Finding a lost propeller with Echo sounder ?

[Ribochet]

Originally Posted by Pikey Dave

It's something to do with the crystaline stucture of the steel

Now for the science bit

Iron (plain carbon steel) is allotropic which means that at low temps it has a Body Centred Cubic (BCC) structure which is magnetic and at high temps it has a Face Centred Cubic structure which is non magnetic.

Stainless steel (austenitic) props have on average 20% Chromium, 10% Nickel and 3% Molybdenum which produces a FCC - non magnetic structure at low temperatures - that also why austenitic S/S fittings do not produce compass deviation

Pheeeeeew glad thats over

[EnglishLes]

Ribochet

As the resident scientist can you explain how aluminium (non-magnetic) can be induced to be magnetic by a moving magnetic field?

I believe this is how mag-lev trains work and also the old fashioned speedometers (the ones with cable drive).

Thanks

[Pikey Dave]

Originally Posted by EnglishLes

Ribochet

As the resident scientist can you explain how aluminium (non-magnetic) can be induced to be magnetic by a moving magnetic field?

I believe this is how mag-lev trains work and also the old fashioned speedometers (the ones with cable drive).

Thanks

Different ball game altogether Les. When you pass an electric current through a conductor, a magnetic field is created around the conductor. This magnetic field interacts with other magnetic fields from either permanent magnets or other electro magnets. That's basically how motors & generators work ( and large Hadron Colliders ). Aluminium is a good conductor, pass a current through it & a magnetic field is created around it, voila!