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Page Title:
Type III n onpos itive drive fri ction (disk, drum, or cone) |
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|  MIL-C-18087A(SH)
Type III n onpos itive drive fri ction (disk, drum, or cone).
3.7
3.7.1 Construction. Nonpositive drive friction clutches shall consist of
flat discs, drums, or mating cone surfaces mounted on driving and driven hubs and
engaged and disengaged pneumatically or hydraulically.
3.7.1.1 Disc clu tch. Disc friction clutches shall be hydraulically or
pneumatically actuated and shall operate in oil unless otherwise specified
(see 6.2). The construction shall incorporate alternating flat discs of steel and
friction material. Cast iron discs may be used when specified (see 6.2). The
friction discs shall be provided with oil grooves, or other means for cooling oil
circulation.
3.7.1.2 Cone clutch. Cone friction clutches shall be hydraulically or
pneumatically actuated and shall operate in oil unless otherwise specified
(see 6.2). The clutch shall incorporate a driven member constructed of forged
steel. The friction member shall be machined from a bronze centrifugal casting or
manganese bronze forging in accordance with table I or shall be of heat-resistant,
non-asbestos composition friction material thermally bonded to a forged steel
drum.
3.7.1.3 Lubrication. A continuous flow of oil for cooling shall be supplied
from the bearing lubricating oil system. The clutches shall use the same oil as
employed for the associated equipment.
3.7.1.4 Di sc and cone requirements. Discs or cones of clutches shall be
moved axially for engaging and disengaging by hydraulic or pneumatic cylinder and
piston assemblies. Surface finish of friction disc and cone friction surfaces
shall be 63 RHR or better. Rubbing faces of discs shall be flat within 0.020 inch
and parallel with 0.002 inch per foot of diameter. Cone surfaces shall have 85
percent minimum contact with mating part surfaces.
3.7.1.5 Splines. Discs and cones shall be arranged to slide axially on
splines machined on shafts or sleeves as applicable. Spline teeth shall have a
surface finish of 32 RHR or better and shall be surface hardened by nitriding or
carburizing in accordance with table I, footnotes 3 and 4.
3.8 Type IV nonpositive drive overrunning.
3.8.1 General. Nonpositive drive overrunning clutches shall be self-
synchronizing clutches constructed to automatically engage the driving and driven
shafts under any condition where the driven shaft is between zero r/rein and the
maximum design speed, while the driving shaft is accelerating from any speed equal
to or less than the driven shaft. Nonpositive drive overrunning clutches shall
also automatically disengage the driving and driven shafts, allowing the driven
shaft to rotate freely relative to the drive shaft upon a reduction in the
relative speed of the drive shaft.
3.8.2 Engagement. The automatic engagement and disengagement shall be
independent of any speed sensing devices and shall not rely on any type of
servomechanism for engagement. The driving and driven shafts shall be coupled
through the engagement of elements integral to the overrunning clutch assembly
Upon initial engagement, the elements shall maintain their relative positions
and share the load among individual elements.
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