Quiz: can anybody tell me why the pivot bolt needs to be in line with
  the center of the rubber bushing? :)

  Paul Lamar

 So you reduce the angular component of the force vector. [It needs to be
 perp to the sensor in two planes]

 Jarrett Johnson

 It's been 24 hours and nobody else has come up with an answer :)

 The answer is the thrust from the engine would cause the sensor
 beam to tend to rotate downwards and give a false torque reading on the
 engine.

 Paul Lamar


So, as the rubber crushes and sags over time, the output will shift?


Matt-

If one keeps it cool it won't sag :)
If it were not for this geometry rubber sag alone would not effect
the reading. For example if one could find a low cost load cell washer
with built in electronics in the right range one would not need
this mechanism.
http://www.loadstarsensors.com/?gclid=CMOOr5Kvy5oCFeZL5QodCVFY2w


I'll be happy with 5 HP resolution.

What we have now are airplanes with anywhere between 150 HP and 250 HP.
There are a lot of crude intake manifolds out there :)

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I just discovered a Honeywell pressure sensor part for $36 that goes up to 500
PSI. That means the sensing hyd. cylinder diameter can be reduced to one inch.
Here is the pdf on the part.  The advantage to that is the piston
is less likely to cock in the cylinder.
DigiKey sells them.


Paul Lamar