Phil Posted August 7, 2020 Posted August 7, 2020 I am interested in making rockets but I don't own a ball mill. I'm under the impression you can get away without one if you're not trying to lift or break shells. If that's the case what are simple core burning nozzleless (preferred) or nozzled formulas that would get me up and running? I plan on using the "5/8 in cohete tooling" from woodysrocks with headings. I have plenty of sulfur on hand but I'm just about out of kno3 and have no charcoal at all. I have a large bag of red cedar pet bedding that I'd like to turn into charcoal to save money. Would it be wise to stuff some of this into a paint can or stock pot (with vented lid) and cook it over a propane grill? I would be able to get it as fine as a coffee mill would allow me, do I absolutely need commercial airfloat instead?
Carbon796 Posted August 7, 2020 Posted August 7, 2020 Traditional core burning " BP " rockets do not use a a ballmilled fuel. It is screen mixed only, as long as you buy your individual chems suitably processed. What size are you wanting to build ?
Phil Posted August 7, 2020 Author Posted August 7, 2020 I'm not sure what the volume would be but the motors will be 5/8" ID 4" long 1" OD tubes. https://www.woodysrocks.com/store/p218/%22Cohete%22_Tubes_-_5%2F8%22_ID_x_4%22_-_50ct.html#/ https://www.woodysrocks.com/store/p215/5%2F8in.__%22Cohete%22__Rocket_tooling___.html#/
Carbon796 Posted August 8, 2020 Posted August 8, 2020 (edited) For the cohete's I'm not sure what their using. I didn't really follow them that closely. I'd just send Caleb a email, and ask what fuel you can use with them. I looked briefly on FW'ing, but the search function kinda sucks. Edited August 8, 2020 by Carbon796
snapper Posted August 8, 2020 Posted August 8, 2020 you will want a small ball mill to grind your chems before screen mixing, putting oxidisers into blade mills followed by fuels is a no no so use seperate blade mills or risk a mixed fuel explosion in the motor.cohetes can use very hot bp or even whistle
BetICouldMake1 Posted August 8, 2020 Posted August 8, 2020 Your cedar charcoal will, if properly prepared, make much hotter BP than commercial airfloat. A blade mill is unlikely to reduce your charcoal enough to really work well, in addition to the risks snapper mentioned. If you're unable to make hot BP, which is difficult without a mill, you would be better off making nozzled core burn rockets which typically use a slower fuel and actually benefit from having slightly more coarse charcoal in the mix to provide a tail.
Phil Posted August 8, 2020 Author Posted August 8, 2020 I have two separate mills for fuels and oxidizers, well one of them is on it's last leg so I gotta replace it. I watched Ned Gorski's video where he makes cohetes and he said preparation of the fuel is by screen mixing OR ball milling which is where I got the idea from. However if it's not attainable I'll do nozzled. The reason I shy away from that was from my previous experience in making sugar rockets. Static test seemed to work fine but out of the 4 or 5 of them I took to launch only one didn't CATO, after using car keys to open the throat of the nozzle of the last rocket it launched fine. The bottom of the motors where the nozzle was were slightly bulged so I figured they were rammed in solidly enough.
Phil Posted August 8, 2020 Author Posted August 8, 2020 Caleb suggested nozzled to me so I guess that's the route I'll be trying. I take it then 75/15/10 screen mixed would suffice. Is a binder appropriate or no. Granulated or no? What mesh screens do I need to get?
Carbon796 Posted August 9, 2020 Posted August 9, 2020 No binder needed. Doesn't need to be granulated, that just helps to cut down on dust, cleaner handling. 20 to 30 mesh is generally recommended for screen mixing.
