Fuel tank mounting

[Timberwolf]

Hi all, finally got the barn finished, roof on, wiring done and strat in, can now start some work on it, rather than just staring, pretending. As always with an inherited part built kit, a bit of tearing down is necessary, and it's been sat for a good while....

Anyhow, on removing the 'saddle' tanks I don't like how it is (or isn't) mounted. It has two ~6mm bolts (spout bolts..... :eek: ) in the upper holes to the chassis rail and then.........nothing else!!! must be 25kg when full, give it 0.75G through the corners and some ones gonna have a petrol bomb in their lap :eek:

From the build manual there should be a spigot in the bottom of the tank to locate in the lower chassis. The holes, complete with attendant grommets, are there but no spigots on the tanks :confused:

The tanks are steel, a good tight fit, with a threaded (very non sva) boss that sticks up through the body work with a turned knurled alloy cap. The fuel take offs have little brass taps on. Only thing is the tanks are a bit crudely made, gas welded, warped quite badly from the heat. Kit was made by hawk in 1989, has a red chassis. Are these tanks from the kit? or has someone fabbed them in the dim and distant past? And what's to be done about the mounting? Do they usually have such thin bolts? Are the spigots usually welded on when manufactured?? How thick/long?

This might be the start of a lot of posts........you have been warned! :)

[strat6v]

sounds to me like a home brewed setup. ally tanks were the usual supplied parts.

[Shaun II]

My circa 1987 alloy tanks have something like a 30mm length of alloy bar welded to the tank bottom, the top is fixed by two 6mm bolts and grommets. They have yet to be tested at more than 0.01G

Gerry once told me that alloy tanks were discontinued because of corrosion issues, possibly true or perhaps production costs. I lacquered mine and they have still started to corrode.

[Timberwolf]

Right then, I'll tart them up and put a spigot on the bottom for now. I've been wanting an excuse for going on a tig welding course for a while, or maybe some of those groovy riveted tanks as per Jag xk13... need some pour in sealer tho'.

I'll have to wash them out and conduct a 'controlled explosion' before welding. A friend had one of those old metal cans which he foolishly started to braze before getting rid of the fumes.... :eek: nearly wet himself!

[strat6v]

Route a pipe from your car exhaust into the tank and leave it running a bit. Supposed to work but i haven't tried it :confused:

[guy mayers]

Route a pipe from your car exhaust into the tank and leave it running a bit. Supposed to work but i haven't tried it :confused:


I have! :) :)

but I wasn't welding the tank afterwards! :p :p

(it works)

Guy

[John]

I've welded tanks before now by filling them with water upto the area you want to weld. works for filler necks but difficult if you want to weld low down.

[chris.richard]

They're not Hawk tanks.

[Arthur]

No idea about Hawk tanks.

But - you wanna weld to a tank? OK, then - dry it out first. Absolutely dry, no rust, no scale, nothing. Fill with water, flush a while with said water, then drain it again. Dry it again.
The problems really occur when you have internal pumps, pipes, filters, baffles, foam, etc - all those nasty little pockets which can trap petrol and release it later when you're not watching .... all those would have to go, or be adequately flushed out/removed/dried out.
Now you're ready to start. Leave the stick welder alone. Use MIG or TIG, and the clever bit is to put a TEE piece in torch the gas line. Lead a free pipe from the tee into the tank, and loosely pack cloth around the neck. Let it blow for a while before you start, and let it blow all the time you are welding (regular welders of Stainless will recognise the "backing gas" technique).
Use inert gas. Some of the low Co2 - filled Argons have an O2 component (my Coogar 5 has 1% Ox, for instance, but Coogar 25 would be fine) Pure Argon (TIG) would be better again. Don't use pub Co2 - it can chemically crack under the heat, yielding carbon and free oxygen.

Disclaimer - what we are trying to achieve here is zero hydrocarbon vapour, and an oxygen level below 11%, under which conditions ignition can not occur. Doing this professionally, I would use gas test meters to prove the hydrocarbons purged to zero (or a at least, less than 2% of LEL (lower explosive limit). We also reduce oxygen to less that 5%. Combustion cannot take place below 11%, so we go to 5% for a bit of additional padding.
If you choose to use the advice herein, you do so at your own risk. If you don't test the atmosphere, it's entirely your own lookout.
Incidentally, loss of limbs / self-disembowelling has been achieved welding to small, but relatively this section tanks. The resulting bang unfolds the steel with a very jagged edge at very high speed. FYI, this has also been achieved by an idiot trying to start a diesel engine by giving it a whiff of pure oxygen through a copper tube. The resulting bang split open the tube an whipped it about. Doesn't bear thinking about.

Oh yes - leaks in welded seams - you can indeed buy slushing compounds, or you can paint the seams in Loctite threadlock (the green stuff). It wicks up very well, expands, and seals. Worth a try, at any rate, and safer than welding.

Hope this is some use.
Arthur.

[chris.richard]

Oh yes - leaks in welded seams - you can indeed buy slushing compounds, or you can paint the seams in Loctite threadlock (the green stuff). It wicks up very well, expands, and seals. Worth a try, at any rate, and safer than welding.

Would this wheeze work for exhausts?

[John]

They're not Hawk tanks.

No indeed! They were Chevette tanks.( Putting another tank in the spare wheel well so that I could get as far as petrol on a road rally. 8mpg!)

[chris.richard]

No indeed! They were Chevette tanks.( Putting another tank in the spare wheel well so that I could get as far as petrol on a road rally. 8mpg!)

I was meaning Timberwolf's!

