to control rudder
and elevator by
using two torque
rods. They sold
for $14.95 each
in the 1950s.
This 1975 Joe Bridi-designed Pattern airplane by Dan Grotzinger won first
place in Vintage RC Planes at this year’s 2016 Toledo Show: R/C Model Expo.
transmitter button was depressed.
The linkage to the rudder would move
the rudder to one side and hold it there.
When the key was released, the SN
escapement would move another 90°
and stop. The next time the transmitter
was keyed, the SN escapement would
move another 90°, moving the rudder to
the other side. It would return to neutral
again when the key was released.
If you wanted two of the same rudder
movements in a row, you had to key the
transmitter twice and hold. You had to
remember the last control you gave and
press and/or hold the button accordingly.
There had to be a better way and it
wasn’t long until someone figured out
how to build a better escapement. The
earliest magazine advertisement that I
could find for a compound escapement
was by Bonner Specialties in July
1954. The company’s ad stated that
its compound escapement was a four-position, self-neutralizing control unit
that gave multiple controls on a single
The advantage of a compound
escapement was that you no longer had
to remember the last control input that
you gave. Each time you pressed the
button and held it one time, you would
get right rudder. Release the button and
the rudder would travel through the left
position and return to neutral.
When you wanted left rudder, you
keyed the transmitter twice and held
it. The rudder would go through the
right position and stop at left rudder.
Releasing the button sent it back to
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