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THE HIGH SPEED
FRONTIER
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- Chapter 4: The High-Speed
Propeller Program
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- ONE-BLADE PROPELLER TESTS
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- [129] Both the 200-hp
emergency propeller dynamometer and the 2000-hp dynamometer were
underpowered for many of the desired high-speed testing
conditions. It was for this reason that the bulk of the testing
was carried out with two-blade propellers. It occurred to me in
1945 that we could double the power loading of our test blades if
a one-blade propeller could be made to work; that is, we could
obtain the same blade operating conditions as for a two-blade
10-foot propeller absorbing 4000 hp. As time permitted, I analyzed
the balancing problems of articulated counter-balanced one-blade
propellers in sufficient depth to convince myself that they were
feasible and practical and they were added to our program. Tests
with the one-blade propellers showed more vibration than the
two-blade propellers because of their unbalanced aero-dynamic
loads but these were not excessive and did not affect the
propeller data (ref. 151). The one-blade propellers (fig. 32) were used principally in the pressure-distribution
programs (ref. 149), and in a few cases, additional force tests were
made after the tubes had been removed and the grooves
filled.
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- The measurement of blade deflections in
these tests, and in general....
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- [130] FIGURE 32.-The
one-blade, 10-foot-diameter propeller.
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- ....the measurement of torsional
deflections of thin-bladed propellers, is often required. An
optical system for such measurements, developed by Corson in the
PRT in 1940, was used in the 16-foot tunnel program (ref. 152). Torsional deflections were applied in the angle
of attack determinations needed for the analysis of pressure
distribution and other propeller test results.
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