Question about bolt forces due to base moment

• Apr 24, 2022

• #2

GregLocock

Automotive

Apr 10, 2001

23,891

Orbiting a small yellow star

It is overconservative in my opinion. I think the majority of the moment will be reacted by the two bolts at +/-7", if the plate is stiff.

Cheers

Greg Locock


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• Apr 25, 2022

• #3

HTURKAK

Structural

Jul 22, 2017

3,359

It is not reasonable and overkilling. If we assume the bracket is rigid enough, the faying surface will transfer the compression stress and a NA will develop around 11 in. from the right first bolt row. In this case, the tension developing at the first bolt row should be in the range of T= 576000/14= 41000 lbs.

 

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• Apr 25, 2022

• #4

Jboggs

Mechanical

Apr 27, 2012

1,065

US

Obviously the front row of bolts is critical. I would look at the problem with this question in mind: "If the front row of bolts failed, what would happen?" The 2nd row of bolts would fail and then the whole body would rotate about either the rear row of bolts or the back edge. The rear row of bolts is the worse case. So I would look at the whole free body diagram as if the pivot point was at the rear row of bolts. I would calculate the moment that the applied force creates about that pivot point. Then the front row of bolts have to create an equal and opposite moment about that same point (the rear row of bolts) to keep the free body from rotating. Right? (Also, the bolts in the center might be helpful in some other sense but they serve no real purpose in this analysis in my opinion.)

 

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• Apr 25, 2022

• #5

dik

Structural

Apr 13, 2001

26,115

CA

If the bolts are snug tight, can you look at the moment caused by the full tension in the bolts x the moment arm?

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-Dik

 

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• Apr 25, 2022

• #6

Jboggs

Mechanical

Apr 27, 2012

1,065

US

I would use the rated maximum load on the bolts as their maximum contribution to the opposing moment.

 

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• Apr 26, 2022

• #7

desertfox

Mechanical

Dec 29, 2002

5,559

GB

Hi JD PE
I would solve the issue by this method.-

https://roymech.org/Useful_Tables/Screws/Bolted_Joint.html

Scroll down to you see the sub heading “bolts withstanding bending forces”

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

 

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