Re: Advice on Primary

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx>

At 04:00 PM 2/22/2005, Tesla list wrote:
> Original poster: "Medina, Benjamin (UMR-Student)" <bamxbb@xxxxxxx>
>
> Hello,
>
> I know this topic has already been discussed but I am still having doubts 
> when it comes to the winding of the copper tubing through the holes or 
> notches of the supports. So if someone could clear this up for me that 
> would be very much appreciated.
>
> As of now this is what I plan on using:
>
> 1. A 50ft roll of 1/4" OD refrigeration copper tubing.
> 2. A 3/4" thick sheet of plywood as the base.
> 3. 5 supports in an L shape cut out from a cutting board I got at WAL-MART 
> fixed to the plywood base with screws (similar to the image below).
>
>
> http://hot-streamer.com/temp/Medinaimage001.jpg
>
>
> At first I thought of fixing the supports to the base and winding the 
> tubing through the holes, but now I am realizing it will be a PAIN!!

More than a pain, well nigh impossible.


>  Therefore, should I slide in the supports, starting at the center and 
> work my way outside, through the entire roll of tubing? Or should I start 
> at the ends and work my way inside?

Feeding tubing through holes, whether the spacers are tied down or not, is 
very difficult.


> Some people prefer holes in the supports; others prefer notches. I am not 
> sure about this. I am thinking that the notches might bend the tubing if 
> one is not careful when doing this. Any suggestions?

Properly formed notches won't have a problem, but if you want holes, why 
not split your supports down the middle (bisecting all the holes).  You'd 
wind up with two basically identical combs. You'd attach the lower half to 
the baseboard, lay the tubing into the half holes, then carefully put the 
top half down over it, and tighten the screws (use nylon screws)


> Say I want 15 turns. While winding the tubing, let's say I run out of 
> tubing on the 11th turn. Is it okay to solder another continuous piece of 
> tubing to the original, to complete the 15 turns or not? I guess, what I 
> am asking is if I need a continuous roll of tubing or not? Will this 
> affect the coupling and/or the overall performance of the TC?

Solder away... If you can find some rod or smaller tubing that just fits 
inside the tubing, you can cut a short piece, shove it in one end, sweat 
some solder in, then shove the other tube onto the "prong" sticking out, 
sweat some solder in, sand the outside, and you'll barely be able to see 
the join. If you hide the join in one of your support blocks...

No detectible change in performance from splicing the tubing.


> Another thing I noticed is the fact that the tubing is double wounded, 
> making it even more tedious to work with it. A guy at Home Depot suggested 
> to unroll the tubing on the floor and then wind it on/through the 
> supports. Any suggestions?

Don't try to straighten it first. Bend the tubing as little as 
possible.  Every time you move it, it gets stiffer.  If you have supports 
on the baseplate already notched (or semicircled), you can unroll the 
tubing into the slots without much trouble, gently increasing or decreasing 
the diameter of the bend.  The tubing is quite springy.  The important 
thing is not to fool around with trying to form it freehand.  Inevitably, 
you'll overbend it, and you'll never get it back to that nice smooth 
continuous curve.


> I appreciate your time. Thanks for the help.
>
> Regards,
>
> Benjamin Medina
> Rolla, Missouri.