Sunday, August 09, 2009

Cut and Drilled Rail Mounts, Drill Frame for Rails

Today I cut and drilled the rail mounts that elevate the center leg rails from the bottom of the frame, and I drilled the frame itself to secure the center leg rails. I'll explain what the deal is with the rail mounts below.

First up, cutting a couple of 4.25"x1.5"x0.5" pieces of plywood. One of these will sit under each of of the center leg rails.

I spent a lot of time centering the center leg, both front-to-back and left-to-right. For my droid, it's 5-3/16" between the vertical planks and the edge of the leg on each side. Front to back, it's 2-31/32" between the cutout of the frame and the front and back faces of the center leg.

After I measured and marked where the blocks should be in relation to the rails, I clamped a block under one end of the rails, and drilled the holes, using the holes in the rails as a template.

Once all four holes were drilled, the blocks are held on with 5/16" bolts.

Finally, the scary part, drilling the frame. I remeasured everything to ensure the center leg was centered within the frame, as I clamped the blocks and rails in place. When everything was secured, it was time to drill the 5/16" holes.

T-nuts will be inserted into the bottom of the frame for these bolts to screw into. I have decided that I'll countersink them ever so slightly, to avoid having the skirt mounts run into them.

Okay, so what's up with those blocks under the rails? I have them on droid #1 also. Why? Because I blindly copied what Mike Senna did. This time, I at least questioned them. It turns out that using these blocks actually causes the location of the tip of the center ankle to be a bit too high, by almost exactly the 1/2" that the blocks raise them. Why would this be desirable, you (and I) ask?

I recently asked Mike about this. He said he did it so that the tips of all three legs would be pretty much aligned, making it easier to perform droid maintenance for those times that the droid must be tilted straight up. If the center leg were mounted to specification, having the droid stand straight up would cause it to stand on only the center leg, and the two outer legs would dangle. By raising the center leg 1/2", the tips of all three ankles pretty much line up.

I even was able to peer through all three ankle bolt holes, they were in a straight line. If I ever change my mind, I can always remove the blocks.

After staring at one droid in my house these last few years, this just looks plain weird to me.

I'm not as close to really being on three legs as it would appear. I still need to drill and pin the pipes together, I need to cut a permanent vertical rail to control R2's lean, and I need to cut down the U-bolt that goes around the outer pipe and through the vertical rail. Still, it's getting a little closer.

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