Saturday, May 05, 2012

R2LA Build Day - May 2012

Droid #2 was head over heels for today's R2LA Build Day.

Mike Senna hosted a build day at his house, and I had two things I wanted to work on.

First, I needed to route out some material in the base of the new R5-D4 dome I recently ordered and received.  Second, I wanted to work on finishing up the drivetrains for droid #2 (hence the reason he was upside down; I needed to remove the feet and partially finished drivetrains to attach the motor mounts).  The R5 dome's base needs routing to allow clearance for the Rockler bearing, upon which it will spin.

At least 20 builders and a few droids were in attendance.  Marc Verdiell demonstrated his impressive droid, including the 2-3-2 transition.

In the meantime, my first order of business was to work on the R5 dome. Since none of us were sure if the base of the R5 dome was hollow, or what even it was made of, I took a "core sample" with a thin drill bit.

We're still not sure exactly what the base ring is made from, but it was solid, and possibly a resin or epoxy material. The key fact it is that it is flat, wide, and needs to be trimmed down so the Rockler bearing can fit inside the dome.

William Miyamoto worked out a way to use Mike's router to trim material from the base ring. In involved drilling three holes in a sheet of 3/4" plywood - one hole for the router bit, and the other two for a couple of segments of 1/2" diameter scrap steel rods that are used as stops. (William and I actually went shopping for a trim router, but Harbor Freight was out of stock on the cheapies, and I didn't feel like spending $140.00 at OSH.)

The stops are inserted like pegs into the 3/4" plywood. To make sure they don't lean or topple over, they are backed by some scrap wood that is clamped down.

Finally, the dome is put down, with the router bit hiding underneath. Initially the router bit is toward the middle of the inside of the dome, but as I slide the dome away from me and up against the posts, the router bit starts routing out material from the base ring as I spin the dome in place. The key is to locate the two steel posts in the proper location. The array of builders films and photographs my potential disaster.

So far, so good on the first pass. The router took out a small amount of material, which is good for the first pass

With a lot more help from William, I made five more passes with the router. We moved one of the steel stops back a little farther for each pass by drilling a new hole location for it, until the circle was routed large enough for the Rockler bearing to fit inside.

However, I'm not quite done. I need to go back to Mike's again tomorrow and repeat today's steps, with the router bit raised a little higher. This will allow vertical clearance for the Rockler bearing.

It turns out that if we raised the bit high enough for vertical clearance for the Rockler bearing on the first set of passes, bottom of the router bit cleared the bottom of the R5 dome's base, leaving a lip of material at the bottom. So another set of passes needs to be done with the router bit slightly higher, now that the bottom part of the base ring has been routed out. That should go a lot more quickly.

I never did have time to work on the drivetrain. Hopefully I can get to that in the not-too-distant future.

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