dagabu Posted June 1, 2016 Share Posted June 1, 2016 So, I made me a PTF gauge today from some stock aluminum. Took about two hours of lathe time and all that is left is to install the gauge. I will be buying a 0-10,000 PSI gauge and since this is a true pressure to force gauge in pounds per square inches, it will read pound for pound. The only problem I had was with the o-rings, I only gave myself 0.002" between the walls so its a tight fit. Also, I am not going to sand it or put a shine on it, this is a working tool and will be dropped hundreds of times by those pressing rockets. Link to comment Share on other sites More sharing options...
gdeputy Posted June 1, 2016 Share Posted June 1, 2016 Great minds think alike! I have a very similar setup i use as well. I seem to have problems with it seizing up if it sits for a few months, I think an issue with the orings i'm using and the oil. I didnt have anything handy and ended up using 80-90w gear oil. Going to switch to something lighter and see if that works better. I find this setup WAY simpler than tearing apart the bottle jack to add a gauge there... Link to comment Share on other sites More sharing options...
dagabu Posted June 1, 2016 Author Share Posted June 1, 2016 I am going to make sure there is a raised portion in the center of the top so that those using it dont push it down on the edge, hopefully that will help to keep it from getting damaged. gdeputy, I use hydraulic oil in it and my other hydraulic stuff, it doesn't bind at all and I don't think I will get any binding from this either. I have "made" them before using a short body ram but it has a 1.5" diameter ram, 1.767 sq in. That is a real bear to figure out loading pressure with due to the constant math for each PSI that you increase. This one will be exactly 1 sq in on the ram, giving it a 1:1 ratio and relief to my hands using a calculator constantly. Link to comment Share on other sites More sharing options...
lloyd Posted June 1, 2016 Share Posted June 1, 2016 Dag,I hate to mention this so far into your efforts... but you only need to do 'pressure conversions' ONCE. You do them, you make a label for your gauge that represents the new FORCE values of certain actual pressures... and you're done. I've mentioned this a number of times on other forums, and people don't seem to understand that relabeling a gauge is easier than making 'custom-sized' plungers and cylinders! <G> LLoyd Link to comment Share on other sites More sharing options...
dagabu Posted June 1, 2016 Author Share Posted June 1, 2016 Lloyd, Please forgive my ignorance but even after reading that time after time, I just CANNOT get the image of how you achieve that without taking the dial off your gauge and making a new dial. I know, Im asking you to be patient with me again.... Link to comment Share on other sites More sharing options...
OldMarine Posted June 1, 2016 Share Posted June 1, 2016 I cut a circle of white plastic to fit around my gauge. I've got the pressures for my different tooling sizes marked in different color inks. That way I only had to do the math once! Link to comment Share on other sites More sharing options...
lloyd Posted June 1, 2016 Share Posted June 1, 2016 (edited) OldMarine beat me to it! Just because the gauge has a dial doesn't mean you cannot make an "overlay" for the dial's lens. And, FWIW... it isn't THAT big a job to pull the hand off the gauge and install a new label over the old dial! Really... it's almost trivial, if you're careful about your work. I even know one guy who just couldn't build up his courage to do that, so he cut a dial-hand-sized slot in the gauge label he made, and just slid it OVER the existing hand. The slot was at "ZERO", so it didn't interfere with an readings! <G> Lloyd Edited June 1, 2016 by lloyd 1 Link to comment Share on other sites More sharing options...
dagabu Posted June 1, 2016 Author Share Posted June 1, 2016 The gauges are oil filled, Lloyd and crimped on. No overlay will work on these. A "ring-around-the-rosy" would but a PTF gauge that is 1:1 seems like a splendid idea. Thanks for the explanation Link to comment Share on other sites More sharing options...
lloyd Posted June 1, 2016 Share Posted June 1, 2016 "No overlay will work on these."-------------Really? Even applied on the OUTSIDE of the lens? Really? The outside of the lens is also oil-filled and unavailable for an 'overlay'? Hmmm.... (just for clarification... the only detriment to labeling on the outside of the lens is "parallax", which is easily dealt with by the knowledgeable reader.) Lloyd Link to comment Share on other sites More sharing options...
dagabu Posted June 1, 2016 Author Share Posted June 1, 2016 (edited) OK, I understand that you see things much differently (smarty pants) than the average person so stay with me on this. If you make a very small overlay and carefully lay it onto the very edge of the gauge, you have a very small circular strip with the lines and numbers... OK, it would really be hard to read and a PITA overall. What the heeel is a parallax? The below explanation doesn't do much for me. "Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight, and is measured by the angle or semi-angle of inclination between those two lines." http://i.ebayimg.com/images/g/S-kAAOSw9mFWG-Kb/s-l1600.jpg Edited June 1, 2016 by dagabu Link to comment Share on other sites More sharing options...
dagabu Posted June 1, 2016 Author Share Posted June 1, 2016 Back to the PTF gauge... I am going to make few more of these as I need to work on my inside boring skills (don't ask) and am looking to do them a little differently. I think I will make them like this: http://www.ametektest.com/~/media/ametektest/products/force_gauges/hydraulic_gauges_load_cell_329_210x360.jpg Link to comment Share on other sites More sharing options...
