[OT] Tube Bender for Mag Loop antenna?

[Elecraft mailing list]

I'm fabricating a remotely tuned magnetic loop antenna. I have the vacuum cap and stepping motor tuning system built and ready for a loop. Do any of you guys/gals especially in 3-land have a rolling tube bender so I can make my 3 foot copper loop? I don't want to hand-bend soft copper and would rather not buy a bender for such limited use. I could possibly build a light duty one but U-channel pulleys that will accommodate a 1.1" OD copper pipe are impossible to find online or even on eBay. If any one reading this knows someone in the Mid Atlantic area who can roll a hoop, or can recommend a source for  >1.1" nylon U-channel pulleys, I'd appreciate it if you could contact me off list. Thanks for your time. PS I don't want to sweat solder an octagon. I'm trying to keep loop R to an absolute minimum.
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[k6dgw]

On 10/4/2016 11:54 AM, rick jones via Elecraft wrote:

> Do any of you guys/gals especially in 3-land have a rolling tube
> bender so I can make my 3 foot copper loop?

I've had pretty good luck with smaller local machine shops when I've had
one-off tasks like this.  In particular, I've found that if one can't do
it, they'll gladly recommend someone who can.  I found one local guy who
wound an inductor for me using 1/2" tubing.  He also fabricated three
teflon bars to support it.  I was in N. Cal at the time.

> PS I don't want to sweat solder an octagon. I'm trying to keep loop R
> to an absolute minimum.

Assuming your "3 foot copper loop" has a diameter of 3 ft, it's
circumference is 9.425 ft.  An octagon with the same loop area has a
circumference of 9.680 ft.  The difference is 0.26 ft [3.06 in].  That
might not be enough to worry about in terms of I^2R loss in 1" copper
tube.  YMMV however.

73,

Fred K6DGW
- Sparks NV DM09dn

- Northern California Contest Club
- CU in the Cal QSO Party 7-8 Oct 2017
- www.cqp.org



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[Don Wilhelm]

Yes, muffler shops (especially the independent ones) are likely to be
willing to do the bending for you.  They have dies for most any size pipe.

They are also a good resource for small welding jobs - it is usually
best to approach them when they are not too busy.

73,
Don W3FPR

On 10/4/2016 5:32 PM, Walter Underwood wrote:
> A friend was making some custom handrails out of stainless steel tubing and found that muffler shops are glad to bend pipe into about any shape you want.
>
> It will probably be an amusing break from the day-to-day to make an antenna.
>
>

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[W8JH]

The soft copper tubing is extremely easy to work with.  We have a 3 foot diameter round oak table in the basement and I made a 3 foot loop by bending the copper tubing around the table as a form.

YMMV.

73,

Joe, W8JH

[David Windisch]

Find a cable, stiff rope, chain, wire bundle, what ever, which barely fits inside the copper pipe u wanna bend, to keep the pipe round so it doesn't kink.
Then find helper and a large tree or other form around which to make ur bend, a little at a time, gently.
Brgds,
Dave, N3HE

Oh, and pull the anti-kink what ever out when ur done <grin>