Fig. 141.—Views of Upper Half of Thomas Aeromotor Crank-Case.
Fig. 142.—Method of Constructing Eight-Cylinder Vee Engine, Possible if Aluminum Cylinder and Crank-Case Castings are Used.
The approved method of crank-case construction favored by the majority of engineers is shown at the top of [Fig. 141], bottom side up. The upper half not only forms a bed for the cylinder but is used to hold the crank-shaft as well. In the illustration, the three-bearing boxes form part of the case, while the lower brasses are in the form of separately cast caps retained by suitable bolts. In the construction outlined the bottom part of the case serves merely as an oil container and a protection for the interior mechanism of the motor. The cylinders are held down by means of studs screwed into the crank-case top, as shown at [Fig. 141], lower view. If the aluminum cylinder motor has any future, the method of construction outlined at [Fig. 142], which has been used in cast iron for an automobile motor, might be used for an eight-cylinder Vee engine for airplane use. The simplicity of the crank-case needed for a revolving cylinder motor and its small weight can be well understood by examination of the illustration at [Fig. 143], which shows the engine crank-case for the nine-cylinder “Monosoupape” Gnome engine. This consists of two accurately machined forgings held together by bolts as clearly indicated.
Fig. 143.—Simple and Compact Crank-Case, Possible When Radial Cylinder Engine Design is Followed.