Tom Kunich said:"Simon Brooke" <[email hidden]> wrote in message
news:[email hidden]...Quoted message said:in message <[email hidden]>, Tom
Kunich ('cyclintom@yahoo. com') said:
Simon, it is apparent that you have some education in mechanical design.
This whole argument began when I said that there wasn't anything to GAIN
by going to electronic shifting. It's only another failure point in an
otherwise highly reliable machine. But jim beam (named apparently from
what he is under the influence of ) seems to believe that derailleurs
which are almost the perfect mechanism, can be markedly improved with
electronics.OK, I hear what you're saying and I'm not sure I agree. It's partly
because
I'm a geek and like playing with toys. But also, one of my bikes - the
one
I ride to work most days - is an old steel Raleigh. It suffers from frame
flex. And one of the problems that frame flex causes is that because the
parallelogram is attached to the back of the frame, and controlled by a
bit of wire that is under tension from the front of the frame, as the
front of the frame and the back of the frame move relative to one another
you get ghost shifts. This is exacerbated on my Raleigh, of course, by
the
fact that it was designed for a five speed freewheel and now has a nine
speed cassette, so smaller distortions of the frame cause ghostshifts
than
would have been the case when it was new...Try this Simon - carefully grease the shift cables where they make the
turn at the bottom bracket and I'm reasonably sure that your ghost
shifts will disappear. I'm 6'4" and weigh 200 lbs and I can't cause a
bike to ghost shift when properly set up. I've had a lot of Peugeots,
Gitanes, old Bottechias, Schwinns and a lot of garbage bikes and none of
them would ghost shift even though the bay area has a lot of hard climbing.Quoted message said:With modern, closer tolerance derailleur trains the derailleur cage is
still attached to the back of the frame but the detents which control its
position are in the shifter mechanism at the front of the frame (or,
actually, on the handlebar...).I can't imagine someone flexing a C50. The C40 is so stiff that you can
feel a distinct difference in handling going through rough 40 mph
downhill esses.Quoted message said:The detents really ought to be in the derailleur mechanism itself.
That's a point of argument. Shimano started out that way and it didn't
work well.Quoted message said:[As an aside a pantograph is not really the ideal mechanism for something
that wants to track across a cassette at a fixed distance from the cogs -
particularly on a machine on which different sized cassettes may be used.
The optimum trajectory for a 12-21 cassette is quite different from that
for a 13-26 cassette. Mind you, I'm not saying I could design a better]We don't care about ideal. We care about workable and the slant
parallelogram is the best working mechanism to date.Quoted message said:If the detents are going to be in the derailleur mechanism, then an
electronically triggered movement is quite a good idea. I can imagine a
mechanical system where a short tug on the cable released the mechanism
one detent, and a longer tug on the cable lifted the mechanism one
detent,
with a user interface much like the SRAM 'double tap' (the cable being
slack between actuations). But an advantage of electronic actuation, as
Mektronic demonstrated, is you can have multiple switch positions so that
it becomes easy to change gear from the tops as well as the hoods and the
drops. And if you have electronic actuation, then taking the energy to
lift the mechanism from the chain seems to me clever and cool.The bottom line is this - todays races could be just as easily won with
friction shifting 7 speed barend shifters as STI. The complex mechanisms
being used are not improvements - they are marketing devices.Quoted message said:Also, it's easy to build an electrical wiring harness into a carbon
composite structure. Thus exposed cables could be a thing of the past,
and
I'd see that as a positive thing.That's a personal choice on your part. I don't see anything in it at all.
Quoted message said:Quoted message said:Well, not quite but I agree that you don't need a lot of power if you're
willing to rob most of it from the drive train. But then you're either
stuck with the Mektronic mechanism which has fixed stops or complex
sensors and micro-adjustable position sensors which in the end would be
quite a pain in the neck without adding anything to reliability,
reducing
costs or weight.I certainly think that if you're going to have electronic gear
actuation on
a racing bike in a sporting context then the energy used to lift the
mechanism ought to come from the competitor's muscular effort in near
real
time - if you're using stored power from a battery charged before the
event that ought to be seen as cheating.Isn't muscle energy stored before the event? (Rolls eyes) Now your
suggesting not just a mechanical mechanism to move everything to the
proper position but also a generator to power the electronics. Time for
Donnelly to explain the facts of life visa vi power.Quoted message said:Quoted message said:The modern bicycle is the end result of a hundred and fifty years of
evolution. It achieved it's peak in the 1960's and everything added
since
then has been only for performance on smooth roads.I'm not at all sure I agree with that. I have two road bikes I ride
regularly, a modern carbon Dolan and the fifteen-year-old steel Raleigh.What difference do you see between your Raleigh and your Dolan? What
about comparing my Basso to your Dolan?
gainsay is not an argument. try again.