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File D 52.415/1 7 FIELD REPORT SERIAL No. 1342
ON CIRCULAR
(HEAVIER-THAN-AIR) ·
PUBLISHED BY THE CHIEF OF AIR SERVICE, WASHINGTON, D. C.
Vol. II November 6, 1920 No. 126
STARTING TORQUE ON LIBERTY, HISPANO-SUIZA,
AND OTHER AVIATION ENGINES
Prepared by Engineering Division, Air Service
McCook Field, July 22. 1920
WASHINGTON
GOVERNMEN f PRINTING OFFICI!:
1920
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STARTING TORQUE ON LIBERTY, HISPANO-SUIZA, AND
OTHER AVIATION ENGINES.
OBJECT.
To determine the starting torque on Liberty, HispanoSuiza,
and other aviation engines to obtain power starter
requirements.
CONCLUSIONS.
Appended herewith is a table of the torque required to
start the reciprocating parts of an engine moving. It is
recommended, however, that in the design of power
starters a factor of safety of at least three on the rorque
available be adopted.
METHOD OF TEST.
The engines were mounted on an electric dynamometer
and, with the engine cold, motor torque was applied
gradually until the crank shaft of the engine started ro
move. This torque was noted. The trials were repeated
with open and closed throttle.
Throughout these tests U. S. A. Specification No. 3501
(paraffin base) oil was used. The viscosity, by the Saybolt
method, of this oil is 85 seconds to 90 seconds at
212° F .
RESULTS OF TEST.
Attached herewith is a table of data obtained.
AVERAGE STARTING TORQUE, POUNDS-FEET.
"O ~ IS tartin!( torque,
E pounds-feet.
~ ... "' " <!)
" " -;;;- "' s:I 'O 0 Throt- "O 'eh ~ Throt-
Engine. .s ~ ~ " s:I tie tie <!) >, -l'l <!)
~ ~ 0 0 open. closed. "... £ g ... ...
"' .0 .; <!) " ------
.0 'O <!) .0 .0 -~ s -~s 8 ! ~ ~ "" 8 8 ... . ... .
" Ji " i "' " """"" " = ";,."tl'l z ~ z P'.l rn z ~s <d ;.,a <las
-------,- - -- -- ------ - ---
Liberty ..••.•.•.•.•.
Hispano-Suiia ..•.•.
Liberty ...• . ....•...
ParJ.-ard . •....•.•.•.
Do ..•.•.••.•...
Rausie ... ..•.. . ....
B.M.W ... ..• .. . ..
12 400 1, 700,5. 00 7. 00
8 300 I, &l0
1
5. 51 5. 91
6 210 I, 70015. 00 7. 00
8 180,1, 600,4. 75 5. 25
12 550,1, 800,5. 75 6. 50
6 17.5,1,650,5.00 6.00
6 18511,400i5"90 7.08
Average air temperature, 75° F.
2 6 130
2 6 106
2 6 133
1 . 3 110
1 l 185
1 3 119
1 3 150
124 156 143
102 101 96
105 135 110
82 87 77 ... - 200 ....
115 147 144
1391 153 145
162@-20 (3)
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