"Bruce Frech" <bfrech@no_spam_verizon.net> wrote in message
news:ODYYc.16498$tI.2279@trndny04...
Quoted message said:g
Yes chordal action is what I was describing, and the numbers agree.
The different size pedal axle was a different year. It was the AX road
system, with 1" threads with the bearings inside the crank region allowing
the pedal to be below the center of the axle. This was a good goal from
the
Quoted message said:biomechanical point of view but the bearings just didn't work
mechanically.
Quoted message said:
Bruce"gwhite" <[email hidden]> wrote in message
Quoted message said:Quoted message said:Other possible benefits were
more cog teeth to give smoother transmission, eg: 48x14 versus
58x17
Quoted message said:Quoted message said:Quoted message said:(roughly the same size when scaled down from 12.7mm to 10mm). This
refersQuoted message said:Quoted message said:to how the contact point radius on the hub varies as the cog rotates.
In truth, I don't so much sense chordal action on a road bike because
road
Quoted message said:Quoted message said:roughness can swamp the perception out due to the road "roughnesses"
much
Quoted message said:higher
Quoted message said:magnitude. I do sense it on smooth roads and the 12t cog, although I
don't muchQuoted message said:use that one much anymore.
I hadn't thought about it (since I don't ride track), but since tracks
are
Quoted message said:Quoted message said:probably much smoother, it is more likely to be sensed by track riders.
IQuoted message said:think Carl implied he was able to sense it, but I'll let him clarify if
he
Quoted message said:Quoted message said:wishes (or any of the other track contributers). Basically one would
hope
Quoted message said:to
Quoted message said:have enough teeth such that the discretization/quantization was not
detectable.Quoted message said:
A couple of things: You can sense it. Generally speaking, I used a 15 cog in
the rear, so the chordal action was not as dramatic as it could have been.
Second, pursuiters are not as explosive as sprinter/kilo riders, so my chain
tension was not as great as others experience and I assume the there is a
relationship between general chain tension and chordal action. Third, and I
think this point is the most relevant and perhaps most surprising to
non-track riders, drivetrain components are not perfectly formed.
Chainwheels and cogs are not round, perhaps hubs and crankarms as well. What
happens is that occasionally the path of the chain goes across the high
spots of both the chainwheel and cog simultaneously, causing high degrees of
stress and friction to the chain. Track riders try to set the spacing of the
rear wheel in the dropouts where the chain is as loose as possible without
it 'derailling' off the chainwheel or cog when it is rotating to minimize
the occurrence and magnitude of the chain tension. While this is not chordal
action strictly speaking, I think the effect is the same.