Re: question for coin shrinkers

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "BRIAN FOLEY" <ka1bbg@xxxxxxxxxxx>

Hi, wow 5,000 fps....a 22-250 rifle barely makes 4,000 fps on a 41 grain
bullet, so faster than a bullet! and i am sure more destructive than a
bullet at close range. be carefull. cul brian f.
----- Original Message -----
From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Thursday, December 28, 2006 4:51 PM
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
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> ***************************************************
>
> 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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