Wear associated with bushings and bearings is one thing... but friction is
altogether different... sort-of. Lemme explain, and you folks correct me
if I step outside the line!!
If there was no friction, there would be no wear, right? It seems to me
that bearings are used partially because of space limitations as someone
suggested before, but also because they impart far less friction due to the
fact that the components within the bearing ROLL. Same thing with roller
rockers, right!? You gain horsepower with roller rockers because there is
less friction at the point where the rocker contacts the end of the valve
stem, right? (Or at least partially right, right?)
When I think of other applications where the use of bearings vs. bushings
might get interesting, I think of the big ends of connecting rods. The way
I think about it, those bearing shells have a lot more in common with
bushings than they do with bearings. Agreed? Ever seen some of the old
Bugatti bottom ends where the con rods ride on big roller bearings? The
crank comes apart at each journal to allow installation and removal of the
rollers. My understanding is that designs like these are as close to truly
bullet-proof as you can get, although they are oviously VERY expensive to
manufacture.
So, my contention is that bearings are far better in these applications
than bushings. More to the point of the original question, there are two
types of needle bearings available for the laygear to ride on. There is an
open-faced needle bearing and a closed needle bearing that has its own
race. The latter is far more durable as it can be installed into a less
than perfect bore. The former bearing will disintegrate if it does not
have a good surface to ride on.
Pete Chadwell
1973 TR6 CF10732
|