This month it’s com­pressed into one big tip

Classic Bike (UK) - - Workshop -

Big bang the­ory

Gareth Pem­ber­ton sug­gests I pub­lish a cor­rec­tion to the sug­ges­tion that tank leaks can be tested by us­ing com­pressed air (Fixes, April) say­ing it is ‘ex­tremely danger­ous and can cause in­jury or fa­tal­i­ties’.

A pro­fes­sional en­gi­neer in the oil and gas in­dus­try, Gareth has come across sev­eral such in­ci­dents, he says. ‘It is pos­si­ble to store high amounts of pres­sure en­ergy in the tank, even with a low-ca­pac­ity com­pres­sor. Air is com­press­ible and will con­tinue to ex­pand if the tank rup­tures. This can cause sharp frag­ments of metal to fly out in the re­sult­ing ex­plo­sion.’

I un­der­stand Gareth’s con­cerns, but the let­ter did say that the breather should be ‘taped over’. If I check for leaks un­der­wa­ter I use a cy­cle pump, as it shouldn’t take much pres­sure to cre­ate a stream of bub­bles and a com­pres­sor in­creases pres­sure too fast to mon­i­tor. I’ve never heard of a tank ex­plod­ing, but have seen one al­ter its shape.

Blow­ing dents out of tri­als bike tanks was com­mon prac­tice, but I re­call speed­way rider Mal­colm Sim­monds telling me he’d done it once suc­cess­fully, or so he thought un­til he tried to re­move the tank and found the tun­nel had moulded it­self around the frame! Han­dle with care.

Cy­cle pump pres­sure was enough to re­veal a Scott rad leak

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