Drill Motor Transmission
 

We had a few problems with our drill transmissions at the Philly regional, which was the first time we gave them a real workout. Fortunately, most were on Thursday, but one happened during the semifinals leaving us unable to steer.

The first problem was with the shifter clips popping out and was easily remedied. The second problem, I think, was caused by the clutch housing separating or shifting slightly away from the gearbox housing and causing the clutch to disengage. At the time, in the rush of the competition, we merely swapped the transmissions for new ones. We figured the little tabs that hold the housings together had broken off. After looking over some of the parts back home, I’m now wondering if the clutch housing just rotated, since it provides all the torque keeping the last ring gear from rotating. (I can’t picture right now whether the mounting hardware grips the clutch housing; we’re using the FIRST provided mounting assembly) If this is the case, then the problem should only occur when running in low (which we do), since the shift ring prevents the clutch housing from rotating when in high.

I was wondering how many teams have had this problem, and if you were running in high.

Thanks

Shifter Clips
 

The Shifter Clips came out twice on us before we realized what was going on. Make sure you secure your shifter clips no matter where you are.

We are running in low, the seperation of the gearbox is caused by improper reassembly. It only goes together correctly one way to my knowledge.

There is a way to put the gearbox together so that the motor actually turns a little bit while switching from backwards to fowards. It has to do with the way the holes in the motors attach to the gear box pins.

Never Underestimate the power of zip ties!

Heheh three zip ties held our motors transmission together.

Amen to that. We had some similar problems before competition, but we fixed everything before we shipped.

We encountered both of those problems during Midwest, along with several OTHER drivetrain problems...

I don't really see any reason for using the drill tranny in the future...

Those drill trannys are very very useful and fairly reliable. Though our team had only one problem it only took five minutes to fix. Can you explain your problems in a little bit more depth?
It sounds like your describing what happened to our team's robot but it wasn't the drill transmission that was causing it. It was the fact that the drill motors did not mesh together correctly.

It's just that a small, solid (all metal) gearbox seems more reliable to me, as I've seen most of the veteran teams go that route. The plastic mounts were incapable of holding the transmission together for us, that's all...

Yeah I found the plastic mounts a bit soft. My friend over tightened the bolt mounts and it deformed the plastic. On the other hand I have heard good things about that plastic in the robot combat community. Of course they have said that it really is not good to use in a gearbox. Then again our team has not really had much trouble with them.

Team 122 had transmission problems at Philly also. At first we noticed that our gear change for some reason stopped reliably locking us in one gear or the other. But once we locked ourselves in high gear with zip ties we had problems turning as well. We took one motor apart and replaced it with a spare (didn't have time to do the other one before the next practice match). Still had problems. But when we got both motors replaced with spare parts and worked on the transmission it started working for us. It gave us a little scare on Thursday, but at least we were ready for Friday!

you've had problems?!?
 

our team has had to switch out modify and epoxy NINE drill transmissions!:ahh: and its kinda hard to drive your robot effecttivly in the semi-finals with one (maybe both) blown out.... but thats what four rounds in a short period of time does

but 5 min epoxy works ALOT better than zip-ties.... and epoxy AND zip-ties works better than both :p

Hello,

This year i have become way to familiar with the drill transmisions.

They shift clips come out all the time and the clutch comes off the reduction assembly. So we used hose clamps to keep the shift clips in and we welded the two clutch disks together. We then take off the whole black clutch ring, the spring, and the pressure pins. The black clutch ring is the on that you turn to adjust the clutch setting, and it just screws off.

We welded the clutch because it causes the transmisson to split in half at the twist joint. All the pressure to keep the clutch fom slipping goes through the twist joint, and we think thats the point of failular.

Another thing we've discovered is that the teams using the kit provided helical-gear gearboxes are the ones having problems. So we have concluded that the transmission is backing the pressure (the saft is pushing on it) and that helps the transmission to split.

Team 481 will be at the nationals, and we are more that willing to help you with all your problems (robot related, that is)

Kevin Antaki
Team 481

IM Me: xpalendocious

Yeah, we popped out both of the retainer clips of our one tranny, and we lost two matches before we realized why, because it would engage temporarily and so we thought it was a battery or electronics problem. In the end, a very nice engineer from the LEGO maniacs, team 96 I belive, came over and helped us, we wound up taking one from the other motor and then used pipe clamps on the two of them.

