does a magnesium engine burn???

[944doc]

I put a contribution on the recent "is this a porsche" post about the 906, having found one for sale on one of the internet car sites. I made reference to the fact that it came with two engine blocks, one aluminium and one magnesium. It occured to me afterwards that my old chemistry teacher used to set fire to magnesium using a bunsen burner, and a spectacular site it was too. Now I'm sure this is a really stupid question, cos the porsche engineers are much cleverer than I, but is there any danger that a race engine at race speeds would generate enough heat to ignite a magnesium engine block?

[silver993tt]

I would think that the engine block is some kind of magnesium alloy. Only pure magnesium is combustable.

[pdV6]

Agreed. There are some lovely lightweight magnesium alloys around.

[nel]

You have to get it damned hot before it would go up because it conducts the heat away - your chemistry teacher was lighting ribbon or powder that's easy to get to ignition temperature.

I know that in car fires magnesium alloys can burn - the same might be true of an engine block if you could get it hot enough.

[944doc]

thanks, all. Knew it was a daft question but it just kept niggling away at me (clearly I have a sad life)

[cyberface]

Aren't old Beetle engine blocks magnesium alloy? They definitely burn, there's some mad motorsport (dirt bikes?) event in the US where they burn them, big white magnesium flames.

I saw a picture of the event ages ago, unfortunately I can't remember where...

[ATG]

Trying to remeber me chemistry lessons, but I seem to remember that Iron has a higher affinity for oxygen than Magnesium. If you chuck iron fillings into a flame they explode.

[cyberface]

ATG said:

Trying to remeber me chemistry lessons, but I seem to remember that Iron has a higher affinity for oxygen than Magnesium. If you chuck iron fillings into a flame they explode.

Try slinging magnesium powder anywhere near a flame, it's pretty spectacular. Remember aluminium powder is used with iron oxide (rust) in the thermite reaction to weld train tracks together - if aluminium takes oxygen from iron then magnesium certainly will...

[pdV6]

Aluminium has such an affinity for oxygen that you will never see pure aluminium in the air - that silvery colour that designers are so in love with at the moment is actually aluminium oxide...

[roygarth]

Just bought a 1968 Fiat 850 Sport Coupe which has Cromodora 'magnesium' wheels. In researching refurbing the wheels I have learnt that the wheels are actually a mix of aluminium and magnesium.

>> Edited by roygarth on Thursday 23 September 15:11

[nel]

pdV6 said:

Aluminium has such an affinity for oxygen that you will never see pure aluminium in the air - that silvery colour that designers are so in love with at the moment is actually aluminium oxide...

Yep - and magnesium is even more reactive than aluminium. According to the nmonic that I learnt at school in the dark ages, the reactivity tables go potassium, sodium, calcium, magnesium, aluminium, zinc, etc. down to the most inert, gold.

[Melv]

Remember the Ford RS 200? Mag gearbox casing and engine.

Ever wondered why they are so rare.......??? Whoosh!!

Pal has one, his 'insurance policy' is a plumbed in extinguisher system..

Mel

>> Edited by Melv on Friday 24th September 07:58

[jeremyc]

Caterham R500s have magnesium bellhousings.

They also used to have very tasty (and light) magnesium split rim wheels.

[marcevo1]

Magnesium in a large lump mixed with aluminium will not burn that easily - needs alot of heat / oxygen to get it going. - oxidised surface keeps it quite stable as well.

nitros and other car parts already burning adds the extra umph you need for the fireworks ;-)

[turbobloke]

Yes you need to get it very hot for things to kick off but when it goes it sure goes, be it magnesium or aluminium or alloy. Think Falklands, exocet, alloy ship

[ettore]

...or the Mercedes crash at Le Mans in 1955. Magnesium = all sorts of nastiness.