BetICouldMake1 Posted August 9, 2020 Posted August 9, 2020 Screen mixing can work but you still need a way to reduce your charcoal. Even the best screen mixed BP won't beat ball milled. It can come close, but it still requires individually milling each component. 20 mesh is fine for mixing but having finer screens, like 40mesh at least, would be good to give you a sense of how fine things actually are coming out your blade mill. Ideally everything is fine enough that it feels like baby powder or corn starch, zero grit at all. 1
Mumbles Posted August 9, 2020 Posted August 9, 2020 A propane grill is probably a somewhat more expensive way to cook charcoal, but it will work. You're on the right track there. If you find your self needing larger quantities of charcoal, it might be worth looking into a TLUD, top lit updraft cooker. It uses some of the wood chips as a fuel source, but is basically a self contained cooker, and is pretty scalable. The yield is lower, but the ease and speed more than makes up for it. To answer a few more questions, nozzleless rockets typically require faster fuels. Milled BP is sort of the standard. I personally don't believe a ball mill is NECESSARILY required for hot BP, but something of a comparable speed is required. DavidF's posts here would be ones you'd want to read. If you used nozzled rockets, you almost certainly want something a little more tame. Using a milled BP equivalent will likely result in exploding rockets. The nozzle provides back pressure which allows and in some ways necessitates a slower fuel. There is more to go into on that, but I wont unless you want more details. On the other hand, if you want to make end burning rockets, sort of similar to Estes rockets, then a fast fuel would be very useful.
Phil Posted August 9, 2020 Author Posted August 9, 2020 (edited) I've tried cooking charcoal before by using a secondary fire to heat a paint can. The TLUD method seems way better but I never put much thought into it and it appears I'd be able to build a small scale version for $15-$20 from lowes with a paint can, 4" duct and a reducer. Much like this guy did here. https://www.youtube.com/watch?v=njgEA-201mo I currently don't have the space or level of engagement in the hobby yet to justify building a large one but I'm certainly interested in trying it out like in the video. The tooling I'll be using will be for cored motors but if I can use it to make cored/nozzled motors I'd like to know more about that since I don't plan on purchasing a ball mill although it isn't completely out of the question in the future. https://www.youtube.com/watch?v=w0uP7t6pQhc Edited August 9, 2020 by Phil
justvisiting Posted August 10, 2020 Posted August 10, 2020 If I wanted to make rockets and I didn't have a mill, I'd try this: I would make nozzled rockets, using 60-30-10 as my formula. I'd use a bullet grinder to reduce my charcoal, and screen it through 40 or 60 mesh, using everything that passes. Assuming the potassium nitrate is crystalline, I'd dissolve it in the smallest amount of boiling water I can use. I'd then add the charcoal and sulfur, and mix it well. When it cools, it will be a slushy mess. I'd spread that out on a non-porous surface, dry it, and run it through a 10 or 20 mesh screen. If the rocket is too weak, I'd try 70-20-10. 1
Arthur Posted August 10, 2020 Posted August 10, 2020 Two things I'll add.First; it's frustrating having variable mixes to do tests with, if the powder isn't consistent then the results will not be.second; If you read Lancaster's book (maybe others) his BP + things formulations clearly demonstrate that small rockets need a hotter powder than bigger rockets can cope with. A small rocket may use straight BP while a inch or a two inch bore rocket tube will use BP + 30 - 100% extra charcoal in mixed sizes to both slow the powder and make a dense tail.
Phil Posted August 12, 2020 Author Posted August 12, 2020 The potassium I got left is prilled kno3 (stump remover) milled to powder in a coffee grinder. I'll probably buy some already processed next chem order because quite frankly $7 a pound and still having to mill it is expensive. Is there a rule of thumb for how thick the nozzles should be and diameter of the openings? Thanks for the info you've guys supplied this far.
dagabu Posted August 13, 2020 Posted August 13, 2020 If I wanted to make rockets and I didn't have a mill, I'd try this: I would make nozzled rockets, using 60-30-10 as my formula. I'd use a bullet grinder to reduce my charcoal, and screen it through 40 or 60 mesh, using everything that passes. Assuming the potassium nitrate is crystalline, I'd dissolve it in the smallest amount of boiling water I can use. I'd then add the charcoal and sulfur, and mix it well. When it cools, it will be a slushy mess. I'd spread that out on a non-porous surface, dry it, and run it through a 10 or 20 mesh screen. If the rocket is too weak, I'd try 70-20-10. Good summary, I did exactly that one year for am impromptu rocket. I also agree that it may need the nozzle to get the thrust Phil mentions. I will say as a way of encouragement though, buy a cheap rock tumbler and make your life easier.
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