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Bolt preload vs. transport screw torque

Bolt preload vs. transport screw torque

Bolt preload vs. transport screw torque

(OP)
I have found several calculations and calculators regarding bolt preload for flanges etc, but I think this is different from the torque/tensile regarding a "free" transport screw or similar e.g. where the underlaying plates is NOT supporting the bolt preload.

Can anyone advise on this subject, formulas, links etc.

Regards

Tommy

RE: Bolt preload vs. transport screw torque

Hi blckwtr

I have heard of transport screws but not a free transport screw what is it? a sketch of what your talking about might help

desertfox

RE: Bolt preload vs. transport screw torque

(OP)
I'll try to explain first;

If you have a weight hanging from the screw this is the bolt load. Then you have a nut transporting this screw upwards. Then the preload in the bolt is then only the weight, and the moment transferred to the nut comes from friction between nut and bolt... This must differ from when you have something to squeeze between bolt head and nut...

RE: Bolt preload vs. transport screw torque

Hi blckwtr

Yes I think see what you mean, the nut is just run up the screw and supports the weight although the nut is not tightened up, so the weight can only transfer its load to the bolt via the nut.
The load in the bolt will only be the hanging weight and yes its different to tightening the nut hard up.
You need to check the threads on the bolt and nut for stripping.

desertfox

RE: Bolt preload vs. transport screw torque

If I understand your problem the only things to be considered are the load, the friction factor between nut and threads, and last but not least is the friction between the nut and the nut landing area.

RE: Bolt preload vs. transport screw torque

(OP)
Thank's for all your good replies, just one more thing regarding nut landing area. is moment calculated on mean diameter or on diameter where inside or outside landing area is equal?

RE: Bolt preload vs. transport screw torque

(OP)
I am talking about the torque between the nut and the support for the nut. On the transport screw there are splines preventing the rotation. So total torque is torque between bolt and nut + torque between support and nut...

RE: Bolt preload vs. transport screw torque

hi blckwtr

Well I don't understand from your answer whether the link I gave you last is of any use, if it isn't of any use then put a sketch of your situation then we can see clearly what your trying to do instead of guessing.

desertfox

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