TRANSACTIONS -OF SECTION G. 652 
A Carliss-Browne two-bladed propeller, of 20 inches diameter and 3 feet pitch, 
was employed in these first experiments; straps and pulleys were resorted to in 
order.to reduce the speed of the screw to 350 revolutions, whilst the motors 
revolved at 950 revolutions per minute. 
The two motors were coupled in parallel circuit, whereas the cells formed one 
series. Hach machine had its own switch and ammeter, and the starboard machine 
could be stopped mechanically by means of a friction clutch on the countershaft. 
Both machines were tested with a Prony brake, and they gave 1:86 horse-power on 
the brake at 950 revolutions, consuming a current of 21 ampéres and 100 volts. 
At 694 revolutions, 100 volts and 83:25 ampéres, the brake horse-power rose 
to 2°78, 
With forty-seven cells on board, the current used by both motors running 
together was 46 ampéres, and the propeller made 360 revolutions; when 
disconnecting one of the motors the current passing through the other was 33. 
ampéres, and the speed of the propeller shaft fell to 250. 
Messrs, Siemens’ dynamos lend themselves very readily to the purposes under 
consideration ; the height of a D, machine is only 10 inches, length 28 inches, and 
width 23 inches. The two machines weigh together 632 lbs., countershaft, 
supports and pulleys 180 lbs., total for the driving apparatus 812 lbs. 
Each Faure-Sellon-Volckmar cell as manufactured by the Electrical Power 
Storage Company for these launches weighs 56 Ibs., and it is capable of furnishing 
350 ampére hours, or a fairly constant working current for 7} hours at full speed of 
boat. 
A cell is made up of forty lead plates, each 73” long by 53” wide and barely 
y” thick, placed vertically in an ebonite box containing diluted sulphuric acid; 
covers are provided to prevent spilling of liquid; the external dimensions of each 
box are 83” long, 8” wide, and 73” high. 
In later experiments with the boat the two D, dynamos were now replaced by 
one D, Siemens machine, this machine being directly connected to the screw shaft. 
The weight of this machine is 658 lbs., the space occupied 15” in height, 30’ 
in length, 28” in width. A new propeller with two blades on the lines of the 
Carliss-Browne type was constructed and experimented with ; its original dimensions 
were 197” diameter, 12-9” pitch, and 103 square inches of expanded blade area. 
With forty-five cells in circuit on board, the current consumed was 57:2 ampeéres, 
and the screw made 630 revolutions; after altering tke blades successively, the 
screw became reduced to 173” diameter, 114” pitch, and 66 square inches of 
expanded blade area; at this point the machine only required 43 amperes of current 
with 46 cells, the screw and armature making 840 revolutions; the speed of the 
hoat being almost the same as originally with a current of 57-2 ampéres. 
More recently Messrs, Yarrow and Company, in conjunction with the 
Electrical Power Storage Company, fitted up another electrical launch, destined 
for the Vienna Exhibition. 
This boat is 40 feet long, with 6 feet beam, and can carry 40 passengers; the 
whole of the machinery and secondary cells are disposed under deck as ballast. 
The motor is a Siemens D, machine which develops nearly 7 horse-power, with 
80 cells and a current of about 40 ampéres, As in the last case, the spindle of the 
armature is coupled to the propeller shaft. The screw is two-bladed, of thin forged 
steel, and was designed by Messrs. Yarrow; its diameter is 19 inches, pitch 
13 inches. The weight of the motor and batteries combined is 24 tons, 
During the trial over the measured mile the speed of this boat was over 
8 miles per hour, the current used at the time being 41-22 ampéres, and the counter 
E, M. F. 1125 volts with 60 cells in circuit. 
The speed of the boat is varied by a commutator, which throws more or less 
cells into operation. 
Forty ampéres is a very economical rate of discharge for these small cells, but 
where great power is required fur a short space of time they can yield as much as 
80 ampéres, aud the same weight of accumulators can furnish double the power, 
but for less than half the time; in this manner very high speeds could be obtained 
with but a moderate weight. 
