[ARC5] Gear alignment

Thu Aug 23 17:39:43 EDT 2012

Hello List-members:
Observation from Ken:  "The main reason is excessive drag in the
capacitor itself, usually due to deteriorated lube, a misaligned
main-shaft, or other such things."

All I can say is this:  "Yes!"  
Once I worked with a very thorough fitter.  When I re-assembled "stuff"
Norm would stand back and watch the process.  He taught me to assemble
an item, but never TIGHTEN anything until the entire mechanism was in
place, aligned and moving freely.  Norm's method seems obvious, but we
don't always follow it!  But then I learned a good deal from that
fellow, including the idea that the obvious isn't always obvious.

73

  Leslie Smith
  vk2bcu at operamail.com

On Thu, Aug 23, 2012, at 08:38, Paddy Ryan wrote:
> Yeah..a common enough problem with the 348..especially when re-fitting a 
> removed tuning mechanism or transferring one from one rx to
> another..never 
> quite fits exactly the same..the screws on the front panel that fix the 
> panel to the chassis can affect the alignment of the mechanism that
> connects 
> the tuning cap gears to the drive engagement..make sure that the panel 
> screws are properly aligned and are tightened without stress..removing
> the 
> variable cap and refitting or transferring to another set is also 
> problematic as it is difficult to fit again exactly as it was in the
> first 
> place..there is no play in any of the screws so the slightest stress can 
> affect the meshing and alignment..most of them have a little backlash
> anyway 
> and in my experience does not detract from enjoying their use..everytime
> you 
> re-fit it it will be slightly different than before but keep doing it
> until 
> you get the best you can..the different makers mechanisms are not 100% 
> compatible but work ok
> 
> -----Original Message----- 
> From: arc5-request at mailman.qth.net
> Sent: Wednesday, August 22, 2012 6:01 PM
> To: arc5 at mailman.qth.net
> Subject: ARC5 Digest, Vol 103, Issue 52
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> Today's Topics:
> 
>    1. Re: [Milsurplus] BC-348 Backlash Again (WA5CAB at cs.com)
>    2. bc459 (Alan Morriss)
>    3. Re: [Milsurplus] BC-348 Backlash Again (Kenneth G. Gordon)
> 
> 
> ----------------------------------------------------------------------
> 
> Message: 1
> Date: Wed, 22 Aug 2012 12:35:49 -0400 (EDT)
> From: WA5CAB at cs.com
> Subject: Re: [ARC5] [Milsurplus] BC-348 Backlash Again
> To: milsurplus at mailman.qth.net, boatanchors at theporch.com,
> boatanchors at mailman.qth.net, arc5 at mailman.qth.net
> Message-ID: <4ed74.1c8ca07e.3d666465 at cs.com>
> Content-Type: text/plain; charset="US-ASCII"
> 
> Dave,
> 
> Any anti-backlash gear and worm pair that I ever saw has several times
> the
> amount of rotation (throw) needed to remove any amount of backlash
> between
> it and its driving worm gear (pinion).  If, when preloaded, there is
> still
> backlash between gear and tuning knob, I can think of five possible
> reasons:
> 
> (1) loose set screws in shaft couplings or knobs.
> (2) end float in the pinion shaft bearings (if that's your problem, then
> the plastic tape must have side-loaded the pinion enough to force the
> balls 
> to
> the zero clearance point of one or two of them, which will pretty soon
> quit
> working as the tape wears).
> (3) weak spring.
> (4) excessive torque required to rotate the capacitor shaft.
> (5) excessive force required to rotate the movable gear.
> 
> Robert D.
> 
> In a message dated 08/22/2012 09:43:28 AM Central Daylight Time,
> arc5 at ix.netcom.com writes:
> > Working on getting a very nice BC-348 going for a friend.
> > Backlash is a common problem with these sets.
> > In this one, the backlash cause was between the gear
> > on the end of the tuning capacitor and the pinion gear
