Wow that zig-zag looks like its made out of 8mm stock.... definately heavy duty.

(EDIT: This post and some replies were originally in this thread: http://www.digitalhome.ca/forum/showthread.php?t=106538)

That's a serious metal bender, wish I'd had access to one of those.
Any more photos to upload?

Wow that zig-zag looks like its made out of 8mm stock.... definately heavy duty.
Pretty darned close to 8mm -- it's 5/16" solid aluminum rod.

We got the rod from two different suppliers.. and it turns out that the metal is slightly different from each. One type bends into zigzags no problemo. But the other kind breaks when bent..

Luckily, we were clever enough to test for that at the outset, and consigned the breaky kind for straight reflector rod uses only.

A GH8 requires about 28' of rod, plus waste (odd sized cutoffs). We're building *eight* GH8s, so that's around 240' of the stuff.

:)

I think the materials cost was around $25/each, give or take a looney. We then added another $5 for wear and tear in the workshop (bits, blades, and sanding belts, other consumables, etc..). So each finished antenna cost about $30.

Mmm.. we did also notice that some of the square tubing used for the center spine has a slight twist to it (from the supplier) -- at least one of my antennas from the build is slightly twisted lengthwise as a result -- I'll have to try and straighten it out a bit before putting it into service. Not all of them have this problem, but I expect at least one other might.

Cheers

Mmm.. we did also notice that some of the square tubing used for the center spine has a slight twist to it (from the supplier) -- at least one of my antennas from the build is slightly twisted lengthwise as a result.
Okay, problem solved!

I simply clamped one end of the finished antenna into a well-anchored vise, grabbed the other end of the tubing with a 3/4" spanner (wrench), and then, well uhm, wrenched it back into a non-twisted straight line. Took all of five seconds or so.

:)

Mmm.. we did also notice that some of the square tubing used for the center spine has a slight twist to it (from the supplier)
Actually, most of the square antenna booming I got came that way, heh. Yep, in the vice and twist.

Go to BusyBee and search for item B2616. That's the exact model I have here.
Pretty nice tools ! It was initially a sticker shock until I realized those were Canadian $, heh. (still pricey)

So, to operate the B2616, the rod is clamped in place so that the bend point is at the edge of the metal block (that part I understand) and then do you push down on the other big bar to do the bending ?

So, to operate the B2616, the rod is clamped in place so that the bend point is at the edge of the metal block (that part I understand) and then do you push down on the other big bar to do the bending ?

No pushing down... more like pushing left. I did a little photoshop to the picture (http://img.photobucket.com/albums/v254/Gremlin5/z0206038.jpg) to show.

We got the rod from two different suppliers.. and it turns out that the metal is slightly different from each. One type bends into zigzags no problemo. But the other kind breaks when bent.

Had the same problem with a piece of flat stock I picked up from Home Depot the other day.

Can you give us other folks an idea which type of uli not to buy or from which supplier? (for us folks that have to buy in Ottawa)

No pushing down... more like pushing left. I did a little photoshop to the picture (http://img.photobucket.com/albums/v254/Gremlin5/z0206038.jpg) to show.
Thanks! Yeah, that's the idea. The tool is just a platform with a rotating "pusher" on a long handle. The "pusher" has a gigantic sleeve bearing on the contact end, so that it doesn't scuff the item being bent.

The shiny round "table top" is interchangeable with another one (included), and there are lots of little bend points that can be bolted down onto it for different types of bends, including making long spirals and the like.

I've gotten a couple of chunks of raw steel blocks, and rounded the corners to make my own bending radiuses (not shown).

Oh, and when I picked up this "machine" last year, the sale price was a little less than the current sale price. :)

Very handy for antennas, and tower brackets, and other odd jobs.

Cheers

Can you give us other folks an idea which type of uli not to buy or from which supplier? (for us folks that have to buy in Ottawa)
The rod from Metal Supermarket is, unfortunately, the breaky kind (6061-T6). So avoid the T6 stuff, or ask if any given shop has rod that is softer than T6. And/or ask if they can special order some for you!

Here's a one-time deal: I bought out all of the (cheap!) bendable 5/16" rod from Cohen and Cohen, except for one final 20' length of the stuff (they'll chop it to fit your car, or you can do it with a simple bolt/chain cutter tool). That final length (there's only one) is slightly bent at one end, but still has enough straight metal for a couple of good zigzags (about 54" for each).

First one there gets it! :)

Cheers

hanks! Yeah, that's the idea. The tool is just a platform with a rotating "pusher" on a long handle. The "pusher" has a gigantic sleeve bearing on the contact end, so that it doesn't scuff the item being bent.
Ahh, the handle just swings from a pivot point. That makes it even easier to construct one from scrap iron pieces I have.

Very handy for antennas, and tower brackets, and other odd jobs.
Yeah, it seems like the most popular use for the benders is to make fancy iron ornate railings/fences/window guards etc.

Is there any appreciable difference in using copper vs aluminum?

I would assume, that copper would have the absolute best performance, but if it came down to cost, how much performance would one be sacrificing to use aluminum rod instead?

Would aluminum reflectors and copper driven elements be a good compromise?

I don't know about impedance in different metals, but at the gauges and distances involved, the resistance is rediculously small (and difference in resistance even smaller).

For example, assuming an 8 gauge element (8.36 mm² cross section) approximately 1 meter long:
Copper: .00205 Ω (17.1e-9 Ωm * 1 m / 8.36e-6 m²)
Aluminum: 0.00317 Ω (26.5e-9 Ωm * 1 m / 8.36e-6 m²)
Steel (typical): .02153 Ω (180e-9 Ωm * 1 m / 8.36e-6 m²)

I'd expect impedance difference to be comparable, if not even closer to 'no appreciable difference'. These values are completely swamped by other factors, such as balun loss.

Conveniently, the modelling software we generally use, NEC2, has a way to simulate different conductances.

And yes, aluminum vs copper is negligible. I sometimes include it in my models just because I'm a little too detail-oriented (except, apparently, when it comes to actually building the things.)

From Post #8 here's how various metals and alloys compare for conductivity:Perfect* Copper Pure Aluminum Silver AL 6063-T832 AL 6061-T6 Brass Phosphor Bronze Stainless Steel

9.9e99 5.80e7 3.77e7 6.29e7 3.08e7 2.49e7 1.56e7 .909e6 1.39e6

* theoretically perfect conductance
.

Heres a good site for the current wholesale prices of metal : http://www.metalprices.com/

Zinc has a conductivity of 1.66e7 for galvanized steel wire. The rate of oxidation should be considered for outside use. Gold would be good and look nice and the security guard hired to protect it could also rotate it.

Feig

mlord

The rod from Metal Supermarket is, unfortunately, the breaky kind (6061-T6). So avoid the T6 stuff, or ask if any given shop has rod that is softer than T6. And/or ask if they can special order some for you!


Did it break as soon as you start to bend it or did it allow for some bending (i am looking for stuff that will allow about a 30 degree bend (150 degree inner angle)

With aluminum wire, use aluminum or zinc plated or galvanized steel screws/nuts/bolts

Will there be galvanic corrosion if driven elements are aluminum, feed lines (and washers) are copper, and screws are brass?