RE: Electric Retracts - Modifying existing Air/Servo-operated Retracts
Here is one option that would work. Depending on the retract type and how much side to side movement there is in the retract drive shaft as it moves from UP to DOWN, you might need to mount the outer race of the thrust bearings to the motor/gear box case/mount or to the retract body. What ever works.
You can get any size thrust bearing you might need from Boca bearing or several other places. As long as the inner race ID matches your output shaft OD most anything will work. Id want sealed bearings for longer life but there are literally hundreds of options and sizes.
If you didnt want to machine some way to attach the outer race to the mount you could just use a cut down heli tail or main blade grip that uses bearings of the same OD. You could also just use a fixed partition on either side of the thrust bearing that rides on the outer race. There are lots of ways to do that.
The key is you want the shaft to run in and push/pull on the inner race of the thrust bearing. So you need to fix the outer race in place some way to the motor mount and/or the retract body. That way all the push pull forces are against the retract body or the motor mount and not on the gear box output shaft.
The push pull forces from the shaft are transfered to the inner race of the thrust bearing by the wheel collar and the coupling via the small washers on either side of the thrust bearing. Those small washer only touch the inner race.
There are bound to be dozens of ways to do that depending on how you mount the motor/gear box and how the retracts are made.