What kind of Press do I need?

[nick2354]

Hello,

 

I am going to be building a press, primarily to press black powder core burning rockets, but In the future I hope to make whistling rockets. I know that the black powder rockets dont need much pressure (half tonne).

 

I dont want to build another press when I begin making whistling rockets, so how much pressure do I need to use, to press whistle mix? From the small amount of Information on the topic, I have read, I think that 10 tons will work?

 

Any help will be more than appreciated!

[Mumbles]

It really depends on the size. 8800 PSI on the fuel is about stardard. Calculate from there.

[Arthur]

Pick a ram force that will give you enough pounds, per square inch of tube bore.

 

A one ton force (auto jack?) will put 2240 pounds onto the rammer. If the rammer is 1 inch diameter thats 2240lbs over 0.5 x 0.5 x pi PSI =2850psi

 

2240lbs on a .5 inch rammer its 11,400psi

 

You will need to scale the press for reliable work at the forces you will want for whistle at the diameters you expect. then you will need to control the pressure applied to other compounds and diameters. Measuring the ram force and relating it to the grain pressure will need some pre planning.

 

I have seen air driven hyrdaulic systems where the drive air pressure determines the achieved ram force so the ram forcecan be controlled by an air pressure regulator, and this can allow a safe distance between the tube in the press and the operator.

[Mumbles]

Nick, ensure you know what your units are to the tonnage of whatever you decide to pick up. A UK ton (metric ton), isn't equivalent to a US ton (imperial ton). 2204lbs vs 2000lbs. Also, the only precise way to apply just the right amount of pressure is with a pressure to force gauge, a driven hydraulic or pneumatic system.

[nick2354]

I am still confused.

 

I tryed Creagens method but it didnt seem to make sense (probaly because I use millimetre's and not inche's)

 

http://creagan.net/fireworks/rockets/presses.html (here is link)

 

I know this may seem like spoon feeding, but could someone show me a calculation using millimetre's, inche's dosent seem to make sense to me.

 

Mumbles: I will have a gauge on the press.

[FrankRizzo]

PM Pyscho_1322. He bought Dan's log-splitter press that you see on that page.

[KAP]

I was wondering what else I could use my log splitter for other than splitting .

I wonder how this would work with Clarks giant steel gerb? Thanks for the idea.

[nick2354]

Frank: I have already made the frame work out of steel for the press, and I will have a gauge on it. Mumbles said 8800 psi is standard, so I am trying to work out what pressure my gauge will read when I have to stop (If this sentence makes sense). At the moment I am using 15mm on the face of the rammer for black powder core burners.

 

I understand that their is a formula to work out the amount of psi I put out on the rammer.

 

Im sorry, if im being slow, I am real crap at maths.

[Mumbles]

The millimeter to inch conversion is 25.4mm/inch. Just divide your millimeter measurement by this number to get inches. 15mm is thus .5906 inches. The math wont work with metric. PSI is pounds per square inch. Unless conversion into inches, the units don't work out obviously.

[FrankRizzo]

Frank: I have already made the frame work out of steel for the press, and I will have a gauge on it. Mumbles said 8800 psi is standard, so I am trying to work out what pressure my gauge will read when I have to stop (If this sentence makes sense). At the moment I am using 15mm on the face of the rammer for black powder core burners.

 

I understand that their is a formula to work out the amount of psi I put out on the rammer.

 

Im sorry, if im being slow, I am real crap at maths.

The gauge will read the pressure inside the jack cylinder. The amount of force applied to your rammers will vary considerably based on the diameter of the piston inside that cylinder. For example, a 1.5" dia piston with 1000PSI of pressure behind it will generate ~1767lbs of force on the rammer, whereas a 3" dia. piston with the same 1000PSI will generate ~7068lbs.

 

What's the diameter of your piston?

[Swede]

Has anyone ADDED a pressure gauge to a cylinder? Your average car jack bottle has no gauge, and I could see where something like that would come in very handy. Even if you don't calculate the actual pressure in a BP rocket, for example, you could determine through a trial and error process that "3,500 PSI on this tooling set with X grams of BP makes a nice rocket." With that knowledge, you can repeat the same rocket successfully by simply pressing to 3,500 PSI.

 

Same with BP pressing. So long as you use the same tooling each time, and the same amount of BP, you can repeatedly ram the BP to the correct density. Consistency is the key.

[FrankRizzo]

Has anyone ADDED a pressure gauge to a cylinder?

Yes. I drilled and tapped the WalMart bottle jack that I used on my first press. It's a bit of a PITA (and messy) to take one apart so that you can drill the channels. You'll need a pipe wrench and a good bench vise to hold down the base while you're wrenching on it.

 

Obviously, drill the horizontal hole on the opposite side of the lever assembly and use hydraulic NPT fittings, not regular pipe fittings, for your gauge connection. I used a regular pipe-grade 1/8"NPT to 1/4" NPT elbow on my jack without problems, but I didn't use it very much before buying my Hobby Fireworks press. Pressures inside the jack cylinder can approach 9000PSI or more when you really wrench on it.

 

AND, you're right..consistency is the key here. But, while you have the jack taken apart, just measure the bore diameter of the cylinder. With that measurement, you can find the area of the piston face that travels up and down that bore. Multiplied by the pressure displayed on the gauge, you have your force measurement. If you then divide that calculated force by the area of your tooling face , you then have the loading pressure on the powder in PSI and can talk with the "big kids".

[GalFisk]

There is a good tutorial on how to add a gauge to a bottle jack on Passfire. After this is done, some relatively simple math can be used to determine the tool pressure from the gauge pressure.

[Swede]

Thanks guys! Fortunately the bottles are relatively cheap, so if I screw it up, it won't hurt too bad to replace it.