Nexus shifter cable pull (was: friction shifters andinternally-geared hubs?)

Okay, I realize that last post was really long-winded, considering I really
wanted to ask just this:

Does anyone have the specs for the exact cable pull per click (with details
if it's not the same for each click) of the 7- and/or 8-speed Nexus
shifters?

(said info is conspicuously absent from bike.shimano.com).

Anybody? Please?

slug said:

So, here's what I've gathered so far:

[blah blah blah blah blah]

So this whole conversion thing may be do-able if I can find out how much
Nexus shifters pull, both per click, and over their range. I haven't had any
luck with this.

Do any of y'all out there have the details?

thanks.
Y.

[blah blah.]

slug said:

So, here's what I've gathered so far:
- You need precise cable pull amounts to shift internally-geared hubs.
- STI/Ergo shifters are precisely indexed for the cable pull necessary to
shift their corresponding derailers.
- If you can find the initial pull-per-click of an indexed shifter, there
are 2 ways you can probably change it:
- 1: replace the notched detent plate with a freshly-machined one with
new notches in it (assuming the initial total cable pull of the device
covers a wide enough range for the intended new amount)
- 2: leave the shifter unmodified and come up with some kind of lever
(bellcrank) to modify the amount of pull between the shifter and the
cable anchor (this assumes the target setting needs the same amount
of pull for each click)
- I can fairly easily find out the cable-pull specs of various indexed
shifters designed for derailers.
So this whole conversion thing may be do-able if I can find out how much
Nexus shifters pull, both per click, and over their range. I haven't had any
luck with this.

-snip-
You might set up a shift system with a bare wire someplace,
paint the wire and a mark behind it on your frame and just
measure the travel per click. (I don't know whether it is
even or progressive travel or what the distances are).

Round Ergos and STi have a mechanism to pull slightly past a
gear and then settle back on the cog center. In an Ergo it's
the peg on the spring carrier - the one that breaks off. You
should obviate that feature for an internal gearbox, i.e.,
use a broken spring carrier.

--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

A Muzi said:

-snip-
You might set up a shift system with a bare wire someplace,
paint the wire and a mark behind it on your frame and just
measure the travel per click. (I don't know whether it is
even or progressive travel or what the distances are).

Yeah, I was figuring I could do that if I have to.. But I think I want to do
this with the 8-speed Nexus, which as far as I can tell isn't available on
its own yet. But it seems like it couldn't hurt to try and dig up the tech
info before I can get my hands on the part. I thought maybe it was in one of
those newsletters Shimano sends to dealers..

I s'pose if I haven't scrounged up the specs by the time I can buy the hub,
I'll just do it myself..

Quoted message said:

Round Ergos and STi have a mechanism to pull slightly past a
gear and then settle back on the cog center. In an Ergo it's
the peg on the spring carrier - the one that breaks off. You
should obviate that feature for an internal gearbox, i.e.,
use a broken spring carrier.

I'm a teeny bit unclear on what you're saying here, but I think I get it. by
"round Ergos," I take it you mean the last few years' models, in comparison
to the older ones I've heard described as pointy? And then as far as the
spring goes: I think you mean that there's no good reason for the shifter to
overpull the cable at first, right? I just want the gear to click right into
place? So if I use a round Ergo, then I should find "the peg on the spring
carrier" (I think I could figure this out from an exploded drawing) and
break it off?

Indexed downtube or bar-end shifters wouldn't present this issue at all,
correct?

Thanks for all the patient explaining, Andrew (and the other patient
explainers I've seen in so many other r.b.t. threads..)

later.
Yoni.