Garey Barrell <[EMAIL PROTECTED]> made an utterance to the drakelist gang
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Terry -
OK. Well it seems to me that the less pressure applied to the cam the
better, as long as the slug rack moves reliably. With today's lower
viscosity grease, it probably does NOT require as much pressure as it
did with the axle grease they used to use.
I'd be interested in what Bill has to say about it. Most likely there
was a "girl" who set up the PBTs, possibly only one or two. This and
the compensation of the PTO's were highly specialized tasks, performed
by just a few. Bill said once that the two or three ladies who did the
PTOs would sit and chat about their grandchildren while cranking out
PTOs on "autopilot".
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 4-B, C-Line & TR-4/C Service Supplement CDs
<www.k4oah.com>
Terry Hart wrote:
"Terry Hart" <[EMAIL PROTECTED]> made an utterance to the
drakelist gang
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Hi Gary!
Thanks for replying to my question.
Yes, I have, and it was very helpful.
I have asked the question because there is always the possibility
that, in the past, someone may have upset the original positioning, to
increase the spring pressure on the cam. There was a fair bit of wear
on my PBT cam and pivots, so I want to be sure that I get the spring
pressure about right.
What I am saying is that if you start with a correctly functioning
PBT, and then the centre screw is screwed in, say one more
turn, and all four slugs are then screwed out an amount that places
the cores back exactly where they were, the tuned frequency of the PBT
(and the 'swish' range) will not have changed. The only difference is
that the spring pressure will be that bit greater (spring slightly
more compressed).
So how was the screw adjuster initial positioning (and the spring
pressure) set up by Drake in the first place?
Bill and I have just been exchanging emails on this and it will be
interesting to see if he can shed some light.
I suspect there may have been 'a man who did this'. If anyone knows I
guess Bill will.
By the way, I found your CD photos very helpful for confirming the
wiring sketches I made several months ago when I removed the PBT and
PTO for a service. As usual, you expect to complete a job within a
short timeframe, and then life gets in the way....... and my memory
aint what it was!
All the best,
Terry
----- Original Message ----- From: "Garey Barrell" <[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Monday, June 09, 2008 4:41 PM
Subject: Re: [drakelist] R-4 PBT cam pressure
Garey Barrell <[EMAIL PROTECTED]> made an utterance to the
drakelist gang
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Terry -
Did you see the PBT notes in my CD? That information is from Bill
Frost at Drake, and number 7 says to re-install slug rack in exact
same position as removed.
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 4-B, C-Line & TR-4/C Service Supplement CDs
<www.k4oah.com>
Terry Hart wrote:
I have just completed a mechanical service of the PBT on my R-4B, to
remove and replace the old, hardened, grease and to polish out some
scoring on the cam and pivots). I am about to re-assemble it all,
but I have a question.
The cam adjusting screw will affect not only the position of the
slug plate, but also the spring pressure on the cam. Small
differences in the slug plate position can be mechanicaly
compensated by corresponding adjustment of the positions of all four
slugs.
This means that it is possible to set up the PBT with a range of
different spring pressures, no doubt with some effect on the 'feel'
of the PBT control and, probably, on the wear on the cam plate and
pivots.
Does anyone know how Drake did it (eg 'take up the slack on the
thin end of the cam, and add one turn of the set screw....'.
Otherwise I will take the safe route and keep it 'as is' !
Terry, G3VFO
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