Peret Posted April 16, 2012 Author Posted April 16, 2012 Does this mean that you don't want to go ahead and made an off the shelf rig? That would be a darn shame since you have the best rig to date. On the contrary, it means I ONLY want to make off the shelf rigs. I'll stand behind those because if anyone has trouble with one, I can investigate with an identical setup. No, my fear is the electronics fall into the hands of one of the haters on Passfire, they screw it up, I can't fix it because I don't know the setup, and then I get abused for ever on the forum. You should understand that, after the time fuse thing. In fact I've half a mind to announce I will never under any circumstances sell one to a member of Passfire, but that would be unfair.
dagabu Posted April 16, 2012 Posted April 16, 2012 On the contrary, it means I ONLY want to make off the shelf rigs. I'll stand behind those because if anyone has trouble with one, I can investigate with an identical setup. No, my fear is the electronics fall into the hands of one of the haters on Passfire, they screw it up, I can't fix it because I don't know the setup, and then I get abused for ever on the forum. You should understand that, after the time fuse thing. In fact I've half a mind to announce I will never under any circumstances sell one to a member of Passfire, but that would be unfair. I am good with that, say the word and I will drop my membership today. I have made mistakes, no human has not, I accept all of my mistakes and have tried to reach out to others in order to make restitution for those wrongs I have committed. I do agree that it would be unfair but I would make a very short list of those that I would sell one to if I were you. Might I suggest that you epoxy your boards (costs about $.50 per unit) with black epoxy so that they cannot be copied, modified or screwed up? It also makes then shock and waterproof. In any case, I will work with you or just buy one from you if you are willing, if not I completely understand and will do my best to control my unbridled lust for the rig you designed. -dag P.S. That was really kind of creepy, wasn't it?
warthog Posted April 16, 2012 Posted April 16, 2012 Well, if you will check my status on Passfire and perhaps look into what I have told Dag of late, you might find we are really in complete agreement. In any case, I like the rig and maybe one day, if you will have me, I will ask you for one once I buy my land. Should happen by the end f the year than the time it takes to get the magazine in place etc plus the inspections and the license... that will be when I will want one. I always have been working towards my own land and license so the end of the year was always in my mind as a date to get it done. This just means fewer people will be welcome on my land is all, which is sort of nice n ow that I think about it.
dagabu Posted August 9, 2012 Posted August 9, 2012 Well kids, after 6 months of hard work by Peret and some metal work by myself, I am proud to introduce to you the ACME Rocket Test Rig by Peret! There will be a fully functional test rig that anybody can use to test motors with thrust up to 220 pounds at PGI this year. Bring your motors and lets see what they can do! I am still working on a printer but if I cant get that in the car with me, I will be happy to email screen shots of the Impulse and or curve to you at no cost. This is the very first field expedient and completely automated test rig that I know of. Press a button, the rig will light your e-match and record the motor burn. Load another motor and e-match, press the button and on and on. There is room in the on-board memory for 18 tests and it takes under a minute to pull everything off the memory and load it to the computer, wipe the memory and go test another 18 rockets. I will leave the details to Peret to go over with you but you will be able to find me in manufacturing all week long starting tomorrow until Friday the 17th. Light er up! -dag
nater Posted August 9, 2012 Posted August 9, 2012 Well, sign me up. Let's see what I can do with hybrid motors. Well, sign me up. Let's see what I can do with hybrid motors.
Peret Posted August 9, 2012 Author Posted August 9, 2012 (edited) Good luck, guys. This will be the first full-scale test of the system. I fired some 1-pound motors with 20 pound thrust and now looking forward to seeing the results with some REAL motors. I'll do a proper write-up on it when I have a little more time. <edit> No need just to be content with a screen shot. The rig automatically saves the data in Excel compatible CSV files, so Dag can copy the actual data files to your USB stick to take home and analyze the hell out of. Edited August 9, 2012 by Peret
californiapyro Posted August 9, 2012 Posted August 9, 2012 any sort of retail price on this rig? I need one
nater Posted August 9, 2012 Posted August 9, 2012 Has anyone put SBR motors on a test stand? Something else we can do next week.
