Looking for a vintage Gas tank

Discussion in 'Painting, Welding, Bending and Gas Tanks' started by scottyo, Apr 21, 2009.

  1. scottyo

    scottyo Member

    Hey Guys,

    Im wanting to fabricate a vintage, big tank similar to hillbilly's one here. One very similar to the kind on derringer bikes. Ive given up on finding a commercially availble one (unless you guys know where to find one) so is there any way to contruct a fiberglass or metal frame around the little 1/2 gallon tank taht comes with most engine kits?

    Im planning on using a firmstrong chief frame to copy the derringer/board track racer style. Im way too tall for a derringer or ridley or spooky tooth bike. The chief has an awkward super curved top bar so I want to sit a big gas tank down on top of it a bit to cover it up. It a stretch but I have the time, just need the know how advice.

  2. ocscully

    ocscully Member

    The tank that is used by Derringer is the General Moped 5-star Top Tank and is or was available from the good folks at Handy Bikes in Ohio http://www.handybikes.com You need to phone them to confirm that they have them as they are not listed on their web site. The tank from handybikes is only $50.00 the downside is that they dont have the clamp on flip cap they use. Also the fuel bung is threaded on the OD for a petcock but its a pretty simple operation to thread the ID for one of the inexpensive petcocks.

  3. wildwestrider

    wildwestrider Member

    I checked with Handy a few weeks back and they sold out earlier this year. They had a couple THOUSAND in stock......all gone now.
  4. SimpleSimon

    SimpleSimon Active Member

    is this the bike you have? http://3.bp.blogspot.com/_pX_MdfgBxgs/RggpjOpQ9fI/AAAAAAAAAN4/yEN23k1c2ug/s1600-h/Review1.jpg

    If so, I'd like to suggest a very straightforward process for making any odd shape you might desire. It's called foam/resin sculpture. Basically, you shape the desired tank in water soluble foam, then you fiberglass it. When that cures, dissolve the foam out, then do a secondary internal coating of the tank with oil proof epoxy gel, put your filler nech and petcock nipple in place and resin in.

    Voila, custom tank. Finishing the exterior is simply body filler and sanding to glass smooth finish, then primer and paint.
    Last edited: May 8, 2009
  5. wildwestrider

    wildwestrider Member



  6. SimpleSimon

    SimpleSimon Active Member

    Not offhand. I began doing this type of thing a long time before there were PC's, let alone the internet. I use foamed alginate - usually just sprayed into a box to make an appropriate sized starting block, then rough shape it to the desired 3D shape. When rough shaping alginate foam, wear a dust mask. Wood rasps and bread knives are great tools for the carving. Make your final object is approximately 1/8 inch smaller in all dimensions than your final finished tank will be (allowing for the fiberglass/resin/bondo).

    For tanks I always just glass the entire shape, then when it is cured I use a hole saw to cut the filler neck opening, and a drill bit for the petcock nipple.

    I know there are some tutorials out there, but I've never looked for them myself.
  7. wildwestrider

    wildwestrider Member

  8. skjjoe

    skjjoe Member

    where do you find foamed alginate?
  9. wildwestrider

    wildwestrider Member

    Yes, thats a good question, and is this something in a liquid form that you spray out....like the expanding foam product that you buy at Home Depot??

    Or, can you buy blocks of it somewhere then shape it?

  10. SimpleSimon

    SimpleSimon Active Member

    Alginate is a gum produced by seaweed. It is chemically extracted and modified in various ways for various purposes. The use most people are familiar with is making molds for dental impressions. I foam the alginate - sodium alginate - by mixing it in an old air driven agitator bucket and shooting it through a spray nozzle with a floccing tip, into an appropriate sized container. Usually I use a cardboard box lined with saran wrap.

    Pre-formed blocks of foamed alginate are almost certainly available from someone on the web, but I've no idea who - when I want a block, I make one. It is NOT an expanding foam - but that's an interesting point. Find out what the active ingredients are in such (many newer formulations are cellusose based), then what solvents will dissolve it once cured. As long as the solvent needed won't dissolve your resin in the fiberglass shell, you are good to go.

    Many years ago (still an undergrad) I wanted to make a thin skinned structural shell for a Subaru 360 powered trike I'd built. Fiberglass on polyurethane foam I knew about, but for a thin skin to be strong enough it needs to be curved and under a pre-tensioned load before curing. So, I talked with some guys, and one of them suggested using a stretch fabric for the matrix into which the epoxy resin would be introduced.

    It took some experimentation, but I built that shell out of resinated spandex. The tricky part was figuring out how to reinforce the larger sweeping curved portions without adding a lot of mass. T-pins are wonderful things.
  11. HoughMade

    HoughMade Guest

  12. HoughMade

    HoughMade Guest


    posted in the wrong place....oops
  13. sjackson

    sjackson Member

    you don't need to use foamed alginate. you can use almost any polyurethane foam. You can get the pink foam insulation from a hardware store and use that. Just tack it together with a couple dabs of wood glue (don't cover the whole surface or you'll have problems when you dissolve out the foam) and carve it from there. Rough out the shape with a hot knife made from an old dc power supply and piano wire and then smooth it out with sanding paper before laying glass. Then just melt out the foam with acetone or something similar. Remember, you'll need to have a way to mount the tank, a place to put a cap and a petcock as well.

    This is important though: make sure to use epoxy resin when fiberglassing. do not use polyester. the polyester resin will attack and melt the foam before you have a chance to put it all together. Epoxy resin is stronger stuff anyway. It costs a little more, but it's what you want to make a fuel tank out of in the first place.
  14. Junster

    Junster Member

    Have you looked on Ebay? There are lots of small used motorcycle tanks with a larger/deeper tunnel in the bottom. You'd have a cap and place for the petcock with a whole lot less work.
  15. sjackson

    sjackson Member

    I tried a 5-star general moped tank (derringer style) and it wouldn't fit on my frame. There was also no easy way to mount it. I looked at a lot of other used motorcycle and moped tanks and realized that no matter what I got I would need to do some work just to get the thing on the bike. Fabricating a tank is the only way to ensure I get exactly what I want, exactly how I want it to look.