Unusual Two-Propeller Arrangements 



Table 3 

 Propeller Data 



amplifier for amplification of the signals from the bridge, and an accumu- 

 lator for feeding the amplifier. The measuring circuit was fed by an accumulator 

 through slip rings, and the amplified signal was led through slip rings to an oscil- 

 loscope and a direct-recording ultraviolet oscillograph with a sensibility enabling 

 it to follow the variation of the stress through a revolution (Fig. 4). 



Electronic dynamometers were used in the self-propulsion tests with the 

 auxiliary propeller system, and each propeller was driven by a separate motor. 

 At each tested speed, the numbers of the revolutions of the two propellers that 

 would minimize the stress variations in the main propeller blade were found by 



Fig. 4 - Shaft equipment for measuring of 

 the stress at the propeller blade root 



1527 



