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By Wheaters
#91197
stinkwheel wrote:
Thu Jul 02, 2020 9:26 am
Yeah, although that's a large, almost totally sealed car tank. I strongly suspect a motorcycle tank with the lid off would give you more of a woosh out of the open cap. Explosions not involving high explosives are dangerous when contained, if the pressure has somewhere to go, it's a lot less of an issue. Not saying it couldn't make a hell of a loud bang mind.

All speculation though, must try it some time. Ask me about exploding cast-iron downspout flame-organs at a rally some time.
Can I have first refusal on your bike? :shock:
By papasmurf
#91198
stinkwheel wrote:
Thu Jul 02, 2020 9:26 am
Yeah, although that's a large, almost totally sealed car tank. I strongly suspect a motorcycle tank with the lid off would give you more of a woosh out of the open cap. Explosions not involving high explosives are dangerous when contained, if the pressure has somewhere to go, it's a lot less of an issue. Not saying it couldn't make a hell of a loud bang mind.

All speculation though, must try it some time. Ask me about exploding cast-iron downspout flame-organs at a rally some time.
Actually the closest to nuclear explosions are thermobaric ones, vaporised petrol is close to that category.
Somewhere on the internet is film of the result of an RPG7 that fired a round with I suspect unknown to the terrorist who fired it a rocket with a thermobaric war head.
By Geoff K
#91254
Very interesting post - and also very timely for me. I am about to fit a new Indian made tank with rear attachment brackets to a late Redditch frame. The original (very rusty) tank does not have these brackets. In light of the above discussion I am now thinking of cutting off the brackets as they seem superfluous and possibly in danger of breaking, which might lead to a leaky tank. I can fit a rubber sleeve around the upper frame and bulk it up a bit to make a snug fit to replicate how the original tank fitted. Any views on this approach? Many thanks all.
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By Adrian
#91258
Redditch abandoned the rear tabs around 1959, but they still had a rear fastening in the form of a spring clip fixed to the underside of the tank with a couple of 2BA screws. This slipped round a rubber sleeve on the top tube. I would not want to rely on just the front mounting to keep the tank in place.

Speaking of front mountings, when you come to fit your tank on the Redditch frame, check for clearance around the extra outside diameter of the headstock casting, as many Indian tank makers don't make allowance for this. Why should they? They've been used to all-welded frames for years. You might find that with the front bolt fitted, the tank won't sit properly on the frame top tube and will be sticking up at the rear. I've had a couple of tanks where I have had to elongate the front mounting holes downwards to let the front of the tank sit properly and use larger washers on the tank bolt. A bit of a bodge, and it does risk damaging whatever paint job your tank came with. I think I also had to add a piece of old inner tube over the headstock to protect the underside of the tank tunnel.

The Indian copies of the small panel tanks seem to be OK with regards to headstock casting clearance, but I had to try three of them before I found one with enough underside clearance to fit over one of our hosts' replica big head castings, and even so I still have to have a chunk of radiator hose stuffed under the tank over the exhaust rocker feed to stop it rattling against the casting. Every tank is slightly different, it seems.

A.
By PeteF
#91259
I had front mountings only for 10k miles without a problem. The back was well wedged in.
By Geoff K
#91309
Thanks for the tips - front mounting holes did indeed have to be filed out a bit to give clearance over the frame top. Quite a bit of bogding and swearing required with the front mounting rubber and tube which is the wider 66 mm one rather than the previous 55 mm. I have left the rear brackets on for now and will see how it goes once I get the engine running... any doubts and I will grind them off. I put a rubber sleeve where the old tank spring clip used to be and it seems quite snug as it is.
By John-M
#91357
The later British Bullets (I think) and Crusaders (definitely) didn't have a bolt on rear mount, they had a clip in the tunnel of the tank that clips over the top frame tube.
My trials tank has a hook at the rear and a rubber saddle over the top tube. The rear of the tank is secured with a thick cable-tie.
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By Nitrowing
#91976
My first proper job was working in a custom bike shop. When the boss had to weld a petrol tank, he'd remove the tank and put it on the work bench. A length of toilet paper would be trailed from the filler and lit. Big whoosh of flame from the filler and he'd get on with welding.

I was already planning on replacing the M10 girders that hold the tank on with aluminum bar. Now I'll make a cut in the rear so that it snaps rather than the tank's tabs :D

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