "tire".

Bob