----- Original Message ----- From: <DTSHIFTER@aol.com> To: <bikevint@tiac.net>; <sterlingcapital@mail.com>; <classicrendezvous@bikelist.org> Sent: Thursday, March 22, 2001 10:06 AM Subject: Re: [CR] mixing spoke crosses
>
> The LH spokes of a (multi-speed) rear wheel do very little to effect
torque
> transmission, due to their inherently lower tension........
The LH spokes in a standard wheel do transmit some torque to the rim, though
it is much less than the RH, but it has nothing to do with the lower tension
or shallower angle relative to the hub. As long as the spokes don't go
slack, either from vertical or tortional loading, they all transmit torque
the same (as a rigid column). The LH spokes transmit less torque because the
hubshell is absorbing the tortional load (actually twisting slightly).
Fatter rear hubshells (like Parallax) transmit torque better because of the
larger diameter.
>
> Spring effect of the left has no "real world" relationship with stress and
> power transmission for the RH spokes. If it did, we would never see the
LH
> spokes of a rear wheel radially laced........
I didn't see the original post, so I don't know what you mean by "spring
effect". But in regards to radially-laced RH spokes, I believe you should
look closely at the Mavic Ksyrium wheel. It is laced radially on the RH
spokes, and the idea has some merits. The radial spokes do actually transmit
some torque - they become very slightly non-radial - but a larger proportion
of the tortional load is caried by the LH spokes (this helps the overall
stability of the low spoke count wheel in accepting tortional load). Also,
the radial RH design (along with the particular spoke/hub interface of the
Ksyrium) helps minimize the differential tension (also helps the overall
stability of the low spoke count wheel).
>
> Torque is more efficiently transferred with a 4x pattern (drive side) as
the
> lever arm (spoke) is 90o to the hub axis. 3x is also very good, and these
> days with materials being so much better that 20-30 years ago, there
really
> is no need for 4x (and 36o hubs!) wheels except tandems and fully laden
> touring bicyles.
>
In principle, 4x does transmit the tortional load better because of the load path of the spokes. But in practice, it's overkill on anything accept a very low geared tandem. Even on loaded touring bikes or mtb's, no one person can exert enough force on the pedals to significantly stress a well-built 3x rear wheel.
> Your argument against fewer crosses on the LH side is not supported by the
> reference to 8-10 speed wheels...."...radial non-drive pattern on 8-10 sp
> wheels actually works pretty well." By "works pretty well" I am assuming
you
> mean "does not collapse"? I think I have addressed why they do not
collapse,
> but consider the following: We never see the RH spokes laced radially as
> they would have no wind-up under load (pedaling) and the fatigue factor
would be enormous.
>
Again, look at the Mavic Ksyrium wheel. Similarly laced wheels could be
built from standard parts, as well. But the risk of flange failure from the
RH radial spokes isn't worth it, in my opinion. I do strongly recommend a 2x
RH, 3x LH pattern for most wheels I build for people, as a long-term use
wheel, and 1x RH, 2x LH pattern for the lighter riders or more limited use.
This is especially pertinent to Campy hubs because of the wide left center
dimension on their rear hubs. I only do the "race lace" 3x/radial for
limited use, and I explain thoroughly why it makes a bad wheel overall. It
does make the rear wheel stiffer laterally, but the differential tension is
WORSE, contrary to popular belief.
>
> As I mentioned in my previous response to Sterling, I generally do 4x on
the
> RH (rear) whenever I am able to do so. Small flange hubs are not well
suited > for this, but it can be done with a little care. I do the LH
spoking (3x;
> 2x; 1x) in whatever I feel like and by what spokes I happen to have on
hand.
That's actually backwards. Large flange hubs are less well suited to 4x
lacing. For a given spoke count and lacing pattern, the larger the flange
diameter, the closer to tangent the spoke leaves the flange. This causes the
spokes to overlap the head of the next spoke. But large flange hubs don't
need the higher cross lacings as much because the tortional load is lower.
This is why tandems still use (and benefit from) large flange hubs. On track
wheels, it's mostly just tradition.
> I like to do 4x/2x as I like the pattern as viewed from the right-side to
the
> left-side of the wheel, and I think that 4x looks more "classical".
>
Assuming the rim and spoke count are appropriately chosen, that pattern will work. But from the mechanical standpoint, it's not optimum. There's just no reason to have the RH 4x, and why risk the spoke head overlap? Lacing the LH side fewer cross is only useful for a miniscule weight savings and lateral stiffness gain, and possibly looks. But for the best combination of durability and performance, it's the opposite of the best chioce.
Jon Schaer