Why magnesium alloy????

Started Apr 19, 2013 | Discussions thread
cplunk
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Re: Yes, really
In reply to Pradipta Dutta, Apr 20, 2013

Pradipta Dutta wrote:

sandy b wrote:

Football helmets, motorcycle helmets, car body parts, M16 stock/receiver. None of them have magnesium. Plastics have many advantage over metal. Thermodynamically more stable. Light, strong and they have give. Tooling and material expenses drastically lower.

And airplanes are made of metal. Regardless of how many examples you cite, you can't deny that magnesium alloy is stronger than plastic.

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787 and a variety of military aircraft are made from carbon fiber.

And what, exactly, is "stonger"? there are a variety of different factors in strength that are different for various materials. Concrete, for example, is very strong and rigid, but once if reaches a point to where it cannot hold it's form anymore, it cracks and fails. Steel, on the other hand, would flex quite easily, and up to a very large amount retain it's original form once the load is gone, it takes quite a bit more pressure to cause it to crack, but comparatively little for it to bend. So, which one is stronger?

Plastics generally flex more readily than a magnesium alloy (or course, there are many different types of plastics, but generally, the common plastics used in a camera I believe that is mostly true).

Magnesium alloy will be more rigid, but once the point of that rigidity is overcome, it doesn't flex much before it just fails (cracks).  Trying to line up the various bits inside a camera and keep them all in the same place in relation to each other with very close tolerances, being pretty rigid is a good thing.

But when you drop your camera, most plastics would flex a bit, and flex back. Maybe taking a couple scratches depending on it's shear threshold. There are very high quality plastics that would probably take a heavy enough bounce that Magnesium alloy would crack, but they likely aren't as rigid. And, everything else attached to that kinda plastic frame would be an issue if the plastic were to flex too much. Of course with a rigid metal alloy, that shock isn't absorbed by the flexing, it's just transferred in to the components...

So, ideally, the frame holding the lens and sensor, and all the other carfully alligned bits would be something as rigid as Magnesium alloy, and the outside of it be much more flexible and able to give a bit of bounce to protect the bit's that can't take the direct impact.

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