Figuring out the force of a pneumatic air piston?

[MrB]

So, i managed to get my hands on a free Norgren RT/57263/M80

 

They state 1870 "N" at 6 bar, but that is a weird number, since the darn thing is rated for 10 bar. And i have NO idea what "N" is. Newton per... square of what?

 

I sort of need to figure out what sort of force this thing actually can generate, to decide if it's worth keeping, or if it should be sent of to a different home.

The link above has a bunch of technical data, in this PDF.

Nothing really tells me that much. So, can someone help me with the math, to figure out what this thing would deliver, on a single square inch. That should be reasonably simple to convert for other dimensions. I'm not entirely certain what sort of head i'll put on this M12 faced rod, but i'll figure that out, if it's worth the time and effort.

 

Also... While it would be great if someone solves the math for me, it don't learn jack sh*t that way, so id someone could explain how they came to whatever result, then i'd be grateful.

 

[AustralianPyromaniac]

Im also unsure what N means although its not Newtons because both units are decimal so the conversion would always be in multiples of ten.

 

Could it be something like, at 6 Bar it will provide 1870 N/cm^2 onto some specific part/ in some specific use?

 

If its any help, to convert from bar to PSI its 1 Bar = 15.5 PSI

 

Regards, AP

Edited November 14, 2017 by AustralianPyromaniac

[bobd]

The spec. is indeed for force (in Newtons (N)) at 6 bar pressure. In other words, if you apply air pressure of 93.3 psi (pounds (force) per square inch), the cylinder shaft will exert a force of 420 (+) lbf (pounds force) on whatever is at the end of the shaft. Force in newtons resulting from air pressure in bar. Unit conversions are a pain, but doable. That force is *just* a force, not a pressure! If applied to 1" square (1 square inch) the force calculated above gives a pressure of 420 psi. If applied to a 1/2" square (1/4 square inch) the pressure wold be 1 680 psi.

Does that help?

Bob

Edited November 14, 2017 by bobd

[Col]

Nicely explained bob.

In metric, 1 Newton is 0.101972 kg/f, at 6 bar the force applied by the piston will be about 190kg/f.

[MrB]

Pretty much meaning that even if i ramp it all the way up to 10 bar, it's not really going to be useful for pyro. You guys rock.

[NeighborJ]

10 bar would make about 700#, you could press bottle rockets.

[a_bab]

8 bar is the regular pressure supplied by the common air compressors, 10 bar being the limit above which your cylinder may fail in a spectacular and dangerous way.

Looking at the specs your cylinder piston diameter is 63mm, meaning a surface of approx 31 square centimeters.
Now, 1 bar of pressure means approx 1kg/sq cm, so we have:

10 bar *31 sq cm = 311 kg of force before you risk breaking you cylinder.
8 bar * 31 sq cm = 248 kg of force
6 bar * 31 sq cm = 186 kg of force (which is "your" 1870N)


It's easy to understand why the larger the cyl surface, the more force the cylinder will make.

In pneumatics wih a regular compressor we need at least a piston diameter of 125 cm to get around 1 ton of force, the very reason hydraulics is better as the pressures are 20x to 60 times bigger then the ones used by pneumatics systems if we need raw force.

Pneumatics in pyro is useful for speed (single star pressing systems come to mind) but not so good for pressing items, not even star plates.

Edited December 4, 2017 by a_bab

[Scotty123]

A few notes:

 

1. Consider the size of what you want to press. If you only wanted to press 1/2" diameter devices (unlikely, I admit) then the up to 700lb force would be concentrated on a smaller area.

 

2. A major issue with pneumatics is that the speed is poorly regulated: if it sticks and then comes free, or if you open a valve wide, it can WHAM! down into the comp. This seems likely to ignite friction or impact sensitive comps, or strike sparks if e.g. you have Ti particles.

 

If I was forced to use pneumatics as a power source for pressing, I would do something like using a shock absorber (or hydraulic cylinder, reservoir and metering valve) to control the speed.

Edited December 21, 2017 by Scotty123

[NeighborJ]

Scotty, there are other options. A pilot positioner can be used on the cylinder. This is a great option to achieve the control desired. The ram can be throttled as fast or slow as you deem necessary. This system is used on automatic valves with great success and precision, it is falling out of favor now for electric/digital controlled systems so it can be controlled and monitored from the other side of the world. Edited December 21, 2017 by NeighborJ