Quote: Originally posted by grndpndr | I cant ignore the respected forum voices any longer.I was evidently so invested in the now suspect data that I took as gospel what was printed in the
data.Forum member Experience trumps paper/pencil in this case most others.How
badly underpowered is the plain PB picrate compared to simple HG fulminate approximately?
I regularly would use 1 gr of ful merc in these composite caps using PA.Mainly due to the abundance of mercury and nitric at the time not really
based on need.Theoretically would a gram/gram and 1/2 pressed to 2.8 paper max density succeed in detonating PA pressed to less than max density '1.5
'to ease detonation somewhat and still reach 6500 mps
min.Experimentation may be in order unless theres experience willing to be shared, alothough as stubborn as I now appear...
Thanks for hanging in there fellas its appreciated. |
I have deleted a majority of my own post for brevitys sake and keep this post somewhat on topic.
Roscoe's reply verbatim
"With regards to the volume efficiency, and "critical mass" of initiators, there is a transition point for a given diameter, where the
"self-accelleration" produces a
"bump" in the output that corresponds to the transition from low order to high order detonation. The difference between mercury fulminate and basic
lead picrate, or normal lead picrate, or lead styphnate, or lead nitrato bis basic picrate, or basic lead picrate - lead nitrate - lead chlorate is a
difference between about an order of magnitude roughly somewhere between 10 and 20 depending on diameter. By that I mean if the "bump" in output for
mercury fulminate is around about a quarter gram quantity in self-accelleration, then the corresponding "bump" in the output for those other materials
is in the range of two and a half to five grams depending on diameter. That's a ball park "guess" because I have not done a careful systematic study
and charting of this transition based on self acceleration of materials which demonstrate low self-acceleration. My interest has been a whole lot more
directed to materials which show an even better self-accelleration than mercury fulminate. There are ways you can improve the sluggish self
accelleration of those primaries that are more generally useful as "primers" rather than initiators, by combining them with more rapid
self-accellerating materials and / or using strong confinement, which helps "kick" them towards the transition to high order at an earlier point.
Thereafter you still must have an additional charge quantity beyond the amount that is "burned off" during the "runup to high order", the additional
quantity which will be the actual
"work performing portion" transferring its high order impulse to the target base charge to be initiated. I haven't seen this described anywhere in
any literature, but this is simply my observation and interpretation of experiments. Some primaries are fine for primers, for "flash igniters" and
they are dependable as "first fire" and low order compositions. Any "relative brisance" sort of figure would likely not reflect performance of such a
material being used in its usual mode and quantity where brisance is not much of an aspect of that low order scheme. That "relative brisance"
quantity is probably from a test where the material was not in small quantity undergoing self-accelleration, but was being used as a relatively large
sample secondary charge and fired by a separate detonator. So the "relative brisance" of a material being tested under conditions different from its
ordinary mode of operation does not provide useful information about the "unboosted" performance of the same material in smaller quantity.
Yeah if you put ten grams of basic lead picrate in a test block and detonate it with a compound detonator, the whole ten grams goes high order at once
and has significant brisance. But if you simply stick a fuse in the sample, five of the ten grams may be burned off in the "runup" which was
circumvented entirely by the
use of a cap to get it going. I hope this helps makes sense of how test data can be misleading unless you have all the details factored into
interpreting the tests.
[Edited on 9-8-2010 by Rosco Bodine] |