is contrary to the usual speed regulation practice. Therefore, the best answer to these con- 
flicting requirements of constant speed under one set of conditions and changing speed under 
another set of conditions is regulation of the voltage supplied to the motor terminals. This 
type of regulation is analogous to a relatively unlimited supply of steam, maintained at a 
constant pressure, being delivered to a ship’s turbine during maneuvers. Stepless control of 
the generator voltage throughout its entire range is permitted rather simply by voltage feedback 
regulation. Thus, an operator can match the carriage speed quite easily by means of the pro- 
portional radio-control circuitry. 
It is phsically impossible, within the weight limitations, to have sufficient battery 
capacity for several hours operation between charges. A choice had to be made between 
changing batteries frequently or charging the battery between test runs without removing it 
from the model. The latter choice permits testing indefinitely with no more lost time between 
runs than that normally taken to prepare for the next run. Since motor-generator sets were 
selected, a lower voltage battery was permissible. Using the nickel-cadmium battery and 
charging it after each run permits the use of a lower capacity and, therefore, lighter battery. 
The charger selected is so designed that it can practically recharge the battery in about 
8 minutes and simultaneously supply the power required to keep the generator sets turning 
over and to keep all electronic equipment warmed up, thus minimizing drift yet imposing no 
drain on the battery. 
Reduced voltage starting of motor-generator and alternator-set drive motors is mandatory. 
In order to keep the amount of equipment in the model to a minimum, the bulk of the starting 
equipment is mounted on the charger. Plug-in connections to the model are made and once 
the generators are started, running contactors located in the model ‘‘seal in’’ and keep the 
sets running whether the power is being supplied from the battery or from the battery charger. 
However, if the source of power is interrupted or if the voltage falls 20 percent below normal, 
the contactors will open and it is necessary to go through the normal starting sequence to 
resume operation. 
Because there is a possibility of losing control of the generated voltage through 
malfunctioning of one of the several links in the control system, a fail-safe provision is pro- 
vided through a tone-controlled contact in the running-contactor coil-control circuit. This 
tone-controlled contact will open if there is any failure or intentional interruption in the 
radio linkage. 
3. SPECIFICATIONS 
The original specifications were set up as a result of the engineering study.” Sub- 
sequent conferences disclosed the desirability for making several modifications to the speci- 
fications. The only major modification was an increase in the power output of the propulsion 
system from 2 hp to 3 hp per channel. This was done to provide greater system flexibility 
and in anticipation of greater power requirements for future models. 
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