[ARC5] ARA, SCR-274-N, AN/ARC-5 Remote Control Box Dials - Questions

[WA5CAB at cs.com]

A possibility that occurs to me is that the numbers marked on the rear of 
the dials might be the ARC part or drawing numbers of the dial disks alone.  
The disk assembly, which is what the numbers in the manuals refer to, are 
three-piece assemblies (disk, thumbscrew, and keeper).  This would be like 
machined parts made from castings (like Land Rover cylinder heads).  The 
casting has (usually) a number cast into it.  That is the raw castinq part number. 
 The finish machined head has a different part number, which does not 
appear anywhere on the head.

In a message dated 6/22/2011 9:07:46 PM Central Daylight Time, 
aaf-radio-1 at aafradio.org writes: 
> On 6/22/2011 5:18 PM, Mike Morrow wrote:
> >Mike wrote:
> >>I went out and took a couple of photos of the ones I have, Mike, and
> >>it's a mixed bag.  Attached are two photos of the dials, front and
> >>back.  The rear view is simply the front view with each dial reversed in
> >>position.  The one on the upper right is for the BC-453, and is yet
> >>another type that is commonly encountered - made of black Bakelite
> >>rather than aluminum.  You can see that the two right hand dials are
> >>both marked C-****, while the rest are all D-****.  Whether that
> >>signifies 274N or not, I do not know.
> >I suppose that the lower right .52 to 1.5 MC dial is the rare SCR-274-N 
> MC-415 dial,
> >or much less likely, an original early-ARA #6052 dial.  It's the first
> >one I've ever seen.
> 
> I have no clue.  The center two in the photos are from ARA's (if I 
> recall correctly), while the left hand pair are from ARC-5 sets.  There 
> are subtle differences that are apparent with study, but without 
> documentation, I'm not sure they are worth more than brief speculation.
> 
> >I also have never come across a bakelite dial.
> 
> I think I have encountered almost as many of those as the aluminum sort, 
> for some reason.  Geographic distribution, perhaps...
> 
> >Those numbers like "D 5611" don't correlate to any part or drawing number
> >that I've ever seen, but the four digits are consistent for each dial 
> type.
> 
> Yes, they are consistent (thankfully) :-) , and they do correspond to 
> some ARC contract drawing listings I have here.
> 
> >There doesn't seem to be a correlation that can be made to the letter
> >in front of the four-digit number stamped on back.  Even the small-font
> >dials of the SCR-274-N MC-213 and MC-214 have the same combination as
> >the large-font dials of the late-ARA and AN/ARC-5.
> 
> I suspect that Mssr. Tauson's speculation about progressive replacement 
> without nomenclature changes is pretty close to reality.  I mean, if you 
> think about it, they all do the job - it isn't like a complex interface 
> specification.
> 
> >The MC-415 is interesting.  I've had two NIB BC-946-B BCB receivers in
> >past 15 years, made by Colonial.  They both came out of the box with the
> >FT-310-A power adapter (for the associated AN/ARR-1) and a small 
> instruction
> >book.  It was surprising to me that there was no MC-415 dial included for
> >the associated BC-450-A.  I wonder where the technicians got one for 
> those
> >rare USAAF uses of the AN/ARR-1 with the SCR-274-N.  I suppose they could
> >leave the dial for the displaced BC-453-B on the BC-450-A and mark it to 
> show
> >the pilot where to find the modulating frequency of the YE/YG homing 
> beacon
> >of interest.  But who knows.  I think most of the AN/ARR-1 sets that were
> >actually installed in USAAF service were like the B-29 installations
> >which used the AN/ARN-7 ADF set to process the output of the AN/ARR-1.
> 

Robert & Susan Downs - Houston
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MVPA 9480