The first order of business was to drill a 1/8" hole at the base of the shaft adapter. The hole needs to go through the thickest part of the motor shaft. The shaft adapter that Vince Sanchez provided already had a 1/16" hole drilled, so I simply had to hit that target with a 1/8" drill bit.
Looks about right to me.
Next, I rolled a 1/8" diameter, 3/4" long steel pin in some JB Weld and inserted it into the hole.
A few taps with the hammer, and it's in. I cleaned up the excess ooze.
Next, it was time to start attaching the dome drive wheel. The wheel fits onto the shaft adapter fairly snugly, but I wrapped a couple of layers of masking tape around the shaft adapter to ensure a tight fit.
I did one last test-fitting on the frame, to make sure that the wheel was at the proper height on the shaft adapter. The wheel does indeed clear the top of the frame, and hits the Rockler bearing just right.
Time to drill. The goal is to drill a 1/8" hole through the top half of the wheel, completely through the shaft adapter, and partially through the hub on the bottom side of the wheel. That's as far as my drill bit can reach!
I should have turned the wheel a bit more so that the drill bit would have shown through the "windows" in the hub, but this is fine.
I jammed some 1/8" steel rod into the hole. It looks like I may have to cut it down just a little...
The rod does indeed go through the shaft adapter, and into the hub on the other side. This is good, it will lock the wheel onto the shaft adapter.
I marked the spot at which to cut the rod. I'm actually cutting the rod just a hair short, so that it will fit completely inside the wheel; yet not so short that I can't pull it back out with needle nose pliers in the future, if need be.
Well, if I have to hack through steel, this is the kind I like.
I inserted the rod back into the wheel, and the fit looks good.
Of course, I couldn't go this far without trying it out on the frame with the Rockler bearing. I attached a 12 volt battery and gave it a spin.
So, the dome drive is almost complete. I will probably use the Dremel drum sander to flatten out the perimeter of the wheel, where it makes contact with the Rockler bearing, to give it a larger surface area of contact. I also need to attach the tension spring, and replace the connectors on the wires.
2 comments:
I never could get a drill bit to go through the shaft on the motor. I bought all the "high speed" bits at OSH and they all failed right away. The shaft on my Saturn motor was some kind of hardened steel.
Ended up taking the motor to a machine shop, they did the hole for free!
Russell
I am using a general purpose Black and Decker drill bit set that I bought somewhat at random years ago. Perhaps I lucked out.
I remember when I drilled the shaft adapters on the first droid, I was very concerned and had doubts about getting it right. For whatever reason, I've had a lot of success with the many times I've done this. Go figure.
-Victor
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