Sunday, December 21, 2008

Drivetrain Work Resumes

A very busy day at Mike's today, working on lots of details for the drivetrains.

The first order of business was to cut a piece of aluminum tube that I had ordered, to match the five other tubes we had already cut. This tube replaces the sixth one we cut during the tutorial DVD shoot, as that one had one of the axle holes drilled slightly out of alignment.

Ho ho ho!

Mike drilled a series of overlapping adjacent holes to allow the band saw blade enough room to get into a slot for cutting the bottom wheel area out.

While Mike was busy with the aluminum tube, I kept busy cutting many, many bushings down to size. There are 3 droids x 2 feet per droid x 4 bushings per foot = 24 bushings to cut down. Mike had already cut several of these before I arrived, but there were plenty left to cut.

Once Mike was done cutting the tube, he drilled the holes for the axels.

The hole saw leaves a small ridge on the inside of the tube, so I filed all of these down smooth.

Mike pressed the bushings in with a vise. A block of wood is inserted in the tube to prevent the tube from caving in as the vise squeezes the bushings in.

Pressing the bushings in can narrow the inner diameter very slightly. Running a 1/2" drill bit through them and polishing the inside with a small Dremel drum sander widens them just right.

The wheels we are using are just slightly too wide to fit in the aluminum tube. Mike and I tried using the bench grinder to slim them down, but we found the rubber was melting into the grinding wheel.

Mike got the idea of using his router with the bit set low, and ran the wheel along the tip of the router bit to shave down the high areas. A horseshoe acts as a router plate. That worked quite well, actually.

Mike and I cut the Delrin rings down to size with the band saw. These go in the wheel and have a keyway cut into them, as do the axels that go inside the Delrin rings.

The last item of business for the day was to insert the Delrin rings into the wheels.

That's it for now. The next time we get together we'll cut the keyways into the gears. After that, it's on to the chain and tensioning gear, and some holes for the motor mounts and channels need to be drilled.


cris said...

what kind of sawblades is mike using in his power saws to cut through the aluminum?

Victor Franco said...


I'm pretty sure Mike had a bi-metal carbide blade, but it might be best to verify with him. I can send him an e-mail, or try to remember to ask him in person when I see him for this Saturday's R2LA build day.