Good find!
You should browse the web more .... I found those pages years ago.

Here's another 2 dug from the depth of my favourites that might interest you.

http://www.rctankcombat.com/articles/speed-control/

This second one is a copy of the page that once resided here .. http://www.x-eng.co.uk

http://www.teamonslaught.fsnet.co.uk/Rotraktor.htm