Human Force to Turn a Bolt
Human Force to Turn a Bolt
(OP)
This may be simplistic but here it goes anyway... I am designing a screw jack and need to have some idea of the typical amount of force a typical human (male 170 lbs) can comfortably exert on a wrench to turn a bolt. By comfortably, I mean without bouncing or sharply jerking the wrench. This force should be independant of the length of the wrench or size of bolt. I realize human strength varies widely, that is why I indicated 'typical'.
Thanks in advance.
Thanks in advance.





RE: Human Force to Turn a Bolt
I think a construction worker could apply easily a force of 100 lbs. provided he has enough room and a good point to react. If he can not, he always can use a longer wrench.
AEF
RE: Human Force to Turn a Bolt
RE: Human Force to Turn a Bolt
RE: Human Force to Turn a Bolt
2 hands would give a maximum of 165 lbf
Steven van Els
SAvanEls@cq-link.sr
RE: Human Force to Turn a Bolt
"Happy the Hare at morning for she is ignorant to the Hunter's waking thoughts."
RE: Human Force to Turn a Bolt
1. Pain threashold -- the area of the wrech at the applied force will effect the tolerable pressure experienced by the operator.
2. The proper use of a wrench involves torque, which implies a force couple -- both hands should be used to generate forces in opposite directions, otherwise your knuckles suffer.
DesignControl
RE: Human Force to Turn a Bolt
RE: Human Force to Turn a Bolt
In appendix S of the ASME Section VIII pressure vessel code there is an equation given that estimates the stress developed in a manually tightened bolt/stud, using standard wrenches as:
Stress, psi = 45,000/[(bolt nominal diameter, inches)^0.5]
we can estimate that
Torque, in-lbf = CoF * Stress * bolt dia^3 * 0.785
where CoF is the coefficient of friction (I usually use 0.17)
we know that
Torque = Force, lbf * radius, inches
so given a standard wrench length you should be able to estimate the force. Remember that this is all based on tightened torque. This may be a little more torque than you want to allow over the full range of the lift, but it will give you some insight into a statistically determined upper limit.
Regards,
Gunnar
RE: Human Force to Turn a Bolt
I've seen this max. value for equipment in the industrial sector as well.