Re: [CR]Hetchins Build / Effective wrap diameter of some shifters


Example: Framebuilding:Tony Beek

From: "Thomas R. Adams, Jr." <kctommy@msn.com>
To: teaat4p@yahoo.com, classicrendezvous@bikelist.org
Subject: Re: [CR]Hetchins Build / Effective wrap diameter of some shifters
Date: Mon, 25 Oct 2004 01:29:29 +0000


The quest for perfection involves two issues: which levers pull the "proper" amount of cable for accurate shifting for a certain rear mech IN THE PARTICULAR USER'S HANDS and which levers tension levels are a good match for the return springs on the derailleur. As you say, Rich, a friction unit will work properly with any friction levers, but there are differences. If the lever pulls a lot of cable, the derailleur shifts faster. If the derailleur was designed for a lever that pulls a small bit of cable and you use a big pull lever, the derailleur may shift "too fast", overshooting the cog you're seeking, requiring a sensitive touch to get a smooth "no chatter" shift.

I had the problem once with a Duopar and Campy DT levers. If felt like you had to just breath on the levers and the back jumped, and it was harder to trim as the derailleur moved so much with each lever imput. I swapped the Campys for a set of Simplex retrofriction jobs, and the shifting was much more attuned to my hand.

Naturally, another person may prefer an absurdly fast (or slow) shifting set up than mine. But you are right in that they will all shift.

The other issue is that some derailleus return springs are too strong for the friction/holding power of the lever. Then you have to torque the friction knob way down to keep the derailluer from shifting to smaller cogs without rider imput. I've got that problem today with a Galli rear mech and a Shimano 600 set of levers.

Of course, after a few shifts on any of my bikes, my brain seems to start applying the appropriate "shifter" coefficient, and I "know" how much to move this lever on this bike for one shift. Just another bit of old rider skill/lore that is quickly becoming obsolete.

Tom (My shifters don't do my thinking for me) Adams, Shrewsbury NJ


>From: r cielec <teaat4p@yahoo.com>
>To: classicrendezvous@bikelist.org
>Subject: Re: [CR]Hetchins Build / Effective wrap diameter of some shifters
>Date: Sun, 24 Oct 2004 18:03:18 -0700 (PDT)
>
>Ahoy !
>
>
>Firstly, to avoid any misunderstands, I will say this is a legit. straight forward inquiry; not being critical nor wise-cracking. I respect and appreciate Harvey's desire to get it right the first time. Don't we all?
>
>
>
>I've been following the discussion and am a bit puzzled. That is, in my naivety, I don't understand the fretting over matching levers and derailleur. I'm thinking: this is a friction installation; universal interchangeability, that's a great advantage with friction; any levers work with any derailleur (some odd exceptions I'm sure; and, of course a quality factor). There's all this scrutiny of compatibility yet, cable stretch or a stop one or two millimeters removed could affect shifting.
>
>
>Can someone explain the need for such thorough technical analysis of matching levers to derailleurs? I didn't think it was such a critical process.
>
>Thanks.
>
>Richard Cielec
>Chicago, Illinois
>
>
>HM & SS Sachs <sachs@erols.com> wrote:
>My quest for guidance on the Hetchins drive train clearly showed that
>there is a lot of difference of opinion about which shift levers take up
>how much cable. So, I did some measurements on the 13 units that were
>lying in the box.
>
>In the table below, please realize that the "effective diameter" is
>appproximate: some of these don't wrap around far enough for an
>accurate measurement, and some don't have their wrap barrels quite
>symmetrical wrt the axle bolt or nut. Like the Campy BarCon wants to
>pull more cable per unit of angular change near high gear than near low.
>
>effective diameter of some shift levers
>
>Diameter
>
>
>
>Brand
>
>
>
>Position
>
>
>
>Model or notes
>
>20
>
>
>
>Campagnolo
>
>
>
>BarCon
>
>
>
>biggest at high gear end.
>
>24
>
>
>
>Shimano
>
>
>
>BarCon
>
>
>
>Spring-loaded
>
>23
>
>
>
>Suntour
>
>
>
>BarCon
>
>
>
>Ratchet
>
>16.4
>
>
>
>Campagnolo
>
>
>
>DT
>
>
>
>raised letters
>
>33
>
>
>
>Cyclo GB
>
>
>
>DT
>
>
>
>for plunger derailleur
>
>18
>
>
>
>Shimano
>
>
>
>DT
>
>
>
>DuraAce
>
>20
>
>
>
>Shimano
>
>
>
>DT
>
>
>
>L422 ratchet
>
>21
>
>
>
>Shimano
>
>
>
>DT
>
>
>
>600
>
>15
>
>
>
>Simplex
>
>
>
>DT
>
>
>
>Al, black plastic covers
>
>15
>
>
>
>Simplex
>
>
>
>DT
>
>
>
>Plastic, chrome trim
>
>18
>
>
>
>Suntour
>
>
>
>DT
>
>
>
>ratchet
>
>20
>
>
>
>Suntour
>
>
>
>DT
>
>
>
>Cyclone (2 versions)
>
>19
>
>
>
>Suntour
>
>
>
>DT
>
>
>
>"aero" w curved levers
>
>If your output is garbled, send me an email with this subject and I'll
>send it as a little xcel file, unless you ask for Word.
>
>Converting from effective diameter to (mm. cable pull)/(degree lever
>moves) is left as an exercise for the reader. If it gets really dull
>this winter, I'll set up a jig and measure derailleur (mm moved)/(mm.
>cable pull), unless someone can find Berto's data. Hint, hint.
>
>What does the effective diameter "data" tell us?
>
>First, Campy ~ Simplex in effective diameter, if nothing else.
>
>Second, the Japanese DT are roughly 25 - 30% bigger than the two
>European models. Move more cable. True for both DT and BarCon, within
>brands.
>
>Third, here I thought Suntour was really smart, and used the same
>ratchet assembly both places. Not true. Really smart in selling lots
>of both is just as good, though.
>
>I hope this is useful. For example, if you are having trouble hitting
>your shifts with that Ultra-7 with a Suntour BarCon, drop down a notch
>in quality and use the Campy -- it works fine on one of my bikes.
>Conversely, for faster shifts choose a bigger effective diameter.
>
>Or confuse your friends. Put a Simplex DT on the bike with a Crane RD,
>and brag about the 170 degree shift sector ( guess) . :-(.
>
>Your mileage may vary. If DC locals want me to measure others with my
>knife-edged Swiss plastic vernier with dial, just bring 'em by. Bigger
>databases are better.
>
>harvey sachs
>mcLean va