thebobman Posted July 19, 2009 Posted July 19, 2009 How safe is mixing BP and Flash for lift?I make pretty good KNO3/Mg Flash, but my BP is a little underpowered, so i mix it 50/50and use a smaller amount to lift shells. I find it works well, and have had no accidents since i started doing it. Could the Sulphur in the BP sensitize KNO3/Mg flash?
firetech Posted July 19, 2009 Posted July 19, 2009 Don't. BP is good enough as it is to lift your devices plenty high. It's very unsafe to use flash as a lift power. You also run the risk of a flowerpot if you're lifting a shell. And yes, sulfur will sensitize it.
Seymour Posted July 19, 2009 Posted July 19, 2009 I suggest that you work on your black powder. An alternative to what you are doing which would still use your black powder as is, would be to use confinement to encourage it to burn at sufficient speeds to make it efficient at lifting. The main reason that it is unpopular to do what you are doing is that the risk of over pressurization is high, with the possible destruction of your shell and mortar. Depending on what your mortar is made of, and where it is, this could be very serious to the safety of you, or others. The risk becomes much greater when larger quantities are used. What you are doing frequently gets a very harsh response due to what I have said. However the same applies to benzolift, and provided that you set the thing off somewhere safe and use a paper/HDPE mortar, I cannot see why anyone should have a problem with you doing this, except yourself, as you are throwing money away. Black powder should be much cheaper when it does not have 50% flash powder in it.
TrueBluePyro Posted July 19, 2009 Posted July 19, 2009 Yeah, if you had seen what had happen to my steel mortar controlled test, flash powder should be left alone and to be only used for what it is meant to be used for and one of them is not lifting shells.
flying fish Posted July 19, 2009 Posted July 19, 2009 It sounds like what you are doing is using a week flash mixture to boost an even weeker BP (I can't see a mortar or shell surviving a "lift" with standard perc flash). I'm also slightly suspicious of the stability of magnesium flash...as "that stuff is pretty reactive!". The most effective solution would be to mill and granulate your BP, and use some good charcoal (Willow, white pine, etc) to get it up to speed. A mill can be as simple as a cheap rock tumbler with american nickels and quarters in it (or something equivelent made of non-sparking metals). It'll be more consistent, reliable, and (as seymour pointed out) cheaper than any magnesium lift.
Arthur Posted July 19, 2009 Posted July 19, 2009 You need good, reproducible BP before you progress to anything else. Having seen the resultant bits of a GRP mortar tube that failed due to boosted BP please do NOT go there. Start with or just buy, good fast BP. use a reasonable amount to get a decent lift height.
Greenman Posted July 19, 2009 Posted July 19, 2009 This might be a little to the side but still important enough for the guy who started the topic: Anyone have a video/clip of a slow lift BP burning? Just to know if what is the minimal burning speed is for lifting... Does lift really have to go away like in the videos you see on youtube, where they go away very fast and you can hear a thump sound?
flying fish Posted July 20, 2009 Posted July 20, 2009 (edited) Do you mean "thumping" when burned out in the open? My BP is more of a slow whoosh than a thump, but it still works for lift: . You don't need blazing fast BP to lift a shell, but if it is really slow, then you might need unreasonably large amounts of it. Just be sure to read up on BP methods. Things like charcoal type, milling and granulation methods become very important. Edited July 20, 2009 by flying fish
dagabu Posted July 20, 2009 Posted July 20, 2009 How safe is mixing BP and Flash for lift?I make pretty good KNO3/Mg Flash, but my BP is a little underpowered, so i mix it 50/50and use a smaller amount to lift shells. I find it works well, and have had no accidents since i started doing it. Could the Sulphur in the BP sensitize KNO3/Mg flash? Please stick to the standards: "The only real way to find out how much of a certain kind of lift powder should be used, is to make a dummy shell having the same weight, size and shape as the shell being launched. Then the amount is upped or downed by trial and error. However, as a starting point, a rule of thumb is to use one ounce of 2FA black powder for every pound of shell weight up to 10 lbs, and 1/2 oz of lift for each pound in excess of 10 lbs. The larger the shell is, the more factors such as mortar length, shell length and shell clearance come into play. If a shell is light compared to the size (like a patern shell where fewer stars are used), a larger amount of lift should be used, and thus the rule of thumb will not apply for this type of shell. For small shells, like those under 3", the generally accepted amount of lift powder is 1/10 the weight of the aerial shell being fired. For example, a 60 gram shell would require 6 grams of lift powder. If you want more altitude om your shell, simply add more lift powder" PYRO-GUIDE
JrayJ Posted July 21, 2009 Posted July 21, 2009 And if one tenth the weight of your shell in lift makes the shell rise to an altitude of 3 feet (like mine did) you need to work on your bp...
Swede Posted July 21, 2009 Posted July 21, 2009 Don't forget the shell to tube fit. If you load 50 grams of great lift powder in a 3" tube and drop in a marble, it might not even make it out the tube. As the shell fit gets sloppy, the effectiveness of the lift drops big-time. It is the gas that propels the shell, and if too much leaks around the shell, the lift height suffers.
Mumbles Posted July 21, 2009 Posted July 21, 2009 Temperature plays a role too. I fired 4 mines. 2 on a frozen lake in March, and two recently where the ambient temp was at least 75F. The cold ones plopped out around 25 feet, while the warmer ones made it to well over 100 feet.
deadman Posted July 22, 2009 Posted July 22, 2009 Why does temperature effect it so much? I've heard of ammunitions being effected by it as well so I wasn't surprised when you mentioned this. I have to assume it has to do with shrinking/stretching, but I can't imagine that would be very drastic. IDK so why does it happen?
Seymour Posted July 22, 2009 Posted July 22, 2009 (edited) Pre-warmed black powder does not absorb so much of the energy in heating up. I'd say that this slows down the initial spread of the flames just enough to make such a difference. Adding some sort of material that absorbs IR well (carbon, metal powders), to an otherwise transparent propellant greatly accelerates the burn, due to pre-warming of the yet-to burn fuel, as EX rocketry members can attest. Little things like this can have surprisinly big effects. JrayJ, while working on your BP is a good idea, see how much difference it makes if you confine your lift in a few layers of paper. This essentiall makes every shell act like it has a tight fit, which as Swede said, can make the difference between stars hitting you, and a shell looking very small way way up there. Edited July 22, 2009 by Seymour
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