Lathes Page: 87
The following text was automatically extracted from the image on this page using optical character recognition software:
b. Primarily, bevel gears may be considered as friction cones roll-
ing against each other (fig. 77). The pitch diameter of the gears
will be the major diameter of these friction cones, while the pitch
circle is represented by the major circumference of each cone. Re-
ferring to figure 77, the lines BC and CD are, therefore, the pitch
diameters of cones ABC and ACD, respectively. Also, points B, C,
and D are located on the pitch circles of the cones. As the ratio of
the pitch diameters gives the ratio of the bevel gears, the diameters
of 2 inches and 3 inches give a ratio of 2 to 3 or 1 to 1.5. It should
be noted at this time that the cone angles of a pair of bevel gears
are such that if extended, they would terminate in a common apex,
point A, figure 77.
FIGURE 77.-Pitch cones of bevel gears.
(1) The tangent of the pitch cone angles of any set of bevel gears
whose center angles equal 90 may be obtained by dividing the num-
ber of teeth in the gear by the number of teeth in the pinion. This
angle, subtracted from 90, equals the pitch angle of the pinion. If
the sum of the pitch cone angles of the gears is more or less than
90, this rule does not hold true.
(2) Although the pitch diameters are calculated for bevel gears
in the same manner as for spur gears, this does not apply to their
outside diameters as the depth dimensions of the teeth are measured
in a plane at right angles to the pitch line. As illustrated in figure
78, outside bevel gear diameters may be calculated by means of the
Outside diameter = pitch diameter + (cosine of pitch cone angle
x 2 addenda).
Here’s what’s next.
This book can be searched. Note: Results may vary based on the legibility of text within the document.
Tools / Downloads
Get a copy of this page or view the extracted text.
Citing and Sharing
Basic information for referencing this web page. We also provide extended guidance on usage rights, references, copying or embedding.
Reference the current page of this Book.
United States. Army. Air Corps. Lathes, book, November 29, 1940; Washington, D.C.. (digital.library.unt.edu/ark:/67531/metadc96655/m1/89/: accessed September 24, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.