[R-390] RF subchassis separation

Chris Farley kc9ieq at yahoo.com
Tue Mar 4 00:51:42 EST 2014 

Ok, ok, I couldn't take it.  Dang instant gratification mentality...

After about a liter of Kroil, some elbow grease, and aome quick n dirty disassembly I won't share here for the fear of being banished, the answer is clear.

There's a screw.  

Yes, there is a "Phantom Screw" holding that shaft in place.  

Tear it apart, apply some Loc-Tite, and pinch it down to be forever forgotten about.  

Of course, I did all this BEFORE looking at the Collins RF gear train assembly drawing again.  I skipped a number, and ta-da a screw is listed.  About 30 seconds later, here are the specs:
AAJD THREAD CLASS 2A 
AAJF THREAD DIRECTION RIGHT-HAND 
AASA THREAD LENGTH 0.312 INCHES NOMINAL 
AASB FASTENER LENGTH 0.312 INCHES NOMINAL 
AASK HEAD STYLE FLAT COUNTERSUNK 
AASL HEAD DIAMETER 0.300 INCHES MINIMUM AND 0.332 INCHES MAXIMUM 
ABQZ INTERNAL DRIVE STYLE CROSS RECESS TYPE 1 
AHYM NOMINAL THREAD DIAMETER 0.164 INCHES 
CMLP THREAD QUANTITY PER INCH 32 
CRSQ COUNTERSINK ANGLE 80.0 DEGREES MINIMUM AND 82.0 DEGREES MAXIMUM 
CYAU SCREW MATERIAL STEEL CORROSION RESISTING 
CYBA SCREW SURFACE TREATMENT PASSIVATE 

Regards, 
Chris kc9ieq


On Mar 3, 2014, at 10:35 PM, Chris Farley <kc9ieq at yahoo.com> wrote:

