Converting New Version Dewalt Transmissions

Drills like XRP 940 have updated internals compared to the internals in the “nothing But Dewalt” paper. Any one successfully converted one of these yet ? Is there an update for the new drills in the paper anywhere ?

I believe getting a pinion gear from another transmission is not an option as the pinion gear has a different ratio now than the gears in the transmission. The challenge appears to be how to make use of the pinion gear on the dewalt motor (which has a much bigger shaft than the FP). One option might be cut the dewalt shaft off, drill a hole in the cut shaft for the FP but that shaft is likely to be pretty darn hard. Another option is try to press off the pinion gear but its pretty small and it wouldn’t be hard to trash it trying to remove it. Anyone don this yet ?

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 :slight_smile:

use at your own risk for now. update at end of season !

Thanks for the descriptions. Using the Dewalts with FP motors is a great answer for many applications.

Is there a chance you could make a white paper about this process?

Thanks for updating this thread Dave. I’m sure plenty of teams will be looking to use the newer DeWalt gearboxes now that the older ones are becoming scarce.

P.S. You and I need to update our profiles to remove our doppelganger team numbers =). I don’t think people realize we’re now both on team 1310…

Will try to. Would like to wait a bit until we are certain we are happy with the results in the competition. I see there is yet another new dewalt 12v 3 speed model and would like to try to verify how its internals differ if any from the 940. Maybe I will try to look at all known models. Also would like to verify that higher voltage 3 speed dewalts are still using the same transmissions as lower voltage ones. May also try to get a source in place for pinion gears for FPs to fit the various dewalts by next competition.