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Unread 21-04-2012, 14:48
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Re: Polycarbonate side plates for lighter gearboxes

Quote:
Originally Posted by akoscielski3 View Post
I have no Idea what kind of Lexan you are using but the Real Lexan is Virtually Indestructible. And I mean the actual brand name "Lexan" not cheep stuff.
Quote:
Originally Posted by Chris is me View Post
It depends on thickness and application. That said, I've never seen 1/4 lexan crack in a gearbox application.
Perhaps I should take this up with AndyMark, then. All I know is that I have several Polycarb TB back plates that my students have cracked by overtightening the screws on the gearbox. I'll grant that they're small cracks, but they're cracks nonetheless. And Rule #1 of cracks is they never get smaller.

Also, one of the recommended methods of cutting (thin) Lexan is to score it and bend it to crack it along the score. Which works surprisingly well if you get a good sharp score.

Also, also, you might want to look into the phenomenon of solvent stress cracking in polycarb. Wiping down a (small) piece of polycarb with acetone is a fun and enlightening demonstration. But even barring that extreme reaction, the Google suggests that aromatics in your cutting fluid or residue on your tooling can be enough to significantly weaken Lexan around areas you've machined. Loctite or superglue are also really bad for Lexan.

Which is all to say that, yes, Lexan is tough stuff, but it's more prone to cracking than your standard 6061-T6 aluminum and more care needs to be taken when using it.
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