Just to share the knowledge...
I spoke with Craig Taylor this morning. I asked him a whole bunch
of questions about gear reliability, and here's what he had to say:
(1) Webster is no longer inferior to Hewland. That was definitely true
8-10 years ago, but today, there's pretty much nothing between them.
(2) He's amazed than autocrossers get as much life out of first, second,
and third gears as we do. Anything over two seasons should be seen as
a triumph. In road racing in an FF with a Mk. 9, even the little gears
should wear out from pitting before they break, but they have much
reduced shock loading forces relative to ours.
(3) If a gear splits, as mine did twice, that's a good sign that it was
just too old or too small for the load. If they pit, or crack a tooth,
that's a sign that something is wrong in the gearbox (or alternately,
they're just too old).
(4) The Webster ratios with reduced tooth count (15-30 vs. 17-34, for
example) will be stronger for our application. Opt for the lower tooth
count gears where possible (15-30, 16-29, 17-28, 16-26, 21-25, 21-24,
19-21).
(5) Since about 1993, gears have been made out of 9310 steel. Before
that, it was 8620. 9310 is stronger for loading, but wears quicker.
Tooth shapes have evolved constantly over the years. Newer gears are
generally better.
(6) Throw away old gears with "W" in the etching. Those are the old
Webster gears made from 8620. They're bad material with outdated tooth
shapes. The top choice are "M" gears; the S gears are in the middle.
Anything you buy new today will be the good stuff from either Hewland
or Webster.
(7) The choice between Redline Shockproof Lightweight and Superlight is
really a question of performance vs wear; the heavier oil won't provide
any significant added protection against shock loading, which appears
to be my big concern.
(8) You can tighten the layshaft nut past the recommended 115 lb-ft in
order to get the cotter pin hole to line up with the castle nut, but
don't go past 135 lb-ft. If you can't get it to line up within that
range, then shave a little off the back of the nut. (I'll need to do
that.)
(9) My fixed-layshaft 12-38 first gear was also slightly damaged when
the second gear broke; the splines are a little beat up. Craig says
don't trust it if the gears don't slide easily over the splines, so
I'm in for a new first gear. Anyone have a 12-38 or 13-38 in good shape
they want to unload?
I forgot to ask him:
- Will closer spacing increase gear life as the shock loading on a shift
is reduced, or is that a minor factor? Our spacings tend to be much
larger than the road racers.
- Some folks have told me that shifting without the clutch reduces gear
stresses. True? For both upshifts and downshifts?
- Would the torsional take-up springs in the stock clutch help reduce
shock loading enough to matter, relative to the mass disadvantage over
a racing clutch?
I'm still debating about optimal ratios for Solo II...
Mark
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