Is Magnesium ok?

[Munchskull]

Recently I was researchin exotic metal and was reminded of Magnesium'a wonderful light weight and structural properties. So my question is: based on recent years rules would magnesium be allowed on a robot in a structural role?

[MaGiC_PiKaChU]

Magnesium is pretty explosive, so if you have some magnesium chips in your electronics, your robot might catch fire. I'd say it would fall under "hazardous materials", but you should ask a robot inspector

[Gravity]

Originally Posted by MaGiC_PiKaChU

Magnesium is pretty explosive, so if you have some magnesium chips in your electronics, your robot might catch fire. I'd say it would fall under "hazardous materials", but you should ask a robot inspector

You also can’t put out a magnesium fire with CO2 or water so be careful.

Ohh, and also don't let it get wet.

[anthonyttu]

Magnesium is not explosive it is used for wheels on high end cars all day long. The shavings or swarf created when machining do need to be handled properly they can catch fire and burn very well once they catch. The little fire starter kits that you scrap the savings off then spark up is a block of magnesium and flint for the spark.
If you have a mentor or sponsor that has a ton of it and machines it regularly great.
If you just want an exotic metal on your robot to say you used it there are way more exotic materials with very wide range of properties i.e. hastelloy torlon.
Willing to bet 6061 Aluminum will still work

[Jon Stratis]

Originally Posted by anthonyttu

Magnesium is not explosive it is used for wheels on high end cars all day long. The shavings or swarf created when machining do need to be handled properly they can catch fire and burn very well once they catch. The little fire starter kits that you scrap the savings off then spark up is a block of magnesium and flint for the spark.

This would have me concerned with respect to machining in the pits... Could I just pick up any old drill and start punching holes in it without any risk of it catching fire? What about cutting a bit off with a hacksaw or saws-all? Do I need to be worried about the little scraps and dust posing a fire risk in the pits?

All of these could be grounds for either not using it or not permitting machining on it at an event - remember, safety is more important!

[Munchskull]

I am familiar with magnesium's firiery tendencies. That said it is my understanding that magnesium only combusts when it melts. This question is purely academic. Also what is the danger if getting magnesium wet?

[techhelpbb]

Ignition requires a mixture with adequate oxygen.
I used to make thermite I doubt your drill will do it unless you rub the bit quite a bit.

DO NOT play with thermite it can be very dangerous.

Originally Posted by Munchskull

I am familiar with magnesium's firiery tendencies. That said it is my understanding that magnesium only combusts when it melts. This question is purely academic. Also what is the danger if getting magnesium wet?

Magmesium when lit will reach adequate temperature to seperate H2O into hydrogen and oxygen (disassociation). Causing an immediate flare up.

Watched a fire truck full of water try to control a magnesium fire..burnt down 10 trees because they added water. DO NOT mess around: magnesium fuses can be used to ignite charges under water.

[ThaddeusMaximus]

There's a difference between "ok" and "suitable". You are building an FRC robot; you need it to be cheap, easily made, and have quick turnaround. Lightness is important, but considering the above three, magnesium doesn't seem to be the right material for the task at hand.

Of course there are exceptions (see: carbon fiber can grabbers in 2015).

[Gdeaver]

If you build with the better AL's you are already using it. It's one of the components of AL alloys.

[Alan Anderson]

The caution against getting it wet might be confusing magnesium for sodium (or potassium or another alkali metal). While it does burn spectacularly as a powder or shavings (or when molten), there is a significant difference between alkali metals and alkaline earth metals. Sodium reacts with water and is likely to ignite the hydrogen produced by the chemical reaction. Magnesium only has issues with water when it's already burning.

[RoboChair]

Using magnesium would only pose an issue if you are using open flame in the pits(which you shouldn't as per the rules), or are producing arcs(which you shouldn't). Magnesium is not some super sensitive substance that will spontaneously light on fire, you deliberately have to try and ignite it unless it is a finely divided powder. Aluminum powder is flammable too. As long as you work with it properly and keep chips out of your electronics I see absolutely no problems.

I would bet money that you can't ignite a size-able block(greater than 0.25" minimum dimension) of magnesium with a blowtorch(not a welding torch) in under 15 seconds. Magnesium shavings or ribbon are a different matter but even ribbon still takes effort. Buy a Class-D extinguisher if you are that paranoid.

[OccamzRazor]

You could also use magnesium alloys that do not have such dangerous properties. You get the weight savings and in general less concerns over volatility.

I believe the .625" dia rod you get every year in the IGUS kit is a magnesium alloy. (correct me if I am wrong?)

[Greg Woelki]

Originally Posted by OccamzRazor

I believe the .625" dia rod you get every year in the IGUS kit is a magnesium alloy. (correct me if I am wrong?)

Nope, it's a hard-anodized aluminum shaft.

[Cory]

I see no real safety risk associated with magnesium in the operation of the robot or in the pits at an event.

That being said, you could burn your shop down if you are milling/turning/sawing it and create fine chips that accumulate and aren't cleared out of the machines.

I don't think it really functionally offers any advantage either. there are very few non-power transmission areas on a FRC robot that benefit from more advanced materials than 6061. Those that do you're usually best off with 7075 or 4130/4140/4340.

[Mike Schreiber]

Wasn't the housing on the NI cRIO magnesium? No one started any fires - although hopefully no one was machining it.