EXPERIMENTS ON THE FROUDE. III 
APPENDIX B. 
RECORDING CHRONOGRAPH USED IN EXPERIMENTS ON THE LAUNCH FROUDE 
AT THE MASSACHUSETTS INSTITUTE OF TECHNOLOGY. a 
By H. A. EVERETT, MEMBER. 
In order to obtain a continuous record and to keep the operating force 
during experimental runs down to the minimum, it was necessary that nearly 
all the measurements be made self registering. With this end in view a 
recording apparatus was designed which should give a continuous record 
of time, crossing signal (for start and finish of run) revolutions (of the pro- 
peller shaft) and thrust of the propeller. 
The records are made upon a continuous band of paper which passes 
under pens operated by electro-magnets. The armatures of these magnets 
move the pens every time a circuit is closed or opened, which makes a notch 
in the straight line that the pen is normally tracing. Figure 30, Plate 60, 
shows several views of the recording chronograph as finally built and as used 
onthe Froude. A, isthe roll of paper which is drawn by the motor M, over 
the flat plate table 7, and above this are shown the sockets for the pens 
with one pen in place. Operating the pens are the electro-magnets FL, E, 
etc., of which there are six. 
The roll of paper is 6 inches wide and is hung in ball-bearings directly 
under the pens. The diameter of the full rolls is approximately 11 inches 
and they contain about 2,000 yards of paper, enough to last from two to 
three weeks under normal running conditions. 
The paper is drawn along by a small (one one-hundredth horse-power) 
electric motor designed for 110 volts direct current which was available on 
the Froude and which is practically standard for marine installations. This 
was desirable as it permitted the use of the chronograph on trial trips of 
other vessels. By means of a variable resistance in the motor line the speed 
of the tape could be varied to give as open a record on the tape as was desired. 
In this connection it is well to note that as the record of time is continuously 
drawn on the tape the necessity for a uniform motor speed is eliminated and 
though the motor ran very uniformly for any given setting it was merely 
incidental and had no effect on accuracy. 
Figure 31 shows a specimen of the tape record, AA is the time record 
which is made by a clock opening and closing the pen circuit every half 
