[HAM] Tone wheels moving off centre in relation to the pickup magnet heads. Was The recapping controversy

[Kon Zissis]

Steve Leigh wrote:
> Thought:  if two tonewheels ran off center, ie; far from centered on 
>the coil pickup, wouldn't those freqs be weak?
 
I have noticed this effect with the upper midrange and treble  TG notes
because the heads of the pickup magnets facing the tone wheels are very
narrow so that this makes any slight off centre movement of the tone
wheel  audibly noticeable. The lower and the midrange frequency TG
pickups have wider  magnet heads  so this means that there is very
little if any change in the audible output of these tone wheels  if they
move off centre.
 
Does anyone know why Hammond chose to use very narrow magnet heads for
the upper midrange and treble tone wheel pickups ?
 
The service manual states that large heads for the lower frequency  tone
wheel pickups  are needed for good frequency output but that narrow
pickup heads are needed  for the higher frequency pickups  in order to
avoid excessive iron losses. What does "iron losses" mean in this
context and how does this affect the outputs of the treble  pickups ?
I know that the term ''iron losses'' is used  when discussing the metal
core of transformers.
 
Would there have been an audible problem if the full size magnet heads
were used  for the higher frequency tone wheels  just as they were used
for the full size magnet heads of the lower frequency tone wheel
pickups?
 
I imagine that it would have been less work for Hammond to simply use
the full size  magnet heads instead of having to do the extra work of
grinding down to size the  front end of the  magnet pickup heads of the
higher frequency tone wheels.
 
With my 1962 C3 I have noticed an audible and measurable  change of up
to 10 millivolts peak to peak  difference in the output levels  of an
upper midrange or treble tone wheel  being centred properly and then
being moved  off centre simply by shaking the TG  when it is mounted on
the four springs. This change in  output levels caused by the tone
wheels moving a little  off centre in relation to the pickup head has
been a real nuisance to me when I was recalibrating the TG to produce a
smooth volume level between the adjacent TG notes.  
 
I have noticed  that with my 1962 C3  that if I cause the  tone wheel to
move off centre by shaking the TG then it stays  off centre  unless  I
shake the TG again . I have oiled the TG every year since I bought  the
C3 in 2002  and  the TG starts up reasonably quickly with the start
switch needing to be held on for around three or four seconds and the
run and start switch then needing  to be held  for  around three or four
seconds  so that the TG is running properly but even so I wonder if the
TG does have some traces of deposits of  dried oil  in the bearings
which causes the  tone wheels to stay in place when they are moved off
centre . 
 
 There are a small number of slightly warbling notes here and there in
the  upper midrange and treble section. It would be a very  time
consuming and tedious job to have to unsolder all the  wires and then
take out the TG to do a through  cleaning as Steve Leigh recommends  but
if a problem with warbling notes does become more apparent in the future
then I will have to consider  doing this procedure.
 
All the best.
Kon