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