RE: question for coin shrinkers

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Yurtle Turtle <yurtle_t@xxxxxxxxx>

I'm not sure 1/2" is overkill. I can show you pictures
of my 1/4" steel diamond plate box, which is bent
fairly significantly under 10 kJ. I believe the
original poster mentioned 20kJ. While there is no
chance my steel will fail, it has deformed enough that
the lid doesn't fit as well as when I first built it.
My lid uses six bolts - three on each side - and still
manages to expel some shrapnel. If the shrapnel really
has the potential to go Mach 7, we need a fairly tight
box.

As to vents, do we really need them? Mine is not
air-tight, but I might reweld it soon. What do the
list's shrinkers think? Is enough wire vaporized or
plasma generated to cause a rise in pressure? Heck if
we have shrapnel going Mach 7, won't that alone create
a shockwave?

Adam


--- Tesla list <tesla@xxxxxxxxxx> wrote:

> Original poster: "Anthony R. Mollner"
> <penny831@xxxxxxxxxxxxx>
>
> Interesting. I have no experience at all with
> quarter shrinking but I have a
> lot of experince with uhhh, exploding things. I can
> say that 1/2" steel
> plate is complete over kill. The most important
> thing here is to have a vent
> of some type for the expanding gasses to escape,
> other wise all you are
> making is a larger "bomb" that had you detonated it
> in the open! The cabinet
> should have an indirect vent that will allow the
> gases to vent but still
> deflect any fragments.
>
> -----Original Message-----
> From: Tesla list [mailto:tesla@xxxxxxxxxx]
> Sent: Thursday, December 28, 2006 1:52 PM
> To: tesla@xxxxxxxxxx
> Subject: Re: question for coin shrinkers
>
>
> Original poster: Bert Hickman
> <bert.hickman@xxxxxxxxxx>
>
> Hi Bill,
>
> A 1/2" thick steel housing should work quite nicely
> for the case.
> Regular mild steel (such as A36) is fine, and I'm
> currently
> experimenting with 304SS and "abrasion resistant"
> AR400. The latter
> material is used for Humvee armor, but you can't
> easily drill or tap
> the stuff), but it is weldable. Thus far, I really
> don't see much
> difference in how any of these materials survive
> being struck by
> hypervelocity copper fragments, and I'd use plain
> old A36 in the future.
>
> I would also recommend designing a cover latching
> mechanism to keep
> the box completely "closed" in order to prevent the
> force of the
> explosion from lifting the lid. Weights alone are
> usually not
> sufficient, particularly at higher energy levels.
> Sound deadening (on
> the exterior or sandwiched within a double wall) is
> also a great
> idea, especially if you are shrinking in a
> residential neighborhood.
> Please let us know what you did in this area and
> results...
>
> For insulating material, I've had excellent results
> using plain old
> HDPE or UHMW. The material is tough, resilient, and
> it gracefully
> responds to high shock. Indirect hits by wire
> fragments mark it up a
> bit, but I've used the material for parts of by
> shrinker and it has
> lasted for over 6,000 shots. Make sure that any HV
> bushings are
> located out of the direct line of fire from the wire
> fragments. The
> fragments will initially spray out radially from the
> work coil in a
> relatively narrow angle. The highest velocity pieces
> come from the
> 1-2 turns that are right above the coin. If you
> locate the HV
> feedthrough at right angles to the coil (i.e., along
> the centerline
> of the work coil axis of rotation), it should last a
> very long time
> with no problems. Be sure to provide sufficient
> creepage distance,
> since copper vapor and dust will collect on
> everything inside the
> blast shield. BTW, you may find it of interest that
> one of the Texas
> coin shrinkers (Paul Marshall) has taken
> measurements of the fragment
> velocity  - some approached a hypervelocity of
> ~5,000 fps.
>
> Good luck and play safely! Give me a holler if you
> have any other
> questions (630-964-2699).
>
> Bert
> --
> ***************************************************
> We specialize in UNIQUE items! Coins shrunk by huge
> magnetic fields, Lichtenberg Figures (our "Captured
> Lightning") and out of print technical Books. Visit
> Stoneridge Engineering at http://www.teslamania.com
> ***************************************************
>
> Tesla list wrote:
>
>  >Moderated and approved by: Gomez Addams
> <gomezaddams@xxxxxxxxx>
>  >This is high voltage, but technically off-topic.
>  >Feel free to reply to me off-list.
>  >I will eventually be building a containment vessel
> (possibly even
>  >with some sound insulation) for coin shrinking
> work coils, after I
>  >get my main pulser rebuilt.  The chamber walls
> will probably be made
>  >from 1/2" steel plate with 1x1" angle iron
> ribs/stiffeners.  The
>  >pulser stores a maximum of 18kJ @ 10kV (wish the
> voltage was higher).
>  >As for insulating materials for the HV
> feed-through area, what
>  >materials have you used?  I was thinking of using
> two layers with an
>  >air gap, possibly with 1/2" silicone resin based
> G-11 on the inside.
>  >I gather the larger the chamber, and more distant
> the walls from the
>  >work coil, the better the survivability.  I also
> assume that high
>  >modulus, high hardness materials like phenolic
> laminates will tend to
>  >shatter, even the linen based ones.
>  >What have your experiences been and what materials
> have you used?
>  >G-10?  G-11?  Polycarbonate?  Phenolic?
>  >Filled polycarbonates?  Delrin?
>  >  - Bill "Gomez" Lemieux
>  >
>  >
>
>
>


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