> 
> 
> Light bulb moment...  The normal angle for an Imperial countersunk screw is *ding* 82°.  Now, a normal #8 countersunk screw has a head diameter 
> of .359" exceeding the max .343" specified OD of that hole.  However his isn't to say a special screw couldn't be used, or WAS used but omitted 
> from all the drawings for some reason.  
> 
> With
> your RF deck already being assembled that far, it would be worth 
> separating the plate and see what things look like from the rear.  Odds 
> are you'll end up taking it off either way to repair.  
> OR,
> If that shaft is loose enough and you haven't much to lose, try pulling
> on it slightly while turning clockwise.  If there IS a screw hiding 
> back there, you might be able to tighten it up that way.  
> 
> Either
> way I agree
> that sloppy shaft should be addressed.. But with the whole assembly 
> together with 5-40 screw installed from the front, it *shouldn't* move 
> at all, unless that hole is badly wallowed out.  
> 
> Chris
> 
> ________________________________
> From: Barry <n4buq at knology.net>
> To: Chris <kc9ieq at yahoo.com> 
> Cc: r-390 at mailman.qth.net 
> Sent: Monday, March 3, 2014 10:14 PM
> Subject: Re: [R-390] RF subchassis separation
> 
> 
> Instead of pressing that shaft in place, perhaps the threads were used with a screw to pull the shaft in instead and then the screw was removed.
> 
> Just a thought.  I doubt that's the case but who knows...
> 
> Thanks,
> Barry - N4BUQ
> 
> ----- Original Message -----
>> From: "Chris" <kc9ieq at yahoo.com>
>> To: r-390 at mailman.qth.net
>> Sent: Monday, March 3, 2014 10:09:56 PM
>> Subject: Re: [R-390] RF subchassis separation
>> 
>> Well I just happened to think, and went to look at a crusty RF deck I
>> have for parts.  That plate sits flush against the RF coil assembly
>> chassis, so if a screw is used it must be countersunk and not sit
>> above the surface of the plate.  I don't really want to separate
>> mine at the moment, but perhaps someone with a gear train assy
>> separated from the rest can chime in.
>> 
>> Chris
>> 
>> Sent from my outdated iPhone wireless thingy
>> 
>> On Mar 3, 2014, at 10:01 PM, Chris Farley <kc9ieq at yahoo.com> wrote:
>> 
>>> I was looking through the drawings to see how that shaft is
>>> supposed to be pressed/crimped into place.  It appears there may
>>> be a drawing missing from the set (SM-D-178900 missing, as
>>> referenced to on SM-B-178901), but here is info gleamed from
>>> drawings of the shaft, the RF gear train assembly front plate, and
>>> the gear train assembly:
>>> 
>>> The pressed-in portion of the shaft is .219" +.001" -.000" by .040"
>>> deep.  That end also has a hole drilled into it, which strangely
>>> is shown without specs, aside from being 1/4" deep and tapped at
>>> 8-32.
>>> 
>>> The hole in that front plate is complicated.  .2187" +.0005"
>>> -.0000" hole.  Countersunk at 82° ±3° to .343" on the front, and
>>> countersunk at 82° ±3° to .248" on the rear.
>>> 
>>> Now I'm no machinist, but that sure seems like it must be a
>>> temporary "hold it in place" plan given the approx .0001"
>>> press-fitand overlapping tolerances, and then probably flared out
>>> from the rear for a more solid fit.
>>> Question is, why does the shaft drawing show the rear hole to be
>>> threaded??  Is there actually the possibility of using a screw to
>>> hold that shaft in place?  One is not shown on any of the drawings
>>> I have seen thus far.
>>> BUT if it IS indeed threaded and they aren't messed up from
>>> whatever pressing or staking took place, or the ID is such that
>>> you COULD drill/tap it, sticking a truss head screw (or a screw
>>> with a <shudder> FLAT WASHER) in there would seemingly be a pretty
>>> easy fix, assuming there is clearance behind the plate.
>>> 
>>> ????
>>> 
>>> Regards,
>>> Chris
>>> 
>>> 
>>> 
>>> 
>>> ________________________________
>>> From: rbethman <rbethman at comcast.net>
>>> To: r-390 at mailman.qth.net
>>> Sent: Monday, March 3, 2014 8:40 PM
>>> Subject: Re: [R-390] RF subchassis separation
>>> 
>>> 
>>> Mark,
>>> 
>>> I've looked at the post you showed in the pic.
>>> 
>>> Since it was highly likely a press fit, it can be "staked" to fix
>>> it
>>> back in place.
>>> 
>>> It won't be a simple task.  I'd seek out someone with machinist
>>> skills.
>>> That would be someone that can help with this.
>>> 
>>> Application of something very like the metal bonding tube that for
>>> the
>>> life of me that I can't remember right now.
>>> 
>>> The combination of "staking" and that compound should make it tight
>>> once
>>> more.
>>> 
>>> By golly!  I think it is JB Weld.  It finally popped into the old
>>> noggin
>>> as I began to sign the end!
>>> 
>>> Regards,
>>> Bob - N0DGN
>>> 
>>> 
>>> 
>>> 
>>> On 3/3/2014 8:35 PM, Mark Richards wrote:
>>>> Now finally doing a rebuild of my R-390A.  Gear train has been
>>>> disassembled, cleaned, and now in the re-assembly process I hit a
>>>> snag:  there's a post which hosts the Differential Gear Assembly,
>>>> and
>>>> it is very loose.  It cannot be screwed down tightly.  I suspect
>>>> that
>>>> this post is press-fit into the gear backing plate. As the post is
>>>> loose, I think this is accounting for the fact that the
>>>> Differential
>>>> Gears are not aligning properly with adjacent gears, nor with the
>>>> front gear cover.  There is considerable mechanical friction when
>>>> the
>>>> front plate is attached.
>>>> 
>>>> So, my questions:
>>>> 
>>>> 1. Can the RF Subchassis be separated from the gear assembly plate
>>>> and...
>>>> 2. Can the Differential Gear Assembly post be repaired?
>>>> 
>>>> A photo of the offending post:
>>>> 
>>>>    http://kumichan.net/private/03-03-2014 20-28-04.png
>>>> 
>>>> 
>>>> I have another complete gear/RF Subchassis that is of dubious
>>>> electrical condition, but is mechanically sound.  If I can
>>>> separate
>>>> gears from chassis, then maybe an option is to swap out the RF
>>>> Subchassis with the good gear set?
>>>> 
>>>> 
>>>> /K1MGY
>>> 
>>> ______________________________________________________________
>>> R-390 mailing list
>>> Home: http://mailman.qth.net/mailman/listinfo/r-390
>>> Help: http://mailman.qth.net/mmfaq.htm
>>> Post: mailto:R-390 at mailman.qth.net
>>> 
>>> This list hosted by: http://www.qsl.net
>>> Please help support this email list: http://www.qsl.net/donate.html
> 
>>> ______________________________________________________________
>>> R-390 mailing list
>>> Home: http://mailman.qth.net/mailman/listinfo/r-390
>>> Help: http://mailman.qth.net/mmfaq.htm
>>> Post: mailto:R-390 at mailman.qth.net
>>> 
>>> This list hosted by: http://www.qsl.net
>>> Please help support this email list: http://www.qsl.net/donate.html
>> ______________________________________________________________
>> R-390 mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/r-390
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:R-390 at mailman.qth.net
>> 
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
> ______________________________________________________________
> R-390 mailing list
> Home: http://mailman.qth.net/mailman/listinfo/r-390
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:R-390 at mailman.qth.net
> 
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html

More information about the R-390 mailing list