OldMarine Posted June 1, 2016 Share Posted June 1, 2016 If your gauge is being viewed from the side rather than straight on the apparent position of the needle will be slightly off from it's actual one. I don't think the error would make a whole lot of difference because it wouldn't be but a few lbs. Link to comment Share on other sites More sharing options...
dagabu Posted June 1, 2016 Author Share Posted June 1, 2016 If your gauge is being viewed from the side rather than straight on the apparent position of the needle will be slightly off from it's actual one. I don't think the error would make a whole lot of difference because it wouldn't be but a few lbs. I am sorry but I really don't understand why I wouldn't be viewing the gauge straight on? The 45° elbow will give me the ability to see it at a flat angle. Link to comment Share on other sites More sharing options...
OldMarine Posted June 1, 2016 Share Posted June 1, 2016 I didn't assume you would but was merely explaining parallax error. In land navigation using a compass it can be a big problem and can lead you to be miles off track but not so much on a pressure gauge. Link to comment Share on other sites More sharing options...
lloyd Posted June 1, 2016 Share Posted June 1, 2016 Dag,You 'assume' too much, I think! A ring extending from the inside of the outer metal housing to just inside the red line would obscure all the existing markings, and leave LOTS of room for nomenclature of your own. And all but just the barest tip of the hand would still be fully visible. It's your deal... I was just trying to show an 'easier way out', using standard components instead of custom-made ones -- something you could do on your HP printer, instead of on the lathe. You certainly are welcome to do it any way you choose, and nobody will find fault with that. LLoyd Link to comment Share on other sites More sharing options...
lloyd Posted June 1, 2016 Share Posted June 1, 2016 BTW... I mean to ask why you spring for the extra cost of an oil-filled gauge when you're dealing with a zero-shock environment? Oil-filled gauges are meant to resist the pump vibrations (etc.) of powered hydraulic systems, but are completely unnecessary in a static-pressure environment like a hand-pumped jack. Lloyd Link to comment Share on other sites More sharing options...
dagabu Posted June 2, 2016 Author Share Posted June 2, 2016 One word answer.... $14.00 Link to comment Share on other sites More sharing options...
lloyd Posted June 2, 2016 Share Posted June 2, 2016 "Fourteen Dollars" is a two-word answer! <G>Yeah... it's hard to beat cheap. But that doesn't change the issue of how to make an 'overlay' scale that sticks on the OUTSIDE of the bezel! Lloyd Link to comment Share on other sites More sharing options...
Maserface Posted June 2, 2016 Share Posted June 2, 2016 I have no dog in this fight, but I just keep a notebook with all of my pressed formulas, and applied pressures expressed in the appropriate units on my dial, right next to the press. It takes longer for me to scratch my nuts than it does to set my pressure for any given device and go. Link to comment Share on other sites More sharing options...
lloyd Posted June 2, 2016 Share Posted June 2, 2016 Bingo, Mase! I have never used a P2F gauge myself, except to help another pyro calibrate his own or to make one for a fellow pyro. It's a 'useless appendage' as far as I'm concerned -- just one MORE tool that accomplishes nothing useful. A pocket calculator and a piece of paper serve as well, and more flexibly. That's most of why I espouse just putting a "stick-on" label on one, instead of going to all the trouble to make 'calibrated' units... Besides, I'm a hydraulics guy, and I KNOW those cheap gauges aren't all that accurate! <G> L Link to comment Share on other sites More sharing options...
dagabu Posted June 2, 2016 Author Share Posted June 2, 2016 Why waste nut scratchin with a pressure settin session, got me a PTF gauge! Many ways to skin 'ole Sylvester, carry on folks... Link to comment Share on other sites More sharing options...
Col Posted October 19, 2016 Share Posted October 19, 2016 If your gauge is being viewed from the side rather than straight on the apparent position of the needle will be slightly off from it's actual one. I don't think the error would make a whole lot of difference because it wouldn't be but a few lbs.I added a tee and an adjustable pressure switch to my P-to-F. Once the pressure switch is set (30 second job) you dont need to look at the gauge at all, just listen for a beep Link to comment Share on other sites More sharing options...
lloyd Posted October 20, 2016 Share Posted October 20, 2016 I don't 'get' any of it. Just a cheap pressure gauge is all that's needed -- plus a tiny bit of pure arithmetic. No, Patrick, not "higher math". If you can multiply and divide, you've got all the tools -- and if you can't, then use a calculator. The diameter of your cylinder never changes. Therefore, the force delivered is always the same at a given pressure. Calculate the pressure-to-force ratio ONCE, and it'll remain the same for the life of your system. I've even made P2F gauges for folks, but never understood their attraction. A simple overlay on the face of an ordinary pressure gauge accomplishes exactly the same thing for pennies. Lloyd Link to comment Share on other sites More sharing options...
Col Posted October 20, 2016 Share Posted October 20, 2016 To be fair you do need a bit more than just a cheap pressure gauge Link to comment Share on other sites More sharing options...
lloyd Posted October 20, 2016 Share Posted October 20, 2016 Noooo.... that and (if you must) a pocket calculator - and perhaps a sheet of paper upon which to write - are all you need. What 'more stuff' are you thinking of? Lloyd Link to comment Share on other sites More sharing options...
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