Would this Simple Hydraulic Press Gauge Work?

The force you measure at the jack handle is the sum of the fluid force and friction. The friction force might be constant or increase with the load on the jack.

I don't why it wouldn't work if you make a plot of luggage gauge force vs fluid pressure (or jack force). I would start at zero and increase to maximum, and then reverse from maximum to zero and see how well it tracks.

Maybe you can remove the handle and replace it with a torque wrench!

I had already thought of the idea of adding a torque wrench to the handle. It would be a simple modification to a jack to make a hole where the handle goes to connect one.

..."I had already thought of the idea of adding a torque wrench to the handle. "...

Sorry we have no record of that....

That sounds like a reasonable method to determine the mechanical advantage instead of taking things apart. You probably wouldn't need a full piston stoke as long as you can measure how much the piston moves with calipers. Perhaps just move the piston an inch or two.

The piston stroke dependens on the height of the item that you compress?!

You certainly would have to measure the piston stroke from first engaging the item until stroke finishes.

Unless you always compressing the same height item, there needs to be an extra thought going into it.

I cant see how the luggage scale works, unless you have the pivot point very close to the cylinder. You need compare 100 kg versus 20 ton, which should mean the arm length needs to compare 1 x 2000. Unless I misunderstand what you are trying to do.

If it works I would think it could be used as a rough scale for heavy items, like tongue weight. Once the item is off the ground the force to move it should be constant and related to its weight.

The torque wrench idea would be much better. The problem with using a luggage scale on the handle is that you have to make sure the force stays at 90 degrees to the handle, which is not the way you would normally do it. Other wise your measured force will increase relative to the actual lifting force.

P.s. on the jack with a gauge idea- we did that quite a few years ago, with a 50 ton arbor press. Used it for rough measurements of load capacity on molded plastic units.

Like Tornado said in #2,determine the mechanical advantage by measuring the handle stroke versus the piston travel.

Then measure the pressure applied to the handle and multiply times the mechanical advantage and you will be in the ball park.

To give a workable amount of pressure (50 pounds) on the handle for 20 tons the ratio should be around 800 to 1 or more,depending on the design of the jack.

That would give a handle pressure of around 50 pounds at full 20 ton load.

A normal press fit for bearings,gears etc. is around 5 tons.

If it does not move at that pressure something is wrong.

Wouldn't it be much easier and more precise to simply put a pressure gage between the pump and the cylinder?

Don't understand the need to measure stroke, its Handle piston area to Actuator piston area. modify the handle base to accept a 1/2" Sq torque wrench and you're almost done

I tried this out with a luggage scale last night. I agree a torque wrench is a better solution the luggage scale was just an easy way to test without modification.

I used the handle that came with my press but not at full length, I used only the shorter part to test this. The handle is only about 8 inches long from where the driving cylinder is.

I put the luggage scale on the end of the handle and did my best to pull at a right angle to the handle. I also put a short length of pipe in the hook of the luggage scale so it was easier to pull. I tried to pull slowly and as evenly as I could.

Comparing the reading of the luggage scale to the reading on my press gauge indicate that this will work. It isn't going to be really accurate but it will certainly get you in the ball park. There was a clear and repeatable amount of force required to pull the handle that directly correlated to the press force on the gauge.

With my 8" handle and luggage scale I could only pull about 115 pounds down before it became too unwieldy to pull. That didn't quite get me to 20 tons but it was enough to see the correlation.

I was able to stop at a specified press force by just looking at the luggage scale and then checking by comparing to the gauge reading.

I imagine putting a torque wrench as a handle to a press should work quite nice. I think the beam style that uses deflection and a scale would be the easiest to use.

The hard part is having something to calibrate it with. I am sure with some math you could get rough numbers but the best way to account for friction and so on would be to have something to calibrate it against.