Apollofrost Posted March 20, 2008 Posted March 20, 2008 Ok, I've got a harbor freight two-barrel tumbler that I load up with steel ball bearings of different sizes for different tasks. Currently it's out of commission due to a broken belt so tomorrow I'll scout around for a gasket the same size and make my repairs. But that's not why I'm posting. A few days ago I left some greenlight stump remover(KnO3) to mill overnight and when I opened the jar in the morning I found... dramatic pause... A golf ball. Somehow the mixture had consolidated into a rock hard vaguely spherical mass and I've got no idea how it got that way. There was no moisture and it was the same media in the same place as the last time I milled any greenlight. Anyways I broke it up into little pieces and put it back to mill only to find a bunch of 10mm balls when I opened it again. So is there some explanation for this or have I just discovered some new form of star roller?
Mumbles Posted March 21, 2008 Posted March 21, 2008 The problem is moisture actually. Your KNO3 possibly has some sort of hygroscopic contaminant in it. I was having the same problem actually with bad quality KNO3.
justanotherpyro Posted March 21, 2008 Posted March 21, 2008 When I mill BP it always clumps into a baseball sized mass, as well as clumping near the ends of the jar. It doesn't noticeably affect the product because my BP always comes out good quality. If you want to try and minimize this problem then dry your KNO3 under a heat lamp before milling.Just make sure not to get it too hot . Let it cool before milling it though.
WarezWally Posted March 21, 2008 Posted March 21, 2008 Seen this happen with ammonium perchlorate, person ended up with a large egg Its the moisture.
pudidotdk Posted March 21, 2008 Posted March 21, 2008 I have the same problem when milling BP, it seems to stick to the walls of the jar.Would adding anti-caking (SiO2) help, or would it be too dangerous like glass powder.
NightHawkInLight Posted March 21, 2008 Posted March 21, 2008 I have the same problem when milling BP, it seems to stick to the walls of the jar.Would adding anti-caking (SiO2) help, or would it be too dangerous like glass powder. I'm thinking more along the lines of a bit of powered graphite. I do not often have problems with the comp forming balls, but clumping to the walls of the mill has been an inevitability if milled long enough. I find it somewhat helpful when making star comps, all you do is dump out clean media on a plate and knock out the comp. However without the clumping the comp would no doubt be more intimately incorporated once the milling time expired.
FrankRizzo Posted March 21, 2008 Posted March 21, 2008 I get clumping in the ends of my jars if the temperature inside the jar becomes too high. I believe the sulfur starts melting slightly and becomes sticky. Lloyd covers this phenomena in his book.
justanotherpyro Posted March 21, 2008 Posted March 21, 2008 I put this in my photo bucket account a few years ago.http://i42.photobucket.com/albums/e301/justanotherpyro/ballofbp.jpgThere is nothing there to show the relevant size, but its about the size of a baseball.
TheSidewinder Posted March 21, 2008 Posted March 21, 2008 What volume ratio (of the total tub-size) are you filling with media, and what type of media were you using when that happened? I vaguely recall hearing that that happens if you don't use "enough" media for the barrel size, or try to make a small batch, less than a certain percentage of the total volume, without adding more. Something like that. Anyone else hear anything along those lines? I'd like to know the answer for the future. And my experience, in an inverse sense, seems to indicate that's the cause, rather than moisture: I've milled mixes that were noticeably... well.... not DAMP, but they sure as hell weren't dry. The KNO3 I had to smack with a hammer, to get small enough chunks broken off the 5-lb or so mas in the bag. Stored in detached garage year-round. And (knowk on wood) I've never had so much as caking on the insides. But I use a full 1/3 to 1/2 of the barrel's volume worth of Brass rod stock, 3/4"diameter, 3/4" long. I'm curious to know what others' experiences have been. M
justanotherpyro Posted March 21, 2008 Posted March 21, 2008 I have since made more media for my jars but this still happens. It doesn't form a single piece this big though. If I mill TT this doesn't happen at all. If I dry my KNO3 before I make BP it helps prevent this. I could use more media definately but it isn't an issue and I can make hot BP in 6 hours with my current set up.
Apollofrost Posted March 23, 2008 Author Posted March 23, 2008 It was a 3lb barrel from the 6lb hobby tumbler filled with 1.5lb of mixed 1/3 and 1/2 inch steel shot and about 5oz of kno3. Drying doesn't seem to have done anything for the mix. I set it out in the hot sun for three or four hours the re-milled it with no change. Oh well. Say, on the topic of hobby tumblers where does everyone buy their non-sparking media? I'm probably just going to run down to the local tackle shop monday and buy some lead weights, but in the future what should I get?
FREAKYDUTCHMEN Posted March 23, 2008 Posted March 23, 2008 Well drying semed to help me solving this problem. Just a vieuw days on the radiator (central heating) will do the trick for me.
TheSidewinder Posted March 23, 2008 Posted March 23, 2008 Say, on the topic of hobby tumblers where does everyone buy their non-sparking media? I'm probably just going to run down to the local tackle shop monday and buy some lead weights, but in the future what should I get? Personally, I bought a 16-ft length of 3/4" Brass Rod Stock, and cut into 3/4" long pieces. Had enough for both of the 6-lb barresl on my Lortone QT66 with a couple feet left over for future use.
justanotherpyro Posted March 23, 2008 Posted March 23, 2008 It was a 3lb barrel from the 6lb hobby tumbler filled with 1.5lb of mixed 1/3 and 1/2 inch steel shot and about 5oz of kno3. Drying doesn't seem to have done anything for the mix. I set it out in the hot sun for three or four hours the re-milled it with no change. Oh well. Say, on the topic of hobby tumblers where does everyone buy their non-sparking media? I'm probably just going to run down to the local tackle shop monday and buy some lead weights, but in the future what should I get?Try drying it under warmer conditions. KNO3 has a MP of 334C so you can get it really hot w/o melting it. I don't really suggest putting in the oven as it will most likely piss someone off but under a hot lamp and really close to the bulb for a while might do the trick. My hot lamp I use gets hot enough that when the material is left a few inches from the bulb for several hours it is to hot to touch for more than a few seconds.
oskarchem Posted March 23, 2008 Posted March 23, 2008 I just made a small test batch of BP in my mill it was 30g total, for a 3lb ball mill. It clumped to the wall, this is the smallest bach I have ever made, and the first time it has stuck to the wall.
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