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MMD > Archives > April 2013 > 2013.04.01 > 12Prev  Next


Force Fit Collars
By Timothy L'Amoureux

There is always the heat and cold method.  When I worked for a crop
protection company that built giant wind machines in the early 1970s,
they had a force fit issue.  There was a large cast iron base that was
driven by a ring gear and smaller pinion gear. The ring gear needed to
be press fit onto the cast-iron base.  The problem was that the ring
gear was about 36 inches in diameter.

Their solution was this: machine the cast iron base so that it was a
hair larger than the ring gear, then heat the ring gear with an
acetylene torch until it glowed red.  The ring gear would just drop
right onto the base with plenty of slop.  As the ring gear cooled, it
shrank and locked itself onto the base.

This approach also applies to smaller parts, too.  I have an AmphiCar
and one of the steering knuckle parts is a press fit but most car
owners don't have arbor presses and pounding brass parts with a hammer
is a no-no.  So the company that still sells AmphiCar parts suggested
freezing the brass bushing overnight and then quickly sliding it into
the steering knuckle (keeping in mind that speed is of the essence
here).  When the part warms, it expands and is, in essence, a "press
fit".

It seems that this method might also work for the parts that are the
subject of this thread.  Maybe both heat and freezing.  Hope this helps
a little.

Tim L'Amoureux


(Message sent Mon 1 Apr 2013, 04:43:35 GMT, from time zone GMT-0400.)

Key Words in Subject:  Collars, Fit, Force

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