I looked through the Archives and found a series of postings
about rebuilding the motor that were written back in January
and February of 2010. In one of them, there was a mention
of some pictures that the writer had taken, and some problem
about getting them into the Gallery/Technical. Was that ever
Also, there are a couple of very descriptive treatises about the
various steps and measurements for the cloth and the leather.
What I'm wondering is; Does anyone have any pictures of an
original motor before it was dismantled? The reason I ask is
because I have seen at least two different methods used with
regards to the pouch leather seal at the hinged end. The most
common method involves a strip of leather that's almost two
inches wide which covers the stationary side as well as the
movable board. The other method uses one inch punchings
which are centered over the hinge. However, I can't swear that
the later method is an original configuration. On the other hand,
I can swear that the former is an original configuration, as
evidenced by the pictures of a 'virgin' motor that is currently in
the shop. I've posted those pictures at:
I believe they show a few things pretty conclusively:
1) The pouch leather strip is two inches wide.
2) The cloth covering terminates 1/2" before the hinge.
3) The span of the bellows is 2-3/4".
4) The maximum possible span is 3".
So, since the maximum span is 3" but the correct span is
only 2-3/4", there is a 1/4" gap on the opposing bellow
when its 'partner' bellow is fully open (with cloth in place).
Obviously, this means that under no circumstance can
either bellow fully collapse and crease the cloth, which
would, no doubt, increase the life span of the cloth.
Interestingly, a couple of the people who posted articles
back in 2010 about rebuilding the motor said that the span
should be 3". The problem I have with that should be fairly
obvious. If the maximum distance the bellow "can" open is
3", then once one side of the pair is covered, it's theoretically
impossible for the other side to open 3" because the thickness
of the cloth on the opposite bellow. But putting that impossibility
aside for a moment, the other thing that's troubling is the fact
that the cloth on the opposite bellow would have to be 'crushed'
tightly, creating a permanent crease that would never go away
while its partner would not have an identical permanent crease
(unless the crease was imparted to the cloth before the opposing
side was covered. (I hope that is written so it's understandable).
Therefore, the amount of effort required to open and close the
two bellows would be different -as a result of the crease.
All this leads me to believe that one other author, who said that
the span of the bellow should be set such that there is a 1/4"
gap on the opposing side, has the right idea, and his opinion
seems to me to be in agreement with the measurements I
extracted from the original motor in my shop. Furthermore, if
you look at the last two pictures in the series (see link above),
you will note that the crankshaft limits the movement of the bellow
such that it is 2-3/8" when full open and 1-3/8" when fully closed.
Therefore, a span of 2-3/4" is more than enough to prevent any
'stretching' of the cloth -which, of course, would be problematic.
In closing, all of this research has left me believing that Aeolian
must have made more than one size of this type of motor. While
the differences between the one I checking and the ones mentioned
in previous postings are relatively slight, they are different. And,
it's hard for me to believe that the people who took the measurements
of the motors they examined were any less diligent than I was when
I took my measurements. However, the things that stand out in my
mind as "most important" are:
1) The leather strip is 2" wide, and there is a 1/2" space between
the end of the cloth and the hinge.
2) The span should be set such that there is a 1/4" space between
the stationary board and the movable board on the opposing bellow.
John A Tuttle
Brick, NJ, USA