# Re: Awesome Quarter Shrinking Capacitors on EBAY

```Original poster: "Paul Marshall" <klugmann-at-hotmail-dot-com>

A good portion of the heat induced in the quarter comes from the rapid
motion of the metal collapsing on it's self. Several years ago I had a
metlab do some metallurgical mounts for me. The average grain size of the
input copper slug was ASTME 4 after shrinking it was ASTM E12. This is a
very suggnificant reduction which occurs in microseconds. This is where
most of the heat comes from. Not from electrical current.

Paul S. Marshall

>From: "Tesla list" <tesla-at-pupman-dot-com>
>To: tesla-at-pupman-dot-com
>Subject: Re: Awesome Quarter Shrinking Capacitors on EBAY
>Date: Sat, 11 Oct 2003 16:02:16 -0600
>
>
>For that matter, the amount of energy needed to squash a quarter into any
>arbitrary shape is a lot less than 10s of kJ... It's the dramatic, high peak
>power aspect that makes it interesting, even if it's hideously inefficient
>(after all, the quarter does get hot, so there's that loss there.)
>I did actully figure this out once (but can't find my notes).. the amount of
>force required to deform the metal is well known (probably somthing in the
>10-20kpsi range (copper's not too strong), and you can figure out the
>geometry, so you can calculate force times distance.
>Here's a quick ballpark.. assume that the quarter is just under an inch in
>diameter (i.e. 3 inches in circumference), and you squeeze it to half size
>(i.e. the force acts over a distance of 1/4"). Further assume that the
>quarter starts out 0.1" thick, and the yield strength of the metal is
>20kpsi.  So, to get it moving takes 3x0.1*20k = 6000 pounds of force.  That
>moves a distance of 1/(12*4) feet, call it 1/50th.. That's 120 ft pounds of
>work.. 170 Joules  (120*4.54 N/lb * meters/3.28 ft)
>
>Even if you're shrinking steel, with a yield of 60 kpsi, it's still only
>about 600 Joules... And yes, there's a kinetic aspect, it takes some energy
>to accelerate the metal flying in.
>
>Another way to look at how (in)efficient the quarter shrinker is, is to look
>at it thermodynamically. The quarter weighs, what, a few grams? (call it 5)g
>Copper melts at about 1100 degreesC.. To melt the coin would require about
>0.3*5*1100 =1650 (assuming specific heat of 0.3) calories, or about 6-8 kJ.
>The quarter gets nowhere near molten (it doesn't even get to 100C), and
>there's no real opportunity for it to dissipate the heat either by
>
>Imagine a big strong screw clamp type device that gradually squeezes the
>quarter...
>
>
>----- Original Message -----
>From: "Tesla list" <tesla-at-pupman-dot-com>
>To: <tesla-at-pupman-dot-com>
>Sent: Saturday, October 11, 2003 1:39 PM
>Subject: Re: Awesome Quarter Shrinking Capacitors on EBAY
>
>
> > Original poster: "Paul Marshall" <klugmann-at-hotmail-dot-com>
> >
> > One thing that I have noticed, in quarter shrinking is that total
>available
> > energy does not always Guarantee success. It seems that the best results I
> > have gotten have been at higher voltages 30kv and above. Even when the
> > energy is equal. For instance, I had a 40kv 32 uf maxwell total energy 25
> > kj. I never went that far most of what I shot was between 8-12 kj. The
> > quarter was under .5". Later I used
> > a 45uf 30kV cap. Even at a full 20kJ I never reached the .5" mark. Now I
> > have a 330 uf 25kV cap which will give me 103 kJ. I will try this out
>soon.
> > This cap is very low inductance.
> >
> >
> >
> > Paul S. Marshall
> >
> >
> >
> >
> >
> > >From: "Tesla list" <tesla-at-pupman-dot-com>
> > >To: tesla-at-pupman-dot-com
> > >Subject: Re: Awesome Quarter Shrinking Capacitors on EBAY
> > >Date: Thu, 09 Oct 2003 15:04:20 -0600
> > >
> > >Original poster: Ed Phillips <evp-at-pacbell-dot-net>
> > >
> > >"Original poster: Mark Broker <mbroker-at-thegeekgroup-dot-org>
> > >
> > >John, an "m" or an "M" always refers to micro.  The standard units for
> > >milli
> > >are rarely, if ever, used.  I always wondered why cap manufacturers
> > >couldn't use "u" for micro - it looks close enough to Greek "mu" and is
> > >certainly much less ambiguous than "M".
> > >
> > >I think most of us have stories of EEs showing their ignorance in front
> > >of
> > >the AAS techs....  And I have no problems admitting that I've been on
> > >both
> > >ends more than once.  ;)
> > >
> > >Cheers,
> > >
> > >Mark Broker
> > >Chief Engineer, The Geek Group"
> > >
> > >         Unfortunately the SI unit nuts are taking over the world (at
> > > least that
> > >of technical magazine editors) and in that system no number is allowed
> > >to be less than 1 or over 1000!!!  As a result, nano and milli are
> > >coming into use in printed literature at least.  It's the "in" thing to
> > >do just like some rules of etiquette or placement of silverware at the
> > >dinner table; no practical value but separates those who "know" from
> > >those ignorant fools who don't!
> > >
> > >         By the way, a 38 millifarad LV tantalum capacitors sounds much
>more
> > >reasonable than a 4 millifard 4 kV oil-filled capacitor!
> > >
> > >Ed
> > >
> >
>

```