Ideas on a motor coupling?

I need to build a coupling to connect to an unusual 12 VDC motor, out of an automobile power window. It has a unusual large gear, and since
the coupling is direct drive I just need to attache it well enough that it will not fall off and will transmit power reasonably well. The gear is 8 teeth, about 3/4" diameter, but only about 1/4" face width. It is also flush with the motor housing, which means that I really don't have enough room to drill through and pin or bolt the coupling on. I also believe the pinion is hardened, so I probably couldn't drill it if I wanted to. It is integral with the shaft so unfortunately I can't just pull it off. My current thinking is that, since it is an 8 tooth gear, with fairly large teeth, I will bore a piece of 6061 to the OD of the gear, and then cross-drill for four setscrews at 90 degree increments. I think that a 10-24 NC cup pointed set screw will fit well between the gear teeth. My main question is how to keep the assembly from sliding off of the end of the gear. I need to attach a wheel to the end of the adaptor/coupling, and I'm not sure at this point if I will have enough room for a pillow block to support the other end. As far as fabrication, I have a 12" lathe, Bridgeport clone VM and a 20" drill press. I don't have an indexer, but I think I can cross drill the shaft with reasonable accuracy.
I've posted two pictures of the actual motor to the dropbox:
http://www.metalworking.com/dropbox/Motorbig.jpg
http://www.metalworking.com/dropbox/Motordetail.jpg
I've also posted my coupling design as I have come up with right now. The picture:
http://www.metalworking.com/dropbox/motorcouplingdrawing.jpg
I created the drawing in Autodesk Inventor. If you would like the Inventor/AutoCad file, I can send that (can't post on the dropbox-not .txt or .jpg).
Thanks in advance for any ideas, Woodworker88 www.lahsrobotics.org
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woodworker88 wrote:

Have you considered dispensing with the gear and its shaft and making one to suit you? It would simplify matters.
Tom
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Learn or produce ? Making a gear is fun to learn , but producing needs to get a handful of small BB's and make flat belt ( crown one , the other is flat ) and get a very efficient gearing down .
If the speed drops too much , use chain drive as in a tiny hand held band saw . Chain is not hi friction and can take a large over load . 150 HP Honda motorcycles use it well . If you have space problems , then you'll have to use gears and hydraulics !
BTW whats the ID of spindle bearings on HF 7 by 10 Lathe ?
______________________________________________ Tom wrote:

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werty wrote:

Whatever...
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snipped-for-privacy@gmail.com says...

That motor appears to be identical to one that a friend of my son used in a robot he built for his senior project last spring. We made a new shaft. As I recall, the output shaft was coupled to the wormwheel in the gearbox by a detented overload device. The sheet metal cover bears on the end of the shaft inside the gearbox and holds the detents together.
I don't remember exactly, but I think the new shaft was just a piece of round stock with a welded-on arm that engaged the detent.
Ned Simmons
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wrote:

Set screws should work OK if there isn't any axial moment.
Another possibility: make the piece you describe, but with an axial hole thru to the bore. Place on gear, pour in some molten Cerrosafe -- a metal that melts at between 158 and 190F -- not even boiling. Then pin the Cerrosafe slug.
http://www.brownells.com/aspx/ns/store/productdetail.aspx?p84
If your motor gets quite hot in operation, you could go to other higher-temperature alloys that are still below 250F. Look in McMaster Carr.
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It looks to me like you have almost got it. If you were to take a Dremel with a cutoff wheel or a similar device and cut into the gear where your setscrews would ride, you can keep them from sliding off. And, if you were to make a few more random cuts and work some waxed paper under the gear (for obvious reasons), you could then bed your coupler in with some JB Weld or something similar and it should be very solid.
Jerry
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wrote:

Your idea shouls work pretty well. Only thing I'd do different is clean up the gear REAL well and mask the back plate, then fill the teeth with JB Weld or equivalent before pushing the adapter on.
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Wow that was a quick response. To sum up my options as I understand them:
I actually was thinking of the low-melting point "fixturing alloy" material. I may try to find a local supplier. For those of you who said it looks familiar, it is the Window motor out of the ~2004 FIRST robotics competition Kit of Parts.
I haven't actually tried opening the motor/gearbox, so I don't know what exactly the other side of the shaft looks like. That detent-overload thing sounds a lot like some of the other motors I have dealt with (read: cursed/smashed in frustration) so I'm not sure if I really feel like going that route. Also, my welding skills are sketchy at best.
Also sounds like JB Weld is going to be a good idea. I think I'll go with the current design, but notch the gear for the setscrews, and then drill the bore all the way through. That way I can inject the JB Weld from the end, rather than trying to put it in the gear area and then trying to squish it on and tighten the setscrews.
Thanks a lot for all of the suggestions, WW88
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Apparently you ignored the request to limit your jpgs to 50KB or less. http://www.metalworking.com/dropbox.html Your first jpg is 1.5MB. I don't think Steve appreciates you Bogarting enough space on his server for dozens of posts by more thoughtful submittals. JR Dweller in the cellar
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JR North wrote:

I was shocked, shocked to find that I wasn't familiar with that verb.
I had to look it up:
http://www.urbandictionary.com/define.php?term=bogart
Jeff
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On Sun, 12 Nov 2006 22:24:14 -0500, the renowned Jeff Wisnia

You never saw "Easy Rider"?
http://www3.clearlight.com/~acsa/introjs.htm?/~acsa/songfile/DONTBOGA.HTM
Best regards, Spehro Pefhany
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On Sun, 12 Nov 2006 22:45:06 -0500, with neither quill nor qualm,

You poor, sheltered dear.

"Roooooooooooooooooooooooooooooooooooooooooooooooooooll another one." Ah, shades of another lifetime...
Yee Haw!
-- <ahem> Chipmunks roasting on an open fire...
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Sorry. I did read the dropbox page but didn't see the 50 KB limit. If you would like to remove the files, I think I have gotten plenty of suggestions, and they are no longer needed. Thank you for pointing out my mistake. ww88
JR North wrote:

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JR North wrote:

I was going to suggest that he compress those pix. a bit also. :-) ...lew...
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woodworker88 wrote:

It will fall off as soon as you have the slightest missalignment of the axes or a rotating side-load. Can you drill through the CL of the gear and have a screw to pull your coupling onto the gear?
Nick
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Measure twice, cut once.
Or use YADRO:
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Nick Mueller wrote:

I really wish I could. It's hardened, not easily fixturable, and I don't have any carbide tipped or solid carbide drill bits down to that size (I would need about a 3/16" or so).
ww88
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Take advantage of the 3 threaded holes on the housing and make a plate retainer. Put a groove into the OD of your shaft, make a plate that hits the 3 bolt holes and has a loose-fit U that will fit inot the groove on the shaft. Since the rotational speed of this motor will be slow, a dab of lithium grease should be more than sufficient to keep things from wearing very fast. This will prevent axial movement of the shaft.
--
Anthony

You can't 'idiot proof' anything....every time you try, they just make
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Anthony wrote:

Hey! Thats a great idea. Why couldn't I have thought of that. :-) ...lew...
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I definitely agree. I'll work that into the mounting bracket (which also has to attach to the threaded holes. I think if I thread the the mounting bolts into the motor, and then use a clearance fit on the retainer, I can tighten the retainer with a nut and lockwasher without affecting the motor mounting itself. Thanks for the idea ww88
Lew Hartswick wrote:

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