Ubehage Posted September 29, 2014 Posted September 29, 2014 Hi guys, I just did some experimenting with BP rocket-motors. And I was not very impressed... That tells me, I am propably doing something wrong. I used a recipe found somewhere on this site for the BP-meal: 60 KNO3, 30 C, and 10 S.I used some 15mm-tubes, for which I already have an end-burner tool to make the nozzle and fill the tube. First of all, none of my rockets went anywhere. So I decided to strap one on to a scale, to see how much propulsion it was giving.. 67 grams!?!That means, besides the rocket-engine itself, it would only be able to lift about 12 grams (including stick and payload).And, let's be honest, that is definitely not right! Can anyone, given this information, enlighten me as to what I am doing wrong?Is it the wrong composition, or is my tool just a waste of money, since such small tubes will never give a good lift?
Mumbles Posted September 29, 2014 Posted September 29, 2014 Wrong composition. The formula you have is meant for core burning rockets. For end burners, you will want to use the hottest black powder you can make. That said, end burners still don't have a ton of lifting capacity. 1
dagabu Posted September 29, 2014 Posted September 29, 2014 Hi guys, I just did some experimenting with BP rocket-motors. And I was not very impressed... That tells me, I am propably doing something wrong. I used a recipe found somewhere on this site for the BP-meal: 60 KNO3, 30 C, and 10 S.I used some 15mm-tubes, for which I already have an end-burner tool to make the nozzle and fill the tube. First of all, none of my rockets went anywhere. So I decided to strap one on to a scale, to see how much propulsion it was giving.. 67 grams!?!That means, besides the rocket-engine itself, it would only be able to lift about 12 grams (including stick and payload).And, let's be honest, that is definitely not right! Can anyone, given this information, enlighten me as to what I am doing wrong?Is it the wrong composition, or is my tool just a waste of money, since such small tubes will never give a good lift? All is not lost, you can still use them to drive a wheel around, a small girendola, add some metals and make a fountain etc. This is a 3/4" ID Endburner Lifting a 3"Ball Shell. http://youtu.be/x1NgsMA_ke4 1
Arthur Posted September 29, 2014 Posted September 29, 2014 Fountains usually have a very short cavity, wheel drivers have more and core burner rockets have a long core (tool spindle) To get good rockets out of an end burner you need hot powder. There is a vid on youtube of Cplmac 2 firing a 12" shell with a whistle motor of some (big)size
nater Posted September 29, 2014 Posted September 29, 2014 I want to say cplmac's rocket was a 2" cored whistle, but my memory may not be accurate. Before he moved, he used to fly large rockets at HPAA shoots regularly. As has been said, you will hot BP with your end burner tooling. Use 75-15-10, milled with a good charcoal and you should be good to go. If you have more of the 60-30-10 fuel left, I would add a little metal to them, press with a nozzle on your end burner tooling and call them gerbs. 1
Arthur Posted September 29, 2014 Posted September 29, 2014 Your existing fuel needs a long taper spindle rocket tool, and may produce good rockets. However as a beginner to rockets concentrate on one tooling and make the best that you can, then try other fuels, and other tools one at a time. You are unlikely to succeed at two types at the same time without a lot of experience. 1
Arthur Posted September 30, 2014 Posted September 30, 2014 Remember that the force of a lifting rocket (motor thrust less total mass) is what causes the rocket to accelerate, a rocket accelerates to a high speed then gains more height while it coasts unpowered before it reaches apogee, at which point it has about zero speed and turns back earthward under gravity. Getting the best point to fire a payload is part of your design, but will be after the burn out of the motor but before or at apogee. As a general indication for BP like fuel, fountains use a spindle about 1D long, drivers use a spindle about 4D long and core burners use a spindle about 10D long. Where D is the internal diameter of the tube. Whistle rockets are much more powerful and are not a beginner topic, they cannot be rammed. Before you make a rocket like cplmac's find the space for the stick to land (it's about 8ft long -an estate agent would use it!). A one mile radius would be a fair start more if you can. 1
Seymour Posted September 30, 2014 Posted September 30, 2014 The end burning tooling will make drilling out a core quite easy. You kind of have a pilot hole in a perfectly centered position. If you are happy to carefully drill out the core (by hand ideally) then I'd suggest trying out a 5mm diameter drill bit. How deep you drill will depend on personal preference and your batch of fuel, but I'd say trying starting at five or six times the tubes ID deep, and then doing tests sequentially deeper until you are ether happy with it, or it explodes, and in that case you just dial it back a bit. 1
stix Posted October 2, 2014 Posted October 2, 2014 Approx. how much fuel did you use, what diameter is the nozzle, how long does it burn for?
