Friday, April 9, 2010

Grabby & Squeezy - Hands part 2

This page covers the shrouds of the hands, and fixing the hands to Bender's arms.

The shrouds are simple conical transitions. From my interests in model rocketry, I had a tool called VCP (Visual Centre of Pressure) which contains a simple little utility for generating the development of a conical transition on paper. I used the package to develop the template for the hand shroud using the arm diameter at one end, the flared diameter at the other end, and the length of the transition being set to the height I choose (83mm to match the arm diameter, but then padded the number out to 95 so I had room to adjust things during construction).
The resulting VCP printout was then cutout, and traced onto the colourbond offcut shown above.
I added some extra depth at the narrow end of the conical section for retaining tabs, and proceeded to cut out the shape.

The first shroud has been cut out, and rolled, the second one hasn't been cut yet. Rolling the colourbond would have been easy if I had some sliprolls, but I don't. I simply clamped some pipe to the benchtop, and pulled the colourbond piece through and manually forced the curve into the metal. I repeated the bending a few times to tighten the curve, then clamped, drilled, and pop-riveted the shroud together.

This picture shows the tabs I cut for retaining the shroud. Knowing the shroud can't move towards Bender's fingers due to the conical shape, I wanted to retain the rear of the shroud by pinching it in the wrist joint. I know if I'd measured and marked everything to the highest degree of accuracy, it wouldn't be necessary, but knowing my welding, the slightest warp would have betrayed the joint, it was easier to make the shroud retained against the joint for a seamless fit.

The photo above shows one shroud fitted to one hand, the second (right) as the two pieces. A small slot was ground into the wrist plate to provide clearance for the pop rivet. All rivets were beaten down flush with the sheetmetal to reduce the protrusion, then later tidied up with bog.

The hand is attached to the arm via the captive retaining bolt in the wrist plate. Prior to welding the spacer pipe into the plates, the bolt head was modified so a screwdriver could be used through the access hole to turn the bolt. The one bolt holds the hand in place, and positioning of the hand is accomplished by loosening the bolt, rotating the hand to a suitable angle, then re-tightening the bolt.

When the bolt is tight, the shroud to wrist seam disappears. There is a small step in the diameters at the seam, but that will be disguised when the painting occurs.

Since I was out of "Ole Fortran" beer, I had to make do with one of the drinks favoured in this area. The Lemon-Lime SOLO is a nice drink, and I can see why the guys in the workshop prefer it on hot days (Isn't that everyday around here?) I know I got addicted to them after one shutdown, so now I try and limit myself to only one can per day.

So what haven't I covered yet? Still to come; antenna, head, eyes, and then painting.

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