buying pre-made couplers?

I've just read Dave Cook's chapter in "Robot Building for Beginners" on making couplers. I have exactly such a need as he describes: a surplus
gearhead motor with a D-shaft, to which I want to connect a LEGO wheel (actually, a LEGO bevel gear which will drive a gear connected to the wheel, but once you get to LEGO parts it's all the same).
Now, his solution of making a custom coupler out of nested tubing is clever and appears to be a high-quality solution. It is also, probably, just barely, within my mechanical skills to do (though I'd need to get a drill press). And it's true, as many of you know, that I am a cheapskate on a tight budget.
However, lately time is even shorter than money, and making these couplers looks like a serious chore. I'd be happy to pay a couple bucks each to save myself the trouble.
So: is there anywhere I can buy couplers on the net, for common input and output shaft sizes, for not-too-ridiculous prices?
Thanks, - Joe
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Jameco's Robot Store has some at this link. They are for .25" shafts: http://www.robotstore.com/store/default.asp?catid61 I found that page (been at thier site many times before) by Googling this: shaft couplers robotics
Also, Gordon McComb's book "Robot Builder's Sourcebook" nad/or his column in Servo magazine is a goldmine of info just like this.
Best of luck ! JCD
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wrote:

Well yes, but the point here isn't to couple two shafts of the same size -- it's to couple two shafts of different sizes.
Actually, it's not at all clear to me what this item actually does: <http://www.robotstore.com/store/product.asp?pidI0&catid61>
What does it couple to what, exactly? It's got a funny shape, as if one side is intended to plug into something, but the description (such as it is) doesn't say what.
Best, - Joe
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Yep - I agree it doesn't describe the purpose very well at all. The point is to be able to use 2 different size shaft couplers, but the "funny shape" matches up in the middle and interlocks the 2 shafts, as well as adding a little tolerance for misalignment, etc. The photo at this link should make it clear:
http://www.stepperworld.com/images/Couplers.jpg
This shows 2 couplers of the same size, but you can have different sizes bores but the middle part (rubber spider) is same size for each coupler.
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Joe Strout wrote:

Without knowing the diameters you're talking about or the torques involved it's hard to provide some suggestions. But for overall store-bought solutions try Stock Drive or Small Parts.
-- Gordon
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Joe Strout wrote:

Joe:
I will tell you how I make my shaft adaptors. I use a drill press and a some taps. I know this is not a direct answer to your question, but I figure some other people can benefit even if you do not. Fair enough?
I start with some hex aluminum stock and cut off a short piece. I make three scribes across the stock to find the center. Using a center punch, I put a dimple in the center.
I clamp the hex stock vertically into the vice and select a drill that is the same size as the smaller shaft. I drill all the way through the stock. Next, I select a drill that is the same size as the larger shaft. Without removing the stock from the vice, I drill half way down the stock. The small shaft will fit snuggly from the bottom, and the the large shaft will fit snuggly from the top.
Now, I rotate the stock 90 degree and drill two small holes for two set screws. Using the appropriate sized taps, I tap the holes and install the set screws. If set screws are not available, I use a regular screw, it does not matter.
-Wayne
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Joe,
My experience is, fitting a surplus motor to a wheel of random choice is pretty much a custom job. The coupler that you saw at Jameco is most likely designed for a specific wheel or motor.
You can get an idea of what it does and how you can make one by seeing below:

http://www.youtube.com/watch?v=K6IxTZjJdAk

Enjoy......
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Joe, would having some tubing that you would simply drill out the center to the appropriate diameter be within your skill set ? If so, I can think of an easy solution to your problem and could come up with a kit for you to test. If you're interested I'll provide more contact info later. JCD
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