Hydraulic press

[keepkool79]

I have a 12 ton press from hobbyfireworks. I’ve been working on strobe rockets and am wondering if all my force calculations are correct. Let me start from the beginning, my first concern is that I am not certain of the hydraulic cylinder's diameter. The press comes with a pressure to force conversion chart so I did some reverse math and figured out what it would be. What I got was close to what a 12 ton bottle jack from harbor freight is and I think that's what it is. Next, I am wondering if the steel frame is strong enough to handle such extreme forces (8000psi). I talked to Steve La Duke and he said a friend of his tried to make strobe rockets and the kept going cato, Steve used the same comp., tooling, and increments. The only change was he used his press which is very stiff and strong.

Other factors I am taking into consideration are that I did not use enough hose clamps on my support sleeve. Someone mentioned that I should use more Vaseline in my whistle mix to slow it down for the hybrid spindle. But this is concerned with presses.

One more thing, my press has a 3/4 inch lynix blast shield on it but after that strobe going cato, I am wondering if it will stand up to that big of an explosion.

 

Any comments would be great, I started a new topic because I think that presses are important and a lot of people do not understand pressure-force conversions. I also need as much information about these things as I can get.

Thanks,

[Mumbles]

I think one main question is what size of rocket are you making? This would help to determine the size you need.

 

The blast sheild should be quite acceptable. It should be able to handle up to 6 lb at least. Looking at the press, I would say it should be able to take it, since it would be designed for large rockets. Looking at the presses they do look pretty flimsy though. Well, like they may have some give. Adding a block to the top of the tooling would spread the force out and reduce any give they may have.

 

If you must, you could probably make a new top for the hobby fireworks press. I would probably use a metal I frame or something.

[EP.]

I think there are people on rec.pyrotechnics that have presses from hobbyfireworks or at least experience with them. I suggest you ask there, I'm sure you can find many more people with press experience there.

 

I'd be interested in knowing more about their products and if they are worth getting, as I have considered buying from them.

[FrankRizzo]

Keepkool,

 

I have the powered version of the large rocket press, with a 12ton "speedway series" jack. I've somehow misplaced my caliper, but when I place my P2F gauge between the two pressing surfaces (no tooling) and apply exactly 1000psi gauge pressure, the Wolter gauge reads 1850. Because the piston in the Wolter gauge is exactly 1sq. in., that means that the piston in my jack is effectively 1.535" in diameter. You have a P2F gauge as well, don't you?

 

Use this equation to figure out your effective piston diameter if you have the gauge:

 

(gauge pressure on jack)*pi*(radius of piston^2) = (pressure reading on Wolter gauge)

 

So

 

(radius of piston) = sqrt [(Wolter pressure)/ ((gauge pressure)*pi)]

 

Or, just trust the gauge and tables that you were provided when you bought the P2F.

 

It's really quite simple to use the P2F. Say your using 7/8" tooling (2lb), just put the P2F on the metal plate attached to the jack, place your rocket tooling on top of the P2F, and pump the jack until the gauge on the P2F reads 3900 for BP or 5280 for whistle/strobe (taken from the supplied table). You will have reached 6500psi loading pressure with the BP number, and 8800psi loading with the whistle number. Who cares what the gauge attached to the jack says, you *know* that you're applying the right loading pressure.

 

If you're getting confused because of the second sheet that Rich provided with the P2F (Rocket Pressure Pressing Conversion Formulas), don't worry about that sheet. That sheet just explains how to calculate the gauge pressure on a tapped jack (such as the one on your press) *without* using the P2F gauge, if you know what your jack's piston diameter is.

 

 

Also, if you're going to rely at all on the gauge that's attached to the jack body, replace it with a liquid filled gauge. The needle won't spike around on you and give erroneous readings.

 

 

 

EP.,

Matt's products are excellent. Try to pick them up at a PGI convention or locally though, as shipping rates are astronomical. Like all the vendors, if Matt hasn't sold everything that he brought, he usually gives nice discounts toward the end of the week. :-) The rocket presses are really nice, the star sorter is ingenious, and the ball mills are nice if you're too lazy to build your own. The star roller is also a great design, but I prefer Kyle's tire roller.

