go kart gas tank

[Tisdelski]

hi guys, i need to make a new tank for my friends vintage kart, it needs to be chromed when finished. the center of the tank is flat, its roughly 9in x9in , its about 3in. deep with a 3/4in flange.
i`m thinking of making this in two pieces (inner and outer) like the original. the center portion is flat. my plan is to ; make flexible patterns, stretch the center, tuck shrink the outside edges and then tip the flanges on the bead roller. if anyone has any other ideas on how to make this please post. thanks gary

[anders nørgaard]

Hi Gary,

I think I'd do it the way you suggested... or use copper, make a simple press form and press the shape (assuming that the 3" depth is total). Copper is softer than steel, can be soldered easily and takes chrome well

[Tony Sanchez]

--Gary, make a good hardwood hammer form and try stretching some sheet steel to a three inch depth. After you complete the stretch your flange will be there. If you need some drawing quality 19 ga sheet metal I'll send you some.
---Tony.

[Tisdelski]

hi guys, thanks for the ideas.
anders; my friend wants to do it in steel like the original. when you say make a press form i`m guessing you mean out of wood? i have virtually no wood working skills, but i do have a saw and a router.

tony; if i was to make a hammer form what would it consist of ? i`m guessing two pieces that hold the flange and then you beat the stretch in the center as the flange is being held? i`ve never made a hammer form or a press form , so if i go either one of these routes it will be a good learning experience.

gary

[anders nørgaard]

Hi Gary,

If steel is what he want's then steel is what it'll be <LOL>
Yes, I did mean a wooden form! Take some pieces of plywood and a sabresaw. Cut the shape of the tank. You said you have a router. Shape the outside of the male part with the router, to fit the shape of the radiused edges and corners of the tank. Put the sheet between the 2 female parts of the form. Assemble the two female parts using screws and place the male part in the "hole" of one of the female parts. Then press till depth of tank half is obtained. Take the form apart, cut the flange to wanted size and one half of the tank is done!

[bobadame]

It's a pretty deep draw. I think I'd make a form from mdf or Bondo.

Then make a strip that would go around the circumfrence of the form and half way up the radius. Bend the short flange at the base and then work the band around the form stretching the flange at the corners.

Weld the ends together. Hammer form it up around the radius. Then a flat top that would be formed half way down the radius to meet the strip. Then trim the two pieces to fit together. Then tack weld and tig weld together.

Or you could make the top and sides from a single piece omitting the corners. Bend the flanges 90 degrees then bend the sides down over the form. Then all you have to fight with is the rounded corners.

[Tony Sanchez]

http://www.metalmeet.com/photopost/data/3108medium/18bacaruda_063.jpg---Gary,
Cut your hammer form from a piece of oak about 14" square. Cut a hole in the center of the hammer form the size of the gas tank (less flange). The more radius that you have in the corners the easier the stretch. Put a 1/4" radius on the inner edge of the hammer form. Now make your clamping piece from some plywood or mdf, 14" square and cut out the center hole about 1/4" larger than the hammer form. Sandwich a piece of sheet metal between the hammer form and the clamping piece and clamp securly. Start hammering and stretching the metal. After you get the depth that you want remove the metal piece and cut your flange.
---Tony.http://www.metalmeet.com/photopost/data/3108medium/18bacaruda_063.jpg

[Tony Sanchez]

---Gary,
Here is a photo that may help explain what I wrote.

http://www.metalmeet.com/photopost/data/3108/medium/18bacaruda_063.jpg

[Tisdelski]

hi guys,
bob, how would a mdf or bondo hammerform look compared to a wooden one?

tony and anders, will i be able to stretch 3 in. ? that seems like a lot. if i was to stretch it this far i`m assuming that this is exactly the purpose of dq. steel. would regular cold roll stretch this much?
thanks for the response guys . gary

[anders nørgaard]

Gary,

In a press form... how do you think the original tank was made? <grin>
Cold rolled... yes you can

[Tony Sanchez]

---Gary,
One of the reasons that I said to start with a 16" metal blank is that during the stretch some of the metal is going to be drawn from the flange area into the stretch area. On some hammer form work you may drill holes and bolt the hammer form and the metal togeather. In this case it would be best to clamp every thing together so that metal can be drawn into the stretch area.
This is exactly what drawing quality sheet steel is for. Try some regular cold rolled it will probably stretch and draw 3 inches. If you need some DQ I'll send you a couple of 16" squares.
---Tony.

[Tisdelski]

hi tony, i think i`ll take you up on your offer to send some dq. . just tell me what i owe you so i can pay up. thanks gary
p. s. this is not a huge rush, ship it when your going that direction

[Tony Sanchez]

Garry, If 16x16 inch squares are all right, I'll send you some on Monday.
Tony.

[Tisdelski]

that would be great! thanks tony