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Unread 24-02-2011, 07:22
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JamesCH95 JamesCH95 is offline
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Re: Steel on a FRC Robot

Quote:
Originally Posted by Tristan Lall View Post
I'm not a fan of ordinary structural steel for FRC robots. The strength to weight ratio is awful[...]

Alloy steels, particularly chromium-molybdenum steels like AISI 4140, are very useful, however. In the annealed condition, the strength to weight ratio is around the same as AA 6061 wrought aluminum. The difference is that you can weld annealed AISI 4140 with negligible loss of strength, while AA 6061 will drop dramatically in strength when welded. That makes welding a viable construction method for high-stress, high-strength parts.

The trouble is, because the steel weighs more, you have to use thinner material. This can be difficult to work with. Also, since 4140 typically comes in solid and tube sections (and doesn't work very well as sheet metal), you'll see it used in space frames, rather than stressed skins.
4130 steel is available in many tube cross sections with very thin wall thicknesses, down to 0.035in. If one was going to make structures out of steel that's what I'd recommend. I'd then advocate the use a weld-in nuts to fasten everything to the frame.
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