How much force does my press exert?

[jmorris]

It's a question I have had before, years ago, after I had more than one press and noticed the force required on one was different than the force required on another, while doing the same tasks. Any way a question on another forum had me take another look at the question and make an attempt at an answer.

I started off building a simple hydraulic load cell, where the piston has one square inch of area and a gauge that reads in pounds per square inch. I placed it in a press I had and pulled the handle with 5lbs of force and found a 8:1 force multiplication but that was with the ram 2" from the top of its stroke. With the linkage most presses have things don't get powerful until you are closer to the dead spot or "cam over" and I can't make a load cell that short.

So I dug around in my stuff and threw this contraption together, that threads in where the die would and transfers the force of the ram to up above the press and I can adjust the point at which I measure.

To keep things simple and repeatable I am thinking of setting a case in the shell holder/shell plate and lowering the gauge to contact the bottom of the case. Then lower the ram and dropping a shim inside the case. This way I can at least make sure I am measuring all of them at the same height/portion of stroke.

When I got it finished I set it in my Co-ax and found that just the weight of the handle, at dead spot point, was applying over 50lbs of force, so I might need to change the gauge or build another cell. When I get some more time, I'll play a little more and post some results.

 

[Walkalong]

I don't know how much, but it's more than enough to crush fingers, or punch a hole in one.

 

[ATLDave]

I have literally ripped the rim off of a steel case holder when trying to unstick a stuck case with my LCT.

 

[someguy2800]

Before I figured out how to properly lube cases I ripped the rims off several 06 cases but never the shell holder LOL. I'm really curious how much force on average it takes to size a larger case like an 06 or 45/70 or insert a primer.

 

[JimKirk]

I am not a math whiz ... not even in the same ball park ... but doesn't the area of your cylinder come into play ? What is in the cylinder air or some non compressible fluid ?

I would also think the "force" would change in different parts of the handle movement arch ... that is why most press priming is at the being of the arch ... being the force is less at that point ...

Just thinking out loud ... that can be dangerous in any form ....!

 

[jmorris]

Jim, yes the cylinder area matters, the gauge I am using is pounds per square inch, so I made the piston surface area 1 square inch or 1.128" in diameter.

It is hydraulic as air is compressible and throw off readings.

The force changes quite a bit at different points, that's why I went to all the trouble to measure just the last little bit of stroke, where all the work is happening.

 

[JimKirk]

Great ... You were way ahead of my dangerous thinking then .... see I told you !

Now if you can adapt it to a sizing die ....

 

[JimKirk]

I had the idea to use an electronic load cell and be able to graph the force over the entire "resizing" of a brass .... or the seating of a bullet ...

 

[Reloadron]

Real nice job and setup.

I had the idea to use an electronic load cell and be able to graph the force over the entire "resizing" of a brass .... or the seating of a bullet ...

I have given some thought to the same. Before I retired I had access to a really nice prototype machine shop and some really great machinist always quick to help me with my little side projects. Unfortunately I no longer have that access. I would like to chart for example pulling several bullets looking at how uniform the neck tension or bullet pull was. I figure that it will take a certain amount of tension (pull) for the bullet to break followed by a lesser tension to drag it out of the case mouth. God, I miss that machine shop. I don't miss going to work everyday but I miss that little machine shop and my old lab.

I have the electronics laying around and while a S-Beam load cell or threaded button cell would be my choice I did have a few 100 Lb cheap aluminum beam types around here somewhere. I even gave some thought to placing a strain gauge on an ole Lee O press or my Rockchucker and building a bridge around it to see what it would do.

Anyway I really like what Jmorris came up with and he always comes up with pretty cool stuff.

Ron

 

[Dudedog]

but it's more than enough to crush fingers

I have tested both of my presses,an old three hole Lee "Deluxe" turret and my LNL progressive and they do have enough force to smash fingers
The LNL does seem to do a better job of it.

Very jmorris

 

[Walkalong]

Anyway I really like what Jmorris came up with and he always comes up with pretty cool stuff.

Yep. He does indeed. A regular mechanical genius.

 

[JimKirk]

Real nice job and setup.


I have given some thought to the same. Before I retired I had access to a really nice prototype machine shop and some really great machinist always quick to help me with my little side projects. Unfortunately I no longer have that access. I would like to chart for example pulling several bullets looking at how uniform the neck tension or bullet pull was. I figure that it will take a certain amount of tension (pull) for the bullet to break followed by a lesser tension to drag it out of the case mouth. God, I miss that machine shop. I don't miss going to work everyday but I miss that little machine shop and my old lab.

