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Old 16th March 2013, 07:30 AM
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dnic dnic is offline
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Join Date: Dec 2012
Member of: Misfits, Australia OMT
Location: Blacky More, Northampton
Posts: 458

Originally Posted by Ceathreamhnan View Post
A scope tube made of 6061-T6 aluminium will have a linear thermal coefficient of expansion of 23.4 ppm/DegC, which is the same as saying 0.00234 %/DegC.
So a scope that is 300mm long will expand by 0.155mm in a change of 40 F or 22.2 DegC (going from 4 Degc to 26 Degc, say).
This is aircraft aluminium, so for comparison, a Boeing 747 that's 231 feet long would expand 1.43 inches. This would be 12.9 inches if the math quoted above were correct, I think.
Brilliant, and I thought I was the the only one awake during the Thermo Dynamics lectures at College back in the 70s.

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