gdeputy Posted October 26, 2013 Posted October 26, 2013 This past year I made some whistle rockets for the first time, and as part of that process I needed a pressure gauge on the press I used to make them. For a short term fix to get to making rockets, I made a simple cylinder that I drilled and tapped for a pressure gague and did the math to convert the PSI based on the cylinder size to the diameter of rockets I was pressing, etc... It worked well enough, but was kind of a pain to have the rocket tube on the spindle, then the pressure gauge/cylinder on top of that. Needed about 3 hands. More ideal is having a gauge integrated into the bottle jack of the press itself, but that was more involved to take apart the jack, add a port, etc. The plan was to do that this winter as a project. First step was to get the bottle jack from my harbor freight 12 ton press apart. After spending about 30 minutes fighting the thing and not getting it apart, I started brainstorming about another approach. What I ended up doing is making another pressure cylinder with a gauge, but made it to fit between the top of the bottle jack and the press. I had to add some length to the springs that retract/hold the jack in place, just used some d-links for that. This way the gauge is there, but I don't have to try and keep it in place above whatever i'm pressing. I've added a couple pictures, as i'm not explaining it very well. I'm wondering if anyone else has already done this approach? The press with the cylinder/gauge in place The cylinder/gauge Different view of the cylinder/gauge
Col Posted October 26, 2013 Posted October 26, 2013 (edited) I use a similar method with a short bodied ram based P-to-F, I have a stack of washers bolted to the bottom of the SBR housing which allows it to sit on top of the jack (no hands). A single washer with an id just slightly larger than the od of the ram piston is bolted to the underside of the press plate which holds the top in place. Yours looks a lot neater than mine but it does the job Edited October 26, 2013 by Col
nater Posted October 26, 2013 Posted October 26, 2013 A number of people, firework hobbyists included, drill and tap the bottle jack to accept a gauge. There are a number of tutorials on the internet to guide anyone through the process. A wrench big enough to get the nut off the jack can be problematic. I think any approach to help the gauge stay in place is a good one. By the time you have a jack, any spacers, a p to f guage and your tooling, you are just asking for the ensemble to topple over or get off center.
gdeputy Posted October 28, 2013 Author Posted October 28, 2013 My original plan was to go with the tapped port for a gauge on the jack like the tutorials you refer to. This setup is what I came up with after fighting with getting the jack apart for a while. The amount of time I spent making the gauge to fit above the jack ended up being a lot less than I would have spent on modifying the jack, if I had managed to get it open in the first place. I had it locked in a vice and was cranking on it with various tools (large pipe wrench, 4" wide channel locks, etc...) and was at the point where I was dragging around the large metal table my vice is bolted too. I know what you mean about keeping everything in line with what is being pressed, tooling, the gauge, etc. Up to this point I've had a f to p gauge in between the work item and the press. With this setup, the gauge is machined to fit into the recess at the top of the press frame, and to fit over the jack itself, so its locked in. Hands free and doesn't make it a balancing act to keep everything aligned.
a_bab Posted October 28, 2013 Posted October 28, 2013 There are some tricks in order to do the jack tapping successfully. 1. Get a large enough vice, bolted to a solid table. My table also dragged on the floor and it was made of steel and very heavy. You really need to put some devils into it.2. It's also the paint that keeps the top screw so solid in place, so use some paint remover to make your life easier. Some WD40 won't hurt either.3. The wrench should have a long handle, so you can apply lots of force. Careful not to ruin the screw head ! The best tool to use it's a 4. Once you manage to open the jack, DON'T remove the pump! There is really no point to do it. Save the little metal ball, and that's it.5. The jack base is made of cast iron, so welding is a no-no. Only a tap will work. Drill the 1/8 tap hole deep enough to accomodate the tap and get you enough thread.
ianagos Posted November 12, 2013 Posted November 12, 2013 Hey I know I'm a little late but where did you get the gauge? Hey I know I'm a little late but where did you get the gauge?
gdeputy Posted November 12, 2013 Author Posted November 12, 2013 The pressure gauge came from McMaster.com. The pressure to force setup I made myself on my lathe.
ianagos Posted November 13, 2013 Posted November 13, 2013 I have a lathe could you describe the process and materials. I also have the same press.
gdeputy Posted November 13, 2013 Author Posted November 13, 2013 Its a simple cylinder made from aluminum, with a piston/plunger that is sealed with a pair of O-rings. Its filled with oil, and is drilled and tapped for the pressure gauge. Top is machined to fit into the top of the press frame and the bottom to over the top of the jack. Sorry for the quick and dirty description, i'll do a rough drawing in the next day or so that should make it clearer. There's nothing special or complicated, though.
ianagos Posted November 13, 2013 Posted November 13, 2013 I get it I just didn't know a simple o-ring seal would be good enough. If I design the piston to have 1 square inch of area would I not have to do conversions? And I was thinking of cutting off the long piston on the bottom because It makes it really hard to press rockets. What do you do?
Col Posted November 14, 2013 Posted November 14, 2013 You`ll have to do the pressure conversions whatever happens but its not difficult
ianagos Posted November 14, 2013 Posted November 14, 2013 Well what conversions would i have to do if the diameter was 1.12837917 inches which is exactly 1 square inch of area.
Mumbles Posted November 14, 2013 Posted November 14, 2013 It does make the math a little easier. Normally you have to take the internal pressure of the hydraulic cylinder, and divide out the area of the cylinder to get the force being exerted. Then you have to take into account the area of the tooling/comp that the force is being exerted upon. Using a p2f gauge takes out that first step. Being 1 square inch the pressure equals the force in PSI, and you can directly convert the gauge reading to pressure by using the area of your tooling.
Col Posted November 14, 2013 Posted November 14, 2013 If you make it 1 sq inch (28.6609mm diameter) you wouldnt have to do any actual calculations, you could just use this pdf from wolter`s website.http://www.wolterpyrotools.com/pcg.pdf Depending on what you plan to press a 3k psi guage is good for smallish stuff, you`ll need a 5k or 10k for bigger stuff.
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