Plastic Welding Fuel Tank - Does This Sound Reasonable?

[JamesLumley 4]

I've been looking into various options for the rally car fuel tank.

 

Option 1: Whilst a fuel cell would be the ideal scenario, funds would currently be better spent elsewhere. (this starts around £400 for an ATL tank) plus all the fancy fittings.

 

Option 2: Custom 30L alloy tank which will cost around £250 (fitted with a gauge and all the required fittings) This would mount in the rear seat well recess (cut out to get as low down as possible) and then necessitate the fabrication of a steel box around the tank (as it can't be exposed within the passenger compartment). This means adding additional weight to the car plus the question of how to fill it up in service ie. do you want to be climbing into the back of the car through the roll cage with a full jerry can every stage - even with a splash well around the filler... and a funnel, the potential to get petrol on the seats/ intercom/electrics/extinguisher etc is all pretty high.

 

Option 3 is to keep the std tank unmodified and continue using the current external tank guards. (Fuel surge is not an issue due to the separate swirl pot)

 

Option 4 is to cut the std tank in half and have it plastic welded back up. (see pics below) This means I can use just half the current tank guard (saving weight), no additional steel box required as tank is outside the pasenger compartment (saving more weight) and there is then room to mount the 4 fuel pumps and swirl pot under the car (making more space in the engine bay) Even the std fuel sender can be maintained.

 

New tank capacity is reduced from 50 to 30 litres so still large enough for long stages (even when we average <4mpg)

 

I've found a plastic welding company who will do the work for between £150-200 (with a guarantee against leakages) Does that sound reasonable?

 

There might be other companies who do this sort of thing (where I can get it done cheaper) but the idea of a guarantee/warranty seems attractive as this isn't the sort of thing you want breaking mid-stage!

 

Interested to hear other peoples thoughts

 

 

[EdCherry 34 1 Cars]

I likey the last idea the most, but thats just because I always thing having the fuel tanks in the compartment is kinda stupid, although surely it would be worth keeping the fuel tank guard if your relocating the swirl pots and pumps to where a bit of the tank used to be?

[Redtop 14 2 Cars]

1st, I wouldn't trust that fuel tank if it was plastic welded. 2nd, check your rally regulations. I thought you are supposed to have a firewall/bulkhead between the driver/co driver and the fuel tank? You may be able to use it behind the back seats if it has an external breather, but still I wouldn't like it in there with me. One with a bag + metal surounding [can be a painfully slow filler] with an external breather might be ok or a double skin one, but again check the regs.

[swordfish210 20]

1st, I wouldn't trust that fuel tank if it was plastic welded.

 

Whats wrong with plastic welding

[steve@cornwall 100]

Whats wrong with plastic welding

 

 

I don't know anything about plastic welding, but wouldn't 30l of fuel + tank guard all on the driver's side upset the car's balance?

[EdCherry 34 1 Cars]

well the car isnt really balanced that well anyway if you think about it, driver, and the engine all on the right hand side pretty much. I think by cutting part of the drivers side tank off and welding it up so its closer to the centre of the car would be a better choice.

[JamesLumley 4]

2nd, check your rally regulations. I thought you are supposed to have a firewall/bulkhead between the driver/co driver and the fuel tank? You may be able to use it behind the back seats if it has an external breather, but still I wouldn't like it in there with me. One with a bag + metal surounding [can be a painfully slow filler] with an external breather might be ok or a double skin one, but again check the regs.

 

Hence why I mentioned the need to fabricate a metal box around it!

 

Don't worry about the weight distribution, I have a battery, accusump and 2 extinguishers to find a home for so it's easy enough to get the corner weighting right. I have the added bonus of a slightly rotunned co-driver (don't tell him I said that!) to balance it out!

 

Does anyone who criticises plastic welding actually know about it or just the usual speculation from "internet experts".

 

There are plenty of industrial companies who specialise in this service so I can't believe they're all still in business if the process doesn't work!

 

I'm happy to rule this method out if there is any substantiated evidence that it isn't safe.

[swordfish210 20]

I don't know anything about plastic welding

 

http://en.wikipedia.org/wiki/Plastic_welding

 

all you need to know

[steve@cornwall 100]

http://en.wikipedia.org/wiki/Plastic_welding

 

all you need to know

 

Similar to me using a soldering iron to fuse cracked plastic aquarium external filters then! It's the only way to make a repair that withstands the water pressure . As such I would imagine it's fine - as with a continuous weld on metal it is often stronger than the surrounding original material

[Sam 4]

Colin Satchell does alloy tanks that go in the standard position but are half the size as far as I know. Maybe worth a phone call.

[maxirallye 2]

Is it worth it? The standard set up works well, particularly if you have already solved surge issues. If you a looking for a small weight saving, surly you will have to add this back elswwhere, along with a couple of hundred other kilos to meet the 1000KG weight limit?

 

Tony.

[Dj_mini 7]

This is my tank it sits in the standard place and uses the standard filler neck. Iv got two standard pumps in there one pumps out of the main tank in to a small bowel then the second pump sits in the bowel inside the main tank to feed the engine so stops surge.

This set up id only expect to cost £150 - £200 so it could be a better a better option for you?

Cheers Dan

 

[cir287 0]

we used to have a 205 one make championship here in Ireland, I reckon every car out there had the fuel tank cut in half and a blank welded on the end. not sure who did the plastic welding but I never heard of one leaking. it also meant that no mods were needed to mount it. It actually worked very well.

this was "acceptable" in the regs at the time but if you are going rallying I'd check the regs first, they may well call for a fuel cell and as you've found out they are a bit pricey.

[NeilGTi85 5]

I currently work for a Plastic Pipe Pre-Fabrication Buisness where we stick pipe to pipe basiclly for cold & hot water services. size's ranging from 15-250mm pipe, holding massive presure's under massive temps and they are garenteed for around 25 years.

 

Plastic welding is very safe if done properly