Shortly after I got my Speed Astir, I had to repair the screw jacks.
It was a lot of work, and my 'fix' didn't last but a couple years.
Last time it failed, I wanted to replace the screw jacks with
something simpler. This works for me.

http://www.youtube.com/watch?v=YP2AD8rtdpA

An $11.00 pair of Razor Scooter wheels, a pair of low-end door hinges,
and some scrounged steel tubing.