Bolt strength in tension?

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wsimpso1

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It’s a little weird.

Weirder than that.

I haven’t started building anything yet but I’d still like to do a Bleriot XI. I’ve gathered two sets of period drawings and between those and existing examples I ought to be able to kludge one together. Anyways the fuselage is held together by brace wires anchored to U-bolts at every cluster. You can sort of make them out here, top and bottom of that vertical piece:
View attachment 128758
This scheme must run with modest tension on the U-bolts, or they would become kinked at the diagonal wires. It also looks from the slots in the upright wooden elements that you tension the diagonal wires by running down the nuts on the U-bolts - true?

However they are adjusted, the working loads in the U-bolts appears to be a small fraction of yield strength. With the bolts at small fraction strength, the nuts are running with small torque - how do you keep them from loosening? Do you run with jam nuts or self-locking nuts (which did not come along until the late 1930's) or are the nuts just constant attention items?

Billski
 

Tiger Tim

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However they are adjusted, the working loads in the U-bolts appears to be a small fraction of yield strength. With the bolts at small fraction strength, the nuts are running with small torque - how do you keep them from loosening? Do you run with jam nuts or self-locking nuts (which did not come along until the late 1930's) or are the nuts just constant attention items?
I suspect the nuts were probably originally constant attention items, or perhaps they were staked or peened to keep them from moving. Wire tension is thanks to turnbuckles (so many turnbuckles) so all the adjustability is there. In our modern world those u-bolt nuts could perhaps be secured with some sort of thread locking compound, or they could be castellated and the bolts drilled for safety wire, or they could be some sort of locking nut. That’s Future Tim’s problem.
 

wktaylor

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Sep 5, 2003
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Midwest USA
In 1985 I was assigned as a POC for SA-ALC's representation for the Fairchild T-46 Trainer program [which was expected to replace the aging the T-37... which I was lead engineer on, at that time]... for metallic materials and fasteners. For this reason, I 'invited my self as an SA-ALC 'observer' to the following committees and never could imagine the benefit and friendships derived from those few years of 'association'....

MIL-HDBK-5# [now MMPDS-##] METALLIC MATERIALS AND ELEMENTS FOR AEROSPACE VEHICLE STRUCTURES
MIL-STD-1312 [now NASM1312] FASTENER TEST METHODS
MIL-STD-1515* [now NASM1515] FASTENERS, SYSTEMS FOR AEROSPACE APPLICATIONS

Available down load for understanding basics of fasteners and 'parts'.

NASA RP1228 Fastener Design Manual
https://ntrs.nasa.gov/api/citations/19900009424/downloads/19900009424.pdf

and from https://quicksearch.dla.mil/qsSearch.aspx...

MIL-HDBK-1599 Bearings, Control System Components, and Associated Hardware used in the Design and Construction of Aerospace Mechanical Systems and Subsystems

MIL-STD-1515* FASTENERS, SYSTEMS FOR AEROSPACE APPLICATIONS
 

FinnFlyer

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Nov 19, 2019
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Bell, FL
Billski, if we torque to near (90%) tensile strength, what remains is only 10% of the tensile strength of the bolt/nut/threads.

This is of high interest to me because the two upper tubes that goes from engine mount upper bolts to out near front of engine/gearbox (PSRU) has rod ends that threads onto 3/8" AN bolts welded to the engine mount. So the tensile strength of the AN6 bolts would only be 10% of what I expected?
 

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