710 PROFESSOR FLEEMING JENKIN’S APPLICATION OF GRAPHIC METHODS 







§ 41. General Conclusions.—The most important conclusion to be drawn 
from the foregoing examples is, that the investigation of the efficiency of any 
given direct-acting engine is rendered comparatively easy by the new method. 
Next in importance may be ranked the warning not to judge hastily as to the 
result of any given modification in proportions or speed. The differences 
introduced by a change of speed are especially remarkable, and show how futile 
reasoning must be as to relative efforts and resistances as to stresses on the 
various parts of the engine, and the efficiency of any design when the inertia 
of the masses is left out of the calculation. 
Further conclusions may be drawn as follows :—1st, that high speeds ie not 
necessarily involve small efficiency ; 2d, that a short connecting-rod is not very 
disadvantageous; 3d, that expansive working, even when carried to great lengths, 
does not necessarily involve a loss of efficiency. 
Table I. gives an abstract of the numerical values obtained with this particular 
engine, but the reader must be warned against considering these results as 
generally applicable to other engines of different proportions. 
TABLE I.—Abstract of Results. 









Example. Pressure. Speed. Efficiency. 
A, Ay : { 2 lbs. per square ae 
eas Uniform Nee Slow, 1 rev. per sec. 8] 
Babs 5 ( 2 Ibs. per square 927 
B, B, Uniform jets \ Fast, 4 rev. ,, 536 
f Cut off 28 = | 
C; Cy Low Expansion~ mean eeuite +| Slow, l rev. ,, s Oy 
CoC. l 819 
|) 92h lbs.’ perr| 
{. square inch. J 
Engine : 
described fs 1 
in § 34. Ae (Oivimmoyig Sos. ne 
D. D. Expansion < mean effective + | Fast, 4 rev. | 61 
a |) "9" Ths per | 
| square inch. J 
a Be Expansion ( jibe Slow, l rev. _,, { be 
3 "4 | Cut off 593 | . 
F, F, : : mean peaed ! 928 
F, F, Practical { | Expansion { Siete >| Fast, 4 rev. _,, ‘017 
18°905 Ibs. per 
Cc : [ square inch. . 928 
CAG, Expansion J | Infinitely slow, 0. 914 
Engine 
described Jets isl, Expansion Slow, 1 rev. per sec. 908 
in § 40, 



