Section IV. ENGINE MEASUREMENTS

Custom Search

TM 9-8000
c.  Horizontal Opposed (C, Fig.  2-41).  Less
common than the in-line and the V-type, this engine is
cylinders placed in a circle around the crankshaft. The
designed to fit in compartments where height is a
crankshaft has only one throw, with one of the pistons
consideration.
The cylinders are arranged at 180
connected to this throw by a master rod. The connecting
degrees to each other with opposing cylinders sharing a
rods from the other pistons are fastened to the
common crankshaft journal.  This engine arrangement
crankshaft through this master rod.  This engine is
almost always is used for air-cooled configurations,
almost exclusively an aircraft engine and is of little
although at least one auto manufacturer is using a
interest when studying automotive technology.
horizontal- ly opposed, water-cooled engine in their
product.
Section IV. ENGINE MEASUREMENTS
Area of cylinder bore =
2-20. Bore and Stroke (Fig. 2-42).
0.785xdiameter = 0.785D
a. Bore. The bore is the diameter of the cylinder.
Area of cylinder bore =
0.785x4 = 0.785x16 =12.56
b. Stroke. The stroke is the distance that the piston
Area of cylinder bore =
center.
12.56 sq in.(81 .02 sq cm).
2-21.
Piston Displacement (Fig.
Piston
b.
Multiply the area of the cylinder bore by the
displacement is the volume of space that the piston
stroke.
displaces as it moves from top dead center to bottom
dead center. The piston displacement is used to express
12.56sqin.x3in. =
engine size.  To find the displacement of an eight-
37.68cu in.(617.37cc)
cylinder engine with a bore of 4 in. (10.16 cm) and a
stroke of 3 in. (7.62 cm), do the following.
This is the piston displacement for one cylinder.
a. Find the area of the cylinder bore. To find the
c. Multiply the displacement of one cylinder by
area of the cylinder bore, use the formula:
he number of cylinders that the engine has.
Figure 2-42. Bore, Stroke, and Displacement
2-27