Twin Disc MG-5170DC, Service Manual

Page: 64 / 250

64
Twin Disc, Incorporated
Preventative Maintenance
Marine Transmission Service Manual #1020667
Torsional Coupling
Do not obstruct the flywheel housing vents preventing the free flow of air for
cooling the coupling. The ambient temperature of the air around the coupling
should be between -6
°
C (22
°
F) and 80
°
C (176
°
F). Assure baffles are installed
properly so hot air is ported out of the housing.
Visually inspect the element after the first 100 hours of operation and every
2000 hours thereafter, or every six months, whichever comes first. Torsional
vibration, misalignment, degradation by contaminants (oil), heat, ultraviolet
radiation, and excessive system torque can cause cracks or other signs of
distress to appear on the surface of the rubber. The above-described items
affect the life of the coupling element.
When inspecting the flexible coupling, look for evidence or conditions
identified in the following steps:
q
Cracks in the surface of the rubber. May be caused by torsional
vibrations, excessive misalignment or exposure to
contaminants (heat, petroleum products, chemicals, ozone,
ultraviolet radiation, etc.) excessive system torques.
q
Separation of rubber from flex plate on coupling plate or
deterioration of the rubber-to-metal bond. See above.
q
Deterioration of the rubber element, as evidenced by
sponginess or by black carbon-like dust on rubber surface.
May be caused by contaminants or excessive heat, either
external or internal to the coupling.
q
Cracked, bent or otherwise damaged flex plate or coupling
plate.
q
Bolt holes in flex plate or coupling plate elongated oval shaped,
not round. This could be caused by improperly assembled parts,
loose parts, vibration or improperly torqued parts.
q
Bolts/nuts—bent, worn or stripped threads.