Of all the teams that have posted here, how many did not remove the shaft locking devices? The drill transmission is pretty well designed and coupled to the First drive train should not get anyone into real trouble. I have found that many teams miss a few simple things when assembling the drive system.
You need to remove the locking pawls, the alignment of the helical gears directly affects the friction reflected to the motor/transmission, drive shafts need to be supported at both ends with aligned bearings, and, as most of you have stated, some positive locking arrangement needs to be made to hold in the shifter clips.
Please let me know if any of these apply to you.

bosch gearbox separation
 

We had the problem a lot in low.
It starts with the fact that the mount doesn't have all of the functions of the original drill shell. The drill shell prevents the clutch end from rotating and from separating (away from the motor at the three prong bayonett connection).
The dsign of the clutch itself produces a thrust force which will drive the clutch apart from the gearbox.
We solved it by drilling holes on the existing mounts and wrapping wire around the black cone housing to hold it together.
I suspect that teams which had few or no problems were those who didn't use the misalignement coupling or those who jammed it so tight along the shaft line that the gearbox and clutch could not separate.
In any case, the blue bayonett prongs are not strong enough to do the job on their own, the mount has to help.
I hope that the designers of the motor mounts take notice and improve their design, because it was pretty nice except for that problem.

Charlie Affel, Mentor, 487

I know that I personally did not modify those drill transmissions one bit. The only two problems we had with them were caused by:
a)my stupidity
b)my cluelessness
Besides that they worked flawlessly. Though there was an odd problem with the clutch were it was working while we were testing and it mysteriously turned so that it was in screwdriver mode during our first test run between then and shipping.

bosh drill trans
 

What was your choice of speeds? High or Low?
What was you final drive ratio?
How big are your wheels?
For us it was low gear, 2 to 1 reduction using the FIRST helical gearing and 10" very grippy skyway wheels.

CA

problems with drill gearboxes?????
 

we have seen no problems at all with the drill gearboxes....the onlything that's prolly killing you is those motor mounts. there is no way they can withstand the amount of torque most team put on them. we simply avoided the plastic and made our own aluminum....we also removed the clutch collar and locked the clutch. next year look into machining your own mounts.

Transmission
 

I think we, team 812 had the worse thing happening with our transmission on both sides. Umm, we stripped the left hand screw twice, the mount for the transmission caused a lot of vibration which evenventually knocked the chains out of alignment, the clips fell out 3 times until we used zip ties, the custom fabricated hub for the transmission of ours got the threads meout of alignment because of pressure and that caused the hub to be completely slanted and we found out that the threads were completely ripped. We ended up going back to cmall parts about 2 times for 2 transmissions. As you can see we had every single problem out there, mainly due to our driver hitting the wall at high impact so many times.

I think these transmissions have been wonderful. It seems as if most of the issues are coming from teams that are using the supplied FIRST tranny. We just tappedsome flexible lovejoy connectors, screwed em in, and put sprockets on another shaft that drives the wheels. We have never had any trouble with them. The thing we have had trouble with is brushes falling out/breaking. The brushes are incredibly delicate compared to last years drill motors, and very exposed.

Cory

The only problem we have ever had was that in soldering on new wires during the build we cracked the thin part of the black plastic endbell that holds the brush hood on the rear of the motor. We just pressed a little too hard with the soldering iron. Anyway, we epoxied it back together and I'll bet that is is stronger than ever. We mounted that motor in such a way that the wire actually pushes together on that piece so it would never have any problems. We also made little mounts for our large #8 wire to the motors to relieve some of the stress on the terminals and endbell. So, besides that minor mishap, the motors have been trouble free. We did not modify them at all and use standard zip ties to hold thm in high gear.

All the drill problems come from teams who drop them, install them incorrectly, or modify them.

Nothing is more true in the case of the drill motors than the saying, "If it ain't broke, don't fix it."

today while showing our robot to a group of third graders something happened to the transmission for the left drill motor and we could drive the left side anymore backwards, this also happened in St. louis to the right drill motor and we had to swap out the transmission. we have made absoultly no changes to it either aside from locking it into lower gear with a zip tie. we are a high torx robot and can push most others around. could this be part of the problem?

I would guess that you didnt remove the drive pins, one or both sheared, and they will glide one way but wedge when you go the other way. Thats what happened to us.

Good Luck