Monday, February 29, 2016

SteamFlash Rocket Motor 10 - Preventing Burnout - the answer is in the hair dryer

A challenge, see video below, is a risk of "burnout". Normally the energy needed to change water to steam keeps the coil at 100 deg C or a little above. If we run out of water or lose water then the coil glows and can melt nearby plastic, or worse.  I searched for fuse wire with the idea of making the coil out of a low melting point wire so it would act as its own fuse. This search found something better, the "thermal fuse". This sends current through a little bead of low-melting point metal. On temperature rise the bead melts switching the current off. This is used for a similar safety purpose in hair dryers and hair straighteners. Looks great - I am thinking of embedding this in the wall of a boiler made of epoxy resin - or in a cutout in a polypropylene tube reinforced with epoxy resin and carbon fibre.  Example ref:

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