RUDDER TRIALS, U. S. S. STERETT. 319 



APPENDIX II. 



RECORDING GEAR. 



The recording gear mentioned above is practically a reproduction of 

 the instrument used on the Froude by the Department of Naval Architecture, 

 Massachusetts Institute of Technology. A description in detail by Prof. 

 H. A. Everett was published in the 191 1 Proceedings of the Society of Naval 

 Architects and Marine Engineers. The essential features are: — 



1. A 0.1 horse-power shunt motor, operating on no volts, direct 

 current; to turn the roll of paper for a continuous record. 



2. A fountain pen to trace a reference or base line for the curve of 

 tension in the chain. 



3. A pen to trace a curve of tension in the chain. The carriage for 

 this pen is connected to the free leg of the dynamometer by a fourfold 

 purchase as described in Appendix i . 



4. Pens to record revolutions of port and starboard propellers. These 

 pens are connected through solenoids to mechanical counters operated by 

 cams on the ship's revolution counter shafts. At each revolution of these 

 shafts, corresponding to ten revolutions of the main turbine shafts, the 

 solenoid circuit is temporarily closed, making a jog on the record of revolu- 

 tions, from which, with the accompanying time record, the revolutions per 

 minute for each turbine can be determined. 



5. A pen to indicate the motion of the helm. This pen is actuated by 

 a solenoid connected to the special helm-angle indicator described in 

 Appendix 4, Fig. 16, Plate 126. From this record helm-angles and rate of 

 putting over helm can be read. 



6. A pen actuated by a solenoid from a push-button on the bridge, 

 for prearranged signals such as "Stand by," "Beginning of turn," "Ship's 

 head turned 10°, 20°, 30°, or 90°, etc." 



7. A pen to mark quarter-seconds of time. This pen is actuated by 

 solenoid by means of a special Chelsea clock which closes the circuit at 

 half -second intervals. 



8. The recording gear is mounted on a mahogany board bolted to the 

 oak table of the dynamometer by carriage bolts. Rubber washers one inch 

 thick were placed between the recording gear and table top to take up 

 vibration. 



