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MMD > Archives > August 2012 > 2012.08.06 > 05Prev  Next

Rebuilding the Aeolian Wind Motor
By John A. Tuttle

Hi All,  I looked through the MMD 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 MMD Gallery/Technical.  Was that ever resolved?

 [ Today I telephoned the author, Dave Geissinger, and we discussed
 [ ways to resolve the problem.  We hope to have the photos and
 [ drawings available soon.  Dave's articles on this topic are at
 [ & 
 [ -- Robbie

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 bellows when its 'partner' bellows
is fully open (with cloth in place).  Obviously, this means that under
no circumstance can either bellows 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 bellows "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 bellows 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 bellows 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 checked 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, New Jersey, USA [delete ".geentroep" to reply]

(Message sent Mon 6 Aug 2012, 16:35:21 GMT, from time zone GMT-0400.)

Key Words in Subject:  Aeolian, Motor, Rebuilding, Wind

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