dangerousamateur Posted July 5, 2012 Posted July 5, 2012 Hi, look at this one:http://www.pyrobin.com/files/100_0787.JPG Most motors expand during ramming or pressing. So how do you get it out of the sleevetube afterwards.....?
dangerousamateur Posted July 7, 2012 Author Posted July 7, 2012 I see. So without press this kind of sleeve is useless to me...
dagabu Posted July 8, 2012 Posted July 8, 2012 I see. So without press this kind of sleeve is useless to me... Without a press you get BP rockets only and not over #1 unless they are nozzleless. Spend $40.00 and get an arbor press. -dag
dangerousamateur Posted July 11, 2012 Author Posted July 11, 2012 Without a press you get BP rockets only and not over #1 unless they are nozzleless.A can you explain that a little? I'm not doing such large rockets anyway, but will a big rubber mallet be insufficient to compact the stuff? And why does that not aply for nozzleless? In my experience even the strongest nozzle is worthless if the fuel is not compacted good enough, it will go boom anyway. Spend $40.00 and get an arbor press.In Europe were rather talking about +200$ for a 2 ton design. And your not done, because the working height is usually far to small. What would you estimate, how many tons do I need for 2lb Rockets?
dagabu Posted July 11, 2012 Posted July 11, 2012 (edited) A can you explain that a little? I'm not doing such large rockets anyway, but will a big rubber mallet be insufficient to compact the stuff? Rubber mallets are about the worse hammer you can use to consolidate a powder. The test I use to show noobs the concept is to measure off 30g of fuse powder (corned 7FA plus fines in size) and use a section of .75" copper pipe with hose clamps securing it closed. Using a 1/4 teaspoon measure, I add one heaping scoop at a time and have them pound the grain with a rubber mallet, a delrin hammer and a steel hammer (yes, I know the risk). I open the clamps and pull out the fuel grain then measure it with veneer calipers. The steel hammer consolidates the grain a full 1/2" more then the rubber mallet and 3/16" more then the delrin hammer. We also look at the rammer after each hammer to show the wear. The steel hammer mushrooms the rammer with just those few blows it takes to pound the column. It would destroy a set in short order. Even dead blow hammers cant consolidate the grain like a hard faced hammer can. We then break the grains by hand, the rubber mallet rammed grains break easily and lots of loose powder grain are released. Only a few grains are released in the delrin rammed grain and none when breaking the steel hammer rammed grain. Anybody can do this with a motor tube support and a rammer to see for yourself the differences. And why does that not aply for nozzleless? In my experience even the strongest nozzle is worthless if the fuel is not compacted good enough, it will go boom anyway. Nozzleless rockets make a lot less pressure and cause less fuel grain deflection that cause cracks and thus CATOs. The effective nozzle opens up as the fuel burns away causing a very flat burn pressure. In Europe were rather talking about +200$ for a 2 ton design. And your not done, because the working height is usually far to small. A 2 ton press is about $300.00 here as well, I was talking about a cheap used 1 ton press. The height issue is easily solved with threaded rod and a steel plate. A hydraulic press is needed for larger rockets. What would you estimate, how many tons do I need for 2lb Rockets? It is recommended that you use at least 5000lpi on BP and 7000lpi on whistle. A #2 rocket (.875" ID) needs the same lpi as a 1/2", 1/4". 1/8" ID rocket, the lpi is a constant, it is the available pounds per square inch that varies from one to another. Hypothetically: You have a 1" ram on a press and it can create 4000 PSI of force PER SQUARE INCH if you pull the handle down hard enough to lift you off a chair. On a .75 ID tube, you will be able to press 7111lpi on the fuel above the spindle. A #2 rocket is .875" will put 5224lpi on the fuel above the spindle. If you were to make a 1" ID rocket, you would have only 4000lpi to work with and that is really not enough to fully consolidate the fuel into a solid grain. -dag Edited July 11, 2012 by dagabu
dangerousamateur Posted July 12, 2012 Author Posted July 12, 2012 Thank you for your answer dagabu. at least 5000lpi on BP and 7000lpi on whistleWell, with the 1 ton/2000 pound press you suggested I'm going to reach about 4000psi on the fuel with an 1lb rocket. Maybe 5000 with playing tricks like extending the handlebar - if the press survives the torture. Not very much... To be really well equipped I think I'll need at least a 3 ton press. That means about 250€ and handling a 50Kg lump of metal...Say - I never worked with such a thing, but compared to theese typical hydraulic presses with hand pumps pressing a rocket with an arbor press must be really fast - is that true in practice?
dagabu Posted July 12, 2012 Posted July 12, 2012 Thank you for your answer dagabu. Well, with the 1 ton/2000 pound press you suggested I'm going to reach about 4000psi on the fuel with an 1lb rocket. Maybe 5000 with playing tricks like extending the handlebar - if the press survives the torture. Not very much... To be really well equipped I think I'll need at least a 3 ton press. That means about 250€ and handling a 50Kg lump of metal...Say - I never worked with such a thing, but compared to theese typical hydraulic presses with hand pumps pressing a rocket with an arbor press must be really fast - is that true in practice? Yes, I use my 2 ton arbor press to make all my rockets under .75" with no cheater bar. For .75" and above, I use the hydraulic press I made. http://www.pyrobin.com/files/100_0923.jpg Pyrotechnics is not a poor mans hobby.-LS
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