Heres my interpretation of "friction of impact":
two rusty balls collide. the impact causes the rusty surface to collapse
creating friction in the material itself. basicly the rust particles create
friction as they are being crushed and as we all know rust is very brittle.
In a ball mill, balls are rolling around colliding with each other pounding
the heck out of anything that gets inbetween the colliding balls. I would
think that (and im just hypothesising here) to create a spark (under these
conditions) it would be necessary to have a inperfect surface (Which could
be said for any surface). Like a file. Rust is a major inperfection that
will cause much friction and thus heat. In my opinion this is why carbon
steel, chrome steel etc is not good for making BP with. It is almost
impossible to prevent them from rusting. My chrome steel balls rust just by
looking at them!
Lets take two balls of unknown material. Make one ball unmovable (in a
vise) and mount the other one on the head of a drill (whatever it takes).
Turn the drill on and attemp to grind the two balls together. I think we
can all agree that if the balls are rusty then they will spark quikly and
easily. If the balls are completely smooth and uncorroded then you may get
some sparks after a little while (as the surface heats up) but very doubt
full if you get them immediately and will also depend on the material.
BUT then again it only takkes one spark!!!!!
If my drill test is indicative of sparking or not sparking than you will
have a hard time making 3xx SS spark. Throw a little grinding wheel
material in there and thats a diff story. Brass? Maybe the friction
coefficients of metal on metal would be indicative of the ability to spark.
I will look some up and see. If so than steel should be significantly
greater than 3xx SS and lead.
Post by Old Dog
Post by Richard J Kinch Post by Old Dog Post by Richard J Kinch Post by Old Dog
Flammable - "Easily set on fire" (Webster).
You evidently harbor opposite meanings for common words, so I can't
hope to correct your other errors.
You don't like dictionary definitions?
Your definition is opposite the correct one, your citation is meaningless,
and your latest response is pointless. Vocabulary matters.
I guess I'd better throw away the Webster's dictionary.
Post by Richard J Kinch
Don't bother with the pretentious quoting of Shimizu. He's more of an
alchemist than a physicist.
I don't recall Shimizu claiming to be a physicist, or mentioning anything about
elixers or transmutation. Must have missed that chapter. What he did primarily
was relate the actual practices of pyrotechnists in the Far East.
Post by Richard J Kinch Post by Old Dog
the use of a device which
generates friction as a test of the effects of impact goes against both
physical principle and actual practice.
The question is whether a material is "sparking" or not, by any means,
including knocking on a cretinous skull. Nobody seems to have a specific
idea of what constitutes "sparking", but given the consequences of getting
it wrong, one can only demand the strictest (most broadly positive) tests
possible, since there is plenty of rubbing and impact action inside a ball
I defy you to cite a material that is non-sparking on a grinding wheel but
sparking on impact tests, for any prudent specification of "sparking".
As I recall, we were concerned with the opposite effect - whether sparking on a
grinding wheel is a reliable indication of the probability of a material
sparking on impact in a mill. Since to the best of my knowledge grinding wheels
are not used to test pyrotechnic materials or media, such a test would have
limited value. It would be rather similar to giving the equivalent of a bathtub
of artificially-sweetened soda to a rat every day and claiming it is dangerous
when the rat develops health problems. Obviously no one can drink a bathtub full
of soda every day; nor would anyone dream of operating a grinding wheel around
mixed pyrotechnic comps. Now, if you were to break up your grinding wheel and
put the bits into your mill with some hard metal media, I predict you might have
problems. I would hesitate to use a mixture of dissimilar very hard media in a
mill, especially corundum with steel.
I have already given examples of materials that ignite easily by friction but
not by impact, and vice versa. That's real world stuff - not theory. You are the
one who said "friction of impact" - I challenge you to cite a reference, since
mine are evidently inadequate in your eyes.
This all begs the question - would you let a physicist loose in your pyro shop?