[keepkool79]

I do not have the p2f converter from wolter's. I spent the money on the press form hobbyfireworks to avoid the cost of the p2f. When you say "speedway series" I am not sure what you mean. Mine is a 12 ton jack and it is red. I do not see a name on it though. Are you going to the open shoot next month in PA. I am hoping to get someone that has a p2f converter to go so I can check my jack. When you use the p2f on your press, is your press right?

Thanks,

[FrankRizzo]

"Speedway Series" is just the brand name of the bottle jack used in my press; it's red like yours. Matt must be taking off the brand name stickers before he ships presses now.

 

Unfortunately, I'm not going to the open shoot in PA. I live in the upper-midwest, so PA is quite a trek for me. I also have work/school commitments.

 

Yep, the pressure gauge on the press matches linearly with what the P2F gauge says. They are not identical of course because the piston on the P2F gauge is exactly 1 sq. in, whereas the piston on my jack is 1.85 sq. in. That means that the P2F gives a reading that's exactly 1.85X what the gauge on the jack says.

 

Use the Passfire calculator to find your gauge reading for your desired loading pressure, assuming that you have a jack with the same piston size (1.535"). For example, if you want 8800 psi of loading pressure on your comp using 2lb (7/8") tooling (for whistle/strobe), you want a gauge pressure of ~2800-2900.

 

Edit: Maybe you could just call Matt and ask him what the piston diameter for your jack is. He has to disassemble all the jacks to install gauges, so I'd imagine he's pretty familiar with the innards.

[ewest]

I have a 12 ton hydraulic press from harbor freight that I'm going to be using when I start pressing whistle/strobe rockets. But, I want to put a blast shield on it first. Now, my question is, can regular plexiglass be used as a blast shield or is it too brittle? Home Depot sells 3/8" thick plexiglass, that's the thickest thing I can find at the moment and I have no idea what else to use.

[iv81]

I have a 12 ton hydraulic press from harbor freight that I'm going to be using when I start pressing whistle/strobe rockets. But, I want to put a blast shield on it first. Now, my question is, can regular plexiglass be used as a blast shield or is it too brittle? Home Depot sells 3/8" thick plexiglass, that's the thickest thing I can find at the moment and I have no idea what else to use.

You can double or tripple the thickness using one over another. It would even be stronger in ply than simmar size width single sheet.

[Frozentech]

I have a 12 ton hydraulic press from harbor freight that I'm going to be using when I start pressing whistle/strobe rockets. But, I want to put a blast shield on it first.  Now, my question is, can regular plexiglass be used as a blast shield or is it too brittle?  Home Depot sells 3/8" thick plexiglass, that's the thickest thing I can find at the moment and I have no idea what else to use.

You can double or tripple the thickness using one over another. It would even be stronger in ply than simmar size width single sheet.

Don't use Plexiglas ! It is to blast shields as PVC is to mortar tubes. If you have have blast while pressing, say, a whistle rocket, Plexiglas (acrylic) can become dagger-like shards. The most recommended material for a transparent blast shield is Lexan ( polycarbonate ) sheet.

 

See http://www.thecalderwoods.org/tom/blastShield1.htm for a good example of the difference between lexan and plexiglass as a blast shield.

 

And yes, Lexan is much pricier than plexiglas. One reason good motorcycle helmets and fighter jet canopies are so spendy

[ewest]

That's kind of what I was worried about, plexiglass shattering. I've been looking a bit (maybe not quite as hard as I could) for info on blast shields for a press but really couldn't find much usefull info. Thanks for the link.

[FrankRizzo]

Hobbyfireworks sells Tuffac (polycarb) blast shields in 1/4" thicknesses which can be stacked on top of each other for added protection.

 

Rocket Press Blast Shield 1/4" $35.00

Rocket Press Blast Shield 1/2" $60.00

Rocket Press Blast Shield 3/4" $85.00

 

Domestic (US) shipping runs $5.00 - $15.00 depending on the number of 1/4" layers.

