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RE: Secondary construction details
Original poster: "Ted Rosenberg by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Ted.Rosenberg-at-radioshack-dot-com>
I used what has turned out to be a great bottom, RFG connection for my $6M
While I don't have a close-up photo yet, I think I can describe what I did.
The 6.25" diam PVC was closed with a PVC disk. The bottom end of the
secondary winding was brought off the tube and inserted into a 2" diam PVC
plug. The PVC plug is about 2-2.5" diam OD and closed flat on one end.
I attached to that flat end a female, chassis mounted, SO-239 from
RadioShack, Cat. No. 278-201 $1.99. It mounts using four, 4-40 screws and
nuts about 5/8" long. I assemble it to the PVC plug and solder the secondary
wire to BOTH the center contact and the shield. Then I PVC cement it to the
end disk. Besure the screws are tight cause you cannot access their nuts
once the PVC plug is cemented.
Then, for my RFG lead I use a short length of #4 welding cable. On each end
is a PL-259 plug, Cat. No. 278-188 $3.99 which usually requires an adapter
for smaller cable. However, with the larger #4, the hole is fine without the
adapter. If needed, you can reem out the hole in the plug a bit.
Using a propane torch with a pre-tinned piece of #4, I attach the welding
cable to both the center and the outside contacts. I simply flood the inside
with solder. Be careful not to heat the Teflon insulator of the plug too
much. Keep the torch towards the back.
I use about 18 inches of cable. I connect that piece from the bottom of the
secondary to a 2 inch by 4 inch heavy guage brass plate mounted on my base
cabinet. The brass plate has two more SO-239 female sockets, attached. The
18 inch cable goes to one and the cable to the ground rod goes to the other.
The plate is my RFG "Interface" if you will.
Of course, the other end of the outside welding cable gets a battery clamp
for clamping onto my ground rod.
Set up is QUICK and easy. and, if I do say so myself, I looks professional!
Ask any questions for more info.
Safety First (those connectors get might hot and cool down slowly after the
Subject: Secondary construction details
Original poster: "Jonathan Peakall by way of Terry Fritz
I am preparing to wind my 6.5" secondary, and had a couple of questions, as
What is the usual arrangement for the bottom contact of the secondary? I was
thinking of using a nylon bolt from the inside of the secondary. Is this ok?
Do most people drill two small holes and pass the wire through one to the
inside of the coil, then back out through the other, or is having the wire
inside the secondary at all a no-no? As for the top, I am planning on making
a disk of the correct diameter and gluing it in, with a brass bolt in the
middle. Any better ideas?
The form I have (pvc sewer pipe) is a little beat up, it's never been used
but has some scratches and so on. I was planning on an acetone cleaning and
then a little sanding with 120 grit. Sound reasonable?
----- Original Message -----
From: Tesla list <tesla-at-pupman-dot-com>
Sent: Thursday, September 27, 2001 1:09 PM
Subject: Re: Motor Sync Problem
> Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>"
> In a message dated 9/27/01 10:48:15 AM Eastern Daylight Time,
> tesla-at-pupman-dot-com writes:
> > I had two flats milled exactly opposite each
> > other and .750" wide. After reassembling the motor, I spun it up and
> > dismay, it did not sync.
> It's possible that 3450 rpm motors need wider flats than
> 1800 rpm motors for best results. I never much trusted the
> dead-pole method of modifying the motors. I go more by
> the width of the flat. I don't think the issue of how wide the
> flats should be for a 3450 rpm motor has been much addressed.
> Usually 1/3HP, 3450 rpm motors have
> larger diameter armatures, but I heard the european motors
> have small diameter armatures like that. I assume you're
> supplying the correct input voltage? If you happen to have
> a step up type variac (0 - 140V output), it would be interesting
> to see if the motor can be forced to lock at 140 volts, just
> for the heck of it. When I modified a small 1/10 HP 3450 rpm
> motor which had a 1 7/8" dia armature, I made the flats 1 1/16" wide,
> but they probably could have been narrower. It worked well.