Burning mag wheels (on purpose)

[pzkpfw]

Hi,

I once read in a car magazine about Volkswagen clubs dumping old transmission cases onto their bonfires - apparently there's magnesium in them.

Now, tommorrow night we have a bonfire at a mates farm, and I've seen some really old "mag" wheels in one of his sheds (only three of them, and very old).

So, some questions:

Is there any way to tell what a wheel is made of? (Maybe a destructive test of a small piece?)

Would chucking one of these rims in the fire be a really stupid thing to do? (Any chance of "explosive" reaction?)

Anyone ever done this?

Cheers,

[ManDownUnder]

Pure magnesium will burn like there is no tomorrow. It's an optional ingredient in various pyrotechnics and napalm...

Mags (or more accurately Magnesium Alloys) are an alloy of Aluminium and Magnesium (mostly Aluminium). Not sure it'd burn but my money is on it doing nothing. Get a file, take off some fine filings and throw them into a fire. If it sparkles you have some fun on your hands...

Some aircraft parts are pure magnesium and if they ever got lit it could be exciting...!

[Ocean1]

Almost all "Mags" contain no magnesium. I know older Alpha's were a high mag alloy and burned very nicely, probably applies to a lot of early european sports car castings. Like the man says, chuck some filings onto a good flame...

Re really silly: magnesium burns rather hot, and most mag aloys need no external source of oxygen. If somat turns to shite run far far away, chucking a bucket of water on it is a seriously bad idea.

Oh, and if you ever need to weld up XL350 cases be very careful or, umm, bad stuff might happen.

[ManDownUnder]

magnesium burns rather hot...

LMAO... ok to define "rather hot". It's like saying the Pope has a passing interest in religion.

And yes -do NOT add water. I don't know the details but it's explosive to the already insane burning process.... Once it's started I advise you stand back. Don't bother trying to do anything about it - you won't.

So don't start it if you have the need to stop it...

Shame really because it's a nice metal to work with (a la the aircraft parts I previously mentioned). Just need to be careful when disposing of swarf etc.

[kiwifruit]

give it a go

stand well back :D

perhaps do it in a hole with the option of pushing a load of dirt over it

video!!

[Ocean1]

LMAO... ok to define "rather hot". It's like saying the Pope has a passing interest in religion.

And yes -do NOT add water. I don't know the details but it's explosive to the already insane burning process.... Once it's started I advise you stand back. Don't bother trying to do anything about it - you won't.

So don't start it if you have the need to stop it...

Shame really because it's a nice metal to work with (a la the aircraft parts I previously mentioned). Just need to be careful when disposing of swarf etc.

Err, 'bout 3000 C as I recall. Warm enough to qualify as rather hot.

Not sure of any additional reaction with water, don't think it's hot enough to liberate further oxygen.... (yoo hoo, BASS?) Just dangerous levels of steam and little to zero effect on the combustion process.

[Tank]

I recommend doing it in a neighbours back yard rather than your own.

[avgas]

If your gonna burn some mags fill up the tyres with oxy/axl.....

[riffer]

Hmmm. I'm pretty sure the RF900 Cam chain cover is magnesium...

If I ever blow up the bike this could be fun. :rockon:

[Bass]

Err, 'bout 3000 C as I recall. Warm enough to qualify as rather hot.

Not sure of any additional reaction with water, don't think it's hot enough to liberate further oxygen.... (yoo hoo, BASS?) Just dangerous levels of steam and little to zero effect on the combustion process.

Sorry to disappoint, but I'm not sure about this one. The 3000 C sounds about right and I know that CO2 extinguishers can make it worse cos Mg burns in CO2, but I don't know if it's hot enough to dissociate water and use the products.
I suspect that small amounts of water would cause molten burning Mg to splatter over a fair area with some pretty nasty consequences though. Thats just extremely rapid steam generation and ensuing violent expansion but.
It would also depend on the proportion of magnesium present. I don't know any specifics, but I thought that Mag's and in fact most mag castings were still mostly ally - but you already know that I see upon reading the whole thread

[The Pastor]

its 2000 degs not 3000 afaik

[mitchilin]

Aluminium will burn if it gets hot enough.Thermite is a mixture of aluminium and rust so even if its not a "mag" it may catch fire.Got a fireman mate who reckons the vw's that got torched would burn thru the road and there wasn't anything they could do.A toolmaker mate was working a lathe too hard on a piece of aircraft magnesium and fucked the lathe when it caught fire.Give it a go though, it's not going to explode it will just burn really fiercely and you may see spots for days

[wildpudding]

I have a good idea....

http://youtube.com/watch?v=rogZBXNqaMo

[Mikkel]

Well, being a firefighter (way back though) I hope I might clear up a few things.

AFAIK both aluminium and magnesium will burn - however, they're both quite hard to set off. As in, you need a FUCKING hot fire to begin with, if you wanna have any hope of igniting it. When they burn, they burn extremely hot with a very characteristic white flame (exact temperature, I do not know and shall therefore not pull any figure out of my ass). The metal does not actually melt in the combustion process (and yes, this is very rare since most solids will have to melt - and THEN evaporate to form combustible components).
As Bass rightly said they can burn hot enough to dissociate the hydrogen and oxygen in water - giving you the perfect 2:1 ratio that'll result in a nice explosion right then and there. However, NOTHING burns in CO2 - all fires need O2 to burn and in most cases CO2 will displace O2 since it's a more dense gas. That being said, I can not exclude the possibility of CO2 dissociating at some temperature, whether it is possible for a magnesium fire to reach this temperature I can not say. Someone with a basic knowledge of chemistry should be able calculate the free energies involved in the dissociation process and figure out the thermal energy necessary.

As for your party. I'd say you'd probably be disappointed unless you got an acetylene blowtorch to set them off with. When they burn they don't burn explosively but steadily. It's not dangerous as such, just don't look at it directly without sunglasses or for long. Oh, pray that some drunken fool does not chuck a beer at it.

Good luck :cool:

[deanohit]

Man, that guy gigles like a little girl!
Cool fire though.

[pzkpfw]

Thanks for the replies, people.

Some more googling now that works over shows a few hits (including this thread, already). Gave a few mentions that the brightness of burning is one of the things to watch out for - damage to the eyes.

Probably give it a go when the kids are out of the way.

Cheers,

[slopster]

You can buy fire starting blocks at camping shops. They have a block of pure magnesium, a file and a flint. You file the magnesium til you have a little pile of powder and then make sparks with the flint and the little pile burns up quite well. We tried for hours to get the whole block to burn up. It is too big, not enough surface area. Even tried getting a bit of Mg ribbon and lighting that up and trying to light the block but no luck. I think the chance of getting mag wheels going is about nil.