I need to pull some bushings and was ging to use a nut and bolt to do it. I am trying to figure out how much force will be applied, or how much tension on the bolt is a way yo look at it. Can seem to do the math right. anyone here point to a website that might explain it?
We no need no stinking web sites.....
Lessee.... I'll proly eff this up, but here goes.
Fine 1" is 12 pitch.
Suppose you apply 75 lbs force (about half the standard male bodyweight) to a wrench 1.5 feet long. That would describe circle 2*pi*r or about 10 feet. That 10 feet of circular motion will produce 1/12 of an inch of axial motion. So the mechanical advantage is 10*12/(1/12) or 1,440,. Then times 75 lbs, or a little over 100,000 lbs??? 50 tons? goodgawd.... Who needs hydraulics?? :) At least for a 75 lb tug on a 1.5 ft wrench. Season to taste.
Can that be right? Mebbe so... Lally columns, right?
Next batter..... :)
The math is right, but in the real world I wouldn't count on the screw being more than about 30% efficient -> 30,000 pounds. It'll be worse than that if the pulling arrangement involves, for example, the nut rotating on a flat washer.
Ned Simmons
Greenlee tools have a thrust bearing that you can use. A good high pressure grease would also help.
John
I have found that antiseize compund works great for lubrication. better than grease or oils. I use several flat washers coated.
Damn, you're good with that!.. But, the average man weighs 150lbs? Where? Vietnam? I don't know anybody (personally) other than my next door neighbors daughter that weighs less than 180 ;-)...
Nor do I own many wrenches 18" long ..
GWE
Even at my worst time in the nam..I was 165lbs, and was being eaten up by a dozen or so diseases...
Those body/mass charts were written by evil dwarves with a hardon for normal people
Gunner
"There are hardly any excesses of the most crazed psychopath that cannot easily be duplicated by a normal, kindly family man who just comes in to work every day and has a job to do." -- Terry Pratchett
Want some?
Gunner
"There are hardly any excesses of the most crazed psychopath that cannot easily be duplicated by a normal, kindly family man who just comes in to work every day and has a job to do." -- Terry Pratchett
Not to nitpick, but I said "standard" male, not avg. Indeed, Merka's average is well above the standard.
The "standard male" comes from ex. physio tables, charts. Actually, it's 70 kg, or 154 lbs. The answer to the problem can be altered by ratio: For a 200 lb man using half his bodyweight, inc the tonnage by 33%; A 12" wrench instead of 18", decrease the tonnage by 33%, in this case. Or just plug in new numbers for the original variables.
HF sells a 48" aluminum pipe wrench, for under $100, I think--$74,mebbe. I'm tempted to get one just to show it off. :)
I suspect 50 tons would strip a 1 inch thread.
A better approximation would include the effects of friction.
Assume the COF is 0.2, then
F = 10*T/D
or for 75 lbf. on a 18 inch moment arm, and a 1 inch diameter thread:
F = 10*(75)*18/1 = 13,500 lbf.
This still ignores the angle of the threads (60 degrees) and doesn't check the threads fot yielding but is much closer to the capability of the threads. Hope this helps.
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