Aluminium Tank

[John Morrison]

Understand from another thread in the TR5 forum, that the modern replacement ally tanks can fail, bcause of the construction methods and the fact that the fixing tags are welded to the sides and not integral to the initial construction as steel?

 

Drat, as I have one to fit sometime, thought I was doing the right thing in having this 'On the shelf'

So thoughts on what I should do to avoid problems, -

 

Thinking reinforcing the tags with say a fillet at right angles to the tag?

and mounting with something like a rubber bobbin exhaust type mount to give some flexibility?

Swop for steel - though I have this some time, unfitted.

 

Thoughts/cures appreciated.

 

John.

Edited July 22, 2016 by john

[john.r.davies]

john,

Can't comment on alloy copies of OE tanks, but I have a wheel well tank.

It is supported on four 'tabs' welded to the sides, and sits on several layers of Viton rubber sheet to cushion it, as well as having rubber pads under the tabs.

All as you suggest.

Since the picture, it developed a crack along one of the tab welds.

I was able to clean it out to the satisfaction of my local TiG welder, who repaired the crack and installed a brace under each, that spreads the load onto the tank wall.

Stress is now in the length of the tabs, and failure would not lead to leaks.

 

John

[Peter Cobbold]

The tabs have to resist the force of 35kg of petrol trying to continue forwards while under heavy braking. Or bouncing over bumps.

So I'm not convinced rubber bobbins would help in securing a full tank.

 

I read somwhere that the steel tank adds rigidity to the rear deck and sides. Its 'structural'.

Cant recall the source...

 

Peter

[ChrisR-4A]

I am sure as with all items there will be the odd one which fails, unfortunately we don't hear about all the ones sold which go on for years with no problems. So I would just like to add that I bought a new alloy tank for my 4A from TR Shop in 2006 and it has done over 25000 miles with no problems.

[peejay4A]

+1

[R J Sampson]

Dan at Revingtons fitted an extra capacity aluminum tank to my 5 as part of a fuel system upgrade. Smell in boot eliminated and all fine after 4k miles. I mostly drive on windey West Wales roads so plenty of sloshing around!

Richard

[Andy Moltu]

One option is to grind off the existing mounts, then get a strap of ali loosely tack welded around the tank and weld the mounts to that.

 

When the body flexes the forces are not directly applied to the tank, but to the strap which is flexible.

The strap may well suffer from stress fractures after a long time but can be easily welded up if it breaks, unlike the tank if the lugs are welded directly to it.

 

The alternative is a tank made of heavier grade ali with beefy mounts.

[john.r.davies]

As some will have already found, the latest episode of Project Binkie is out:

 

 

This one is mainly concerned with fabricating an alloy fuel tank, and Nick Blackhurst takes a little time to explain why he is NOT making it to be fastened in by tabs.

It is, of course completely custom made, and fits like ... oh, hand in glove - there is no better simile!

But he insists that straps to support the tank are a far better way.

 

Apart from that the fabrication is a joy to see, including many of the famous Bad Obsession team's home-made tools and devices.

See the video, enjoy, and be educated at the same time.

John

Edited July 24, 2016 by john.r.davies

[peejay4A]

I get the theory but why are we not plagued with complaints of aluminium tanks with tabs splitting all over the place?

[mike3739]

I get the theory but why are we not plagued with complaints of aluminium tanks with tabs splitting all over the place?

Great question Pete more than worth a thought!

 

Cheers

 

Mike.

[john.r.davies]

Read post 2

John

[peejay4A]

Total so far. One. And that's not a standard location.

[Andy Moltu]

I get the theory but why are we not plagued with complaints of aluminium tanks with tabs splitting all over the place?

 

I know of quite a few that have cracked.

[peejay4A]

How many Andy?

[Guest ntc]

Look and learn http://www.tr-register.co.uk/forums/index.php?/topic/58771-binky-episode-13/ yep then add a firewall.

Edited July 25, 2016 by ntc

[peejay4A]

Yes Neil. I've read this thread and watched all the Binky episodes. How many tanks have failed?

[Guest ntc]

Yes Neil. I've read this thread and watched all the Binky episodes. How many tanks have failed?

Pete

I know of four and that was enough for me.

[peejay4A]

Thanks Neil. I must be one of the lucky ones then....so far.

[Guest ntc]

Pete

Just fit a firewall and you should be ok.

[Alec Pringle]

Hi Pete,

 

I know personally of more than a dozen TR tanks that have failed over the past 30 years, all aluminium or stainless steel, and I've heard at second hand of a few more . . . . . but I haven't heard of any similar mild steel failures. Hardly an unusual occurrence, it's one reason why competition tanks are 'lifed' - the failure rate of so many tanks, in all sorts of cars, in years gone by.

 

A Neil observes, the fitment of a pukka rear firewall reduces body flex significantly, as does a decent rollover bar - and therefore reduces some of the stresses potentially affecting the tank.

 

Cheers

 

Alec

[Andy Moltu]

How many Andy?

 

Within the Leicester Group - 3.

 

AFIK from different suppliers but had all developed cracks around where the mountings were welded to the tank.

[peejay4A]

Very interesting, and concerning. How were the problems resolved?

[RogerH]

Hi Folks,

having worked with Ali (and other exotic metal) in aviation for many years you get a feel and respect for the stuff.

 

Pure Ali is useless you must use an alloy. Ali alloys are heat treated for whatever purpose you want to use them in.

If you are welding an Ali alloy heat treatment is a must. Either side of the welded area is a serious weak spot (line) - it is the heat affected zone.

This would require heat treatment to help it along

 

In aviation you wouldn't want to stress a welded Ali part. Why are aircraft Ali fuselages not welded - because they will break.

 

So you need the correct material (easily sorted)

the correct heat treatment (probably not done)

the correct assembly (could be done, but!!)

 

If you miss out on one of those you will eventually be in trouble.

This also applies to stainless steel (rubbish stuff if in the wrong place) etc.

 

When using some sort of encircling band with tabs attached you must be careful of fretting. Ali alloys like to fret

 

Has anybody considered using a fibreglass band with mild steel tabs laid in.

Or bonding (adhesive) the tabs on

Or rivet the tabs on

Or spread the load over the tank with bigger feet on the tabs

 

What is wrong with a mild steel tank?

 

Roger

[john.r.davies]

Seems that group experience matches that of the Binkie team, and mine.

Beware of cracking where alloy tabs meet the tank. Consider straps to secure an alloy tank.

 

If I may, a slight but relevant diversion;

In Binky 13, Nick rejects mild steel as the material to fabricate a tank from, because he was "unsure of its long term exposure to" and a word that he slightly mumbled.

It sounded like "toluene" or "toluol".

The first is a constituent of petrol, a phenol with a methane side arm, instead of a hydroxyl group.

The second the German spelling of the same stuff.

Why was he worried about this? I can find nothing on toluene attacking mild steel, except that the first inhibits corrosion of the second in the face of sea water and cassava fluid (!!!), and a table that rates carbon steel as "Excellent" as a container.

I've asked on the BO website and had no sensible reply from the assembled fans.

 

Apart from weight, and the inevitable corrosion from environmental exposure, whats wrong with mild steel for tanks?

 

John

 

PS Writing my Q as you posted Roger, and you were addressing the construction of an alloy tank, not its chemical reactivity.

The Binky Boys used steel straps, cushioned with high density rubber against the alloy tank. I hope (as no doubt do they) that this will abolish fretting

Sketch below shows how my spare wheel well tank is secured. The dashed line shows the extra brace I added, after the weld (!) cracked, where the original tab joined the tank wall. J

 

Edited July 26, 2016 by john.r.davies

[Don H.]

...In Binky 13, Nick rejects mild steel as the material to fabricate a tank from, because he was "unsure of its long term exposure to" and a word that he slightly mumbled.

It sounded like "toluene" or "toluol"...

 

I heard Nick Blackhurst say "tolulene". Not an uncommon mispronuciation of toluene by non-chemists. I guessed at the time that he was thinking ethanol and didn't get his terms right.