[Arthur]

Chris,

No, the Loctite seal won't work with exhausts. It burns out somewhere around 250 degrees C. (which is how you release threadlocked threads - just give them moderate heat with the torch, and the loctite turns to dust).

Arthur.

[Timberwolf]

Thanks for the very comprehensive advice Arthur! I have welded tanks before using the comprehensive washing out technique - using agricultural spray tank washing out detergents, works a treat. I'll be very careful in this case, self disemboweling is, I understand quite uncomfortable, and a very distinct possiblity with petrol fumes. Isn't petrol weight for weight more explosive than dynamite given the right circumstances? Can't remember where I got that nugget from!

Chris, you're very certain these aren't Hawk tanks, why? steel verses alloy?

I'm sure these tanks need some 'up dating', although they fit into the bodywork/chassis very snugly - they only just come out - they do need some lower support or I'll get metal fatigue very quickly. I'm going to suss out alloy tanks too, mainly for looks, the steel tanks aren't heavy, quite thin guage. But the black + Alloy look of the more expensive and tasteful of the classic cars is where I want to go. 'Quality lasts after the pain of expense fades' to paraphrase some one clever.

Something else..........I've read somewhere on here that you need to clearance one of the tanks during the twin cam to v6 24v swap. My chassis is a twink and I've got a 24v loitering with intent... :cool: Doing all the welding in a oner would be nice and then I've got a good pattern to work from to make the ally ones from.

Anyone any practical info on rivetted alloy tanks? how is the seam best sealed? or maybe a bladder inside is the best way to go? Tig course is on whilst i'm abroad :( .

[SUSIT]

Morning,
I had a tank made to my specification by a chap in Wales, SMS engineering.
Alloy & Foam filled (I supplied the foam) holds 56 litre and is a real ackward shape. The welding is some of the best I have seen. Inc post etc it cost £215. I made a carboard model and sent that down with some drawings of critical measurements.
For the cost involved I dont think its worth trying to do yourself, my IMHO.

Chris Smith is also able to get componets made in Alloy at good price's and quality

[Timberwolf]

Nice Tank! is that for a corse?

I'll have to weigh up the pro's and cons of a diy route, pro's might be: increase in personal skills, personal satisfaction and perversely the frustration (which is when you actually learn), cheap. Cons - also the frustration, Poss leaky tank, time involved in making the mkI II & III until it looks 'right', cost of scrap.

We have some wonderful SME engineering over here due to the nuclear industry, I'll drag the old tanks around and get some quotes.

Are the aston and monza type tank lids sva compliant?

[SUSIT]

Nice Tank! is that for a corse?

I'll have to weigh up the pro's and cons of a diy route, pro's might be: increase in personal skills, personal satisfaction and perversely the frustration (which is when you actually learn), cheap. Cons - also the frustration, Poss leaky tank, time involved in making the mkI II & III until it looks 'right', cost of scrap.

We have some wonderful SME engineering over here due to the nuclear industry, I'll drag the old tanks around and get some quotes.

Are the aston and monza type tank lids sva compliant?


Almost, its for my Allora. In the accident that I had with the car the Right hand tank in the original Stratos location became ruptured in two places, first by being bent and second by being pushed in to the altanator which acts as a great angle grinder on alloy.
As a result of that I wont compete in rallies with the tanks in the original location and would ensure the tanks are foam filled even if I was only using the car for road use.
They can be retro filled. Chris R has done so and Sando had his foam filled when they were modified to fit his 24 valve Kappa engine.

Cant help on the SVA thing - anyone else?

[Timberwolf]

hmmmmm. All interesting stuff this, and it's just the first queery.

I can understand the fear of tank rupture, crashed my old beach buggy a few years back - rear ended an avenger, wrote him off and ruptured my tank, a few dodgy moments until the firebrigade landed.

Only way of avoiding this is a bag tank, ie a bladder inside a rigid container as in the ATM system £1k + each I believe for a custom fitment, x2 for a strat = :eek: ! I wonder what the bladders are made from? A fuel proof bag with two equally fuel proof holes in it can't be beyond the wit of man! Then stuff it full of off the shelf fuel foam whack it in a nice rivetted alloy tank and bob's your uncle!!

But then you need to seal the bag to the filler and out lets, could be mechanical sqeeze seal with gaskets or an adhesive seal. A look out for a ~ 25 litre flexible petrol resistant bag/bladder then. Neoprene springs to mind as does polypropalene. Must do some digging!

What are space hoppers made of?.............. :eek: :D

Aren't sunday afternoons great? there specially designed for musing on stuff like this you know!

[SUSIT]

Really they are for building replica Strats but I have to watch the grandprix despite most of it being boring. Still gives me a chance to search the web for interesting info.
The topic of bladder tanks has been on the forum before, use the search facility and you should find it.
The Perez VK Stratos has bladder tanks inside kevlar casings but its a tiny bit expensive.

hmmmmm. All interesting stuff this, and it's just the first queery.

Aren't sunday afternoons great? there specially designed for musing on stuff like this you know!

[Sptwoman]

Chris Smith's fabricator is making me a pair of foam filled alloy tanks. Foam is becoming more expensive now because it appears the FIA are banning the stuff so there's less off cuts to use!! Blanders are the way to go I believe...
You can buy SVA Astons from Europaspares.com but they're 3 1/2" diameter. I'm using Astons but they will sit further down inside the rear clam for the SVA.... May grow back after!!

[chris.richard]

Chris, you're very certain these aren't Hawk tanks, why? steel verses alloy?


Not aware of Hawk doing steel tanks, and Gerry would not produce something badly engineered like those mountings of yours.

[Sptwoman]

Chris, Gerry's tanks were alloy but are now steel!! Totally agree Gerry = Quality.