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From: murray@sun13.scri.fsu.edu (John Murray)
Newsgroups: sci.electronics
Subject: Re: What are some typical characteristics of mechanical relays?
Message-ID: <2651@sun13.scri.fsu.edu>
Date: 1 Apr 91 18:42:05 GMT
References: <2640@sun13.scri.fsu.edu> <1991Apr1.004857.17286@colorado.edu>
Organization: SCRI, Florida State University
Lines: 38

In article <1991Apr1.004857.17286@colorado.edu> rainer@boulder.Colorado.EDU (Rainer Malzbender) writes:
>Hmm...will that be enough ? (Don't feel like doing a Jackson problem
>right now :-). For reference, the power requirements of the second
>Princeton-MIT mass driver design (a = 5000 m/s^2, vmax = 112 m/s, bucket
>mass = 1kg)) were V = 668 volts, Imax = 6315 amps, di/dt =
>58.6 amps/microsecond. Run that through your average mechanical relay!

Well, the only reason I'm using 40V is my 28V (adjustable 20-40V) 10A
(continuous) heavy duty lab power supply. Built for NASA, you could throw
it off a bridge with impunity. I thought about a railgun, (better for low
voltages) but was discouraged by the sliding-contact problem.


>In contrast the first one had an acceleration of 33 g's and used mechanical
>switches to trigger the coils, so maybe it's doable. I know there's been
>a magnetic-weapon discussion here before, and I don't want to reopen it,
>but the Germans had trouble with electromagnetic cannon during
>WWII due to melting projectiles. I don't know anything about coil guns,
>but their efficiency must be a lot worse than mass drivers, which have
>pretty good coupling between drive and bucket coils.

Efficiency is not what I'm worried about. This is pretty much an "Amaze
Your Friends!" (and amuse myself) project. Also, I guess I could just build
half of a mass driver and toss the bucket out of the thing - technically still
a coilgun, I guess, since I wouldn't bother decellerating the bucket.

Thanks for the hint about how Survival Research Labs did their 200mph
molten-iron thrower ;-)


>Rainer Malzbender                                Save a dinosaur - buy DEC.
>Dept. of Physics (303)492-6829

-- 
*Standard Disclaimers Apply*|        ---Get Out Of HELL Free!---
John R. Murray              |The bearer of this card is entitled to forgive
murray@vsjrm.scri.fsu.edu   |Himself of all Sins, Errors and Transgressions.
Supercomputer Research Inst.|                                -- D. Owen Rowley