From: liz@poppyrecords.invalid.invalid   
      
   Bill Sloman  wrote:   
      
   > On 22/12/2025 6:37 am, john larkin wrote:   
   > > On Sun, 21 Dec 2025 16:58:41 +0000, liz@poppyrecords.invalid.invalid   
   > > (Liz Tuddenham) wrote:   
   > >   
   > >> john larkin  wrote:   
   > >>   
   > >>> On Sun, 21 Dec 2025 15:40:21 +0000, Jeff Layman    
   > >>> wrote:   
   > >>>   
   > >>>> On 21/12/2025 05:08, Bill Sloman wrote:   
   > >>>>   
   > >>>>> This is roughly equivalent to insisting that petrol-engined car won't   
   > >>>>> catch fire if you shoot a bullet into the petrol tank.   
   > >>>>   
   > >>>> It won't catch fire. You can search for this yourself:   
   > >>>>   
   > >>>> bullet gasoline tank fire   
   > >>>>   
   > >>>> It's a myth, mainly as a result of many Hollywood movies showing cars   
   > >>>> exploding from a single bullet to the tank. Even multiple bullets fired   
   > >>>> into a tank won't cause the fuel to ignite. You need an incendiary   
   > >>>> bullet, and even then you might require more than one.   
   > >>>   
   > >>> We (the good guys) got a great advantage in WWII, with planes that had   
   > >>> self-sealing gas tanks.   
   > >>   
   > >> I think you will find the Germans had them before WWII broke out but we   
   > >> didn't develop them until later.  Apparently the UK research was bogged   
   > >> down by mission drift or 'specification-runaway'.   
   > >   
   > > Old cars had gas gauges that used a float and a wirewould pot, inside   
   > > the tank. It didn't blow up because the mix in the tank wasn't   
   > > flammable.   
   >   
   > Wrong. The mix of air and gasoline vapour inside the gas tank can be   
   > flammable.   
      
   ...but generally isn't.  (It has a very narrow flammability range.)   
      
      
   >The wires inside a wirewound pot never got hot enough to   
   > ignite the mix. I   
      
   You appear ot have misunderstood where the risk comes from.  Wirewound   
   pots can make bad contact and generate small arcs which have quite   
   enough energy to ignite petrol vapour within the range of flammability.   
   The high concentration of the vapour is what stops it igniting.  In-tank   
   fuel pumps with commutators are safe for the same reason.   
      
   Ford came up with an idea that did away wth the carburettor: their   
   system drew concentrated vapour directly from the fuel tank and diluted   
   it with air to give the correct concentration for the engine.  They   
   never put it into production and I imagine the need for a completely   
   reliable and foolproof flashback arrestor was one of the major   
   objections to it.   
      
      
   --   
   ~ Liz Tuddenham ~   
   (Remove the ".invalid"s and add ".co.uk" to reply)   
   www.poppyrecords.co.uk   
      
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