Fisher Price Motor Into Drill Gearbox

[Travis Hoffman]

Originally Posted by David Bridge

That would be team 177... Not only did we press new gears onto the motors to allow them to interact with the planetary gears inside the bosch transmissions, but the original design also called for a worm wheel reduction to be used to move our arm (we actually did this to both motors and ran them together to get double the power) this effectively gave the motors a 70+x reduction which we thought would have been and awesome way to hang, folding the entire robot up without having to worry about backdrive or not having enough power... however we were having trouble getting a good mate between the worm wheel and gears and and the set up was so powerful that it kept tearing the wheels apart (they were brass) so we finally wound up eliminating the worm gear and just using the fisher prices through the drill transmission as our winch

Team 48 also used this method with great success on our lift mechanism. Two FP's mated to two drill transmissions were coupled to the second stage chain lift system on our arm. Those babies are what enabled our robot to hang so quickly and reliably all year. After the anti backdrive pins failed to keep the bot suspended in the air during the finals of the Buckeye Regional, we ultimately removed them from the drill trannies and added a servo actuated ratchet lock system to the lift to keep the robot hanging. The system was flawless after that.

I will ask the mechanical designers to explain their methods in a later post.

[Peter Matteson]

I'll try to answer as many of the questions as I can. I have a white paper prepared but have been having trouble posting it.

First of all we welded the clutches in order to permanently disable them. This is fairly easy and works well. We initially left the anti-backdrive pins in the motors but later removed them to alieviate other problems they caused in favor of dynamic breaking with the Victors. We also locked the transmission in low gear. For an output we welded 7/16" deep sockets to 1/2"-10 (going on memory for that) nuts that we threaded onto the output of the transmission. We then locked these in place with a ground down Bosch reverse thread screw into the inner part of the output.

For the motor we used a bearing seperator and a hardened pin on an arbor press to remove the pinnion gear. We had already removed the pinnion gears from the drill motors in the same way. We then created an adapter shaft out of drill rod for the problem Sandrag pointed out. We made a .002" press fit on one end for the gear to go onto and at the other end did the same for the motor's output shaft. We pressed the gear onto the adapter first then onto the motor shaft.

As mentioned we also made a sleeve to cented the FP motor in the drill transmission and tied the whole thing together with thrust plates that also worked as anti rotation. We tapped the pre-existing holes in the motor housing for 6-32 to accoplish this.

If it worked this time attached will be a tif file that contains most of the infor required to do this except for the output and drill transmission mods. Certain dims are flagged as needing to be checked because we had to tweak them to get things to work correctly.

-Pete

[Edit] I actually thought more people would be asking about the vacuum generator that actuated our shifting mechanism than this. [edit]

[Jack Jones]

We (#1447) mated both the FP and Bosch motors to DeWalt three speed trannys, which are superior to the Bosch trannys - the shift ring gears are all metal and will shift on the fly, especially if you radius the inlets.

We cut our own 32-15 pinions out of 0.3" titanium on our (USA-TARDEC) watercutters and pressed them onto the motor shafts. Used Loctite 680 retaining compound just to be sure the press fit would hold. Drive setup worked great except that our mounts didn't hold the trannys well enough; they wanted to spin, so we retrofitted a bolt through the nylon assembly. Too bad that our proto-type was only used for photo-opps, we'd have discovered the problem well in advance instead of staggering through so many matches