How to measure the amount of pressure applied by a pneumatic cylinder?
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  1. #1
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    How to measure the amount of pressure applied by a pneumatic cylinder?

    Im going to try to build a wine / cider press for my wine and cider making hobby. I have a big *** expensive pneumatic cylinder i bought from hgr industrial for like 15 dollars. German made and brand new.

    Apples i can press the sh*t out of so ill just open the air valve full bore easy peasy.

    Grapes on the other hand you need to watch the pressure u apply to the skins as you can press out too much tannins from them and the seeds. So i was hoping i can set something up similar to what they have on hydraulic presses that have a gaucge that tells you the force being applied to what your pressing. Id probably press to a certain pressure, release the cylinder, mix up the skins for one additional press at the same pressure and then be done with that basket of skins.

    Anyone have any idea how id go about measuring and controling such pressure/applied force?

    Im figuring that the air pressure in the cylinder would be different than the actual pressure being applied by the ram but possibly this is just a simple calculation of the type pneumatic cylinder i have and a simple formula for setting air pressure via a regulator at the cylinder???? Am i on the right track here???

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  2. #2
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    Re: How to measure the amount of pressure applied by a pneumatic cylinder?

    Also dont really know what this thing is, as the yellow caps should be the in and out for the air.Name:  image.jpg
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  3. #3
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    Re: How to measure the amount of pressure applied by a pneumatic cylinder?

    ID x 3.146- diameter x pi in pull direction. No deduction for rod in push. Multiply by air psi to obtain inch pounds of force.
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  4. #4
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    Re: How to measure the amount of pressure applied by a pneumatic cylinder?

    The yellow caps are where you could put fittings like the one already on the cylinder... usually there will be extra ports around the cylinder ends just to give you more mounting options of how you plumb it.

  5. #5
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    Re: How to measure the amount of pressure applied by a pneumatic cylinder?

    ID divided two, then squared X 3.1416 will give you the area of the piston. Now take that number times psi to get force.

  6. #6
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    Re: How to measure the amount of pressure applied by a pneumatic cylinder?

    Quote Originally Posted by M J D View Post
    ID x 3.146- diameter x pi in pull direction. No deduction for rod in push. Multiply by air psi to obtain inch pounds of force.
    Area= radius squared x 3.14 or Area= diameter x .7856. If the holes under the yellow plugs have no threads they're for mounting truninons to the cyl. If it only has one air connection it's probably equipped with a spring return. If so and I don't know how critical your force applied measurement is but with a spring in it it won't be a constant.
    Mike
    Last edited by mla2ofus; 04-13-2019 at 04:17 PM.
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  7. #7
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    Re: How to measure the amount of pressure applied by a pneumatic cylinder?

    Quote Originally Posted by mla2ofus View Post
    Area= radius squared x 3.14 or Area= diameter x .7856. If the holes under the yellow plugs have no threads they're for mounting truninons to the cyl. If it only has one air connection it's probably equipped with a spring return. If so and I don't know how critical your force applied measurement is but with a spring in it it won't be a constant.
    Mike
    Yep. Area of top of piston in square inches x psi of air = pounds of force

  8. #8
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    Re: How to measure the amount of pressure applied by a pneumatic cylinder?

    Okay so the male shaft diameter is 1.76”

    So 1.76 divided by 2 equals .88
    .88 squared = .7744 x 3.14159 = 2.433 x 80psi for example = 195 lbs of force per square inch?

    Another thing is that the male shaft may be 1.76” in diameter but im going to have it pressing grapes in a basket prob 12-24” wide. So im going to have the male shaft threaded to a push plate the inside diameter of the press basket/ bin. How will this change the equation?

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  9. #9
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    Re: How to measure the amount of pressure applied by a pneumatic cylinder?

    Post the diameter of the piston. With the way it will push you don't need to figure the shaft area. Piston dia. in inches and the fraction expressed as a decimal ( for example 7 3/8" would be 7.325") x .7856= piston area in sq inches x air pressure= total force in inches. Then you'll need to figure the area of the push plate in sq inches and divide the force amount by the push plate area to find how many pounds per sq inch is exerted on the push plate if that's necessary. It sounds like the grape pressing is going to be trial and error by starting out with low air pressure and keep working it up until you reach the desired effect. I think for the grapes a hand brake valve like used on 18 wheelers would work real good for pressure control because as soon as you raise the handle it dumps air pressure off. If the cyl doesn't have an internal return spring then a couple of expansion springs attached to the push plate would save having to plumb air to the shaft side of the piston.

    HTH,
    Mike
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  10. #10
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    Re: How to measure the amount of pressure applied by a pneumatic cylinder?

    Short example since I lost my full reply.

    4" bore air cylinder with 80psi line pressure will exert 8.88 lbs of pressure per square inch of a 12" diameter pressing plate.
    My name's not Jim....

