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From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Performance analysis of a C.A.V. Z.C. starter motor on a Goshawk engine.

Identifier  ExFiles\Box 35\4\  scan 044
Date  26th August 1921
  
X.4384

26.8.21.

X.3247 - PERFORMANCE OF C.A.V. Z.C. STARTER MOTOR ON "GOSHAWK" ENGINE WITH 8.4 RATIO AND ESTIMATED FLUX ETC. X.4384.

Motor torque, allowing 90% torque efficiency. 64.7 lb-inches.

B.H.P. 1.28
Speed 1240
Engine speed 148
Amperes 195 Volts 8.85
Efficiency .55
Static torque 71.2 lb-inches (say) at 195 amperes.

Φ = (T b x 10^8) / (1.41 x P Z C)
= (71.2 x 2 x 10^8) / (1.41 x 4 x 84 x 195)
= 154,000.

Polar face 2.625 x 1.500 = 25.4 cm^2

B = 6070

Top tooth area = 3.33 x .225 x 2.7 x 6.45
= 13.06 cm^2

Btt = 11,790 lines per cm^2
Bbt = 17,700 " "

E = (Φ Z N / (60 x 10^8)) x (P/b) = (154,000 x 84 x 1240 x 4) / (60 x 10^8 x 2)

= 5.35

V = 8.85
V-E = 3.5
R = .0152
C = 230 amperes.

EFC.
  
  


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