[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: question for coin shrinkers



Original poster: Mddeming@xxxxxxx In a message dated 12/29/06 4:38:47 P.M. Eastern Standard Time, tesla@xxxxxxxxxx writes:
Original poster: Bert Hickman <bert.hickman@xxxxxxxxxx>

Hi Anthony,

A chemical explosion and a "coin shrinking" electrical explosion
appear to have major differences. While a considerable volume of gas
is typically evolved in the former case, much of the electrical
energy (that's not expended in forming the coin and stretching the
coil) apparently goes into kinetic energy in the ejected fragments.
Although there is an initial pulse of high pressure (or even a
shockwave near the actual arc plasma), the actual volume of gas in
the chamber shortly after the electrical explosion is not much more
than the that beforehand. The arc plasma disappears quite quickly,
and the copper vapor rapidly cools and condenses.

I currently use 1/4" steel lining inside 1/2" thick Lexan. With
replacement of the inner liners, this arrangement has withstood 6,000
shots at up to 6300 joules, and can be operated safely only to ~8000
joules. Based on my observations, I believe that doubling or tripling
this energy level (as Bill wants to do) will require using thicker
material or much more frequent plate replacement. The increased
thickness not only provides brute strength against hypervelocity
fragments, it also provides significant inertia, helping to prevent
plastic deformation of the entire plate. Repetitive impact by
hypervelocity copper fragments can do a surprising amount of damage.
As an example, here's a "before and after" view of a fragment
"catcher". Made from 3/4" thick steel, it required replacement after
only ~1500 shots at 4000 - 6300 joules:
http://205.243.100.155/photos/HVStuff/SteelBlocks2.jpg

Best regards,

Bert

Hi Anthony, Bert, All,

Back in the 1950s when I was blowing up rockets in Maine made of 1020 steel, I found that for a stationary facility, boxing in a test stand with 4X4s notched "Lincoln Log" style, with a top of 2X4s, all surrounded and covered with damp sandbags absorbed a lot of. shock, metal, AND sound. While this is not practical for a portable facility, it never failed.

Matt D.