Am I calculating this rocket press pressure correctly?

[Mallomar]

Hi All:

 

I am trying to get a handle on how to properly press a rocket.

 

The press I have was from Hobby Fireworks, and is the one that Ned describes in the first picture on this page: http://www.skylighter.com/fireworks/how-to-make/hydraulic-rocket-press.asp

 

If I understand this correctly, I need to first calculate the pressure on the tool. The jack has a piston of about 1.75", and has a gauge on the bottle.

 

So:

1.75" = 0.875" radius

0.875 squared = 0.7656

0.7656 x 3.1416 = 2.41 square inches

 

So if the force on the gauge = 1000 psi, then the pressure on the ram = 1000 x 2.41 = 2410 psi

 

I think all this is all correct. What I am unsure of, is do I now the same calculation again, using the size of my tooling?

 

So if I have 1" tooling:

1" = 0.5" radius

0.5 squared = 0.25

0.25 x 3.1416 = 0.7854 square inches

 

So now, 1000 psi on the guage = 2410 psi on the ram, and the pressure on the composition = 2410 x 0.7854 inches = 1892.8 psi

 

If I am pressing meal D powder for a stinger rocket, what pressure should I aim for?

 

Thanks!

[Col]

1000psig x 1.75" diameter ram area (2.405) / 1" diameter tool area (0.785) = 3063psi

I`d use at least 4000psi , around 1300psi on the gauge.

[Mallomar]

Thank you very kindly for the speedy reply!

 

I'm not sure where I went wrong in the calculation, but I will figure out that later. I will go press some comp with at least 1300 psig right now.

 

Thanks, you have made my saturday night!

[Mallomar]

Good call on the pressure. Looks like just over that pressure and I split the cases every time.

[Col]

aye, most middle of the road convolute tubes are around the 4000-4500psi mark when it comes to unsupported burst pressure, good quality ones will take over 6000psi. Using a support sleeve is a good idea, especially with a press.