flying fish Posted July 27, 2009 Posted July 27, 2009 (edited) I have been trying to make bottle rockets using the following method: Press around 1.5 grams of 76/23/1 benzoate whistle mix (tried without binder/ petroleum jelly) into 1/4" ID tube using ghetto tooling consisting of a bamboo skewer (pointed tip) with duct tape wrapped around it (the skewer forms the core). They were pressed in a vice. The motor was attached to a bamboo skewer for stabilization. Results: Rockets flew with a not-so-loud whistle, only up to about 40-50 feet. The motors seems somewhat fragile, as in whistle mix will fall out of it if you drop it. I guess this is expected without a binder, right? Desired improvements:- less fragile motor- Higher flight So here's one of the main things I am confused about - Does the petroleum jelly do anything besides keeping moisture out? Does it help hold the propellant together at all, or is the pressed benzoate enough to keep it together? And in these small rockets that I am making, could I use a binder if I wanted to...like Nitrocellulose Laquer? Now the next problem is height...I'm just not getting enough thrust. Of course, I just used an arbitrary shape for the tooling...that of the bamboo skewer that I had sitting around. I also tried making the taper on the skewer more flat rather than rounded by grinding, but the result was the same. I have a feeling that getting more thrust will have to do with tooling geometry, right? I guess for now I will look around to find the appropriate tooling dimensions... (edits: as I'm pulling together a little more information I omited/re-phrased some of my questions) Edited July 27, 2009 by flying fish
Sambo Posted July 28, 2009 Posted July 28, 2009 (edited) I have found the petroleum jelly does bind it together somewhat, although i do make some high power whistles from Dan Creagan's site. They do not contain the vaseline binder, i have found these to be just as hard as the ones with vas. The benzoate seems "waxy", i think this helps.Your problem could be not pressing to a high enough pressure, this would cause the lack of whistle as you describe and the crumbling fuel. On the core note, generally the longer the core the more thrust until the core is too large and it will cato. Experimentation is needed to establish a good core length and diameter that suits your fuel. You will probably need some stronger tooling to do this though and also maybe a tube support (depending on what tubes you use). Try adding some vas (1-2%) and extending the bamboo skewer core, you could also try lighting the core of the ones made on the current tooling to see if they achieve more thrust. Edited July 28, 2009 by Sambo
flying fish Posted July 28, 2009 Author Posted July 28, 2009 Thanks! I think you have pointed me in the right direction. Yes, I will probably need tube support then. I pressed them until they started developing kinks...any more and the tubes probably would have broken. I thought that the weak tooling/tubes and other unconventional methods might actually work due to the small size of the rocket (bottle-rocket size), and the fact that I'm not really looking for high performance (just 100 feet or so of flight maybe). But of course I'm probably mistaken .
Richtee Posted July 28, 2009 Posted July 28, 2009 (edited) Fish..I dunno if you tried the WM I sent along with you, but that stuff is NC bound and FAST. It will self contain in like 3-5 grams. Not only does the vasline bind, but it SLOWS it down to rocket fuel. You COULD bind the stuff I had with a dampning of acetone, but all my results were C A T O. Impressive..but not the point. Edited July 28, 2009 by Richtee
flying fish Posted July 28, 2009 Author Posted July 28, 2009 Thanks for the advice! I haven't tried that batch of whistle mix for rockets, but I have used it for shells. For kicks and giggles I broke some of my plastic 1-3/4" "festival balls" with the pure granulated whistle! I love it for that purpose...makes people doubt that they were plastic shells with zero layers of pasting or spiking. For 3" shells, I've sprinkled some in the middle as a booster, which also works quite well. I whipped up a new batch of whistle for my bottle rockets on sunday...Milled the benz/ Fe2O3 for about 3 hours and then mixed in the perc. I've heard some say (namely in a skylighter newsletter) that you are supposed to mill the crap out of the benzoate...like 8+ hours. Considering that things are not optimized, I'd bet I could get away with the NC laquer binder thing without CATO. It might not work, but it might be worth the try. While I'm at it I'll also try pressing the riced WM you gave me with acetone, as you suggested.
fredjr Posted July 29, 2009 Posted July 29, 2009 After seeing this thread yesterday I made some 1/4" tooling, taking pictures. I don't have time to wrtie a tutorial today but next monday I should have time. Using just a drill press, files and sandpaper.http://www.pyrobin.com/files/07-29-09_1120.jpg
flying fish Posted July 30, 2009 Author Posted July 30, 2009 Hey, nice tooling! I might try to do something similar to that. I'm curious how your 1/4" rockets went if you made any yet...
dagabu Posted July 30, 2009 Posted July 30, 2009 (edited) Hey, nice tooling! I might try to do something similar to that. I'm curious how your 1/4" rockets went if you made any yet... I have been using Ned Gorski's recipe for a while and it is great!! http://blog.skylighter.com/fireworks/2009/...histle-mix.html Edited July 30, 2009 by dagabu
Swede Posted August 5, 2009 Posted August 5, 2009 I agree, nice tooling. I went nuts making a NASA-grade split sleeve support for bottle rockets, and it isn't needed. All you need to do, as done here, is drill a hole to allow a sliding fit of the tube into the support. It'd be nice to make it as smooth as possible, or polish the ID a bit, because once the rocket is loaded, it'll probably be pretty firm in there, but all you need is a brass rod the same diameter as the tube, and gently press/slide the loaded motor out of the sleeve. Well done, fredjr.
firetech Posted August 6, 2009 Posted August 6, 2009 Fred, how do you make the core in the rammer so dead-center? It seems almost impossible for me with my drill press...
fredjr Posted August 6, 2009 Posted August 6, 2009 Take a block of hard wood and clamp it solidly to the drill press shelf. Bring shelf up, position wood block close to drill bit and lock in place. Drill a hole the size of the ram through the wood. Switch drill bits, removing the bit down through the hole in wood, DO NOT move shelf. Put the ram in the hole. Drill the ram, the hole will be perfectly centered.And yes I did use my dremel and a tiny buffing wheel to polish the inside of my support sleeve. To remove rockets I press the spindle and rocket through the sleeve, then remove spindle from rocket. The rockets I made flew great, nozzleless BP on long spindle and whistle on short one.Sorry the tutorial will have to wait, too busy getting ready for the PGI convention.
firetech Posted August 6, 2009 Posted August 6, 2009 Thanks Fred. I've gotten pretty close just eyeing it, but it never turns out the way I want. I'll give your method a try.
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