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Re: Rotary gap motors


 Es> Mark,

 Es> I received the motor for my rotary gap yesterday.  It is rated at
 Es> 10,000 rpm at 115 v ac or dc.  I tested it with my variac and tried to
 Es> measure the speed using a tachometer that I built from a kit for
 Es> measuring the speed of airplane props.  It seems to be running at
 Es> 15,000 rpm with no load.  Does that sound reasonable?  I know I need to
 Es> control it to keep it the rpm somewhere between 4000 and 5000.

 MG> That sounds reasonable to me, the only thing I'm wondering about is
 MG> this motor being run at 5000 rpm is going to be low on torque, but I
 MG> don't think it will cause a problem, it will simply take a little more
 MG> time to come up to speed.
 MG> By the way, is that an old Heathkit "thumb tach" they sold about 25
 MG> years ago? I'd love to have one of those, or the diagram / parts list.
 
 Es> When I get the gap finished, I want to build a wooden box to sit over
 Es> the top of it.  I was planning to mount a fan on one end and drill a 2
 Es> or 3" vent hole in the other end - to provide some cooling.  Is a
 Es> 100cfm fan large enough?

 MG> On my gap, I have a 1" wide by 4"tall slot in the box on each side of
 MG> the wheel and I use a 12vdc muffin fan run at 25 volts to blow air into
 MG> the box, I did this because I did'nt want to run a 110vac line over to
 MG> the coil itself. I run the DC voltages over to the coil for the gap
 MG> motor and fan using coax, the shield is negative as well as ground, the
 MG> positive is the center conductor. The coil discharges hit the DC feeds
 MG> constantly but it causes no problem, its simply conducted to ground via
 MG> the shield. This system works fine on my system (5KW) but for higher
 MG> power or longer run times (>30 sec at a time) it would be better to use
 MG> better cooling.

                          Mark Graalman
   

 Es> Thanks,  Ed Sonderman





... Alias, Mark the spark
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