Alan,
Since nobody else has stepped up yet I'll try to answer your questions. The change on gears last year really threw us for a loop. I had a drive system all designed but it was not feasible to construct with the gears available. We considered making our own but decided that we didn't have the resources to figure out how in the time available. Consequently I've been developing sources for "cut your own" gears just in case.
Our machine shop frankly refuses to even attempt cutting any gear teeth. (Sprockets are a different story) They just aren't equiped for it. BUT they do have the gear design module for MasterCam. I have checked with several EDM (Electro-Discharge Machining) houses in our area and they have indicated that they can burn gears out of any common material directly from the MasterCam file. Many have similar software themselves and can create their own pattern if you give them the proper parameters (pitch, face angle, bottom radius, etc).
It ain't cheap, but it's not terribly expensive either, especially for 2-4 gears. Expect to pay a premium of 10-40% over a catalog gear. But less than a custom gear made conventionally as most of the cost for just a few custom gears comes from the setup.
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How about the Diametrical Pitch and Pressure Angle of the Drill Motor and Fisher Price motor pinion gear? I also understand that the gears may be metric so the Module system may be used (Is the Fisher Price motor Module .8 and the Drill Motor .7 ?)
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Dr Joe has posted this information a couple of times. They might be in the old forum. I don't remember the numbers off hand.
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What materials would you suggest, 1/4" plate steel and round shafts?
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The shaft depends on how you plan to connect to the rest of the system. I like D shafts myself. The material thickness depends on the face width you require for your load.
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Do you have to Heat Treat the gears once you cut them? Can you do that with a torch?
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I wasn't planning on heat treating, I try to design stuff like that out. While a torch might work in the hands of somebody who knew what they were doing, I'd much rather use a heat treat oven. Since gears would be such a small load you might get a local heat treater to run them for free in the same load with a paying customer.
One note about published gear design guides. They add factor to factor to factor so your gear teeth wind up much stronger than they need to be if you add everything on. Remember that those design guides are intended to be used for things that are going to operate for millions of cycles and both the designer and operator need to worry about getting sued if something breaks. So they tend to give answers that are over designed for our application