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    Re: How to measure the amount of pressure applied by a pneumatic cylinder?

    Quote Originally Posted by outdoort View Post

    Anyone have any idea how id go about measuring and controling such pressure/applied force?

    Im figuring that the air pressure in the cylinder would be different than the actual pressure being applied by the ram but possibly this is just a simple calculation of the type pneumatic cylinder i have and a simple formula for setting air pressure via a regulator at the cylinder???? Am i on the right track here???
    i wouldn't bother to much with the math. trail and error on the various things you want to crush is required. simply change pressure to suit each item.

    controls are fairly simple. pressure regulator will determine max force. but also i would use flow controls to limit the cylinder speed so it doesn't hit the grapes etc at high speed.
    in this case i would use flow control on both sides. a basic input flow control for the downward stroke. this controls cylinder fill rate and limits cylinder return speed. also have a one way type flow control on the other side of the cylinder. this limits the exhaust air on the downward stroke which controls the rod speed. that stops it from flying down and hitting the grapes at high speed. the one way allows full return flow so it retracts faster.

    i can't see if that cylinder has cushioning at all. but the flow valves will helps with that (so the piston doesn't hit the end of the cylinder to hard).

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    Re: How to measure the amount of pressure applied by a pneumatic cylinder?

    Or post up the data plate/model# for the cylinder..... then we might get some specs on it

  13. #13
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    Re: How to measure the amount of pressure applied by a pneumatic cylinder?

    https://specken-drumag.de/uploads/pd...edPOWER_EN.pdf

    Was able to find the spec sheet on this cylinder. I have the skp 125-10/130-81

    Pretty confusing reading this stuff for someone who hasnt had experience with pneumatic cylinders before. That screw cap i posted above i didnt know what it is, is for hydraulic oil as this is a special type of pneumatic cylinder with a special hydraulic force feature. I was expecting about 15” of shaft pushout but all i see in this link is 130mm of fast stroke and 20mm of max force stroke. That doesnt add up to much stroke for the application here. My press buckets are going to be 15” tall or so.

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  14. #14
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    Re: How to measure the amount of pressure applied by a pneumatic cylinder?

    Quote Originally Posted by outdoort View Post
    Okay so the male shaft diameter is 1.76”

    So 1.76 divided by 2 equals .88
    .88 squared = .7744 x 3.14159 = 2.433 x 80psi for example = 195 lbs of force per square inch?
    D00d. Use the units so you can cancel them out algebraically.

    First figure the area (in SQUARE INCHES) of the top of the piston.

    Area of a Circle = Πr˛ = (3.14) x (.88 inch) x (.88 inch) = 2.43 in˛ = 2.43 SQUARE INCHES

    Now multiply the area of the top of the piston by the pressure.

    2.43 SQUARE INCHES X 80 POUNDS PER SQUARE INCH = 194 POUNDS

    Quote Originally Posted by outdoort View Post
    Another thing is that the male shaft may be 1.76” in diameter but im going to have it pressing grapes in a basket prob 12-24” wide. So im going to have the male shaft threaded to a push plate the inside diameter of the press basket/ bin. How will this change the equation?
    Ok, you know that you will have 194 pounds of force. Now divide that amount of force by the number of square inches of yor presser. If your presser is 12" wide and circular, it will have an area of (3.14)x(6 inches)x(6 inches) = 113 in˛ = 113 square inches

    So you will have 194 pounds of force spread out over 113 square inches, or about 194/113 = 1.7 psi

    If your basket is 24" wide, you'll have 194 pounds spread out over (3.14)(12 inches)(12 inches) = 452 square inches

    194 pounds/452 square inches = 0.43 psi

    Instead of fat women squashing your grapes, you'll have skinny mice...better make the bars of your potato masher small and few and far-between...or get a more powerful cylinder.
    Last edited by Kelvin; 04-15-2019 at 02:42 PM.

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    Re: How to measure the amount of pressure applied by a pneumatic cylinder?

    Bore is what matters. Not rod. Not even piston. Bore.
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  16. #16
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    Re: How to measure the amount of pressure applied by a pneumatic cylinder?

    Quit dickin' around, and go here http://www.pneumaticsonline.com/Calc2.asp

    Last edited by farmersammm; 04-15-2019 at 05:15 PM.

  17. #17
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    Re: How to measure the amount of pressure applied by a pneumatic cylinder?

    Air PSI multiplied by the area of the bore (piston area) gives you how much push youll get. Divide that by the area of your masher to figure the PSI on whatever your mashing. Throw it all out the window and experiment till you get the results you're looking for. Just for comparison a normal average guy has about 8psi of ground pressure with both feet on the ground. Your cylinder with a 12" masher is going to about the same a 3yr old, I think you're going to need something with more jam than that air cylinder or a lot more air pressure.

