I decided to cut my gas tank to lighten up a bit. It was  40lbs and after cutting it i expect it to be about 18lbs. A decent savings.

Started with this.

 

 

Then made a first exploratory cut. the Red line depotes where the second real cut was made.

 

So now i had to make an endtank for the ...tank.

looking at it its a gooft profile

I could have traced the ouyline on a flat peice of card or something and traced it onto something else. But i decided that sucked so i got some masking material and spread it on a sheet of stainless. Then i laid the end of the tank onto the mask and spraypainted around it. and so ended up wit a better...i think profile of the tank .

i cut that out and then started the grinding and fiting and grinding and fitting and grindeing etc etc etc etc. Below is halway fitted. i have one area that i cut too much out of but it should be able to form in.

Love that spray bomb template technique. You are full of useful tricks.

I assume this was a new tank. If not, what did you do to neutralize the gas remnants before cutting? Just filled it with water and then let it dry?

Bob

It is a used tank. I used a very thin cuttof wheel (1mm maybe) on a 4" angle grinder and didnt have any issues. I didnt clean it out till after i cut it but the tank had sat empty almost a year though. From what i have read its the heat from welding that really causes the problems with fumes. Even so we are going to back purge it when we weld it.

The guy that was supposed to weld it for me flaked. So i did it myself. I talked to a welder friend of mine and he told me the flux core woild work ok. after trying to chase down a helium tank i gave up and just washed it again then filled it almost to the top with water. I know the back of the stainless sugared but it wont flake of or anything so its cool.

 

I flipped it over and filled it up with water again and found a few very small seeps so i closed them up.

Then i pained it.

You might want to use something else to check for leaks. The surface tension of water is higher than gasoline I believe, so the gas might leak in places the water won't.

Re: backpurging, I have seen a shadetee mechanic pipe the exhaust from a car into an empty gas tank they were welding to prevent it exploding.