re-form the fuel tank

has anyone any experience of making their plastic fuel cell change shape at all? i'm hoping to make some changes that'll mean that i just want to press in the bumpy bits a little that are situated under the rad flaps near the leading edge of the tank.

i may have mentioned this on the old site.

regards

Taffy

i've heard of folks filling the tanks with boiling hot water and some air pressure to gently expand them. not sure if thats what you mean or not, but its supposed to be good for an extra 1/4-1/2 gallons most times

cheers ammo!

yes and even done it myself but it is meant for alloy tanks IMhubleO.

i will put exhaust fumes through the tank for 20 minutes and then use some form of heat and an iron.

see how it goes.

regards

Taffy

Taffy

I may be (well Ok I am) a bit slow on the up take and I don't really understand the banter above. However heres what I think......

If you want to increase the volume of a plastic tank then doing what Ammo says works well. This is needed in Sidecarcross as the current crop of single 700cc 2-strokes drink the go-go juice very fast. We just fill the tanks with boiling water, screw on a fuel cap with no breather and shake vigerously, the water heats the trapped air and pressure is generated all by itself. (Warning this is dangerous and should only be attempted by idiots)

However on a plastic tank this would be no good for pushing in the "bumpy bits". Hot water doesn't make the tank very pliable, it is mostly the pressure from the trapped and heated air, which gets quite high, that does the work. But a hot air gun (paint stripper) does make the tank reasonably pliable, but can also burn it, the best way is to heat it from a distance for a long time not close for a short time......... The kitchen oven is also good for this set to about 200 degrees but will make the whole tank floppy at once.

If you are trying to alter the form of a fabricated aluminium tank I think that it would be best done cold and annealed. Altering the shape of aluminium at raised temperatures can seriously affect the grain structure for the worst. The easiest way to anneal aluminium is to smear the outer surface with washing up liquid, green stuff, and heat the aluminium from the other side to the washing up liquid until it just goes brown, remove the heat and allow to cool as slowly as possible. This will anneal the aluminium to its softest state, I would then cold form it, annealing in stages if needed. To heat it I would wrap the tank in loft insulation as thick as possible and blow a blow torch flame through the cap, but not on the metal i.e. just heating the air internally. Aluminium doesn't have an enormous heat capacity, that is to say it doesn't need much energy to heat up a given volume, what it does have is excellent conductivity so if you try to heat a lump of it up in air it conducts the heat to all of its surfaces and looses it to the air. But if you isolate it thermally you will raise it to annealing temperature easily.

What sort of tank is it, Plastic or Ally?

Ben
JBSracing

it's the standard plastic tank. i've got a little project underway that means i can remove the radiator sidepanels but there are bumps on the tank that snag at the inside edge of your knees.

good acvice and still useable.

cheers

Taffy

Taffy,
As mentioned by JBS, a hot air gun is THE tool to use for moderate area mods on plastic tanks. I just installed Berg's original 1 gallon aux tank just behind the shock and could NOT have installed it without the ability to mold several areas by heat. I actually changed several long edges and corners substantially to allow it to fit the frame perfectly.

You can tell when the plastic is ready to mold (move) by when it turns from a fairly flat finish to a glossy finish....then you can change it's shape quite a bit. Anywhere I wanted to make a concave "blister", I would heat that area just as per above and then use the round end of a ball peen hammer to make the indentation.

remember, you must hold the plastic in your new desired shape for several minutes while the plastic cools down. If you remove the molding object too soon (the hammer in my example), the plastic can spring back. If you reheat the plastic again, the shape will return almost to it's "pre heated" condition (plastic memory), and you'd then have to start over.

As JBS mentioned, you also want to make sure you are not too close or you will bubble/burn the plastic. So, if you notice any bubbles forming, you are too close! I use a heavy duty "Master Heat Gun" capable of 750F to 1000F, but only use the cooler setting and stay back 4" to 6" while continuously moving in a small circle or waving back and forth a few inches. Any closer than 4" inshes or so and even the cooler 750F setting will bubble/burn the plastic. Remember, since plastic is actually a good heat insulator, it will take some time to bring it up to temp before it is sufficiently pliable. Bring the plastic surface temp up too fast and will you burn the top layer/s while the larger mass below remains relatively cool and undisturbed. When heating plastic, the key is "the slower the better".

great advice rustie and i'mn printing it off. ready to go!

Taffy

http://www.omeromoto.com/special_parts.htm

some interesting radiators here that drop well below the level of the exhausts it appears. the frame we've seen before. tha alloy tanks aren't cheap but they're not silly either. they do two sizes at 6.2 and 7.2 litres.

regards

Taffy