dangerousamateur Posted May 19, 2015 Posted May 19, 2015 I have a question about those "conversion gauges" people put under in their presses:http://www.wichitabuggywhip.com/fireworks/rockets/wolterPtoF.jpg Wolter sells them with different PSI ratings. Where does the PSI rates come from? Is that based on the instruments piston surface? I mean it measures a force, like a scale measures the weigh force. Why don't they use a newton dial?
nater Posted May 19, 2015 Posted May 19, 2015 (edited) The PSI rating is just how high the gauge reads. You want to use a gauge that allows you to clearly read the pressures you will be pressing at the most. IE: If you are pressing a large star plate, it will need to read a higher pressure than if you are pressing tiny rockets. As an example: If your target is 50 psi on the gauge for a 1/2" rocket and your gauge reads 10,000 PSI, it will be hard to find the 50 psi mark. The gauge on my press does display Newtons and PSI. Most people are not as familiar with Newtons as a unit, most, if not all, texts are written with the target pressing forces in PSI on the composition. That is probably why the sellers offer gauges which read PSI. The reading from the PtoF gauge comes from the surface area of the piston inside the PtoF tool. The ones sold by Wolter are 1 square inch. It takes a little math to convert the reading from the gauge to the target PSI exerted on the comp. Edited May 19, 2015 by nater
dangerousamateur Posted May 19, 2015 Author Posted May 19, 2015 The reading from the PtoF gauge comes from the surface area of the piston inside the PtoF tool. The ones sold by Wolter are 1 square inch. It takes a little math to convert the reading from the gauge to the target PSI exerted on the comp.Thanks. I find this irritating. indicating the force would be more logical (to me).It's about the pressure on the composition anyway.
nater Posted May 19, 2015 Posted May 19, 2015 No single, mechanical tool would be able to read the exact pressure exerted on the comp when using different sizes of tools. The difference in surface area between the piston on the tool and the surface area of the comp being pressed is the reason a conversion is needed. One could build an electronic tool where the user would enter the total surface area of the comp being pressed and a screen would display the pressure on the comp. 1
calebkessinger Posted May 19, 2015 Posted May 19, 2015 Dangerous man... If you are irritated about it you should find a way to DO exactly what you want done. With todays electronics it CAN be done. Nothing stopping you but time and money. We are all Gladly awaiting your results !! Yes, I'm being a little sarcastic and silly.. Most everything we do in pyro requires math and figuring. From making a formula to pressing stars there is plenty of math to be done. Once you get set up and are using your press regularly it's really not a terrible deal to do a little figuring every now and then.. pretty soon you will have all the standards written down somewhere and it takes no effort to just adjust the pressure on your pump to the predetermined standard.
ddewees Posted May 19, 2015 Posted May 19, 2015 Just buy a press for each size rocket/device, then you'll only have to set it once. 2
dangerousamateur Posted May 20, 2015 Author Posted May 20, 2015 Calculation is not my problem. I was just irritated, because they did not state that the piston is a square inch. Ok, obviously it must be Are there other instruments, maybe cheaper ones, that could do the same job?120$ is a lot of money. Do you know of similar cheaper devices sold for some non-pyro application in the same force range?
nater Posted May 20, 2015 Posted May 20, 2015 You were already on Dan Creagan's site - did you see this page? http://www.wichitabuggywhip.com/fireworks/ptof/ptof.html Wolter's PtoF tool has a 1 sq in piston, it says so on his site too. The one Ben Smith sells has a different size piston and he too lists the size, he also has tables with common target pressures for different tools with the gauge readings for his presses and PtoF gauge.
calebkessinger Posted May 21, 2015 Posted May 21, 2015 Yes 120 bucks is a lot.. butliquid filled guage 26 bucks + 10 shipping = 36harbor freight hydraulic ram. 40 bucks + 6 shipping = 46 That's 82 bucks for something you still have to work on...Nah.. a wolter or bens gauge is very reasonable.
Rocketier Posted May 21, 2015 Posted May 21, 2015 (edited) I made an xls file to calc Kg to psi. This calc is made for several tube sizes. Change the Kg in the yellow part of the xls. Tube diameter is in mm.calc.xlsx Edited May 21, 2015 by Rocketier
dangerousamateur Posted May 21, 2015 Author Posted May 21, 2015 Nah.. a wolter or bens gauge is very reasonable. OK, thank you. Uhm yeah... wolter or firesmith...? If I order such a thing, which would you prefer?
nater Posted May 21, 2015 Posted May 21, 2015 The ones from Firesmith are a little larger, that makes resting the tooling on them a little easier and helps everything stay aligned. The ones from Wolter have 1 sq in pistons which eliminates one calculation when you figure out how much pressing force you need. In the end, those are both very minor advantages. Both makers build high quality tools. The calulations for pressing force only need to be made once. When you have a chart for the tools you use, the process goes quickly. Stacking the tooling or plates in the gauge and keeping it all square with the press is also easy. Like all that for a non-answer?
MrB Posted May 21, 2015 Posted May 21, 2015 Load-cell based? Needs to be one freaking amazing load-cell, but i'm sure it could be done.B!
calebkessinger Posted May 21, 2015 Posted May 21, 2015 The press I just shipped had one Dan... I have a wolters gauge. with his chart it works quick and easy..
nater Posted May 22, 2015 Posted May 22, 2015 (edited) Dan, a club member had a press from Ben outfitted with a hand knob to adjust the relief valve easier. It can be done. I still want an electronically adjustable valve so I can set it up with an arduino board to program pressures. Edited May 22, 2015 by nater
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