But I don't have a lathe - - Part II

In August of 2005 I posted a message that offered a few hints about
some alternatives to the lathe. In that message I said, "The most
common thing used to rotate the work is the ubiquitous quarter-inch
drill-motor."

I did so because I assumed everyone would be familiar with the many
jigs and fixtures designed to clamp a drill-motor to your work bench,
allowing you to use it as a grinder, scratch-wheel or whatever.

Turns out, a lot of folks had no idea in the blue-eyed world what I was
talking about. (Which tends to happen more often, the older I get :-)

Back in the Good Ol' Days, whenever that was for you, when you finally
got rich enough to afford a quarter-inch electric drill-motor there was
a whole raft of accessories and attachments you could buy to go with
it, allowing your drill-motor to serve as a drill press, bench grinder,
tire pump and so on. The most basic of those attachments was a sturdy
base that bolted to your bench and to which your drill-motor could be
fastened. Chuck a wire brush in your drill-motor and you had a
scratch-wheel; a mounted grind-stone turned it into a bench grinder.

So what's that got to do with the lathe business?

I recently told a feller how he could use a piece of brazing rod as an
antenna. Even gave him a piece of sixteenth-inch brass rod to get him
started. He had to order the connector because he was using a BNC
fitting and all I had was some big ol' PL-259's - - what they usta call
'UHF' connectors, even though they weren't. UHF, that is.

The reason he had BNC's was because he ran a lead to the belly of his
plane soz he could attach his rubber ducky. And it worked a treat, so
long as he was in the air. But once he landed, his rubber ducky was
down in the weeds and so was his signal, which ain't much using that
small of an antenna, which was about nine inches long.

Quarter-wave for aviation communication frequencies is about two
feet... something like that. (I'll let all the experts jump on that
one :-) So I suggested he replace the rubber ducky with a quarter-wave
and see if that didn't help.

When the feller got the BNC connector (eighty cents but he had to send
away for it) he sees that the center pin is smaller than the brazing
rod. In fact, the center pin is about .050" whereas the brazing rod
was an honest sixteenth of an inch. (The idea here is that the brazing
rod REPLACES the center pin.) Now, the truth is, a BNC connector --
the female part -- is more than willing to accept a .0625" dia pin,
assuming you put a bit of point on it and don't just jab it in there.
But he was afraid of ruining the connector on his belly pan so he came
by the shop and asked if I'd turn down the brazing rod to match the BNC
connector.

Which I did. But what surprised him was that I didn't use the lathe.
I'd just gotten the cylinder of an itty-bitty steam engine secured to
the cross-feed... had the boring bar all set up and had spent mebbe an
hour getting ready to make a cut that would take about ten minutes and
didn't want to tear it down and start over. Nor did I want to do the
work with someone peering over my shoulder.

I pulled the drill-motor stand out from under the bench, installed the
drill-motor then clamped it down. Chucking a sixteenth inch bit, I
used a piece of scrap wood as my 'tail-stock' and pushed it onto the
spinning drill bit, which gave me a sixteenth inch hole on exactly the
same level as the chuck of the drill-motor. Then I replaced the drill
bit with the piece of brazing rod, inserting its free end through the
hole I'd just drilled in the scrap of wood. I used another C-clamp to
secure the scrap of wood to the bench, roughly aligned with the
drill-motor, so that about half an inch of the rod was poking free on
the other side. Then I turned on the drill-motor and used a fine-tooth
single-cut file to 'machine' the end of the brazing rod about .050",
givertake. All of which took less time to do than to describe.

--------------------------------------------------------------------

Last summer I hinted that not having a lathe didn't mean you were dead
in the water when it came to producing a few turned parts. Some of the
comments I got told me that Common Sense was pretty uncommon stuff on
RAH because the simple truth is that even when DO have a lathe... and a
milling machine and a whole shop full of tools, often times you can do
a job faster using whatever happens to be available, plus a bit of
common sense.

