Your press

[cplmac]

EDIT: And what the hell were you doing up at 3:55 am, LOL.

 

I was just finishing up pasting in my first 8" shell. It will be airborn in about three hours here, as for the increments and your ramming trouble, I ram with a 2 pound plastic dead blow. You can really whack the hell out of it with that hammer, and I've had great success with it so far.

[TheSidewinder]

Well, I use a 4-pound short-handled steel sledge. I'm also using those crappy tubes from Skylighter/Firefox with a cheap PVC sleeve, so I suspect that's why I'm having to use the method I do. I go RIGHT to the edge of splitting the tubes, even with the sleeve.

 

I have no such trouble with the Super Bottle Rocket tubes I bought from Steve Majdali, though, but then they're so small and well-made that I don't need to worry. I can use a full ID increment on those.

 

And I *DO* have a nice assortment of 1-pound and larger NEPT tubes, but I'm saving them for now. No sense wasting them on something I can't launch from my back yard anyway.

[cplmac]

I love those 1 pound NEPT tubes, I use a ton of them for girandolas. I need to get a couple more bundles from Jim next month.

[cplmac]

I just got done rebuilding the air cylinder on my air over hydraulic press.

 

http://pyrobin.com/files/pa280005.jpg

 

It started to just exhaust air rather than cycle the cylinder and last week it finally just stopped cycling the hydraulics altogether. For anyone who has an air over hydraulic press let me pass on what I learned from this. The first time I took it apart and cleaned it up and reassembled it I couldn't really tell what was wrong, everything looked in pretty good order. Turns out the piston itself has the valve built into it. It's a plastic piston with rubber o-rings to make the seal, the internal valve in the piston was seizing. I disassembled the piston valve and shaved the sides down to the point that it would freely move back and forth inside, put it all back together and the cylinder works like new again. The first time I didn't see this valve, you have to unscrew a plastic cap on top of the piston that shows no sign that it is in fact a cap. There are two small pinholes in the top that you have to insert long needle nose pliers or some type of pins that you can get leverage on to twist it off. Anyhow when you get it off you can see clear as day how it operates and what went wrong. I would assume that this is probably a common cause of trouble for the presses that lose their air cylinders, so for anyone with a similar air over hydraulic setup hopefully this will save you an extra teardown like I had to do.

[Swede]

cplmac, that press looks awesome. I like what appears to be a welded frame for a blast shield. AND you have a pressure gauge, lucky guy!

 

I appreciate the tips on rebuilding that air-over system. I replaced my old bottle jack in my press with a 15 ton air-over, and it is a slick setup, but the day is coming, I'm sure, when it conks.

[FrankRizzo]

Cpl,

 

It's a *very* common problem if you're not lubricating it regularly. Make sure that you squirt a bit of air-tool oil (Marvel brand is good) into the air supply line every so often.

[Aquarius]

So, I finally got my press back.

It's got an hydraulic driven piston of two inches in diameter, a working pressure of 1100 PSI and a max pressure of 1600 PSI.

The pressure it will excert depends on the final diameter of the rammer, I know.

 

And this brings me to my problem: I have no way of controlling the applied pressure, other than using the lever that controls the flow of oil.

If I calculated right using the Passfire caculator, it will be "just right" for a 1 inch rocket.... way too big for everyday use.

 

I thougt about the press gauges that Wolter Pyro has, but as I also have other uses for my press.

I 'm fiddeling with the idea of fitting a pressure gauge to a t-junction on the pipe leading to the piston after the valve.

This way I can calculate the right pressure using the calc, and read the pressure gauge to know when correct pressure is applied.

 

Any comments or views appreciated.

[jacob]

You should definitely get a pressure gauge, Wolters should work fine but hooking one into your hydraulic line will likely be much cheaper, another thing to consider is an adjustable pressure relief valve (some control valves have them built in so you might already have one) while not necessary it is convenient, you can just set the pressure you want and the valve will open when you get to it.

 

Can you get a picture of your press?

[tentacles]

Definitely look into getting a relief valve and a pressure gauge (the gauge is dead easy, just put a T in the hydraulic line). Wolter sells a relief valve for a possibly reasonable sum. I'd suggest checking ebay and surpluscenter.com for that kind of hydraulic stuff.

[cplmac]

Cpl,

 

It's a *very* common problem if you're not lubricating it regularly. Make sure that you squirt a bit of air-tool oil (Marvel brand is good) into the air supply line every so often.

 

I add three drops of marvel every time I fire up the press. There was a lot of lubrication in there, the problem is that the piece of crap piston/valve is made of friggin plastic.

[Aquarius]

Bumping this thread a bit: My hydraulic press is now (nearly) complete, with powerpack, pressure gauge etc. Works ok, but I think it might be a bit overkill for smaller stuff, the press is powerfull as hell. I'll see if I can upload a few pics if there is interest.

The power pack range up to a good thousand PSI, so it has a lot of potensial... It even buckles when I use REAL pressure, might have to weld on a few supporting beams on the sides to keep it from flexing...

 

The reason I'm bumping has to to with the relief valve and regulating the pressure:

Due to the brute force on the press, I have problems controlling the applied pressure. At 250-300 PSI it tends to split my homemade 5/8 inch casing (without a pressing sleeve, I know, I know).

