FRICTIONAL LOSSES IN INTERNAL COMBUSTION ENGINES. | 
Retardation Tests on 40 H.P. National Gas Engine.—continued. 
Ref B.P.g| Retard-| Frict. ae Distrib. 
; Part of Machine. ‘y. | ation | Torque of 
_ ow Friction 
Us R= Zin ——— NL 
550 per cent. 
‘0001 i Ol 1 
05 2 
“0002 3 10 2 
7 | Layshaft and valve gear 
(2) — (3) 
Wom 
S 
(as) 
i=) 
— 
or 
bo 
8 | “Gas friction.” 1 17 20 25 
2 30 "67 39 
3 50 | 1-74 34 
9 | Connecting rod pro-| 1 3 "03 4 
portional to (6) 2 4 210 + 
5 *20 4 
10 | Piston 1 we 38 “40 55D 
(5) — {(8) + (9) 2 or Bi | Us) aks 
3 ng On) | Dea ae 
The friction-horse-power losses are well shown by the 
curves drawn in Fig. 2. From these curves it is seen how 
rapidly the losses increase with increase in the speed 
of the engine. Hspecially is this so in the case of ‘*‘ Gas 
friction.”’ 
The equation of the total friction-horse-power curve 
may be taken as 
colon 
F.H.P. = ‘8N 
from which it is seen that the total horse-power lost at the 
the normal speed of the engine, 250 R.P.M., is 10°1 H.P. 
Since the friction-horse-power depends on the two factors 
—resistance to motion and speed at which this resistance 
is overcome—the resistance must be proportional to N°. 
This resistance is directly proportional to the coefficient 
of friction, since the pressure on the rubbing surfaces 
remains constant throughout the range of speeds. There- 
fore, the average coefficient of friction throughout the 
