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Another factor in the risk of removing cylinders

Bolt preload is a very clever thing. The bolt feels no change in tension, until its preload is exhausted. This dramatically affects fatigue failure susceptibility.

Some mechanic used a bit of sealant around the bolts, and some of it ended up under the cylinder base, and prevented bolt preload working.


Shoreham EGKA, United Kingdom

Structural preload is for sure a clever thing but the bolt actually feels much reduced change in tension with varying loads, not zero change. The level of reduction is a function of the relative stiffness of the (stiff) clamped assembly and the (relatively flexible) bolts. If the clamped assembly is stiff and the studs are long, it’s closer to zero variation and zero fatigue stress. That’s how head studs on a car engine work but the cylinder base studs on an aircraft cylinder are short and the case is aluminum so it’s not so true there, especially if there’s goop between the cylinder and case half. So in order to limit the stud fatigue stress to an acceptable value it has to be done by the book even if the goop doesn’t extrude leaving no preload.

A good reminder regardless.

Last Edited by Silvaire at 18 Sep 03:31
2 Posts
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