$100 chinese 4" vise deflection + DIY force gauge

Re: $100 chinese 4" vise deflection data

.....yes. We ARE talking about pressure. This is a hydraulic cylinder in reverse.

A 1" piston with 100 pounds on it....will produce 100 psi.

A 4" piston with 100 pounds on it will create 25 psi.

A 4" piston with 400 pounds on it, will create 100 psi.
 
Re: $100 chinese 4" vise deflection data

Take your example of the hydraulic brake system if the pedal produces 1000 psi of force there will be 1000 psi of pressure in the hydraulic line, less minor loss, going to the caliper. Reducing the size of the caliper will not change the pressure in the line but it will reduce the total force that the brake can apply to the wheel. When you are talking about a clamping pressure of 3000 pound in you original post are you not talking about total clamping force rather than psi.
 
Re: $100 chinese 4" vise deflection data

Glenn_ca said:
Take your example of the hydraulic brake system if the pedal produces 1000 psi of force
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Just to be clear, force is not measured in psi, and, the pedal produces a psi in the hydraulic fluid based on the piston size attached to the pedal.

There will be 1000 psi of pressure in the hydraulic line, less minor loss, going to the caliper.
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Ok.

Reducing the size of the caliper will not change the pressure in the line but it will reduce the total force that the brake can apply to the wheel.
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Correct.

When you are talking about a clamping pressure of 3000 pound in you original post are you not talking about total clamping force rather than psi.
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"Total clamping force" doesn't have a definition besides one we make up for it.

If you turned the vice on its head, you could use it as a jack to lift something, and say "the vice can lift 3000 lbs" with a certain torque on the handle. It doesnt matter if that 3000 lbs is all in one spot on the jaw or evenly distributed on the jaw. It just matters that its touching the jaw. The 3000 lbs remains the same. And by that same logic, the same amount of force is exerted on our force gauge piston regardless of how much of that piston is between the jaws.

Now on the other side of the piston, in the fluid, the diameter of that piston comes into play, and the force in LBS gets distributed over a certain area, and we have LBS PER square inch, which is dependent on piston size, and represents the pressure of the hydraulic fluid.

"Clamping pressure" would not be measured in pounds, it would be measured in PSI.
 
Re: $100 chinese 4" vise deflection data

Andre said:
Were not talking about weight, were talking about pressure.

Piston size DOES matter. Imagine a hydraulic cylinder, with a piston face that measures one square inch. Pump 100 psi of hydraulic fluid into it, it can lift 100 pounds. Try that same 100 psi into a cylinder with a piston face of 10 square inches, and it can lift 1000 pounds.
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BTW Andre, to make your experience a little more enjoyable, make sure you figure out what oring you want (and where you're going to get it) before you pick out a reamer. Standard oring gland dimensions may or may not permit a cylinder area of 1 square inch. And given that this is a fairly high pressure gland you may want to stick to conservatively designed oring glands.
 
Re: $100 chinese 4" vise deflection data

Maybe I need to rethink this. I will be back.
 
Re: $100 chinese 4" vise deflection data

The Oring actually acts as a piston too. So as long as it fits airtight and the bore is of the correct diameter I should be set, right?

I'll bore the hole to 1.1xx diameter than fit a piston, the bore is really the critical part.
 
Re: $100 chinese 4" vise deflection data

Andre said:
The Oring actually acts as a piston too. So as long as it fits airtight and the bore is of the correct diameter I should be set, right?

I'll bore the hole to 1.1xx diameter than fit a piston, the bore is really the critical part.
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Yup. If you made the bore 1.125 it would be within the error in the gauge, and there are standard O-rings available for that bore.
 
Re: $100 chinese 4" vise deflection data

heres parkers calculator showing the 1.125" bore oring..looks like a 2-314

parker is only rating it to 1150 psi unless you use backup rings..I'm not sure how conservative that is. I certainly do not use backup rings on the one I made.

this application is pretty mild: no movement, no temperature swings, no chemical attack. it does have a few thousand psi to deal with but mine seems to have worked with just an oring. But I would try and stick to the gland geometries within a few thou at most or you might get the oring popping out or impossible to press into the cylinder

note: there are other standard orings that would fit the same bore, with a different piston groove and diameter..and you may get lucky and find these at a hardware store near you
 
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