6squirrels Posted February 22, 2012 Posted February 22, 2012 I have a question in regards to ramming, and I couldn't find anything in the forum already. In safety, it's always said that one should never ram anything with metal powders in it. But, in a list of non sparking metals to use for tooling (rocket spindles, ball mill media, etc.), aluminum was on that list. What are people's takes on ramming a composition, let's say for a rocket, that had aluminum powder in it? If it doesn't spark, why isn't it safe? Or is it that when it's in powder or flake form it's more likely to spark? -6squirrels
FrankRizzo Posted February 22, 2012 Posted February 22, 2012 (edited) That is just a good general rule, but is mostly concerned with metals that spark (titanium, ferro-titanium, iron filings, etc.). A bright aluminum would be ok to ram, but I would never ramm mixtures containing dark flake aluminums (German dark, Indian blackhead, etc.). Be aware though that the aluminum will not really add much in the way of sparks, but will instead cause the charcoal tail to be brighter orange. Edited February 22, 2012 by FrankRizzo
6squirrels Posted February 22, 2012 Author Posted February 22, 2012 also, maybe a little off topic, but what is dark aluminum? differences between normal Al / "bright" Al?
6squirrels Posted February 22, 2012 Author Posted February 22, 2012 and what are the alternatives to ramming? if something needs to be compressed a lot but has a sparking metal or other non-rammable material, how would one achieve this?
FrankRizzo Posted February 22, 2012 Posted February 22, 2012 Dark aluminum is what is ordinarily used for small salutes, as the particle size and geometry is sufficiently small that it becomes very reactive. The advantage is that the aluminum can burn faster than it takes for the paper casing to rupture, producing a louder report when all of the gas is released at once. Bright aluminum is normally used for silver stars and glitter compositions. It's also usually coated in a waxy substance called stearin, which gives it a characteristic smell (like a box of crayons, IMO), and causes it to coat your fingers and work surfaces in a silver "paint". Here are some photos: Bright aluminum (source: Skylighter product page) German Dark Aluminum (site:pyroguide.com)
FrankRizzo Posted February 22, 2012 Posted February 22, 2012 and what are the alternatives to ramming? if something needs to be compressed a lot but has a sparking metal or other non-rammable material, how would one achieve this? You need to use a press, as it brings on the pressure slowly. For small motors, you can use an arbor press, but anything over 1/2" in diameter should probably be pressed with hydraulics if possible. Arbor Press (Dan C's design) Homemade Hydraulic Press (Ned G's design)
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