There are two reasons why gear oil is placed in the trunnion.
1) Lubricate the threads of the trunnion and the vertical
link.
2) Act as a barrier to water, thus preventing rust of
a safety critical item. [Do you want a wheel dropping
of at 85 mph on the motorway :-}]
I believe the reason that oil is used in preference to grease is that
gear oil can flow a lot easier than grease.
This ability to flow is important during cornering, when the vertical
link displaces some of the oil in the bottom of the trunnion forcing it
up the trunnion thus ensuring that the threads are well lubricated. When
the wheel is straightened the vertical link rises leaving space that the
oil will refill easier than grease. Therefore if grease is used it
quickly becomes compacted by this rise and fall of the vertical link,
Leaving space for water to become trapped.
Oil filled trunnion
+----- Vertical Link
|
v
} { } { . = Oil
}-{ }-{
}.{____}.{
|........| <- Trunnion
----------
Grease filled trunnion
+----- Vertical Link
|
v
} { } { 0 = Grease
}0{ }0{ ~ = Water
}0{____}0{
|~~~~~~~~| <- Trunnion
----------
Note, please take these ramblings with enough salt to make it palatable.
What I've outlined is the mean of a number of different conversations.
The opinions expressed by people varied from "Grease is OK" to "Refill
the trunnions with oil every month".
Anyway that said I've still got to remove the grease that the garage
pumped my trunnions with when they replaced them for its MOT. Which
reminds me, is there some form of certificate of roadworthiness in the
states ?
Iain McWilliams Inmos Ltd, Bristol | EMail(UK) ukc!inmos!mcwill
---------------------------------------| or mcwill@inmos.co.uk
The opinions above are my personal | Internet: mcwill@inmos.com
views and do not refelect Inmos policy.| UUCP:(US) uunet!inmos!mcwill
|