  18. #18
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    Re: How to measure the amount of pressure applied by a pneumatic cylinder?

    Quote Originally Posted by Boostinjdm View Post
    Bore is what matters. Not rod. Not even piston. Bore.
    Wouldn’t rod area need to be subtracted from bore area to calculate force for one direction(in) ?
    Edit- probably not important for OP’s fruit crushing application.
    Last edited by jpump5; 04-15-2019 at 05:37 PM.
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  19. #19
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    Re: How to measure the amount of pressure applied by a pneumatic cylinder?

    No fabricators here

    If you don't wanna keep a chart by the press to give ya force per pounds of air...……………………………...USE A GD LOAD CELL UNDER THE WORK PAN/WHATEVER...….geesh

    Hell it's just grapes. Say for instance...……………….what would be the weight limit on doods/doodettes stompin' on the grapes How about shoe size...……...gotta lotta variances there High arches.....low arches......

    The average wine snob couldn't tell box wine from the "good" stuff that comes from France (assuming the French stuff is any better than stuff grown right here in Oklahoma)

    Beer is for the palate, wine is for discussion...……..God Knows it ain't for drinkin' (Yuk)

    Slightly fruity. Essence of loam. Bit of sunshine. Musky. Long in the nose...………..Gawd……...it's endless prattle. Goes perfectly with ballet.

  20. #20
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    Re: How to measure the amount of pressure applied by a pneumatic cylinder?

    Quote Originally Posted by jpump5 View Post
    Wouldn’t rod area need to be subtracted from bore area to calculate force for one direction(in) ?
    Edit- probably not important for OP’s fruit crushing application.
    http://www.pneumaticsonline.com/Calc2.asp

  21. #21
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    Re: How to measure the amount of pressure applied by a pneumatic cylinder?

    Quote Originally Posted by Kelvin View Post
    D00d. Use the units so you can cancel them out algebraically.

    First figure the area (in SQUARE INCHES) of the top of the piston.

    Area of a Circle = Πr˛ = (3.14) x (.88 inch) x (.88 inch) = 2.43 in˛ = 2.43 SQUARE INCHES

    Now multiply the area of the top of the piston by the pressure.

    2.43 SQUARE INCHES X 80 POUNDS PER SQUARE INCH = 194 POUNDS



    Ok, you know that you will have 194 pounds of force. Now divide that amount of force by the number of square inches of yor presser. If your presser is 12" wide and circular, it will have an area of (3.14)x(6 inches)x(6 inches) = 113 in˛ = 113 square inches

    So you will have 194 pounds of force spread out over 113 square inches, or about 194/113 = 1.7 psi

    If your basket is 24" wide, you'll have 194 pounds spread out over (3.14)(12 inches)(12 inches) = 452 square inches

    194 pounds/452 square inches = 0.43 psi

    Instead of fat women squashing your grapes, you'll have skinny mice...better make the bars of your potato masher small and few and far-between...or get a more powerful cylinder.
    http://www.pneumaticsonline.com/Calc2.asp ………...

  22. #22
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    Re: How to measure the amount of pressure applied by a pneumatic cylinder?

    Quote Originally Posted by mla2ofus View Post
    Post the diameter of the piston. With the way it will push you don't need to figure the shaft area. Piston dia. in inches and the fraction expressed as a decimal ( for example 7 3/8" would be 7.325") x .7856= piston area in sq inches x air pressure= total force in inches. Then you'll need to figure the area of the push plate in sq inches and divide the force amount by the push plate area to find how many pounds per sq inch is exerted on the push plate if that's necessary. It sounds like the grape pressing is going to be trial and error by starting out with low air pressure and keep working it up until you reach the desired effect. I think for the grapes a hand brake valve like used on 18 wheelers would work real good for pressure control because as soon as you raise the handle it dumps air pressure off. If the cyl doesn't have an internal return spring then a couple of expansion springs attached to the push plate would save having to plumb air to the shaft side of the piston.

    HTH,
    Mike
    http://www.pneumaticsonline.com/Calc2.asp …………...

  23. #23
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    Re: How to measure the amount of pressure applied by a pneumatic cylinder?

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  24. #24
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    Re: How to measure the amount of pressure applied by a pneumatic cylinder?

    if you have a log splitter, just adapt your press bucket and screen to fit onto the splitter and your done....make a steel plate to go over the wedge and your in business...

  25. #25
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    Re: How to measure the amount of pressure applied by a pneumatic cylinder?

    Kelvin gets the A+. The cylinder pressure/force is meaningless unless you calculate the force ACTUALLY applied to the grapes in the pan thingie. That is a function of square inches, as he calculated.

    But...…….in our collective haste...…..we've completely overlooked the load factor (Oh My!!!!) How deep are those orbs of deliciousness piled in the pan????????? IT MATTERS YA KNOW!

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