Peret Posted August 9, 2012 Author Posted August 9, 2012 We can't really settle on a price until Dag and I work out how much we put into these things and agree what our time is worth. My original aiming point was a ballpark $300, I can't see it being far out. The development is sunk cost and I'm not looking to recover it.
nater Posted August 19, 2012 Posted August 19, 2012 Very nice rig gentlemen, and very easy to use. I tested a 3/4" motor with hybrid 2 fuel and a 3/4" motor with Dan Thames' HP-140-C whistle fuel. I am looking forward to seeing the results. 2 members of our club did have one concern about the design. They prefer a horizontal motor mount to remove the effect of gravity and the changing weight of the motor as it burns. They admit the difference is minor, but does play a part when you are building a huge girandola with 50 or more drivers. Personally, I don't think that is a big issue at all, especially for my needs. I will be in for one of your stands when they are ready. The single button operation and everything being self contained is far more important to me than the orientation of a burning motor. Did anyone manage to CATO a motor on it last week? I told Dag I was concerned one of mine might pop, but he assured me it would not be a problem. It functioned flawlessly anyway.
Peret Posted August 19, 2012 Author Posted August 19, 2012 I'm pleased to hear it worked well - I'm looking forward to seeing the results too. I have not yet seen any results from a hybrid or whistle. Hopefully we'll get enough results eventually to compile a reference table. The rig is capable of measuring and accounting for the fuel loss at the end of the burn, though it isn't in the software at the moment, and the curve would not be accurate because there is no way of separating the weight loss from the thrust while the motor is burning. Based on the limited testing I've carried out myself, the weight loss is negligible compared to the thrust (in the order of 1%). A horizontal rig is certainly possible. It would be more complicated mechanically because it would need a ball bearing slide or similar to avoid errors due to friction. The same electronics could handle it. If anyone feels motivated to design a horizontal rig I can certainly help with the integration, but I don't have the time or the mechanical facilities to do the whole thing. We are pretty sure the rig as constructed would survive a very substantial CATO without damage
dagabu Posted August 19, 2012 Posted August 19, 2012 I just rolled in, it will be a few days till I have data etc... Two CATOs were recorded and the system is still 100% functional. I will be bringing it to Boom Town this next weekend for more testing. -dag
nater Posted August 19, 2012 Posted August 19, 2012 Peret, I only brought up the horizontal motor mount because two builders in my club asked me to. When they looked the rig over, they agreed it was very nice and an awesome, self contained unit. They mentioned doing the calculations to account for the motor weight, and I will let them know the software can figure that. I don't think they will be customers anyway, not because they don't like it, but because they have built a stand for themselves already. I am glad to hear it recorded some CATOs without incident. I am also glad it wasn't me that tested it in that manner . Every single one of my motors performed exactly as I hoped. (headers not so much) One round tripped, but I was testing someone else's fuel on my spindle to compare the difference in tooling design.
dagabu Posted August 20, 2012 Posted August 20, 2012 I will record some end burners and SBRs this weekend to test the whole idea of the fuel loss but honestly, I am guessing it was much hot air and not of much value rather then a real concern. -dag
Peret Posted August 20, 2012 Author Posted August 20, 2012 I think it's just hot air too. I'm all for accuracy, but there's a trade-off and some things are not worth bothering with. Even for a weak BP motor, the loss of fuel weight will be less than 2% of peak thrust, plus the error is on the safe side - the impulse will be slightly larger than calculated, owing to the loss of weight, so the rocket will lift slightly more or go slightly higher than calculated. I might just calculate and display the fuel weight loss, for completeness.
