[ARC5] Part 6743 - tuning cranks and flexible drive cables for the ARC-5 sets.

[Clare Owens]

Hi Leslie,

Many years ago (1960-1962) I had access to the 3rd floor storage attic of
the Electrical Engineering Dept. of the University of Buffalo (New York)
since I was a student and working part time as a lab assistant.  The attic
was full of WW II surplus and I was able to buy a few things.  There were
two boxes of little brass "things" with internal splines and I took about a
half dozen of each size.  Each box had 500 maybe more pieces.  They are
brass two piece construction held together by small steel pins.  I think
they were the ends to be swaged onto the flex tuning shafts.  Why didn't I
just buy both boxes and save them?  Well...

I still have the pieces I bought that day and am using the five small ones
with set screw knobs to tune some of my command set receivers.  I just
measured both sizes and also took several very close up pictures.  If you
want I will send you some pictures, but they are large, 1.7 to 2.4MB each,
so your email would have to accept attachments of that size.  I'd send one
per email.

An interesting project.  If someone had access to en EDM machine on off
hours perhaps some interesting things could be made...

Clare

On Fri, Apr 8, 2011 at 2:24 AM, Leslie Smith <vk2bcu at operamail.com> wrote:

>
>
>                    Tuning cranks and drive cables.
>
> http://aafradio.org/garajmahal/flex_drive_cables.html
>
> Mike Hanz has published a page giving details for the Bendix flexible
> drive used in various sets, including what we call "command"/ARC-5 sets.
>
> I am trying to understand these drawings, and the fabrication of these
> cables.  As I understand the drawing, the thread used to fix the
> flexible cable on the ARA, SCR-274 and ARC-5 receiver families is 1/2
> inch x28 threads per inch.  I would like to recieve confirmation that I
> understand this correctly.  (The other alternative is 27 tpi, and Mike
> seems to discount this for the "command" sets.)
>
> I would like to find a detail drawing for the tuning crank, ARC-part
> number 6743.  Can any-one on this list tell me if a drawing of this part
> exists, and if "yes", where I can find this drawing?
>
> In the absence of a drawing, I turn to the drawings and photos from the
> web-page above, "flex_drive_cables".  A drawing is given of the cable
> assembly, "ARC-5 drive cable details" and that drawing (3rd from bottom
> of page) shows a female splined end, part 6788.  I believe this slips
> over the male spline on the receiver.  This is the end of the 3 gang
> tuning capacitor.
>
> Is my understanding correct?
>
> Assuming the detail in the paragraph above is correct, can anyone give a
> source for a female splined end?  I don't refer to a surplus or NOS
> cable, or a part from the ARC-5 component list, but simply a part that
> can be adapted to make a "nice" but non-original tuning crank or
> flexible drive.  I'm sure I can get ONE splined thing-o, but what if I
> want two or a dozen?  NOS is not a possibility here.  I have spoken with
> a competent tradesman, on the subject of fabricating the spline.  His
> opinion:  A tool to broach as many female splines as I want can be
> easily got - for about $1000.  Probably correct, so I will look
> elsewhere for a solution.
>
> There are plastic solutions available, of course.  A length of common
> flexible air line (eg Festo) will fit over the spline nicely, and could
> be pressed into service for little cost.  A nice fit, but not such a
> nice thing to put on a "command" receiver, I'm sure.
>
> Turning to other items in the Mike Hanz' drawing ("ARC-5 drive cable
> ..." consider part number 1167.  This looks suspiciously like a locking
> device that might hold a tuning crank in place.  I believe the internal
> thread in this locking device is 1/2 inch 28 threads per inch.
>
> Is my understanding correct?
>
> To make this thread I will need a 1/2 inch 28 tpi tap.
> Can anyone on this list tell if these can still be bought?
> I found a #12G 28 threads per inch from a local supplier, (Blackwoods)
> but I have no idea about the diameter of a #12 gauge tap.
>
> Is there a possibility that #12 gauge is 1/2 inch?
>
> I see no other tapping tool from Blackwoods with the correct diameter or
> tpi.  Blackwoods supplies an extensive range of tools, and if a tap
> isn't available from here, then it ain't to be got.  I would rather buy
> a tapping tool than try to adapt a butchered cycle axle as a tap.  I'll
> say no more than that.
>
> Looking forward to interesting and well informed replies!
>
>
> Les Smith
> ex VK2BCU
>
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