Breaking Pots? A few years back we came up with a solution in 2005, we engineered a POT Holder and custom spring idea. Basically what happens is if you over turn the pot instead of the pot breaking if it is directly connected to the shaft and special spring will slip instead to protect the pot(the spring is connected to the pot shaft and the other end to the actual shaft). The spring is wound on a wooden cork and allows no slippage during regular use, so you don't lose any precision in your pot readings, it only activated AKA slips when the pot reaches its limit. I have posted a link below to a picture of what it looks like. In the picture look for the white color HDPE holder with a pot at the bottom of it. You can kind of see the wooden piece to the spring, but if you want more details just ask and i will try to get more pictures for you.
http://http://aceshigh176.org/drupal/index.php/v/2007/Scrimmage/100_0143_001.JPG.html?q=gallery