Newsgroups: rec.crafts.metalworking
Subject: Re: 1994 NAMES exhibition
From: wjc@ll.mit.edu (Bill Chiarchiaro)
Date: Fri, 6 May 94 17:30:43 GMT

In article <demers-050594090136@mac-208-43.htc.honeywell.com>,
demers@src.honeywell.com (Bob DeMers) writes:

|> All this talk about model engines reminds me of an early radial piston
|> aircraft emgine that I saw at an aviation museum.  It was rather bizarre in
|> that the crankshaft was fixed and the cylinders rotated around in a solid
|> chunk, carrying the propeller.  I can't imagine it was too successful, kind
|> of like hanging a big reation wheel on the front of the plane.  I have
|> always thought that it would be cool to build and run one of these.


  The type of engine you're referring to is called a rotary engine.
It looks very similar to a radial, but has the fixed crankshaft as you
mentioned.

  They were used in a number of airplanes of the World War I era, one
of them being the Sopwith Pup.  Two of the more important rotary
engines were the Gnome and the Le Rhone.

  Indeed, the rotating mass of the engine did act as a significant
gyroscope with the result that the airplane "preferred" turning one
direction to the other.  In other words, when turning, say, to the
right, the nose would climb and the plane would loose speed.  On the
other hand, you could do a fast, diving turn to the left.  Of course,
the "sign" of these effects depends on the direction of rotation of
the engine.

  Another idiosyncrasy of the rotary engines was that they did not
have throttled carburetors.  Once started, the engine ran flat out.
Duty-cycle control was used to reduce the engine's time-averaged power
output.  Remember the movies of World War I aviation?  As a plane
would be coming in for a landing, you would hear the engine running in
bursts.  This was because the pilot was momentarily pressing an
ignition kill switch to cut the engine's output and thus modify the
plane's speed and height.

  Yet another quirk is that the rotaries used a lubrication system
that I believe is similar to that of a two-stroke engine --- a
lubricant was mixed with the fuel or fed in with the fuel and air.
Castor oil was the lubricant used, and apparently a great deal of it
was spewed out by the engine.  This was why the early pilots wore silk
scarves; they didn't like having castor oil running down their necks.
Also, unrestored airplanes of that vintage were found to have a
shellac-like substance coated onto parts of the wings and fuselage.
This was "fossilized" castor oil.

  Rotary engines are truly neat to see and hear run.  There are some
aviation museums around the U.S. which have rotaries and operate them.
One is the Owl's Head Transportation Museum in Owl's Head, Maine (my
brother is the director...).  Last time I checked, the museum was
flying at least one rotary-powered plane, a Sopwith Pup.  The airframe
is a replica, but the engine is an original Le Rhone.


Bill Chiarchiaro
wjc@ll.mit.edu