Drill Motor Clutches

Just a quick question what do other teams do to the drill motor clutches to make them perform better? If anything?

The way the drill motor clutches work is that when you turn that cone shape black plastic “thing” from 1 toward 15 until drill, (can’t think of a better word right now… you know, the thing with the numbers around it and the drill bit symbol), it screw inward toward the motor direction.

When that happen, it compress a large spring that’s sitting on a series of little metal balls. The harder you compress the spring, the harder it push onto the steel balls, and the harder it engage the ring gear (with little bumps) under it.

So, at the “1” setting, spring is barely pressing onto the ring gear, and that ring gear will be slipping if the drill output shaft is pushing against light resistence. The higher the number goes, the harder the spring compress onto the ring gear, and the more resistence drill output shaft can push against without slipping the ring gear.

That is why at 15 or “Drill”, the drill will keep drilling until you stall the motor, or you lose your grip on the drill handle.

So, to completely lock the ring gear in place, there’s two ways:

A length tube that replace the spring so the steel balls will constantly engage the ring gear without room to back out,

Or tap the holes (M6) for the steel balls and screw in M6 set screws to constantly engage the ring gear in place.

This way, you won’t have to worry about drill slipping out of clutch anymore.

Sorry for the poor description. You should take a look at Dr. Joe’s drill advice in the white paper section @ http://www.chiefdelphi.com/forums/papers.php?s= (on page 3)

There are a few pictures in that word file that will help you visualize the set screw method.

I’ve also heard about modifying the drill motor/transmission so it doesn’t “brake” (come to a stop) after cutting the voltage. Anyone have drawings on how to do this or know where I can find them?


The same document Ken talked of also shows how to remove the little rollers from the assembly. I think these may be the ones you are talking about. Also the speed controller has a jumper for brake/coast.

Our team (40) also cleans all the grease out of the clutch. Then we regrease it with our “special grease” and the motors actually draw 1 less amp. However it does take an experienced person about 1 hour to do this, which is a very bad downside if you want it to run now.

There are white papers on this subject. I have one in the whitepaper section of this site. Chris Mikus has one on Nuts4FIRST.net.

Basically, the no-back clutch feature is a disaster waiting to happen (in my opinion). It is easy to remove the small cylinders that provide this feature. Highly recommended.

Joe J.

The “no-back” roller, or the locking pins stop the transmission from back driving. You will notice its effect when you get a normal drill and try turning the chuck. That’s why you can put the drill bit on without the chuck giving away.

It is recommended that you take apart the drill transmission and take those little pins out, because they will break when output shaft experience a lot of load, like when a drive train is being pushed by another strong drive train when sitting there.

To take them apart, just open the transmission, and take out all the planetary gears until you reach to the back of output shaft. You will see two tiny pins sitting back there.

Only bad thing about this, is your robot will be rolling around… So if you are not telling the drive train to push back, other robots can easily push you away.

We decided to keep those pins for the 2000 robot because it kept rolling off the ramp… But that’s probably the only reason whe people would want to keep them in.

According to Dr. Joe’s Drill advice, we have tapped out the ball bearing holes and inserted long M6 set screws to “lock” our torque limiter.

Even with the set screws in, under high torque our torque limiter will slip about 30 degrees as the set screws move from one set of “humps” to the other set of “humps”.

Question: Is it wise to “notch” the ring to give the set screws a positive engagement into the torque limiter ring? Will this weaken the gear? We think this may help our 30 degrees of slippage when going from forward to reverse.

Neill Means
Team 933

We notched them in at least one prior year.

It worked okay.

You should “sharpen” the set screws to a square corner in this case so that they sit in the notches better.

Joe J.

*Originally posted by kacz100 *
**Just a quick question what do other teams do to the drill motor clutches to make them perform better? If anything? **
We totally eliminate the front half of the trans assembly. We use the the planetary section to shift gears, then attach the trans to a custom “shell” that houses the planetary ring which is inside the stock housing. We mount the 4 planetary gears on a custom outshaft and use roller bearings to support the shaft instead of the bushing and loose ball system the stock unit uses. I have the system modeled in Autocad 14 both in 3D and in 2D. Last year we used the stock bearings and I stiil have the drawings for that system as well. Last years machine worked flawlessly with this setup, this years should work the same with the added ability to shift and added torque from the addition of the Atwood motor to the hole shooters.:cool: