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Variable Pull Shift Brifters?
Perhaps I'm just showing off my ignorance, but, here goes... My understanding is that the difference in compatibility between different cassette / rear derailer / right shifter sets -- for example Shimano 9 speed, 10 speed road, 10 speed MTB, 11 speed road, etc. -- is the amount of distance between shift points. By shift points, I refer to both cog-to-cog cassette spacing and gear-to-gear cable travel. The former is only related to the latter by designed ratio, one of SRAMs marketing gimmicks IIRC.
Now, it seems to me that it should be mechanically simple to adjust the amount that the end of the rear derailer cable travels for a given pull on a brifter lever. I assume that this is not common simply as a planned obsolescence profit generator. Sheldon Brown mentioned the alternative cable attachment method that alters ratio slightly for one particular mismatch. So, my question is, what else is available in this regard? Are there small maker brifters that can be adjusted to a variety of pull/release travel distances? Are there intermediate -- within the cable run between shifter and derailer -- mechanical devices that are available? Or, are there reasonable easy to construct mechanisms for the bike hacker with limited metalworking equipment? Sorry if this is a repeat, but most of what I read on the subject relates to specific pairs of components, i.e. ErgoPower 10 + Dura-Ace 10 or whatever. I'm trying to get at whether there is a more generally applicable solution that will allow one to upgrade components over a period of time without having to buy a whole groupset at once. |
Variable cable pull is easy to imagine in theory, but not so easy in practice. The cable winds onto a drum, so all that's necessary is to change the drum diameter, according to the desired cable travel. this is far easier than trying to vary the click spacing. OTOH, when you look at it, varying the drum diameter isn't all that simple in practice, though it could probably be designed to be so.
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justinzane, It maybe possible with electronic shifting, but it seems impractical with mechanical shifting. Even Sheldon Brown's advice to anchor a shift cable to the opposite side of the screw is a bit iffy.
Brad |
The wisdom you seek is here:
Shimergo | CTC Indexing bicycle drivetrains are simple machines. Despite this, only a small minority of avid cyclists (and even shop mechanics) ever really figure out the relationships between shifters (cable pull), derailleurs (mechanical advantage) and cassettes (cog spacing). If you read the CTC article, and truly understand it, then you have what you need -for life. I am not aware of shifters that feature the ability to vary the cable pull. There are some hack solutions out there for adjusting derailleur mechanical advantage (such as the alternative cable pull trick). Or modifying the shifter cable pull. These can work fine. Most of my bikes feature a mix of derailleurs and shifters that strictly not 'manufacturer recommended'. For example, I use Campy 10-speed Ergo levers with the older generation of Campy indexing derailleurs. This allows me to run Shimano 10-speed cassettes and hubs. Cheaper and far more available than the Campy equivalents. Works perfectly every time. Understanding indexed shifting at a deep level will allow you access these optimal solutions. And avoid endless frustration working on kludge solutions that will never be compatible. Wisdom here comes from understanding the numbers. If you know the cable pull of the shifter, the mechanical advantage of the derailleur, and the cog spacing of the cassette, and you run the math, and it should work, then it will work. For me, this approach has never failed. I have no respect for hack mechanics who suggest that: "perhaps you should just try a Suntour derailleur with Shimano 8-speed shifters on a 9-speed cassette and see if it works". This demonstrates that the mechanic does not have a clue what they are doing, and they are wasting everyone's time. It all starts with accurate numbers, and then running the math. Good luck. |
Originally Posted by FBinNY
(Post 17075706)
Variable cable pull is easy to imagine in theory, but not so easy in practice. The cable winds onto a drum, so all that's necessary is to change the drum diameter, according to the desired cable travel. this is far easier than trying to vary the click spacing. OTOH, when you look at it, varying the drum diameter isn't all that simple in practice, though it could probably be designed to be so.
http://bikeforums.net/attachment.php...hmentid=402222 [TABLE] [TR] [TD="align: left"]Cyl. Thickness[/TD] [TD="align: left"]Nested Dia.[/TD] [TD="align: left"]15° Travel[/TD] [TD="align: left"]1:1.7 Travel[/TD] [/TR] [TR] [TD="align: right"]10.34[/TD] [TD="align: right"]10.34[/TD] [TD="align: right"]1.35[/TD] [TD="align: right"]2.30[/TD] [/TR] [TR] [TD="align: right"]0.45[/TD] [TD="align: right"]11.24[/TD] [TD="align: right"]1.47[/TD] [TD="align: right"]2.50[/TD] [/TR] [TR] [TD="align: right"]0.68[/TD] [TD="align: right"]12.59[/TD] [TD="align: right"]1.65[/TD] [TD="align: right"]2.80[/TD] [/TR] [TR] [TD="align: right"]0.23[/TD] [TD="align: right"]13.04[/TD] [TD="align: right"]1.71[/TD] [TD="align: right"]2.90[/TD] [/TR] [TR] [TD="align: right"]0.91[/TD] [TD="align: right"]14.85[/TD] [TD="align: right"]1.94[/TD] [TD="align: right"]3.30[/TD] [/TR] [TR] [TD="align: right"]0.21[/TD] [TD="align: right"]15.26[/TD] [TD="align: right"]2.00[/TD] [TD="align: right"]3.40[/TD] [/TR] [TR] [TD="align: right"]0.25[/TD] [TD="align: right"]15.75[/TD] [TD="align: right"]2.06[/TD] [TD="align: right"]3.50[/TD] [/TR] [/TABLE] Now, I only threw the core, 2nd, 3rd and last rings into the image, but the rest are similar. Since they are nested and very infrequently changed, the shims do not have to have any significant strength themselves which should make manufacture easy. Manufacturers can easily mass produce pistons, rings and valves that work at vastly higher temperatures, pressures and duty cycles than anything on a bike. I truly fail to see why this is difficult, other than protecting profit associated with brand image and expense. |
There is no "electronic" shifting. All that the Campy and Shimano "electronic" systems are are amazingly marked-up micro controllers, battery packs, stepper motors and simplistic sensors. They make the RaspberryPi look like a supercomputer and they are electrically operated mechanical devices at heart. Any modifications to these electro-mechanical shifters would be simpler as a purely mechanical system. And, I've seen both Shimano and Campy trying to wall these overpriced doodads off from their other high-end lines.
Sorry to be rude. Being an electronics and software guy professionally, seeing things that are so abusively over marketed to leverage the ignorance of potential customers is like watching someone be mugged. |
didnt campagnolo used to make downtube shifters
with replaceable plates that control the angle of shifter movement between gears? |
Rohloff with a rotary shift sequence is easier to (3rd party) make a servo motor AboutUsPage. Melbourne Australia.
Di2 Alfine 11 speed is passing thru several marketing layers , each needs to pay its expenses thru markups .. Utopia is nowhere.. |
Look up Jtek's Shiftmate. They accomplish a lot of what you are asking about.
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You've asked and answered your own question, so since you don't need my input I'm out.
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ShimErgo... That's the article I had in the way-back of my brain apparently. I've read it.
Your right that that is what I am looking for; but more universal. What I want is a brifter than can be adjusted, not on the fly, in the shop, so that when one goes from a formerly affordable 7 speed to an affordable now 9 to an affordable in a couple of years 11 speed cassette/derailer one does not have to throw away or sell at a loss a perfectly fine set of brifters that one's hands know by instinct. Imagine for a moment someone with a car hobby... They have an old car that they love and have painted, chomed, etc. They decide to replace the 4 cylinder engine with a rebuilt 6. They do not have to change the transmission to accomplish this. They could instead decide to replace the 5 speed manual with a 6 speed. The engine stays the same. The two changes are not integrally linked. Or a gamer who decides to upgrade his GPU (graphics card). She can keep her CPU, RAM, everything else; and then later upgrade another component. Make sense? |
Why is brain surgery so expensive when everybody's brain is made of the same stuff?
RIP OFF! |
Originally Posted by justinzane
(Post 17076202)
Imagine for a moment someone with a car hobby... They have an old car that they love and have painted, chomed, etc. They decide to replace the 4 cylinder engine with a rebuilt 6. They do not have to change the transmission to accomplish this. They could instead decide to replace the 5 speed manual with a 6 speed.
