Big tank

[Beeza]

Has anyone ever seen one of these large tanks? The smaller one is a genuine goldy tank with the bashed in bit to clear the GP carb. Both are headed to the platers soon, so I thought I'd post a few pic's of them bare.
Cheers Thomas

[BritTwit]

Thomas
Can you post pictures of the underside of both?

[trevinoz]

The big one looks like it has been blown up with pressure in attempting to remove dents.

[Beeza]

The big one looks like it has been blown up with pressure in attempting to remove dents.

No chance there Trev, the tank is mint, not the smallest ding in it.

Thomas
Can you post pictures of the underside of both?

[BSA_54A10]

IS the big one steel with a copper flash or full copper because I can see a lot of what looks like solder on it.
With a hinged cap on the right, it was intended for a pre-unit B series single and the big badge indent says Gold Star.
However the indent underneath says twin so perhaps an RGS
However I can not see why any one would want to carry that sort of weight penalty unless it was a special tank for an endurance event and cut out a couple of fuel stops.

[chaterlea25]

Hi,
Is there any chance its an Indian made copy?
Some of them seem to be oversize but I have not seen one with a depression around the fixing bolt hole
Repro tanks usually do not have the double diamater piece for the tank bolt just a plain tube with a washer at the bottom

John

[trevinoz]

Thomas,
The big tank is typical of a blow up.
The top should look the same as the other as should the rear tunnel.
The welds on the bottom don't look factory so you could assume that the bottoms have been out at some time for repair.
Measure the distance between the bottom studs and compare.
When they are blown the distance increases.
I'm not trying to be a smart idiot but I have seen tanks which have had the air treatment and they looked like yours.
Trevor.

[BritTwit]

Why not measure out 4 gallons of water and check the capacity.  If it was pressurized, it would distort but not increase capacity.  Maybe it's just late and my logic is distorted.

[bsa-bill]

t would distort but not increase capacity.

Know what you mean but in theory the above can only apply to a perfect sphere

[BritTwit]

I posed the question of the tank to Ross Thompson, who has more experience with British tank repair than anyone on the planet.
His reply:
Hi Dan
"I had a look at your photos of the BSA tanks. I would say that the mystery tank is an original BSA tank. That someone has put air pressure inside the tank and has puffed it. You can see by the welds at the rear of the tunnel where it has split and then welded up. The tunnel of the tank has been spread at the front.  Also when tanks are puffed you'll get that sucked down look of the top centre amount as the mystery tank has'.

[Beeza]

OK, it is steel but a lighter gauge, the chrome was removed but the copper is still on. It's not an Indian one, they have a seam weld front and back. BSA have a lap weld front and back. Measuring the tank over the centre mount, from the seam weld up over and back down to the seam weld on the other side, this tank is 25mm (1 inch) longer, so there is physically more steel!
It hasn't been blown up!! Air does not create a perfect pressing where the centre bolt is, nor raise the metal quite evenly at the back and front. Air does push out the two big depressions in the base and generally reward you with a crease or two somewhere around there as well. This is not from my experience (I would never pump up a tank), but I've seen results of this.
I do intend to find out its capacity, as I've been told BSA did provide a 5 gallon steel tank for the RGS. I feel we are getting closer to finding this out.
The welding at the back end, although not neat, I'm guessing was to make the standard base fit the larger body. Also the, 'pressed in' top of the body seems to be there, so as a standard through bolt tube could be used.
Thanks for all the feed back so far.
Give my regards to Ross Thompson, and also show him my thoughts and photos.
AAAND MORE PHOTO'S

[kiwipom]

hi guys, not knowing anything of blowing up fuel tanks with air but I am thinking that if I were to do something like that I would use water or oil and hydraulically do it, to my mind it would do a careful stretching of the metal, just my thoughts, cheers 

[BritTwit]

Beeza
Thanks for the additional photos.  I see the crease where the  seat cut out is perfectly formed and not caused by pressurization.  Same with the center mount hole.  Earlier, I had considered it an Indian reproduction, since the take considerable liberties with accuracy.  Additionally, I don't think they understand the concept of copper-nickel-chrome.

[trevinoz]

I think that you will find that the 5 gallon tank was aluminium alloy.

[Sluggo]

Interesting topic, would be cool to find out the end result if the mystery is ever solved.  I looked at it as well as possible of a "Blow up" tank, but for many reasons I dont think it is.   It is NOT inconceivable that someone did make these as a repop or replacement and not just in India.

I got some wonderful metal work done on my 1948 Speed twin tank and 2 other bits by a local craftsman who is not in the MC trade but took them on as an interesting challenge.  But sadly,, metal work takes a toll and he no longer accepts jobs.
But I know a few other folks who also roll and form steel and alloy, including a local engineer for a well known international manufacturer of trucks who in his spare time built a custom hand formed steel body for a customized car.

But certain aspects of those tanks point to die forming, 2 ways to do that, one a short term limited production buck (Often hardwoods) or a hardened steel form buck and a plate pressing (Very expensive and still only good for so many pressings)

I will be submitting a tech article for several clubs newsletters this winter on the dangers of dent removal and the right and wrong ways to do so.   I have several wonderful examples to use that were victims of DPO Bodgery.  One was a Norton tank owned by of all people a structural engineer.  (I wouldnt live or work in any structure that guy worked on) He should have known better, but tried to blow out dents with compressed air.  Tank looks like an elephant stepped on it.

I will say in summary, DO NOT DO NOT DO NOT DO NOT, NO NO NO NO.........NO! use compressed air, frozen water or hydraulic pressure to remove dents.

Here is why, The dent will be the LAST part to pop out or return to shape.  Learn mettalurgy and its characteristics.  When a dent is formed it is stretching and distorting the metal which in effect makes it HARDER than the surrounding parts.  You CAN anneal or soften the metal and often required after metal forming or hammer work.  But the dent is harder and therefore the last item to move.  Now, if you made a reverse die, you could in theory use compressed air or hydraulic pressure because this would hold all the other surfaces in check and only the dent would have the opportunity to move.

In order to do proper metal repair you have to have a good grasp of the dents creation and then reverse it in that order, There is some really good you tube videos on dent removal, metal shrinking and metal forming.  Ron Covell has some excellent books, videos and seminars out as well.