Calculating PSI from Torque
Calculating PSI from Torque
(OP)
The customer's print calls out 250 ft-lbs of torque mininum on a weld. This part is cylindrical via a progressive die. And this part is welded to complete the cylinder. A round bar (1 foot long, close enough) is inserted into the inside diameter of the part.... on the other end of the bar there is a 0.75" air cylinder pushing up on the bar. The cylinder radius block attached to it (to easily make the conversion) The part is constrained in a fixture. There was a gage made sometime ago... In which someone calculated 50 PSI=250 ft-lbs. I Disagree. I calculated appx 565 PSI. Obviously there are other factors such as the friction created by seals, rings, etc in the cylinder. Let's consider them negligable.
Torque=P(A)Dist
Cylinder area @0.75"=Appx 0.442..... pi*(.375^2)
So 250 ft-lbs=P(0.442)*1 ft
Divide both sides by 1 ft (ft cancels out)
Next, divide both sides (0.442)...=565 PSI
Torque=P(A)Dist
Cylinder area @0.75"=Appx 0.442..... pi*(.375^2)
So 250 ft-lbs=P(0.442)*1 ft
Divide both sides by 1 ft (ft cancels out)
Next, divide both sides (0.442)...=565 PSI





RE: Calculating PSI from Torque
RE: Calculating PSI from Torque
RE: Calculating PSI from Torque
RE: Calculating PSI from Torque
RE: Calculating PSI from Torque
RE: Calculating PSI from Torque
RE: Calculating PSI from Torque
You're gonna' need a bigger cylinder.
RE: Calculating PSI from Torque
250ft.lb is not a huge amount of torque really.
RE: Calculating PSI from Torque
RE: Calculating PSI from Torque
RE: Calculating PSI from Torque
RE: Calculating PSI from Torque
if you don't have a 500psi airsupply, why not apply the torque mechanically ?
RE: Calculating PSI from Torque
1" square hole to match a standard torque wrench's drive square (designed for hex sockets) in a piece of material suitable for welding or other connection to your 'foot long bar'. Torque wrench then acts like an extension along the axis of your bar and can be set to any torque required. Modified to take the foot long bar into account.
RE: Calculating PSI from Torque
You could do the job with a 1/2" drive torque wrench. Something like: htt
RE: Calculating PSI from Torque
Just looking at it, you can tell there's no way you're getting 250 ft-lb out of that @ 50 PSI.
Another possible flaw is that the stroke looks pretty short. You might be pushing the cylinder to the stop w/o twisting the part enough to develop 250 ft-lb of torque.
Do you have a clue by four at your desk? You may need to use it.
RE: Calculating PSI from Torque
RE: Calculating PSI from Torque
250 ft-lb, applied with a 1-1/2 - 2 ft. bar would be a tough lift to do too frequently throughout the day, also call for a big counterweight on the table.
RE: Calculating PSI from Torque
they might even pay you for the work-out
RE: Calculating PSI from Torque
I love your idea. very simple and cheap. I realize this seems like a very fundamental/simple idea. But it isn't going to be a problem using the end opposite of the ratchet side? I would assume not. And does the Square head on the wratchet drive have to be press fit into the square (fixed) hole?
RE: Calculating PSI from Torque
aldumoul - Ever used a socket set? Ask your technicians if they have one you can look at. Perhaps you know them by some other name. http://w
" But it isn't going to be a problem using the end opposite of the ratchet side?" Yes. Hopefully the images +/or seeing these things in the flesh will help.
RE: Calculating PSI from Torque
RE: Calculating PSI from Torque
Weld the OD surface of it onto the end of your one foot bar in such an orientation that any ratchet or torque wrench when fitted to the socket acts as an extension to the length of your one foot bar, turning it into a 2/3/4 foot bar with a torque setting.
Then torque on your part = (torque setting on wrench/length of wrench) * (length of wrench + length of 'one foot bar')
RE: Calculating PSI from Torque
RE: Calculating PSI from Torque
Wouldn't you want to divide the reading by 2? Also, When you hold a normal (stock) torque wrench - How does the torque wrench take in account how far away you are from the object in which the force is being applied?
RE: Calculating PSI from Torque
RE: Calculating PSI from Torque
RE: Calculating PSI from Torque
Force=50 PSI(0.75in^2/4)*pi
=22.089#
Of course F=P/A
They then calculated 22.089#/(0.75in^2/4)
That doesn't make any sense to me. Considering they do not put the Torque equation in equillibrium with the pressure. Trying to explain this to my boss who doesn't have an engineering degree hasn't been fun.
RE: Calculating PSI from Torque
"they effed up the calc" should be sufficient. or a simple demostration ... use your set up to drive a torque wrench, supply 50psi and get the torque reading.
RE: Calculating PSI from Torque