Cog belt shred-o

Stan V

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I have 1.8" deflection on the belt when it is cold
I run with a quarter inch deflection when cold, 1.8" seems excessive. What am I missing ?
 

jcarleto

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Someone once told me, "Gates belts shrink and get tighter when they heat up." This is, at worst, wrong and at best, a misunderstanding of what really is going on.

Gates has a recommended tension for all their belts. For the belts typically used in aircraft, a rough estimate is 1/4" play per foot of unsupported length. This seems loose, for those used to V-belts. The problem is that typical aircraft cogs are so large that when they (not the belt) heat up, the coefficient of expansion due to heat is enough to over-tension a belt that was already tight when cold.

Gates belts don't shrink with heat, but large metal cogs expand. It is best to set the belt to the tension after a significant warm-up.
 
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eddie

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stan that is 1/8" of play sorry about the error.

Best regards,eddie.....
 

dinoa

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It's not the belts that shrink. It's the metal heating when the engine warms up that tightens the belt. It halved the deflection on a Rotax 505 reduction I had.

Dino
 

jcarleto

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Dinoa,

Yes, perhaps I should have put that at the top of my post rather than at the end. To put my own experience in practical terms, I often took off with a "relatively" loose belt and returned with one that was "banjo tight."
 
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