9 Aug 2006 tbenedict   » (Master)

Another big thanks to Botnerd for certifying me as a Journeyman. I appreciate it.

Update on the ROV: I fabricated the plexiglass motor mount, got the motors fitted, wired up the tether and the control panel, and would've finished except it was late (10pm) I had to get up early for work (6am) and I had no #8 screws to mount the terminal strip for power distribution (RATS!)

The frame fabrication went great. Seriously low-tech, but here's the deal: I drew the ROV up in Rhino3D (very nice 3D modeling and CAD package), converted the frame to a flat 2D shape, and printed it 1:1. The printout was stuck to a sheet of plexiglass using Super77 adhesive. The trick is to spray the paper with a thin coat and let it sit long enough to get tacky. The idea is to wind up with the consistancy of a Post-It. Once stuck on the plexi it was time to cut.

Holes came first. I used normal twist drills. With light pressure at the bottom of the hole you can avoid most chip-out problems, but overheating was an issue. At one point I made some spade drills for drilling plexi, but didn't have one in this size. All the holes were drilled to take a #8-32 tap. I didn't wind up tapping any, but that way if I want secure threaded anchor points for ballast, I've got them.

The shape itself was cut out on a scroll saw. I used too aggressive a blade, so I got some chipping. A finer skip-tooth blade with reversed teeth on the bottom would've been better. I even have them, so I'm kicking myself. But not hard. It's a prototype.

The 3D forming was done using a heat gun and a wooden form. My "form" consisted of a bunch of 2x4 and 2x2 lumber and some quickclamps. Cheesy, but I got nice 90-degree bends in the plexi. Only problem is the wood surface isn't smooth and now I have wood grain patterns on my plexi. Ah well.

The frame itself came out great and the motors zip-tied right into place. Wiring the umbilical was a snap, and with all the holes in the plexi there were plenty of places to anchor the motor mount into the ROV frame.

Only thing left is power. Then it's time to test!

Tom

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