[ARC5] [Milsurplus] BC-348 Backlash Again

[WA5CAB at cs.com]

No.  Oldham couplers came about a decade later.

Robert D.

In a message dated 08/22/2012 16:36:04 PM Central Daylight Time, 
1oldlens1 at ix.netcom.com writes: 
> 
> 
> ----- Original Message ----- 
> From: "Kenneth G. Gordon" <kgordon2006 at frontier.com>
> To: <Arc5 at mailman.qth.net>
> Sent: Wednesday, August 22, 2012 10:01 AM
> Subject: Re: [ARC5] [Milsurplus] BC-348 Backlash Again
> 
> 
> >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
> 
>      I am not familiar with this equipment but by any chance 
> does it have an Oldham coupler?  These couplers can cause a 
> lot of rotation play which may seem to be backlash. I've 
> found on the Collins sets that do have Oldham couplers that 
> they must be clamped together before tightening the set 
> screws.
> 
> 
> --
> Richard Knoppow
> Los Angeles
> WB6KBL
> dickburk at ix.netcom.com 
> 

Robert & Susan Downs - Houston
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