Ski Builders Forum

I know I'm being ignorant, but I cant find the numbers on how much pressure a pneumatic press can put out. Im looking for a figure in lbs. My mold is made for a single hose, 9" wide by 78" long. Im hoping to get 45 psi. I dont know if this number is right, but I'm getting 63,180 lbs of pressure over the entire press. This number cant be right.

someone more knowledgeable than I will chime in but these calcs are all over this place.

I am kinda scared thinking about it but.

78 x 9 x 45 = 31,590 x 2? = 63, 180?

that's why we build them with i-beams with bridge-bolts.

Haha thats the biggest calculation I've done since getting my ME degree, sad .

Ya I wasnt sure about multiplying it by 2, but there is a top and bottom mold, so it may be right. If anyone can give an acurate number I'd appreciate it.

I am quite curious about this. I tend to think you don't need to multiply by two, but I have no proof either way. I'd love to hear something decisive.

multiply by 2 aply when you are using 2 firehoses...

contact patch is what you need to measure. Fully inflated your hose may not be in contact for the whole nine inch width. (This is why we use cat tracks). In essence though your calcs are seemingly correct. psi times actual contact area. At 70 PSI my press is taking about 120,000lbs of pressure.

In other words your press needs to be insanely strong to press at a high psi.

63, 180 is wrong

9" wide flat, we could approximate 7" contacting the mold when inflated (to be safe, I think it will be less). Assuming every inch of the 78" contacts the mold you'll have

78in x 7in x 45lbs/in^2 = 24,570

Long story short, if you didn't engineer your press to handle that load take out a life insurance policy ASAP.

tantrum wrote:63, 180 is wrong

9" wide flat, we could approximate 7" contacting the mold when inflated (to be safe, I think it will be less). Assuming every inch of the 78" contacts the mold you'll have

78in x 7in x 45lbs/in^2 = 24,570

Long story short, if you didn't engineer your press to handle that load take out a life insurance policy ASAP.

Actually, you are wrong.

The air bladder is making contact on the top and the bottom. The calculation should be 78 x 14 (7 on top 7 on bottom). You have 1092 square inches of contact. Multiply that times your intended pressure of 45lbs per square inch and you see that you need to make sure that your press can withstand about 50,000 lbs of pressure not including your safety factor.

Determining actual force at the laminate is a differet topic.

perfect. that is just what I was wondering. With that, I have some great ideas, and ill post once I get the press made. thanks