--------------------------------------------------------------------

As for the COM antenna, you dip the tip in a solder pot, which in my
shop was a .22 cal. shell casing fulla solder and heated with a torch.
To secure it in the male BNC connector, which was the crimp-on type,
intended for coaxial cable, you distress the brass near the tip to give
it some tooth then slide a Delrin collar down the wire to fill the
ferule. Now you squeeze it, compressing the ferule onto the collar and
the collar onto the rod and seal the whole sheebang with three
graduated lengths of heat-shrink tubing. And there's your COM antenna.
Cost you mebbe a buck. (No, I don't what the SWR will be -- I've no
idea what kind of ground-plane he's got.)

When you install your brazing-rod antenna (or any other, for that
matter), wrap the connector with 'Coax-Seal.' That's a brand-name, by
the way. Radio type personnel usually got some in their pocket. If
not, you can order it. It looks like electrical tape only thicker and
not as wide and has the texture of unvulcanized rubber. Wrap the
connector then mold the edges of your wrappings with your fingers.
(I've been atop radio towers down in Mexico where the osprey-**** was a
foot thick and the only thing left of the antennas was the Coax-Seal,
which was still pliable after twenty years.)

-----------------------------------------------------------------------------

So... did going to a half-wave antenna solve his 'Say Again' problems?
I donno... yet. A better solution would be to position the antenna
somewhere on the TOP of the aircraft. Yeah, I know... you're flying
OVER the tower. But trust me here, they'll hear you just as good...
and a whole lot better when you're on the ground over behind the
hangar.

-R.S.Hoover

wrote in message
oups.com...


Quarter-wave for aviation communication frequencies is about two
feet... something like that. (I'll let all the experts jump on that
one :-) So I suggested he replace the rubber ducky with a quarter-wave
and see if that didn't help.

Close enough. With brazing rod, it is closer to 22.5", but what the hell.
Most likely he will be staying down in the bottom end of the band anyway, so
23-24" should work just fine.



When the feller got the BNC connector (eighty cents but he had to send
away for it) he sees that the center pin is smaller than the brazing
rod. In fact, the center pin is about .050" whereas the brazing rod
was an honest sixteenth of an inch. (The idea here is that the brazing
rod REPLACES the center pin.) Now, the truth is, a BNC connector --
the female part -- is more than willing to accept a .0625" dia pin,
assuming you put a bit of point on it and don't just jab it in there.
But he was afraid of ruining the connector on his belly pan so he came
by the shop and asked if I'd turn down the brazing rod to match the BNC
connector.

An alternative method (and one that is a little easier on the center pin of
the mating female connector) is to turn the brass rod down at the end to the
diameter of the center conductor of RG-58 coax so that it fits into the
little hole in the end of the pin that comes with the connector.

Just about a tenth of an inch turned down to 0.025 or so will work just
fine, thank you, and you can do it with either a file or a grinding wheel.
Just so it sticks into the little hole in the end of the pin a short ways.

While you are at it, grind a little bit off of the brass rod a half-inch up
from the pin end. Not too much, now, just a few thousandths and about a
tenth of an inch long. The edge of the grinding wheel will be just fine, or
a rat tail file will work also. It doesn't have to be square -- rounded is
actually a little bit better. Sort of like the old coke-bottle shape.

Now put that ground down rod end into the center pin and solder it without
getting solder all over the business end of the pin. Stuff the pin into the
connector body until the pointy end of the pin is flush with the bottom of
the connector.

Now mix you up some of that good epoxy and fill the open end of the
connector (the part that has the brass rod sticking out of it) up to the
top. Why did you grind that little dipsy-doodle into the rod? So that if
the epoxy loosens up with the rod over time that the rod won't depart the
airframe and do great damage to landlubbers. Don't worry about it loosening
up with the connector body. That's what the threads that would have held
the jam nut are for. THe epoxy will fill those threads AND the dipsy-doodle
and bind them tight together.

