kpknd Posted March 24, 2014 Posted March 24, 2014 I went out and fired off a few small 1/4" I.D. rockets to test out the sugar fuel I made a couple months ago. They went real well, I was curprised because they where mixed and screend by hand only. I made two fuels, a 65-35 and a 63-27-10, The 65-35 had better power and lift then the 63-27-10 that contained sulfer and started slowley. But I was pleased.
jl88 Posted March 24, 2014 Posted March 24, 2014 I used to be very into sugar rockets, but as they get large they were becoming unreliable. Also the fact that the fuel absorbs water like crazy made them too unreliable. Even a half day of exposure to air couldrender a rocket useless. I tried sulphur in varying percentages and found that it didn't help performance at all. For smaller rockets, 2lb or smaller, adding 1-2% iron oxide can greatly increase burn speed. They launch like bullets! I used red iron oxide from Bunnings. It's a cement dye if you need a reason to legitimately buy it :-) some 3lb rockets can handle this faster fuel, but the case must be fairly strong and nozzles consolodated it a press. Any bigger than this though it is better to use cast fuel grains. I generally made rcandy in an electric skillet by dissolving all ingredients in just enough water, and the boiling the water off (slowly and carefully) then I let it go hard, powder it, and dry it further in a food dehydrator. Then it is stored with lots of desiccant. Much more powerful and clean burning. But must be consolidated extremely well or you may crack a fuel grain and explode. (The same as screen mixed fuels) Be carefull though, that increased burn speed will increase case pressure. This my lead to a CATO. Here is a link to a PDF that has some great info on various sizes / power outputs. It uses PVC motors as tubes which I used for years, and never had a single pvc pipe explode. Fired so many of them it's not funny. Maybe 300 succssful flights or so over 1lb. Had at least 40 CATO's trying to dial in fuels, nozzles and core lengths, but only ever blew out nozzles or bulkheads. Even after roughening up the inside of the tubes. But if PVC does explode, it's very dangerous. So I switched to paper and tubes and feel much better about it. Also it litters less because you can't always find your work! Lol http://pyroforum.nl/files/file/72-easy-pvc-rockets/
kpknd Posted March 24, 2014 Author Posted March 24, 2014 Thanks for the link jl88. I make lots of BP motors and have tooling up to 6lb. but like to go back to the simpler stuff once in a while. I used PVC before but got a little concerned about shrapnel. Did you roughen the inside ends of the PVC before ramming the clay?
Mumbles Posted March 24, 2014 Posted March 24, 2014 Now that file is a blast from the past. Jason was a friend and a member here a long time ago when he wrote that. We lost touch after he got kind a government job for the DoD I think.
jl88 Posted March 25, 2014 Posted March 25, 2014 Yeah always roughened them up. (I'm not just making that up, it was in my first post lol) First just with sand paper, later I used a dremel tool with a wire wheel. I found that if I used iron oxide in the mix I needed to go up at least 1 or 2 drill bit sizes(instead if the recommended diameter in PVC rockets) in most cases to prevent CATO. Or omit the iron oxide. That PVC PDF was a great information for starting new sizes, so thank you to you both mumbles!
kpknd Posted March 25, 2014 Author Posted March 25, 2014 Looked at the PDF, liked what I saw and ordered a copy of the book. I think a lot of these designs would lend themselves well to BP too.
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