loose motors

[ivanslost]

hello all you smart poeple

we are a new team, so like most others we are having trouble with motors. they are kinda loose and we dont know if thats normal, good or bad so if anyone knows anything abour this please contact me asap.

[Gadget470]

what do you mean by "loose"?

The motor itself shakes around? the gear or gearbox is flimsy?

Please be a bit more descriptive

[f22flyboy]

I've noticed a slight problem with one of our drill motors moving back and forth inside the plastic mounting bracket FIRST provided. There's about 1/8" of slop in the mount and we can't figure out why because the other motor is tight and running fine. I was skeptical about using plastic brackets in the first place and I hope it doesn't come back to haunt us during competition.

[AJ Quick]

There should be some slop in the rotation of the motor... that is the transmission engaging. If there is a huge amount of rotational slop, the left handed screw could be loose.

[Andy144]

Your definition of loose might be tiny or huge so give an approx amount of slop that the thing is rotating before engagement and then we can tell you what the dillio is!

[f22flyboy]

its not the rotational slop, the entire motor and gearbox is moving forward and back inside the mounts.

[Caleb Fulton]

We've noticed it, too, but it hasn't really been much of a problem for us.

[sanddrag]

Our gearboxes stay put but one motor can rotate a little in its mount. No biggy, runs fine.

[Dick Linn]

Lacking a more complete description of the symptoms, I would check the alignment of all mounting holes and components on that side. Make sure that you have the motor and drill gearbox are mated, seated and aligned properly. The motor and gearbox shafts should be absolutely parallel, in the same plane. If they are mounted on the same flat plate or surface, one side should be good, but you may not have the shafts parallel in the other. Remove the motor mount bolts, grab the drill transmission clutch collar (with the numbers) on both sides evenly, pull it snug toward the big gearbox shaft and see if the mounting holes for the motor mount bracket still line up. I put my thumbs on the big gearbox, fingers on the drill gearbox and just squeezed evenly on both sides toward the big gearbox. (We did this before marking and drilling any holes and also before tightened anything.)

Verify that the motor shaft in the big plastic helical gearbox is securely retained on both ends, with no end play. It should not move end-to-end. Also run the drill motor with just the one aluminum hex adapter screwed on (no plastic shaft coupler) and see if it runs true or wobbles. We have one motor that wobbles and one that runs fine, and I have heard others mention this. (We have a replacement aluminum hex adapter coming tomorrow.)

I also noticed that the hexagonal aluminum adapters were a very snug fit in the black plastic coupler and didn't readily fit all the way in due to the tolerances of the molded plastic. As they ran, they would drift back and forth when driving from forward to reverse if they were not properly seated. I gently tapped them in (using a soft-faced hammer or wooden block) until they completely bottomed out on the web in the center of the black plastic adapter. After inserting and removing the sharp-ended aluminum hex pieces several times, which sort of machined out the imperfections, I then beveled the sharp edges of the aluminum (inside the adapter part) so that they can be inserted and removed relatively easily (not sloppy!). I figured that this would reduce misalignment and stress and allow it to be more easlly butted up squarely against the big gearbox. That takes care of axial misalignment.

We did a lot of minor part fitting and smoothing to get the shafts, keystock, adapters and all carefully assembled and everything pressing nicely and squarely against a shaft collar that is riding on the inner race of the big gearbox bearing. I hope the plastic hex shaft adapter thing serves the purpose of absorbing a bit of shock and minor misalignment...

Hope this helps you. You can find the problem and fix it! Let me know how it goes.

[f22flyboy]

I found the problem - the (relatively) cheap plastic mounting brackets provided by FIRST are not exactly precision engineered. One of them fits snugly while the other one has about 1/8" of slack (on the longitudinal axis of the motor). I either have to come up with new drill mounts in 4 days or just lower my standards

[ROB at RAGE]

We put about two loops of black electrical tape around the center to get rid of the slack.

We are considering making a a rear aluminum clamp on the motor body to aid in cooling and to not block the air exit holes form the motors like the first on dose.

[Dick Linn]

We did the same thing with 2 layers of tape! In addition, we cut some small pieces of rubber matting (about 1/4 inch by 3/4 inch) and carefully placed these on the rear of the motor where it's about 1 inch in diameter. It's just thick enough to grip the motor firmly when everything is snugged down.