An investigation is made into the design and performance of “staggered” 6-cup anemometers. It is found that the optimum cup arm radius to cup radius ratio (R/r) for both these and 3-cup anemometers is indeterminate; the value to be used in any design only depends on the speed of cup rotation required for a given wind speed. The calibrations for such instruments were linear at all settings of R/r. Distance constants as low as 0.5 m were obtained at an optimum setting of cup wheel spacing to cup radius (L/r) of 2.5 for wheels of all polystyrene construction.
Tests of 6-cup, 3-cup and propeller anemometers in a sinusoidally fluctuating air stream demonstrated that the percentage overestimation of the mean wind speed varied from 3% (for the Gill 4-blade propeller) to 11.5% for the 3-cup (lipless) anemometer of all polystyrene construction at a gust amplitude of 0.5. The 6-cup anemometer had a marked superiority in these tests over the 3-cup anemometers and also had lower starting speeds.