 

200 PSI on the gauge should be around 6500-7000 psi on the 5/8 " rammer, using the Passfire calculator. That is if my guess of the piston is right. The piston itself has a OD of 2 inches, but since it is a double working cylinder, there will be a flange on the piston inside. I do not know the diameter of this (yet).

Is the central cavity/hole in the rammer taken into the equation when calculating pressure, does anyone know?

If not, the actual pressure applied will be quite a lot higher, since it is calculated from a circular even surface.

 

So I'm playing with the idea of using the pressure relief valve to control the maximum pressure applied.

After inspecting the system, I THINK I might have located the pressure relief valve.

Is it a turnable screw right next to the controlvalve/lever? It is protected with a threaded closed nut.

 

My idea is to "set" this valve with the valve to 200 PSI and use it as a constant when ramming. And another question on ramminmg BP rockets: What is the "preferred/optimal" pressure, I see Passfire state 6500 on strobing and whistle rockets, 8000 on endburners.

 

Puh...

[Swede]

I'd love to see some pics. Where did you get the power pack? Is the gauge simply measuring the pressure of the fluid in the pack?

 

I'm fairly certain ALL power packs have some sort of adjustable pressure relief. Give it a try. It should allow bypass of the fluid back into the reservoir.

[Aquarius]

@Swede: The whole shebang is taken from a discarded garbage comprimator. Powerpack, piston, lever, hoses etc all came from there, and for free.

It looks quite different now...

The only money I spent was 100 $ for materials and welding of the H-frame, including putting the stuff together. And for the tee-coupling and pressure gauge, maybe 50 bucks.

 

The gauge I put on the hydraulic line, between the lever and the piston, where it measures the pressure of the liquid into the sylinder and piston.

Again, thanks for all help.

 

 

I'll play with the suspected relief valve and see what happens. And if I don't get overexcited, I'll try to remember to take a few pics and post them here.

[tentacles]

Is there perhaps a manufacturer's label on the power pack? If so, go to their website and look up some diagrams or manuals. The relief valves I've seen are almost always a grub (hex key screw with no head) and locked down with a nut - loosen the nut and adjust the screw counterclockwise to lower the pressure. I think you're going to find the lowest reliable setting is around 500-700psi. I saw some special relief valves for lower pressure applications, but big $$ ($150+) and they only went up to about 800psi. So for big stuff you'd have to change out the relief valve.. Another option may be an in-line relief valve of suitably smaller caliber.

[Aquarius]

Played around a bit with the valve connected to the operating lever, and unfortunately it's a bit like Tentacles said: It does work, but only down to a around 500 PSI. And that is still twice as much as I wanted. I guess stis is more of a choke valve than a relief valve.

 

But Tentacles: You say it's on the powerpack? I got the impression it would be somewhere around/on the op lever. I looked at the powerpack also, but the only hex screw I fund seems to be a third outlet. I'll check it out as when when the motor is NOT running!

 

So I guess there's no shortcuts here: Eigther I'll change the cylinder and piston (not an option), buy a new pricey choke/relief valve (not an option eigther) or actually watch the gauge

 

But playing around with the different adjustments still work to some degree, pressure is easier to control. So thanks guys, appreciate it.

Edited January 10, 2009 by Aquarius

[tentacles]

The relief valves are usually on the powerpack as that allows you to keep the system pressure down - and it's a much smaller loop for recirculating the fluid back to the reservoir.

 

Here's a picture of mine, pardon the paper towel and such... The reservoir had a slight leak at some point and the towels are there in case. As a side note, never use HCl to clean off rust... it works great.. then it rusts again really quick.

 

 

It's entirely possible that your relief is installed in the spool (valve), as I would imagine the unit is double acting (has two hoses going to the cylinder). The 12V packs always have one mounted in the pump.

Edited January 10, 2009 by tentacles

[Aquarius]

I found another valvescrew (i hope) on the powerpack.

Will give it a try tomorrow, just finished my ballmill, and it turned out nice. At least it turns...

[wolfy9005]

See if you can find someone who can make an adjustable frame from steel. That way you could get a few different bottle jacks, and just attach them, depending on the pressure you require. And steel(assuming it's made properly, of course) should allow the maximum amount of pressure into the object to be pressed.

 

Alternatively(and more expensive), see if you can buy an old hydraulic cylinder from a salvage/scrap yard. Then you just need to get a pump and associated fittings/hosing to hook it up, and(hopefully) you can vary the pressure to achieve the results you want. You can get them up to 30cm(commonly), and they can easily supply the required pressures

[derekroolz]

So why is it neccasary to use a 12 ton press....what does it compress

[Mumbles]

Why do you keep drudging up old threads? You might also want to quote the relevant post that you're referring to. Without it, your post makes absolutely no sense.

[inonickname]

I think he wants to know why presses are used. They are used to remove voids from rockets..

[pyrogeorge]

My new rocket-comet press.

 

http://img23.imageshack.us/img23/6162/pressi.th.jpg

[scarbelly]

Pyrogeorge: have you considered adding a blast shield? also, when you press with that do the plates flex?

[pyrogeorge]

No i don't plan to add blast shield now,i don't press whistles,only bp rockets and comets..

No they don't flex.They are 12mm thickness.

[scarbelly]

How much did that all cost you?