[ARC5] Help with tuning knob ideas for ARC-5 receiver

[Mike Hanz]

Neil's description below is the sort of innovative thinking that seems 
to be lost in the western colonies since King George died. :-)   More 
seriously, a process for fabrication of the brass female spline has been 
one of those things for which I have never seemed to get a tuit, round 
or otherwise.  A number of years ago one of the list members told me 
that he was going to use a wiggle broach at his work to turn out a bunch 
of them, but I don't know if he ever followed through on the idea.  I 
can recall my dad and his friends making such parts for various needs in 
pretty much the same way, but the time it takes to prep and actually 
cast the part seems to be a dying art here in the United States.  I do 
remember my dad warning me not to use soldering flux when casting the 
part - you don't want the internal form adhering to the new part unless 
you don't care to remove it.  Some of the metal filled castable epoxies 
could probably be used - they are pretty durable in the kind of service 
that the female spline fitting sees in a command receiver.

The retaining nut which Neil describes has a 1/2"-27 thread, which is a 
very oddball size from 19th C. gas light days - same pitch as the larger 
Bendix commercial equipment nuts at 
http://aafradio.org/garajmahal/flex_drive_cables.html .  While 27 
threads per inch is used on 1/16" and 1/8" pipe fittings, unfortunately 
it misses the 1/8" size here in the US in OD by a tenth of an inch., and 
there isn't a Metric equivalent that is a finger tight screw-on - a 1mm 
pitch is of course 25.4 T.P.I.   I broke down and simply bought a tap 
for the size.

73,
Mike

On 10/23/2010 5:15 AM, Neil wrote:
>> What do I need in order  to replace that cable with a regular knob
> The very first ARC-5 receiver I bought in 1965 had a brass pipe
> fitting (like those found in car fuel lines) screwed onto the threaded
> chassis connector. The threads were a perfect match, so there
> are compatible threads out there guys.
> The pipe fitting had a quarter inch hole thru which passed a quarter
> inch brass shaft extension of the usual ham type.
> The grub screw was not used and was not present. The female
> end of the shaft extension had been filled with solder in such a way
> that it could slide onto the spline and rotate it.
> It looked like the constructor of this device had heated the female
> end of the extension shaft and filled it with solder, then pressed it
> up onto the spline while the ARC-5 was held vertically with face
> down and the solder still hot. After waiting for the solder to cool,
> the brass pipe fitting was passed along the coupling and screwed
> on. Its function was to stop the extension sliding off the spline, and
> support it whenever there was perpendicular hand movement on the
> knob.
> The solder could have been easily renewed if it showed signs of
> wear, although it showed no such wear for me even after several
> years of tuning up&  down 80m.
> Of course, the quarter inch hole thru the fitting may have been
> drilled out from some smaller diameter, so you don't have to look
> for an exact match.