Help with window motor

[HWRobotics]

What is the best way to attach a metal disc or an arm directly to a window motor's face? We're trying to use it to power an arm but we want to figure out the best connection without wasting the motor...
-hw robotics team

[Joel Glidden]

My team has made couplers for the window motors in previous years. I posted a drawing of one of them in this thread. Put that hole pattern in whatever you want to drive w/ the window motor and you're golden.

[Kevin Sevcik]

I think the easiest way would be to use the plastic window motor coupling provided by FIRST. It's a ~4in diameter black plastic disk thing with a coupling on one side for the output gear of the motor and a keyed hole on the other. So you could attach a keyed shaft to the disk or something. Alternatively, you can bolt things to the plastic disk. All in all, highly convenient. If you're missing them, they can be ordered from MMH Ventures.

If you want to be really fancy and you have the equipment, of course, you could just mill out the center of the disk to slide straight onto the gear with some fancy CNC work. I'm guessing you don't have access to this, though, so go with the FIRST provided coupling.

[Frank(Aflak)]

Originally Posted by HWRobotics

What is the best way to attach a metal disc or an arm directly to a window motor's face? We're trying to use it to power an arm but we want to figure out the best connection without wasting the motor...
-hw robotics team

Here is an idea I have been kicking around (we will probably use it this year on ours, too).

Take, say, three bolts. Whichever length/size is best for you.

Epoxy their heads to the rotating plate on the window motor (you know, the one with the gear in the middle of it). You could probably do welds, too, but I would be super careful about that. Disassemble the motor before attempting a weld.

drill the appropriate holes in your plate, put it over the bolts, and tighten nuts down.

We are considering this for mounting our stuff on our window motors this year. We considered a straight epoxy, but we wanted to be able to remove the stuff if it gets broken, so we will just do the bolts.

[Kevin Sevcik]

I'd personally worry about epoxy standing up for an entire robot season, but that's just me. Welding would be better, but I think that could be skirting rather close to the no modification ruling. One of the Q&A ruled against modifying the output gear of machining it, so welding seems iffy to me.

[Frank(Aflak)]

Originally Posted by Kevin Sevcik

I'd personally worry about epoxy standing up for an entire robot season, but that's just me. Welding would be better, but I think that could be skirting rather close to the no modification ruling. One of the Q&A ruled against modifying the output gear of machining it, so welding seems iffy to me.

Really? I though the gearboxes were always considered fair game . . . ?

Hmm, we are using ours in a very light application, so i think epoxy will be OK for us.

Was the warning about breaking the gearbox or about the legality of it? I thought the rules said the gearboxes were fair game?

[Joe Ross]

Originally Posted by Frank(Aflak)

Was the warning about breaking the gearbox or about the legality of it? I thought the rules said the gearboxes were fair game?

Only gearboxes that aren't integral to the motor are fair game. The worm gears output stages of window and van door motor may not be modified. <R62>

[Kevin Sevcik]

Answered 1/29/03

Q: <R62> Can we modify or remanufacture the output gear on the window motor? Can we take the output gear off and manufacture a pulley instead?
A: No, you may do neither. Your Kit should contain two couplers you can use to connect the window motors to other items such as pulleys.

Although this seems slightly contradictory to a later Q&A that seems to say you can make modifications to the internals of the gearbox:

Q: Can we add a spacer to the window motor output shaft in order to reduce the play in this part?
A: Yes, as long as you do not electrically modify the motor.

What's even more confusing is that R62 seems really to contradict BOTH answers.

• It is acceptable to modify the mounting brackets and/or other structural parts of the motors (output shaft, housing, etc.) as long as the electrical system is not modified and the integral mechanical system of the moving parts (bearings, bushings, worm gear output stages, etc.) is not changed or removed.
• The gearboxes for the Fisher-Price, Drill, and Globe motors are not considered “integral” and may be separated from the motors. FIRST will not provide replacement for parts that fail due to modification.

Which seems to say that the output shaft/gear CAN be modified, but the internal gear system CAN'T be modified by adding spacers to reduce the backlash. All in all, I'm going to be asking for clarification about this later tonight.

[jonathan lall]

This year we quickly lathed an object with a cylindrical hole that fit over the window motor gear. We then stuck set screws between some of the teeth through the object. Problem solved.

[Eric Bareiss]

Before we can tell you what the best way to do it is we need to know what your machining capabilities are.

[OneAngryDaisy]

Originally Posted by jonathan lall

This year we quickly lathed an object with a cylindrical hole that fit over the window motor gear. We then stuck set screws between some of the teeth through the object. Problem solved.

Stole my idea- 341 did this in the last 'hanging' year, this never failed throughout all of our competitions.. I took apart our old winch a while ago and the window motor in 2000 has a significantly different worm gear, this years gear should still be sufficient... i hate to say this, but even though set screws inhale audibly they work beautifuly in this case

[Frank(Aflak)]

Originally Posted by Kevin Sevcik

Answered 1/29/03

Although this seems slightly contradictory to a later Q&A that seems to say you can make modifications to the internals of the gearbox:

What's even more confusing is that R62 seems really to contradict BOTH answers.


Which seems to say that the output shaft/gear CAN be modified, but the internal gear system CAN'T be modified by adding spacers to reduce the backlash. All in all, I'm going to be asking for clarification about this later tonight.

I don't see the seat motor mentioned. I was operating on the assumption that gearboxes were fair game and was planning on removing its worm gear: it is probably classified as integral, however, so I will need to do something else (although I really don't want the weight entailed by a CIM motor on our arm)

yeah, they prohibit playing with 'worm gear output stages.'

Man, I thought that motor was going to be golden. What if we leave the worm gear on, but modify it so that we can drive our stuff directly from the motor's shaft? Meh, doesn't work under the new "spirit of the rule" thingy. Oh, well. That means we need another victor884 on our control board. Good thing we have 4 + 4 from last year.

[Tytus Gerrish]

we removed the hub and welded a 10tooth #35 sprocket to it and then re attached it It workd Great for our upper arm

[tenfour]

We cut a peice of round steel bar. We then machined the pattern internally of the window motor. This creaded a socket that slipped over the output gear.

This was a really high tech custom CNC job that required expertise. I would say that if your team can do it, then do it. Its a real cracker jack output shaft!

[sanddrag]

Originally Posted by tenfour

Its a real cracker jack output shaft!

If by "cracker jack" you mean "top quality" then yes it is. They came out really nice and work very well because you can weld right to them. If anyone has any questions about our CNCed couplers, let me know.