nater Posted August 20, 2012 Posted August 20, 2012 I think it's just hot air too. I'm all for accuracy, but there's a trade-off and some things are not worth bothering with. Even for a weak BP motor, the loss of fuel weight will be less than 2% of peak thrust, plus the error is on the safe side - the impulse will be slightly larger than calculated, owing to the loss of weight, so the rocket will lift slightly more or go slightly higher than calculated. I might just calculate and display the fuel weight loss, for completeness. I mentioned it, because feedback was asked for and it was some feedback I received from builders I respect. I don't think they are full of hot-air, but I don't think the slight error is THAT big of a deal, at least for me and most builders. I think there are more factors with fireworks rockets that are more difficult to control than any error in a thrust curve due to the orientation of the test. I am more concerned with comparing the lifting capacity of different fuels on my spindle. I am also interested in testing the Hybrid fuels with different ratios of whistle to BP as well as the difference in thrust from different types of charcoal and techniques for blending the BP. All of those tests depend more on consistency from test to test rather than the effects of gravity and weight loss of the motor.
Peret Posted August 20, 2012 Author Posted August 20, 2012 I didn't mean any disrespect, bad choice of words really. It's important to account for loss of fuel weight if you want to, say, match orbits with the international space station, or drop a nuke on Dallas while sparing Fort Worth. It's probably equally important to make sure your 'dola doesn't have excessive power that would make it fly into the spectators, which I understand is a regular hazard at present. I'll work to improve my math package.
nater Posted August 20, 2012 Posted August 20, 2012 Peret, big dola's are what these builders were talking about. They often build dolas with many, many drivers and are known to use sensitive comps to drive them. They both agreed with me that for every other use, it is perfect. I can't stress enough how impressed everyone was with your design. That one comment, by two builders was the only concern I heard. You have hit a home run with this design and I heard several other people say that you have just built the standard test stand. You guys should be proud.
Peret Posted August 20, 2012 Author Posted August 20, 2012 Well for what it's worth, I already started sketching out a horizontal design using a pair of ball bearing drawer slides.
nater Posted August 20, 2012 Posted August 20, 2012 Well for what it's worth, I already started sketching out a horizontal design using a pair of ball bearing drawer slides. That might be unnecessary, you must enjoy sketching something up.
dagabu Posted August 21, 2012 Posted August 21, 2012 Peret, big dola's are what these builders were talking about. They often build dolas with many, many drivers and are known to use sensitive comps to drive them. They both agreed with me that for every other use, it is perfect. I can't stress enough how impressed everyone was with your design. That one comment, by two builders was the only concern I heard. The reason I say they may be full of hot air is that the two people I think you are speaking about already have load cells and are begrudgingly resisting the new all in one device. I was told the very same thing by two rocketeers at convention and then asked them how they measured the motor thrust themselves to account for fuel loss. They also mount the motors vertically in their test stands... Hot air, like I said. There is no way to have a frictionless test rig but the design that Peret came up with offers less friction then even a roller bearing horizontal design. I am all for a horizontal design but the use of linear bearings will add cost to the test stand. On a positive note, I have received parts for three more stands and will be working with Peret to get them ready for sale. -dag
nater Posted August 21, 2012 Posted August 21, 2012 The guys I was talking to loved the all in one device, just not the motor mount. But enough of that. Parts for 3 you say? When will you take a deposit?
dagabu Posted August 21, 2012 Posted August 21, 2012 The guys I was talking to loved the all in one device, just not the motor mount. But enough of that. Parts for 3 you say? When will you take a deposit? I will defer to Peret about deposits and a price. What would you like so see for a mount? -dag
nater Posted August 21, 2012 Posted August 21, 2012 I would prefer a vertical mount. Less complicated base design with no slides or roller bearings to wear out.
dagabu Posted August 22, 2012 Posted August 22, 2012 Sorry guys, no joy, you didn't record the rockets. I wish there had been enough time to make a card showing the instructions but I think you did the same thing I did the first time I used it and forgot to arm the system by pressing the small black button by the light. I just tested the system and it works fine but all of your files are flat lines indicating that the button was not pushed. -dag
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