[Rickertsen2]

While some of the motors may "take the heat", its a good design practice to attempt to minimise the load on the motor when the assembly is static. Counterweights help greatly with this. Another option is gas shocks like the ones used to hold up car trunks and hatchbacks. They not only put out alot of force but provide some dampening. Worm gears are definately a good idea as well. I would highly recomend them. I should note that the gearset in the van door motor is NOT a worm gear set. It is a healical gearset which can be backdriven.

Also, if you plan on using PID, you must make every effort to minimize the amount of backlash in your system or else put the sensor directly on the motor. Chains are especially bad about backlash unless active tensioners are used.