I have the electronics laying around and while a S-Beam load cell or threaded button cell would be my choice I did have a few 100 Lb cheap aluminum beam types around here somewhere. I even gave some thought to placing a strain gauge on an ole Lee O press or my Rockchucker and building a bridge around it to see what it would do.

Anyway I really like what Jmorris came up with and he always comes up with pretty cool stuff.

Ron

I only wish to have the resources to make some of my ideas come to "life" .... metal working tools .... electronics ....more skills & Oh one of the most important ... $$$ ... !!!

I failed to say ... JMorris ... great job on the "device" ... !!!

On different press ... Never found any brand lacking in the ability to smash fingers and poke holes ... even the Lee wackamole will work for that !!

We have also proved that cheap load cells can be accurate .... in the electronic scale thread .... right?

 

[Blue68f100]

That's a good idea. The key to your setup would be getting all of the air out of the cylinder and guage. Gauges are know to trap air. Maybe putting it in a vacuum chamber and pulling a vacuum will exhaust all of the air out. I'm surprised the Delrin (plastic if tha's what it is) body is strong enough to take the force with out expanding increasing the volume. But again the gauge should give you real numbers.

Like ReloadRon I too at one time had full access to an R&D machine shop. But those days are long gone. I no longer have any of my strain gauge equipment to do any stress work, any more. I do have a small handheld readout used on a portable scale some where around here but not the necessary parts to build it out.

Jmorris, Like your solutions to a lot of common problems that are never explore but wondered about. I would thing someone here with a mechanical engineering degree could calculate the force these presses make if they had all the measurements of the press linkage. But like you said it a variable curve due to way the linkage is setup. The only problem would be in accurately measuring the arms pivot lengths. I know there is enough force to fatigue fail the operator arm during normal operation. So the load has to be up there.

I think that most AP presses generate more force than a std SS press. Since that are doing 4-5 functions at one time. I know like many others you do not want to get your fingers in way of them. They down right don't care that they will smash/pinch your fingers in a heartbeat.

 

[jmorris]

I would thing someone here with a mechanical engineering degree could calculate the force these presses make if they had all the measurements of the press linkage.

Before I left the university there was a 2d dynamic motion software that just came out that would have been perfect for this application. I used it designing some hydraulic grappling arms. Measure all of the different presses and CAD the linkage in 2d and you could see every load and force you would want anywhere you want. It was called Working Model but at $3000 for single user and $600/year "mantenance" fee, I have to go with the cheap solutions, now that it's my pocket.

 

[WelshShooter]

I don't know how much, but it's more than enough to crush fingers, or punch a hole in one.

100%! I almost crushed the top of my index finger one time. I use the RCBS primer pocket swager which requires a die to be screwed into the top of a press and the case is loaded onto a swager in place of the shell holder. I hand-fed a case into the die but got a bit over-enthusiastic and almost crushed my finger as I lowered the press handle down with nothing more than the weight of the handle. My finger was throbbing for a few hours, thought I broke a bone. I'm much more careful when raising/lowering the ram.

 

[Reloadron]

Before I left the university there was a 2d dynamic motion software that just came out that would have been perfect for this application. I used it designing some hydraulic grappling arms. Measure all of the different presses and CAD the linkage in 2d and you could see every load and force you would want anywhere you want. It was called Working Model but at $3000 for single user and $600/year "mantenance" fee, I have to go with the cheap solutions, now that it's my pocket.

I know that drill. Our ME guys were using Pro-E and the annual seat licenses were several grand per year per seat. My world was EE and I used Cadence Unison Suite stuff. The software was over 10K and my annual seat license was about 5K but both the Pro-E and Cadence stuff were incredible software. I worked in a sort of skunk works part of our facility and I had the pleasure of working with some of the best ME types I could have hoped for and some of the best tool and die makers and machinist I could ever want. I actually enjoyed going to work. We made a lot of models using Nylon which worked out well. We could machine it, thread it and it fit our needs real well. When I needed fixturing for my electronics all I had to do was draw a rough cartoon (literally) and those ME guys made it happen.

I have tested both of my presses,an old three hole Lee "Deluxe" turret and my LNL progressive and they do have enough force to smash fingers
The LNL does seem to do a better job of it.

That may have some possibilities. The audio level of the scream should be proportional to the force applied. So if that proves true and the scream is linear we could convert the scream to force in the software.

