Drill Transmissions Wobbling???

[aaronbr28040]

Tonight we assembled one of our transmissions for the robot. Upon assembly we noticed that the transmissions were wobbling. We took the motors off the transmissions and ran them and they still have a wobble. We could not think of a cause for this problem as we have not done anything to the gearboxes to cause this problem. Has any other team experienced this problem this year or in the past? We would appreciate any help.
Thanks

[Rhs953]

Whe have the same problem. I would like to know the answer tool.

I didn't break it!

[Rhs953]

Just a thought. Try tighting the mounts. the hex cuplings arn't truning "true" so maybe it will work how knows.
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I didn't break it!

[aaronbr28040]

If we tighten down the mounts it will cause the motor to bind, I wouldnt suggest trying it unless you want to replace your drill motors.

[Crop-Circles]

Originally Posted by Rhs953

I didn't break it!

Hmmm, I remember hearing that from our drivetrain team an awful lot...

We had a similair problem last year. We blamed many things(the frame, the wheels, Dave, etc.). This year we fixed the problem with one simple equation.

Drill motor=bad

At some point I would like to know what really went wrong, but that's all I know for now.

[Rhs953]

I took a close look at it and it seemd to be the hexagnel cuplink the connects to the drive shaft. It acts as if you would put a drill bit wrong into a drill. It wobbles the sameway. Thus It would seem that the position to the hole is slightly off.
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I didn't break it!

[greencactus3]

Originally Posted by aaronbr28040

If we tighten down the mounts it will cause the motor to bind, I wouldnt suggest trying it unless you want to replace your drill motors.

will it really? we haven't run our drill motors yet but we have already mounted them. i'm pretty sure we tightened the mounts quite snugly. well, not to the point to where the plastic (mounts from the kit) will crack, but quite tight.
is that bad? how do you know how tight you should crank it

[Rhs953]

NO don't tighten the motors. It will cause the motors to bind. Then you'll have to buy a new motor for oh about....$70. Just look at my last post.

[Joe Johnson]

The drill tranny is one of the "Great and Terrible" things of FIRST.

They are great because they have a lot of engineering all baked in for you.

They are terrible because they can set a lot of traps if you don't know what you are doing (and even if you DO know what you are doing sometimes).

I really don't like the current drill mounts for 2 reasons. #1 the output shafts cannot take a side load. #2 The drill motors are not really held very well.

We used the drills & drill mounts last year. They were BY FAR our highest failure system on out robot. We are not using them this year.

Joe J.

[Matt Adams]

Originally Posted by aaronbr28040

We took the motors off the transmissions and ran them and they still have a wobble. We could not think of a cause for this problem as we have not done anything to the gearboxes to cause this problem. Has any other team experienced this problem this year or in the past? We would appreciate any help.

I suggest you take the drill motor out of the transmission and and spin it by hand. Do you feel anything catching? Perhaps the windings on the motor are poor. This happened to us last year, and we simply returned it to FIRST and got another. If one motor is particularly bad.. it might actually be a manufacturing error. If one motor runs significantly poorer than the other.. this might cause you to raise a red flag.

Just a thought.

Good luck everyone!

Matt

[Rhs953]

There is a solution to the problem. If you loosen the pillow blocks this will allow the akles to give a little so you dont ruin the motor. Just a thought.

[aaronbr28040]

Originally Posted by Rhs953

There is a solution to the problem. If you loosen the pillow blocks this will allow the akles to give a little so you dont ruin the motor. Just a thought.

We dont have our motors directly driving to the axles. We have them in a two motor transmission that uses the drills and the chips so the pillow block positioning really isnt relevant for us. I know it has to be something in the drill transmission itself as we can take it off of our transmission and the problem still persists with both motors. I dont think it is just one motor that is a "dud" it appears that both of them have the same problem.

[Rhs953]

then possibly loosen the motor mounts or what ever your axels are mounted on.

[sanddrag]

We torque all of our drivetrain bolts while the motors are running. This ensures the best alignment of things.

[aaronbr28040]

I have tested the motors and gearboxes both on and off of our transmissions so it appears that it is either the shaft or the coupler supplied by first that is causing the problems, anyone have any solutions to that problem?