Friday, April 9, 2010
The arms were made from the same size pipe as the legs, but needed a significantly more aggressive curve coming out from the shoulder. I marked up the 12,2,and 10 o'clock line as I did with the legs, but placed the cut lines closer in the are with the tightest curve. When I cut the 300 degree segments, I cut them wider by using the 2.5mm wheel, and making distinct V cuts, instead of simple straight cuts. The cut, but not bent, arms are shown on the welding table.
The welding table will be the subject of a page in the future, I'm rather pleased with how it turned out.
A closeup of the cuts showing the V cuts in the 300 degree segment. As I bent the pipe I had to tweak these cuts here and there to get the tighter curve for the upper arm.
As with the legs, I omitted to photograph the welding process, but it basically was grind out the cuts to remove the surface rust, then weld the cuts closed, and fill the open cut on the 60 degree segment cuts. The welded arms are seen laying on the ground in the last photo in the legs pages.
Now to make the shoulder/arm joints...
These shapes were made in the 4mm sheet I'd used everywhere else. The one on the left is the ellipse shape to match the arm pipe when cut at 45 degrees, the one on the right was welded into the shoulder joint (see the body page for this). The central bolt will be used for retaining the arm, and the smaller bolt will engage with one of the eight radial holes to lock the arm in one of eight positions. The photo shows the nuts I used to hold the bolt heads in place until they were welded in place from the back.
The above photo shows the ellipse plate welded to the arm pipe. I cut the arm at 45 degrees and then tack-welded the ellipse plate in place before grinding the closer fit, and then finishing the weld.
How did I mark the 45 degree cut on a the curved pipe? - A trick I read about used by blacksmiths was employed. I filled one of the quench buckets near the door with water to the brim, then carefully laid the pipe into the surface of the water so the waterline would mark the 45 degree line. Then I removed the pipe and highlighted the line with engineer's chalk. - The original blacksmith trick used coal dust floating on the water's surface to mark the line, but the rust on the pipe showed the line for me.
The "nut" on the central bolt was whipped up by welding a short length of 3/4" pipe to the nut, and then slotting the end for a scrap of sheet. A few tack welds and I have a long-reach wing-nut.
The photo below shows the wing-nut being used from inside the body to hold the arm in place at the shoulder joint.
A progress photo of the arms and legs attached. The arms were later shortened since I had deliberately made them longer than needed until I finalised the design for Bender's hands.
Next... Grabby and Squeezy - a.k.a Bender's hands