Wednesday, July 13, 2011

Tank fab for GL1000

Tank build for GL1000.  The tank's shape looks simple from the outside, but its actually pretty tricky underneath. The tank Honda designed sat below the seat between the rear wheel and transmission case. That puts the center of gravity lower and to the rear (when it's filled), and protects the tank in the event of a crash between the frame rails.
I've thrown all that good design out and built one to sit where it usually does, on top of the frame between the rider's knees! I wanted to move the battery into the space where the old tank lived, just in front of the rear wheel and centered. The old tank is rusty and will kill the carburetors. 
As it stands

I expected A FEW leaks after welding up, but it was leaking like a sieve. I didn't bother to count.
Flux core TIG welding is very dirty. There are lots of pin holes and potentials for voids. This also has a lot to do with welding technique and prepping the weld areas correctly, but.. 

 
Filler Neck welded in

I'm grinding the welds down flat and laying another wider & hotter bead over them. So far this has filled any voids and killed leaks along the seams. I'm using pressurized air and soap to find pinholes, then grinding and laying a wide bead over the area. I don't think I could do such wide, flat beads with as much penetration if the first pass welds were not done. The top and bottom halves were shaped and tacked. Then the tacks were stitched together at the same heat, alternating sides to keep distortion low. All the tacks and stitches are hammered flat, then stress relieved. I did the tacking and stitching at the lowest heat with the wire feed a little higher than normal. Once all of the leaks are out and the pressure holds at 50PSI for a few hours, I'll etch the inside with a solution of phosphoric acid in water, dry it with MEK and use the liquid polymer liner to seal it. Then the outside will get smoothed/sanded and painted some color. 

1 comment:

toxonix said...

UPD:
The tank is now free of leaks, holds 120PSI air pressure steadily. I'm surprised that it didn't blow itself to pieces holding that much air. I'm etching the inside with some phosphoric acid in hot water for about 30 hours. Next I'll clean it out again it with MEK and pour in the tank liner.