When the Olland-Cycle principle was originally adopted, both clocks and electric motors were considered for the power supply. In addition to the tendency of clocks to stop at cold temperatures due to freezing of lubricants and unequal expansion of the parts, the movement of the clockwork in discrete steps limits the accuracy of sampling. For these reasons, electric motors are preferred.
The motor now in use has been built to meet the following specifications:
(a) 6 to 7.5 volt operation.
(b) 1 RPM gear train.
(c) 20 to 40 milliamperes drain.
(d) Speed change at low temperature to be no more than 20%.
(e) Constancy of speed during any single revolution not to deviate by more than 0.3%.
To check the performance of these motors at cold temperatures, a series of testswas run on the motors now in use with the average case seen in Figure 32. The loss in RPM was more than
Figure 32. Speed tests of Olland-Cycle motors.
desired, but the motors continued to operate at a steady rate. As long as the speed of revolution does not vary markedly within a single revolution, the error is not serious. In early flights made at prolonged cold temperature, erratic performance