Just to let you know, we converted 2 DC940 Dewalts to FPs. DC940s use a newer 3 speed transmission design than that in the "Nothing but Dewalts" doc. But they appear to be all metal etc.
- We bought brand new DC940s for ~$40-$45 off Ebay. This is recommended as you need both the pinion gear and the front motor plate off the dewalt motor. Also it is way cheaper than trying to buy individual parts.
- There is a video on the internet re how to take off the chuck. One came off easily, the other one we could not remove the internal (reverse thread) locking bolt (loctite too good for small torx head) so we cut off the front of the chuck (with a angle grinder), ground a slot into the hardened locking bolt with a dremel and removed it with a large screwdriver. Then unthreaded remainder of chuck with big pliers. Sounds difficult but it was surprisingly easy and quick.
- the dewalt motor pinion is NOT the same tooth count as the planetary gears in the transmission (unlike in the old dewalts). We chop sawed off the pinion gear and got it EDM drilled to the FP shaft size (appears 0.126 -> 0.127 should be ideal, we did 0.125 and it was way tougher than it needs to be getting the pinion on the FP shaft).
- unlike the old dewalts, there is no urgent need to make a new plate to mount the motor. We took off the front plate of the existing motor and drilled mounting holes for the FP and had to do a tiny bit of grinding and then the "nose" of the FP fit tightly inside the "nose" of the Dewalt front plate.
- we also mounted a small muffin fan in the back of the casing to give the FP maximum cooling air.
A great side benefit is we took the 12v speed controller out of the dewalt and attached a surplus 40a breaker and a 60a meter we had lying around and a battery connector and now we have an outstanding portable motor test setup.
So far the dewalt has tested okay in a number of robot hanging tests (including the anti-back (and forward) rotation system inherent to the 3 speed dewalts. We just hope the new transmission (and anti-rotation mechanism is as durable as the older transmissions are (given we are hanging a 150lbs robot off it
use at your own risk for now. update at end of season !