 

-The website is still fubar

Call Matt @ 815-499-0806

or email hobfir@essex1.com

[ewest]

Yes, I saw Hobbyfireworks shields a while back, but I was trying to avoid mail ordering. I have to mail order EVERYTHING and I'm sure the postman is wondering what the heck I'm up to, but thanks for the tip.

 

Today I found a place I can mail order some Lexan in different thicknesses and sizes. I just need to get outside and measure the press and see what size I'll need. Then I can decide who to buy from.

 

I need to get on the ball, the 4th is right around the corner.

[Mumbles]

I was looking here for Lexan:

 

US Plastics

 

I was going to go with 3x 1/4" sheets. 12"x24" would be sufficient I imagine for all things I would be doing in any forseeable future. Seeing as how I don't have my press built yet, I have no need for any lexan though. It is one of my next projects though. I am just theorising about design.

[ewest]

I found some Lexan at Modern Plastics. Comparing the two sites, they look to cost about the same. But at least that'll give me a couple choices, Thanks.

 

It does look like it's cheaper though to go with (2) 1/4" thick sheets stacked up instead of buying a 1/2" thick piece, so that's something to consider.

 

I'll also need one like 24"x24" seeing as my press is a little larger that 12" wide. Shoot, the blast shield is going to cost me more than the entire press did!

[ewest]

One more question, while we're talking presses and blast shields. Maybe this should be a separate thread but, WHY do whistle rockets cato on the press? Is it mainly because of overpressure? And just how concerned should I be?

 

Reason I ask is because I just got a golden opportunity to go play for a weekend at my uncle's land, he's got about 85 acres and I can press and shoot to my hearts content. Only problem is I'll be going in a week and I won't have a blast shield on the press by then.

 

I plan on making nothing larger than 1lb rockets and I do have Wolter's P2F converter. As long as I don't press the whistles over 5280 on the Wolter P2F converter, could I get by without a blast shield?

 

I'm not going to tempt fate by never getting one, I just won't have it in a week and I'd really like to make some whistle rockets given this opportunity. What do you guys think?

[Mumbles]

Lexan isn't the only choice for a blast shield. Just go get some wood, and temporarily attach it. An oak 2x10 or some 4x4's would be just fine. Lexan's main advantage is it is clear. A simple mirror set up so you can see what is going on is also just fine. I have no idea where you got the 5280PSI thing by the way. Whistles have to be pressed up around 8000 to 9000 PSI if you want them to function. You can always be by without a blast shield, but the question is, do you feel lucky enough to do so. Like I said before, I recomend the temporary solution of wood. It will be able to hold up.

 

The blast shield also doesn't need to cover every square inch of the front of your press. It only needs to cover the area directly in front of where you are pressing. This enlies the only problem I have with Dan Williams' press design. It goes down too far. I would only have it go down to roughtly the top of the press. Then one could pump the jack straight on. With the arm off to the side like it is, your hand is at risk incase of explosion.

 

Pic of Dan Williams' Press

[FrankRizzo]

Mumbles,

 

He's using Wolter's P2F gauge, where 5280 corresponds to 8800 PSI loading-pressure on 7/8 diameter tooling.

 

 

Ewest,

 

Check your documentation; you probably want to stick with 3880lbs on the P2F, which will correspond to that same 8800PSI loading pressure for your 1lb tooling (3/4").

[Frozentech]

One more question, while we're talking presses and blast shields. Maybe this should be a separate thread but, WHY do whistle rockets cato on the press? Is it mainly because of overpressure? And just how concerned should I be?

Whistle mix in general is more energetic and sensitive and has a more dangerous reputation than BP. A BP rocket under 6500 PSI, if it ignited would make a dangerously large salute and likely cause injury, but a whistle rocket would almost as bad as a flash salute that size. I suspect the BP rocket cato would burn and bruise you, the whistle would take large hunks off you.

 

Like Mumbles said, you can always use oak or other wood as a shield. Have fun, and take videos !