> > that drives it.  No amount of removing, cleaning,
> > re-lubing and spring-retensioning corrected it.
> > Couldn't see a non-destructive way to mesh the
> > two gears tighter.
> > The anti-backlish gear on the end of the tuning cap
> > just does not have the "throw" needed
> > to take-up the slop between it and the pinion.
> >
> > I cleaned-way all the oil and grease from the pinion.
> > Cranked the tuning cap all the way closed.
> > Then cut a strip of plastic electrical tape and fed it
> > into the gear mesh point, cranking until I could grasp
> > the end and bring it around, pressing the ends together,
> > and then ran the gear back and forth to seat it.
> > Used a soldering iron to remove the excess tape,
> > leaving a little tab.
> > This filled the slop and completely eliminated the backlash.
> > Yes, the plastic tape will wear-out eventually.
> > Does anyone know of a better and non-destructive
> > product for taking the slop out of this mesh point without
> > "poisoning" the lube in the tuning cap anti-backlash gear?
> >
> > 73 DE Dave AB5S
> >
> 
> Robert & Susan Downs - Houston
> wa5cab dot com (Web Store)
> MVPA 9480
> 
> ------------------------------
> 
> Message: 2
> Date: Wed, 22 Aug 2012 18:00:15 +0100
> From: "Alan Morriss" <mohawk at clara.co.uk>
> Subject: [ARC5] bc459
> To: <arc5 at mailman.qth.net>
> Message-ID: <E10270D6CF9F4480B46F9007D89F8ADD at alan>
> Content-Type: text/plain; charset="Windows-1252"
> 
> hello guys , i was fortunate to obtain what looks like a nice BC459 on
> ebay 
> . it wasot too expensive at ?45.45 ($73.39) . this means that my search
> for 
> a PA cover plate and bottom cover is scaled down . however i would still 
> like to fit them to the tx to restore it .hopefully it will be around
> longer 
> than i will ! alan
> 
> ------------------------------
> 
> Message: 3
> Date: Wed, 22 Aug 2012 10:01:19 -0700
> From: "Kenneth G. Gordon" <kgordon2006 at frontier.com>
> Subject: Re: [ARC5] [Milsurplus] BC-348 Backlash Again
> To: Arc5 at mailman.qth.net
> Message-ID: <5035105F.29171.46CF2F9 at kgordon2006.frontier.com>
> Content-Type: text/plain; charset=US-ASCII
> 
> On 22 Aug 2012 at 12:35, WA5CAB at cs.com wrote:
> 
> > Dave,
> >
> > Any anti-backlash gear and worm pair that I ever saw has several times
> > the amount of rotation (throw) needed to remove any amount of backlash
> > between it and its driving worm gear (pinion).  If, when preloaded,
> > there is still backlash between gear and tuning knob, I can think of
> > five possible reasons:
> >
> > (1) loose set screws in shaft couplings or knobs.
> > (2) end float in the pinion shaft bearings (if that's your problem,
> > then the plastic tape must have side-loaded the pinion enough to force
> > the balls to the zero clearance point of one or two of them, which
> > will pretty soon quit working as the tape wears). (3) weak spring. (4)
> > excessive torque required to rotate the capacitor shaft. (5) excessive
> > force required to rotate the movable gear.
> 
> Dave:
> 
> Adding somewhat to what Robert has listed above, it has been my
> experience that if the tuning capacitor has a lot of drag, for any of a 
> number
> of reasons, backlash, even with the split-gear anti-backlash units, and
> everything else (shaft couplings, end bearings) are correct, backlash
> will
> never be acceptable. The main reason is excessive drag in the capacitor
> itself, usually due to deterioriated lube, a misaligned main-shaft, or
> other
> such things.
> 
> In your case, I would, if possible, remove the main-tuning cap and check
> to
> see how hard it is to rotate. It should be rotatable with one finger.
> 
> Ken W7EKB
> 
> 
> ------------------------------
> 
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> End of ARC5 Digest, Vol 103, Issue 52
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