nesc39 Posted November 19, 2014 Share Posted November 19, 2014 I was reading a new gorski article on making a force gauge and have some questions. Here is the article http://www.skylighter.com/fireworks/arbor-press-force-gauge.aspHe describes how the surface area of the press will define what the psi reads on the gauge. This makes sense because it's pounds per square inch and the press area in this article is 2.2 inches(approximately) The problem I have is how is the ram rated? Harbor freight says 10tons so is that 20,000pound per inch or is that 20,000 pounds/2.2" area so it's really rated at 9000. What if you reverse the scenario and using the ram as intended. Would you apply 20,000psi to the ram? 20,000psi would really be 44,000pounds on the piston after you factor the 2.2area. This is so confusing. How about car tires? Most tires are roughly 44psi but the inner area of a 15" tire is way different than a 20" tire. Let's pretend the tire had an inner surface area of 100". Well a rating of 44psi would mean you needed to be at 4400pounds at the gauge? Obviously it would explode so are we really putting .44psi in our tires? What about the compressor tank it's coming from. Something isn't right? Link to comment Share on other sites More sharing options...
ddewees Posted November 19, 2014 Share Posted November 19, 2014 Force is different... you don't have to worry about the cylinder diameter if you already know the force being applied. This spreadsheet makes it pretty easy, but I would still encourage you to try and figure it out. It takes a little while (in my experience), then it all makes sense. https://www.dropbox.com/s/z57yt6gtjjgj4fb/Rocket%20Motor%20Pressing%20Chart%20Creator%20V1_1.xlsx?dl=0 Link to comment Share on other sites More sharing options...
nesc39 Posted November 21, 2014 Author Share Posted November 21, 2014 So is his article correct? I can think of a million things that would change the scenario.... For instance what if he were pressing into a thin walled tube compared to a thick tube on top of his ram. Would it be different? Im lost Link to comment Share on other sites More sharing options...
Col Posted November 21, 2014 Share Posted November 21, 2014 (edited) Thin or thick wall wouldnt make a difference, its the inside diameter that matters. If your press pushes with a force of 1 ton, its a ton regardless of the ram size. When you convert the force into psi, thats when you take the rammer area into account. Edited November 21, 2014 by Col Link to comment Share on other sites More sharing options...
marks265 Posted November 23, 2014 Share Posted November 23, 2014 You can't use a car tire in this analogy because air is compressible, hydraulic oil not so much. Also when you pressurize a car tire it expands somewhat equally in all directions, but mostly as designed of course. Compared to hydraulics the tire will fail (burst) at much lower pressures. A hydraulic cylinder is designed for linear motion with the ability of much higher pressures. Because the ram of a hydraulic cylinder is usually much small than the piston, the piston becomes a multiplier for mechanical advantage. When you pump on the handle of a bottle jack you push a little bit of oil with a small piston into a big area which is the piston area of the jack. This gives you an advantage to put a lot of pressure in a small area somewhat easily. This is where the math comes in because the oil pressure is measured, you know the piston diameter and your rammer diameter. That's where the article comes in.The wall of the tube and tube construction in general only relates to the ability to handle the forces applied to it. Even when using sleeves or supports. Pressure to force gauges take the unknown out of the hydraulic system being used. SO if you have your Pressure to force gauge and use your buddies rocket press your gauge would be more consistent for you vs watching the gauge on your buddies press. Mark Link to comment Share on other sites More sharing options...
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