Ron

 

[Rule3]

If you look on your I- Phone, I think there is an APP for this!

 

[hdwhit]

One of the great things about THR is that people will not only think to ask these kinds of questions in public, but then they - or someone else - will come along, build the apparatus and conduct the experiment.

Bravo.

 

[Varminterror]

I would personally use a load cell - piezoelectric. Then a series of dead length bars could be used to determine the force generated at any point in the stroke.

 

[Reloadron]

I would personally use a load cell - piezoelectric. Then a series of dead length bars could be used to determine the force generated at any point in the stroke.

Without getting well off the topic my choice would not be a piezoelectric load cell sensor and here is the why:

Piezoelectric load cells work on the same principle of deformation as the strain gauge load cells, but a voltage output is generated by the basic piezoelectric material - proportional to the deformation of load cell. Useful for dynamic/frequent measurements of force. Most applications for piezo-based load cells are in the dynamic loading conditions, where strain gauge load cells can fail with high dynamic loading cycles. It must be remembered that the piezoelectric effect is dynamic, that is, the electrical output of a gauge is an impulse function and is not static. The voltage output is only useful when the strain is changing and does not measure static values. However, depending on conditioning system used, "quasi static" operation can be done. Using a so-called "Charge amplifier " with "Long" time constant allow accurate measurement lasting many hours for large loads to many minutes for small loads. Another advantage of Piezoelectric load cell, conditioned with a Charge amplifier, is the wide measuring range that can be achieved. Users can choose a load cell with a range of hundred of kN and use it for measuring few N of forces with the same Signal/Noise ratio, again this is possible only with the use of a "Charge amplifier" conditioning.

The above quote taken from here but the same descriptive data can be found in any number of places. piezoelectric sensors are more suited for shock and vibration measurement as an example. Gun related along the lines of the force of a firing pin or a chamber pressure spike. There are what has become quasi-static measurements where piezoelectric sensors have their place. The problem is for dynamic measurement like shock and vibration they are great but for static force measurement I just do not see them as a good choice. I am not saying your suggestion is bad, I am simply saying I wouldn't do it that way for the reasons I mentioned.

Now I need access to a machine shop. Ohio winters are long, grey and cold making for good hand loading and other inside projects.

Ron

 

[Varminterror]

I guess it's a matter of what you're familiar with, I work with certified scales every day, pull a load on, park brakes off of the scale, stop motion, read. Most of the older load cells are traditional strain gauges, but more and more are piezo cells, and more accurate than they used to be, on the order of ~1.5% or less of gross.

I'd also be interested to back out the leverage with a vernier, quick and dirty, as a guy should be able to estimate pretty easily what the compounding factors would be throughout the stroke based on the moment arm lengths.

 

[Reloadron]

I guess it's a matter of what you're familiar with, I work with certified scales every day, pull a load on, park brakes off of the scale, stop motion, read. Most of the older load cells are traditional strain gauges, but more and more are piezo cells, and more accurate than they used to be, on the order of ~1.5% or less of gross.

I'd also be interested to back out the leverage with a vernier, quick and dirty, as a guy should be able to estimate pretty easily what the compounding factors would be throughout the stroke based on the moment arm lengths.

I agree and while being retired is nice we do tend to get away from the technology curve. Maybe this winter I'll play around with it as more than once I have given it some thought. I do have a pile of strain gauges and somewhere a few actual 100 Lb load cells. Maybe a pizeo approach would be worth chasing too.

I really like the approach jmorris used. Really pretty simple and obviously works.

Ron

 

[243winxb]

Collet Die-

With a press without having an over center feature, apply about 25 lbs. of pressure to the handle once it bottoms out to resize the case. On most presses, this translates to over 600 lbs of pressure on the ram.

From LEE knowledgebase.

 

[Reloadron]

Collet Die- From LEE knowledgebase.

With a press without having an over center feature, apply about 25 lbs. of pressure to the handle once it bottoms out to resize the case. On most presses, this translates to over 600 lbs of pressure on the ram.

Uh OH, maybe I will need a bigger load cell? My first curiosity was measuring the uniformity of pulled bullets as in neck tension or bullet pull but the sizing force at the ram would be nice to measure too.

Ron

 

[Ole Joe Clark]

I have tested both of my presses,an old three hole Lee "Deluxe" turret and my LNL progressive and they do have enough force to smash fingers
The LNL does seem to do a better job of it.

Very jmorris

You don't need a gauge to figure that out.