Plastic inner tanks?

Carbonfibre · May 16, 2011

As it seems affordable GRP tanks are pretty much finished commercially now, I wonder if HDPE plastic inner tanks to fit within either OE GRP tank shells, or under custom made alloy shrouds, would be of any interest?

Cost wise the HDPE inner would be every reasonable, and would be perfectly ok with Efuels. Only downsides would be that fuel capacity would be reduced a little, and obviously appearance of the underside would not be the same.

Tintin · May 16, 2011

Carbonfibre said:
As it seems affordable GRP tanks are pretty much finished commercially now, I wonder if HDPE plastic inner tanks to fit within either OE GRP tank shells, or under custom made alloy shrouds, would be of any interest?

I generally like the idea but have some doubts about its implementation. The two GRP roadster tanks I have on the shelf appear to be pretty different internally - hardly surprising as they were most likely done in wet hand lay-up with relatively cheap and thick materials. An HDPE tank (in terms of a rigid structure) that would suit all tanks will be very, very limited in volume. Judging by the numbers these tanks sell in I guess a FKM-bladder would be competitive despite the higher material cost and more versatile.

Tim

Brithit · May 16, 2011

I'd go for something like that if it was available, and the $$$ wasn't too high.

geo46er · May 16, 2011

Hi CF,
I used to work in a factory that made rotationally molded plastic parts, I wonder if a gas tank could be mounted on such a machine. Unfortunately there is a good deal of heat involved which would probably damage paint, but maybe it would work with unpainted tanks. Another possibility would be to inject pre-melted plastic into the tank as it rotates.

GB

Carbonfibre · May 16, 2011

The idea is for a completely new HDPE plastic tank a little smaller than the OE GRP ones, so it will fit underneath an original tank, which has had the bottom removed to allow this. Capacity is going to be a little less, but maybe its an idea which would appeal to anyone with a GRP tank which is cosmetically fine, but is concerned over the fact that before long its likely to start leaking?

DavidT · May 16, 2011

I'm failing to see the point - surely the tooling costs of making an inner tank would be the same as making a replica (or a reasonable copy)? I looked into getting a larger plastic tank for my Hypermotard which, although hidden, is a very complex shape and is only ever going to be produced in small numbers. The price wasn't outrageous. Have a look at these..

http://www.ca-cycleworks.com/products/t ... -fuel-tank

Personally, I would rather buy a good quality part that fits properly even if it's not an exact replica.

David

swooshdave · May 16, 2011

http://www.clarkemfg.com/

These folks have been around forEVER. I have an old fiberglass Triumph tank made by them, since about the time I was born. Plus they are close by.

If there was a reasonable demand I bet they could make a Roaster replica tank for a acceptable cost.

Carbonfibre · May 16, 2011

Would users be happy with plastic tanks in the natural as moulded state, or is painting likely to be required? Main reason I mentioned using the original rotten GRP tank as a shroud over the plastic, is there would be no need for painting, and this would be quite a saving.

Tintin · May 17, 2011

Carbonfibre said:
Would users be happy with plastic tanks in the natural as moulded state, or is painting likely to be required? Main reason I mentioned using the original rotten GRP tank as a shroud over the plastic, is there would be no need for painting, and this would be quite a saving.

Painting a HDPE tank is a major PITA and definitely needs large production runs to make it cost efficient. Unpainted HDPE tanks are deteriorated by UV light and so soft that you can mark them with a fingernail. Foils don't work well etc. Na, not that appealing ....

I'd propose something else: Take a mould from a GRP tank and use a pre-formed soft HDPE liner as an inner bladder for a properly constructed new GRP tank. If it is done correctly the bladder can be used to compact the laminate by being appropriately pressurized. Lots of possibilities worth the effort over reusing the old GRP stuff.

Tim

Carbonfibre · May 17, 2011

Plastic tanks can be painted no problem, if this requirement is taken into account during the production process. However painting is going to add quite considerably to the cost, and means an HDPE tank is a not less attractive commercially. Natural unpainted HDPE tanks have been widely used on dirt bikes for many years, and as far as I know are not affected by UV and certainly dont mark easily.

Making GRP tanks which are fully resistant to all commonly used pump fuels is something that is pretty straight forward, but due to many producers continuing to make composite tanks which are effected by Efuels. I get the feeling that very few end users would want to buy a GRP tank now, and even less sure they would want to buy new GRP tanks with HDPE bladders, which would cost considerably more than a new Asian steel tank.

Cheesy · May 17, 2011

Carbonfibre said:
Plastic tanks can be painted no problem, if this requirement is taken into account during the production process. However painting is going to add quite considerably to the cost, and means an HDPE tank is a not less attractive commercially. Natural unpainted HDPE tanks have been widely used on dirt bikes for many years, and as far as I know are not affected by UV and certainly dont mark easily.

Making GRP tanks which are fully resistant to all commonly used pump fuels is something that is pretty straight forward, but due to many producers continuing to make composite tanks which are effected by Efuels. I get the feeling that very few end users would want to buy a GRP tank now, and even less sure they would want to buy new GRP tanks with HDPE bladders, which would cost considerably more than a new Asian steel tank.

They do mark easily, lighter colours also discolour/stain easily, in addition to this they 'breath' so stickers/decals have a very short lifespan. Almost all dirt bikes now have the tank covered by radiator shrouds so some of these are not such a problem. UV resistance can be a massive problem with PE, if you were going to sell to NZ/Oz this would require some pretty serious testing.

Carbonfibre · May 17, 2011

Pretty much all of the tanks made for modern bikes are HDPE, either in natural as moulded finish with shrouds or for dirt bikes as is. If cosmetic appearance of an inner tank covered with a modified Norton GRP original tank is an issue, then its possible to paint HDPE no problem, but no real reason for this, as the GRP would be shrouding the HDPE fuel cell.

Plastic inner tanks?

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