eoneuk Posted March 18, 2015 Posted March 18, 2015 My question is does nozzle design appreciably affect the performance of a 1/4" bottle rocket? Currently I just use a straight-through hole and am basically satisfied. However, with the fuel configuration being equal, would a "flared" nozzle contribute to additional height and/or lifting capacity? Just want an opinion to see if it is worthwhile looking into other alternatives. Ed
FlaMtnBkr Posted March 18, 2015 Posted March 18, 2015 (edited) I don't know the answer to your question in such a small size rocket. But have you tried a nozzle-less rocket? You can use the hottest BP you can make which are quite reliable in such a small size. They really have some snort and you can get a little more powder in without the clay nozzle. I actually haven't tried them in 1/4" but have made tons of 3/8" rockets which are actually some of my favorite rockets. They are quick to make, can get lost in the clouds with a small 1-2 g flash payload, and are small enough to shoot on our property without much worry of fallout. The report shreds the end of the tube which usually makes it helicopter back to earth. But they are so lightweight they wouldn't do much damage. They are also powerful enough to lift a decent payload such as a festival ball shell to a good display height. I imagine a 1/4" could do similar but might be a bit low. Might be worth playing with. I know that wasn't what you were looking for but might give you some ideas. Edit: clarification Edited March 18, 2015 by FlaMtnBkr
pyrokid Posted March 18, 2015 Posted March 18, 2015 When I was making bottle rockets before I had proper tooling, I drilled out the nozzle using a drill bit. Results were inconsistent. There was large variability in core length, and there was always some unsightly and potentially detrimental flaking of the clay nozzle. When I made my tooling, it was simple enough to incorporate some convergent/divergent elements into the nozzle geometry. There was essentially no additional cost, and only the potential for increased performance, so it was not a hard decision. Use http://www.flashnet.dk/rts/ to play around with design.
insutama Posted April 3, 2015 Posted April 3, 2015 I have bottle rocket tooling and I found that the nozzle is waste of tube best to use just bp these bottle rockets with the core sure don't burn for long it's almost like a mini burst that sends it shooting up. When I made a bottle rocket without tooling I made a clay plug then bp for the rest of tube then next I drilled a nozzle just threw the clay and I find these rockets go higher and burn longer than the cored rockets made with the tooling does anyone else notice this? Im sure the cored rocket made with the tooling would probably be able to lift more of a payload.
FlaMtnBkr Posted April 3, 2015 Posted April 3, 2015 Yes, core burners burn the thrust phase in a fraction of a second where end burner takes a few seconds to burn. A lot of times core burners almost sound like a controlled explosion as they take off. The rocket where you just drill thru the clay probably go higher because they are so light that they don't have much momentum and slow down quickly. They are more of an end burner and get pushed higher with the long burn. Just keep playing and you will learn all kinds of things and start experimenting. Have fun!
insutama Posted April 4, 2015 Posted April 4, 2015 (edited) It kinda feels like the tooling rocket that's a core burner isn't as good as the end burner it defiantly dosent go as high would it be able to lift more? Edited April 4, 2015 by insutama
dagabu Posted April 6, 2015 Posted April 6, 2015 It kinda feels like the tooling rocket that's a core burner isn't as good as the end burner it defiantly dosent go as high would it be able to lift more? Yes, core burners lift a LOT more by weight than an end burner can. Overall, the geometry of the nozzle in any rocket less than 3/8" or 10mm is irrelevant due to the tooling and materials needed to form the nozzle. A flat nozzle (no convergence or divergence) works just as well as a fully flared nozzle in these novelties. Putting just a tiny taper on the first rammer is good but don't go overboard.
Maxim Posted April 6, 2015 Posted April 6, 2015 Some times the end burning rockets do not even fly, the BP must be very hot. The conus nozzle is used to stabilize the flying. And it is gonna be a pain to make such tools for small rockets about 9 to 12 mm.
dagabu Posted April 6, 2015 Posted April 6, 2015 Some times the end burning rockets do not even fly, the BP must be very hot. The conus nozzle is used to stabilize the flying. And it is gonna be a pain to make such tools for small rockets about 9 to 12 mm. True, that is where reactive charcoal and a ball mill become a necessary part of the propellant prep.
pyrokid Posted April 6, 2015 Posted April 6, 2015 Hey dagabu, in your experience, how much do pressing pressures affect lifting power on these small rockets?
dagabu Posted April 6, 2015 Posted April 6, 2015 Hey dagabu, in your experience, how much do pressing pressures affect lifting power on these small rockets? Good question! There has been much flurry about dropping pressures on comps as of late. There are several proven cases of 2000 LPI used to compact BP that have given solid grains and good progressive burns. It seems that we may have gone too far with pressing and make the grains too solid allowing for cracking as the propellant "relaxes" over time. Whistle is know to do this more than other propellants. I guarantee you that if you use a hammer on 1/4" (6mm) column, you are exceeding the 2000 LPI and are probably exceeding 10,000 LPI! Tap a 1/4" motor, fly one and see for yourself. 1
insutama Posted April 12, 2015 Posted April 12, 2015 Ya the black powder i made burns super hot i am super impressed by the speed of which it burns it burns as fast as a slow flash mix i milled for 4 hrs then granulate with alcohol and no binder. Burns like a hot damn
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