Ubehage Posted October 2, 2014 Author Posted October 2, 2014 I did not weigh the fuel alone, stupid me. I filled the 15x100mm tube about 3/4, as I had seen on Youtube.The nozzle is almost 2mm wide, and it burned for 4-5 seconds.
stix Posted October 2, 2014 Posted October 2, 2014 I did not weigh the fuel alone, stupid me. I filled the 15x100mm tube about 3/4, as I had seen on Youtube.The nozzle is almost 2mm wide, and it burned for 4-5 seconds. Ok, but given your previous info around 15-20 grams I would think? You should research specs for Estes motors "C" class. (similar to your rocket motor) Approx. 13 grams of fuel, burns for 1.5 secs delivering a max thrust of 1.5 kilos!! Why the big difference? Well, your fuel doesn't burn fast enough. Please don't just "drill out" just to get something out of your fuel - as suggested, stick to 75/15/10 using "end burners". If that doesn't work well then you really need to look at your methods of making bp which are well documented here. Also 2mm nozzle with a 15mm diameter is pushing it - about a third of the ID (5mm) should be enough to begin with. Like I said, Don't do core burners unless you are sure what you are doing. Stick with the end burners and if you can't get good results, then go back to step one, ie. making good black powder. Don't be impatient, safety is the main thing - I've read enough "go wrong" stories on this forum to make me shudder knowing the stupid (uninformed) things I have done in the past. Be Safe. Cheers. 1
DeViL Posted October 3, 2014 Posted October 3, 2014 Hello I'm new on that forum, I want to retrieve some information about pyro tech, and also want to share what I know about pyro tech, so can help.I have an formula for rocket propalation : 10 Kno3 , 3 Charcol , 1.5 Sulfer , It's worked fine for me. Making video and even rocket tube making procedure coming soon.And also you can use any blank cotton thread tubes as rocket bp container. thank you.
sora Posted October 8, 2014 Posted October 8, 2014 (edited) You mean these type of paper made bobbins? Yes, once I used them a lot as end burner rockets and then shifted to core burner ones. I also used aluminium made fluorescent lamp starter casings as end burners. Edited October 8, 2014 by sora
Seymour Posted October 8, 2014 Posted October 8, 2014 Like I said, Don't do core burners unless you are sure what you are doing. Stick with the end burners and if you can't get good results, then go back to step one, ie. making good black powder.While there are many valid ways to progress in this hobby, I was making core burners and fountains with 6/3/1 for a while before I got on to end burners, and it worked well for me. To be honest I think the greatest hazard is from under powered rockets, which probably tend to more often be end burners. Core burners more commonly fly well or explode, which should cause nothing but a fright and some frustration. I understand and respect your advice to do things one step at a time, and resist the urge to fully chase the early excitement which can lead to accidents. In my case, while I won't deny being young and too keen did not lead to greater risks, I was making do with what I could do with screened together chemicals while I obtained the parts for a ball mill, and using screened KNO3, Charcoal and Sulfur one is pretty much limited to core burning rockets and charcoal fountains. In this case since Ubehage already has 60/30/10 it seems to make sense that he makes use of it, though I concede that this would be easier and safer to use in fountains, and that having a ball mill, making 75/15/10 for end burners is an ideal first choice for rocketry. 1
stix Posted October 8, 2014 Posted October 8, 2014 Fair enough Seymour, I can see your point on most of it, but your comment "Core burners more commonly fly well or explode, which should cause nothing but a fright and some frustration." is 'exactly' my point. I think the possibility of a pressed bentonite/fireclay nozzle randomly propelled at great speed is something worth due respect and consideration. Anyway, nice to hear from a fellow pyro from "across the ditch" Cheers, Steve.
stanlyh Posted November 5, 2014 Posted November 5, 2014 Hi, have same problem with end burner driver burns 9 second and have no thrust case is mako from ppr tube ID 20mm symikary for paper ID 19mm but much cheaper..
dagabu Posted November 5, 2014 Posted November 5, 2014 Hi, have same problem with end burner driver burns 9 second and have no thrust case is mako from ppr tube ID 20mm symikary for paper ID 19mm but much cheaper.. Made, paper, Skylighter?
stix Posted November 6, 2014 Posted November 6, 2014 Made, paper, Skylighter? Perhaps "made" , "polypropylene" , "similar" ?? So Stanlyh, How much bp are you using, ie. weight, length - nozzle diameter?
Col Posted November 6, 2014 Posted November 6, 2014 More info on the motor specs would be good.Heres a short 3/4" id endburner test, total fuel 34.3g (not the hottest bp), grain length 90mm, nozzle 4.5mm expanding to 6mm.Total flight weight 103.5g including the stick and a small salute. http://youtu.be/T18n-f6HJ9U
Col Posted November 6, 2014 Posted November 6, 2014 Hi, have same problem with end burner driver burns 9 second and have no thrust. Case is mako (made) from ppr (paper) tube ID 20mm symikary for (similar to) paper ID 19mm but much cheaper..Hey Stix, not polyprop he`s using 20mm id tubes made from paper which are cheaper to source than standard 3/4".
stix Posted November 6, 2014 Posted November 6, 2014 Hey Col - I like it. Around about 5g's at max thrust.ie. maximum thrust/total rocket weight (500grams/104) Not bad. I'd probably prefer a bit more grunt over less time. Nevertheless, a nice graceful curve in acceleration. Cheers.
stix Posted November 6, 2014 Posted November 6, 2014 Hey Stix, not polyprop he`s using 20mm id tubes made from paper which are cheaper to source than standard 3/4". Nah... I beg to differ - I think he DID mean PolyPropylene Random copolymer tubing. I think I'm correct - If I'm wrong, it would be only other time since 1978 - and anyway, I'm fine with that. That's only twice in 36 years or so. Anyway, I guess we await the op's clarification ... whoops, sorry, I meant . Cheers.
Col Posted November 6, 2014 Posted November 6, 2014 These are for a 12" dola so i dont want them too nippy or it`ll rise too fast and be too high for anything except salutes
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