MIL-STD-1227B
We = weight of engine = 40 pounds
Weq = weight of equipment in pounds
= 0.01 inch
Therefore,
(d)
From design chart (see figure 6) determine final spring force
Fs = 1,850 pounds
(see figure 7) which is a function of L
(e)
Determine factor
L = distance of CG of equipment from engine equipment mounting
pads, and D = distance of equipment support from engine equip-
ment mounting pads.
Example, L = 8 inches
D = 14 inches
= 2.5
Fact or
Determine maximum permissible force (see figure 8).
(f)
For
= 2.5
Weq = 80 pounds
Maximum permissible = 5,1OO pounds spring force
Note. This value is higher than the final spring force, and the four shock
mounts are suitable if the natural frequency and total deflection of the
mounts are within the design specification.
(g) Determine natural frequency and total deflection (see figure 9).
For static deflection
=
0.01 inch
F=
1,880 CPM
Natural frequency
The total deflection
o=
0.61 inch
F shall not be greater than
70 percent of the engine governed speed.
5.5 Power transmission requirements. The driven unit shall be connected
to the engine drive shaft by one of the following methods. Torsional vibra-
tion determinations shall be made as specified in 5.5.5.
5.5.1 Rigid-quill coupling. When a rigid quill coupling is used on the
driven equipment shaft, the coupling shall be in accordance with figure 10.
6
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