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Sunday, June 29, 2008

Modified skin blocks

Well as I mentioned in a previous post, the skin blocks I received were not what I wanted for my droid. I want to remove my droid's skins without having to remove the legs.

So I came up with a technique where small 6/32 bolts would protrude through the front of the mounts so you can lay the skins over them and thread a small nut and lock washer over them tightened with a small wrench. This can easily be accomplished with the legs attached.

My first attempt was a lesson as I broke the tap off on my first try. And it was a bad break where I couldn't thread it back out. So the lesson taught me to drill out much of the back material of the skin mount so I wouldn't need to tap so deep. Because the 6 NC32 tap I used is pretty thin and breaks easy.

The first step is to re-drill the threaded holes in the skin mounting block with the drill bit that comes with the 6 NC 32 tap. Going all the way through the block shows you where to drill the material in the backside of the mount with your large drill bit. I think using cutting oil and a drill press is a must. The drill press insures a nice straight bore. And the depth gauge on my press gave me uniform depth which was nice.

After drilling at least 3/4 of the blocks back material, new threads were cut with the tap. And then I threaded 1/2" 6/32 bolts into the blocks. I used the small bolts that were in my vex robotics hardware. After threading them into the mounting blocks, I mixed up a batch of epoxy to pour over the heads of the bolts in the back. The epoxy is just extra insurance to keep them from moving at all while removing the nuts holding the skins. Probably overkill but it only took a few minutes and I had the epoxy on hand.

I drilled the holes in my skins and made the holes a little oversize so the bolt threads wouldn't be stressed out while removing and attaching the skins. The skins went on nice and the new setup looks similar to the original .040 screws. I'm glad I didn't use a thumbscrew as that would have looked more obvious.

Also I will only use the mounting blocks above and directly below the shoulder hub. The lower ones I don't feel need to be attached to the skins even though they will be on the frame.


Mike D. said...

Glad your back! I kept checking and wouldn't you know it, once I forget to check for a few days you post 3 new articles!

R2 is looking good, nice catch on the location of the mounting screws now instead of later.

One tip on tapping aluminum, it tends to be "gummy" so a good lubricant is a must on the tap. In a pinch I've used Ivory Soap but if you have a tool supply shop near, the correct tapping lube is better.

FloridaRobot (Jim) said...

Hey Mike ! Good hearing from you again. Yep, I used some tapping lube and it definitely helped.