[R-390] RF subchassis separation

Mon Mar 3 23:14:36 EST 2014

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 Sent from my outdated iPhone wireless thingy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
> > 
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