In the Spring 2003 Issue of
Reno From the Pits
This report focuses on the Unlimited Class and is aimed at the
techies and gear heads. It spotlights the “behind-the-scenes” goings-on
that keep these remarkable racers in top form. It presents
a day-to-day description of the scuttlebutt and overview of mechanical issues
and tweaks made to the racers.
Engine Development Costs
It is said that an engineer is one who builds for a dime what any fool can build for a dollar. This is certainly true of aircraft engines. Doug Culy explains how analysis of historical data can help predict the costs of new engine programs. Engine development is a big enough effort that its cost is frequently a noticeable fraction of the net worth of the company doing it. Because of the inherent risk and consequences of engine programs, manufacturers and their big customers study historical development program data so as to be able to predict the cost of the next program.
The Design and Operation of
Hollow-Shafted, Constant Speed Propellers
Part 2–The Curtiss Electric Propeller
The Bell P-39 Airacobra and P-63 Kingcobra were very uniquely
configured single engine WWII fighters that had their propeller reduction
gearboxes mounted in the nose of the airplane, the V-12 Allison engine bolted
amidships behind the pilot, with a 10 foot long, two-piece driveshaft coupling
the two together. This left space immediately behind the propeller reduction
gear to mount a 20 mm or 37 mm cannon, which fired through the center of the
propeller hub.
The Allison Engineering Company:
Reduction Gear and Spring Coupling Mechanisms in the 1920s
From the very beginning of powered flight, designers of propulsion systems
realized there was a basic incompatibility between engines and propellers with
regard to their respective speeds of rotation. Yet it wasn’t until WWII that
really reliable reduction gear designs capable of handling high torque inputs
came into being.
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