(My Rat Shack still has BNC connectors; yours may have gotten rid of the
small parts.)

Jim

That's interesting. I made one in San Diego before I moved up here in '75.
It has been in fairly constant use for 30 years and never failed, even
though it is my antenna of choice for lash-ups and dog'n'pony shows at fly
ins.

Hm.

Jim


Dear Jim,

My initial efforts used that method. Unfortunately, both examples
eventually failed due to a fracture at the soldered junction between
the center-pin and the radiator. After that I simply filed a point on
the rod and allowed it to serve as the center-pin.

On 19 Mar 2006 15:11:28 -0800, wrote:



If you want to retain the stock center-pin, I suggest you stick to wire
rather than rod, using fiberglas arrow-shaft stock or even Nyla-flow
tubing to give the radiator sufficient body. Injecting epoxy into the
nylon tubing then clamping the tubing straight until the epoxy cures
results in a surprisingly rigid structure, although I've never used
that method for an aircraft antenna.

-R.S.Hoover


if you stripped the shield off of the end 25 inches of coax, threaded
the conductor in the nylaflow tube and filled it with epoxy, wouldnt
that work without needing a connector?

serious question.
Stealth Pilot

Yep. Except that you need to provide for a ground plane of some sort.
Although it works (somewhat) just as you describe.


if you stripped the shield off of the end 25 inches of coax, threaded
the conductor in the nylaflow tube and filled it with epoxy, wouldnt
that work without needing a connector?

serious question.
Stealth Pilot

On Tue, 21 Mar 2006 06:51:35 -0900, "Ron Webb"
wrote:


Yep. Except that you need to provide for a ground plane of some sort.
Although it works (somewhat) just as you describe.


if you stripped the shield off of the end 25 inches of coax, threaded
the conductor in the nylaflow tube and filled it with epoxy, wouldnt
that work without needing a connector?

serious question.
Stealth Pilot


well that makes for a very cheapo antenna.
run the coax to the centre of a 2ft x 2ft sheet of thin aluminium, use
a rivnut in the centre of the sheet, epoxy the coax into it and run
the nylaflow out into the airstream.

my tailwind's antenna installation is done using standard aircraft
parts and has about 25" of round wire with the static eliminating ball
on the end. now in theory that round wire has more drag than a 25"
long 3ft chord section of aerofoil.

I wonder whether the aerofoiled (squashed) nylaflow would sit there or
would flog around in the airflow.
has anyone used veedubber's suggestion?

Stealth Pilot

On Wed, 22 Mar 2006 02:39:44 +0800, Stealth Pilot
wrote:

On Tue, 21 Mar 2006 06:51:35 -0900, "Ron Webb"
wrote:


Yep. Except that you need to provide for a ground plane of some sort.
Although it works (somewhat) just as you describe.


if you stripped the shield off of the end 25 inches of coax, threaded
the conductor in the nylaflow tube and filled it with epoxy, wouldnt
that work without needing a connector?

serious question.
Stealth Pilot


well that makes for a very cheapo antenna.
run the coax to the centre of a 2ft x 2ft sheet of thin aluminium, use
a rivnut in the centre of the sheet, epoxy the coax into it and run
the nylaflow out into the airstream.

my tailwind's antenna installation is done using standard aircraft
parts and has about 25" of round wire with the static eliminating ball
on the end. now in theory that round wire has more drag than a 25"
long 3ft chord section of aerofoil.

I wonder whether the aerofoiled (squashed) nylaflow would sit there or
would flog around in the airflow.
has anyone used veedubber's suggestion?

Stealth Pilot
Grab an aerodynamic antenna post off a late model car, cut it and
thread it to fit into a connector, and you have greatly reduced your
antenna drag.
*** Free account sponsored by SecureIX.com ***
*** Encrypt your Internet usage with a free VPN account from http://www.SecureIX.com ***