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Don't look very ergonomic but you could always get some of these.morphos
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Originally Posted by justinzane
(Post 17076202)
. . . Imagine for a moment someone with a car hobby... They have an old car that they love and have painted, chomed, etc. They decide to replace the 4 cylinder engine with a rebuilt 6. They do not have to change the transmission to accomplish this. They could instead decide to replace the 5 speed manual with a 6 speed. The engine stays the same. The two changes are not integrally linked. . .
Make sense? |
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In MTB land I run 7,8 and 9 speed cassette+shifters combos with the same 8 speed Shimano Derailleur. 10-speed is another realm, though.
In roadie land, I swap out Sachs, Sram and Shimano 7-speed cassettes/freewheels on a bike with the same 7-speed shifters and derailleurs. If running 6,7,8,9 speed MTB stuff, only a few tricky combos you have to worry about, really. You just gotta know that Sram MTB rear derailleurs require numbered Sram shifters and that solves well over half your problems right there. You can also actuate 7/8/9 speed Shimano road rear derailleurs across shimano or Sram 7/8/9 speed cassettes with Shimano brifters that match the cassette gear count no problemo. They won't do so well with MTB front derailleur/crankset, though. I think there are far more feasible matches than there are of auto engine/transmission combos from the 90s and aughts. |
"Manufacturers can easily mass produce pistons, rings and valves..."
Auto manufacturers produce millions of units, bicycle manufacturers thousands or even only hundreds of units. The economies of scale are vastly different. |
The Modolo Morphos brifters can shift multiple manufactures/speeds.
Shimano 7,8,9,10 speed; Campagnolo 9,10 speed, and also Index 5,6 speed. morphos |
Originally Posted by dsbrantjr
(Post 17077633)
"Manufacturers can easily mass produce pistons, rings and valves..."
Auto manufacturers produce millions of units, bicycle manufacturers thousands or even only hundreds of units. The economies of scale are vastly different. |
Originally Posted by justinzane
(Post 17076202)
ShimErgo... That's the article I had in the way-back of my brain apparently. I've read it.
Your right that that is what I am looking for; but more universal. What I want is a brifter than can be adjusted, not on the fly, in the shop, so that when one goes from a formerly affordable 7 speed to an affordable now 9 to an affordable in a couple of years 11 speed cassette/derailer one does not have to throw away or sell at a loss a perfectly fine set of brifters that one's hands know by instinct. I am only aware of 2 takes on this, the Modolo Morphos shifters and Campagnolo Ergopower levers, where there is the ability to change the indexing rings. I have never used the Modolo levers, but have read mixed to negative reviews. Campagnolo has changed their shifter internals several times since the introduction of Ergopower in 1991, so you cannot upgrade certain generations of shifters beyond a certain point. I have spent a lot of time digging around in and servicing Ergopower levers, and I know that you cannot upgrade the old 8-speed levers to take a 11 speed indexing ring. I suppose if you'd drop a few hundred thousand bucks on Valentino, he'd be willing to manufacter a custom indexing ring for say: 12 speeds, but short of that, I think you should focus on easier solutions, such as modifying the length of the cable pull after the cable exits the shifters. Or thinking completely out of the box, I might suggest jumping off of the n+1 cog merry-go-round of planned obsolescence that the bike manufacturers have hoisted on us for the last few decades. 11 speed drivetrain? It is an absurd joke that has gone well past the point of diminishing returns; it is only meant to sell more stuff. |
Modolo Tried years ago, to make a brifter to use with Campag and Shimano wheels ..
https://www.google.com/search?q=Modo...w=1663&bih=959 |
Justinzane, bring a really big line of Credit to the next big Taipei bike Trade show and shop your idea over there
where much of the bike business is concentrated .. I'm one who got off the marketing more is better band wagon at 7.. which works fine with friction Levers, the pull variation is in my hand. |
Two thoughts. First, I think your nested idea wouldn't work; there's stress on these components and you need to vary both pulley diameter and number of clicks, and you are always going to lose in your garage all the outer layers you aren't using. Second, the length of pull is a little more subtle than implied by the Shimergo tables. There's a progression of pull length to try to get linear motion out of the RD which pivots in a circle. The reason C10 shifters work on S8 cassettes and derailleurs is that the 1st and 8th position are controlled by the stop screws on the derailleur and only the second through seventh clicks need to be a reasonably close match. I found this last year when I was studying, but I can't find the link right now... it was an older forum post from pre-Shimano-11. Some of it is out of date about newer hardware, probably.
At the time I was trying to find a way to get brifters to index a NR derailluer - I've gotten over it since then. Campy 10 shifters pull an average of 2.83mm of cable per shift, but that cable pull is not uniform. The first five shifts are only 2.5mm, the next two are 3mm and the last two are 3.5mm. SRAM shifters pull a uniform 3.1mm per shift, so even Campy 10 shifters are really not a good match with SRAM RD. I know that Lennard Zinn posted info about a Campy/SRAM setup but it makes no sense to me. It would take a Campy shifter 6 clicks to pull enough cable for 5 shifts of a SRAM RD. That's a major error. The 11 speed shifters would be far worse since they only pull an average of 2.6mm per shift and those pulls are not uniform either. SRAM's 1:1 actuation ratio is used on their mountain bike components, not their road bike components. You cannot, for example, use their mountain bike derailleurs with their road bike shifters for a touring setup. The road bike actuation ratio is around 1.4:1, which is what Campagnolo used on their previous iteration of indexed shifting (pre-2001). Their cable pull at the shifter is linear so every shift pulls the same amount of cable for every shift, which is different than what Shimano and Campagnolo uses. Suntour was the only other company that I'm aware of that used a linear cable pull at the shifter but they spaced their cogs accordingly. Shimano (and SRAM, by default) use evenly spaced cogs on all of their cassettes and Campy's cassettes are almost evenly spaced. How does SRAM get away with it? They have that little linkage arm thing on their derailleurs that allows the derailleur to move the same amount for a given amount of cable pulled whether it is at the beginning or end of the throw, unlike Shimano, Campy, and Suntour indexing rear derailleurs, which move less as the derailleur moves closer to the spokes. |
Originally Posted by Dave Mayer
(Post 17078384)
I get it. There are 3 variables in indexed shifting: the shifter cable pull, the derailleur mechanical advantage, and the cog spacing. You want the ability to modify the cable pull within the shifters.
I am only aware of 2 takes on this, the Modolo Morphos shifters and Campagnolo Ergopower levers, where there is the ability to change the indexing rings. I have never used the Modolo levers, but have read mixed to negative reviews. Campagnolo has changed their shifter internals several times since the introduction of Ergopower in 1991, so you cannot upgrade certain generations of shifters beyond a certain point. I have spent a lot of time digging around in and servicing Ergopower levers, and I know that you cannot upgrade the old 8-speed levers to take a 11 speed indexing ring. I suppose if you'd drop a few hundred thousand bucks on Valentino, he'd be willing to manufacter a custom indexing ring for say: 12 speeds, but short of that, I think you should focus on easier solutions, such as modifying the length of the cable pull after the cable exits the shifters. Or thinking completely out of the box, I might suggest jumping off of the n+1 cog merry-go-round of planned obsolescence that the bike manufacturers have hoisted on us for the last few decades. 11 speed drivetrain? It is an absurd joke that has gone well past the point of diminishing returns; it is only meant to sell more stuff. At my current low level of skill and fitness, a 3x7 is really quite fine, though 8 or 9 on the back would not hurt. I know that I really cannot get added value from 10 or 11 tight spaced gears. I'm not that capable a cyclist at the moment. When looking at bike shops, though, DNP is the only? maker of 11T-## freewheels for older bikes. For cassettes, Bicycle Cassettes - Modern Bike shows: 7sp - 13 choices 8sp - 18 9sp - 49 10sp - 73 11sp - 35. That looks like one either has to live with ever decreasing choice and stay off the train or throw away good bits every few years to buy new. :) Thanks. I appreciate the insight and experience. |
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