Low-end vs. high-end components
05-25-14 | 08:50 PM
#101
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From: Melbourne, Oz
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No, not at all - you missed what I hope will be the case:
Given the chain angle scenario I went into, the two big rings can likely be stacked as close as cassette cogs (or perhaps even closer), so it should be possible for the FD to shift the chain onto the big ring before the inner plate contacts the middle ring, if not with a bit of overshift.
It looks like there's room between the plates for two close rings and a chain, perhaps even without trimming given the Yaw FD angles them.
See, with the inner plate touching the chain, and a ~1mm gap between the chain and the big ring (I reckon that spacing looks about right for the 53t/50t gap), there's a further ~2.5mm - plenty. I think the lens might've been off to the right a tad, so there should even be a bit more gap than it looks.
Another wrinkle is the maximum gap on the cage, but given the existence of a 34/50 option and no (AFAIK) compact version of the FD, my 15t gap should be within spec.
Given the chain angle scenario I went into, the two big rings can likely be stacked as close as cassette cogs (or perhaps even closer), so it should be possible for the FD to shift the chain onto the big ring before the inner plate contacts the middle ring, if not with a bit of overshift.
It looks like there's room between the plates for two close rings and a chain, perhaps even without trimming given the Yaw FD angles them.
See, with the inner plate touching the chain, and a ~1mm gap between the chain and the big ring (I reckon that spacing looks about right for the 53t/50t gap), there's a further ~2.5mm - plenty. I think the lens might've been off to the right a tad, so there should even be a bit more gap than it looks.
Another wrinkle is the maximum gap on the cage, but given the existence of a 34/50 option and no (AFAIK) compact version of the FD, my 15t gap should be within spec.
Last edited by Kimmo; 05-25-14 at 09:02 PM.
05-26-14 | 01:02 AM
#102
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Joined: Jul 2004
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From: Brooklyn NY
Bikes: Kuota Kredo/Chorus, Trek 7000 commuter, Trek 8000 MTB and a few others
I'm going to assume you mean half-decent stuff rather than the pressed steel plate junk at the bottom, and say that since DS is a new system involving more cable pull, the difference is mostly down to geometry. In other words, once DS extends to the low end, the difference in performance will be marginal. The short cable pull of previous Shimano systems requires higher precision, so there was more benefit in spending... SRAM's geometry should make for a minimal performance difference across the range. By 'performance' here, I'm only talking about the reliability of shifts, not how quick they happen or how nice they feel.
And why is performance only reliability of shifts? Speed, sound and feel are definitely part of performance. I'm more pleased about the feel of DS shifting than anything else. All it takes is a flick of my thumb. AND it is fast, quiet and reliable. I actually prefer this feel over my Chorus brifters.
But people on this forum have stated that 7 speed mtb gear is all we ever needed, and it worked great. Well, compared to 10 speed, it doesn't. My thumbs are the proof.
Last edited by zacster; 05-26-14 at 01:08 AM.
05-27-14 | 04:41 AM
#103
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From: Melbourne, Oz
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105, or even Tiagra these days, is pretty swish kit. Dunno about the MTB stuff so much, but it's a similar scenario... I think there may be more levels though.
And why is performance only reliability of shifts?
Last edited by Kimmo; 05-27-14 at 04:45 AM.
05-27-14 | 12:52 PM
#104
Senior Member
Joined: Aug 2007
Posts: 546
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From: NorCal
Bikes: 2009 Surly Cross Check Frankenbike
I do most of my own mechanical work on my family's bikes. I don't have vast experience and I have never worked on high-end components, but I have found that working on mid-range parts like Shimano Deore LX and 105 and Campagnolo Mirage is a much more enjoyable and satisfying experience than low-end parts. Forged clamps instead of stamped sheet metal that bites into your paint, beautiful cast housings, etc.
This is not about function and I have always had to stretch my money so I understand being frugal. I'm just saying that after working on low-end parts, I really appreciate better ones.
This is not about function and I have always had to stretch my money so I understand being frugal. I'm just saying that after working on low-end parts, I really appreciate better ones.
05-27-14 | 02:33 PM
#105
Bicycle Repair Man !!!
Joined: Sep 2007
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From: YEG
Bikes: See my sig...
A young lady came to a bike event where we were providing free tune ups and had a bent hangar and a bent Shimano 7 speed SIS derailleur (TY20)... her bike was fitted with pure entry level stuff from the big box store.
I straightened the hangar and then lined up the derailleur and had told her the shifting might not work properly (because things were really bent) but with grip shifts that did not seem to have seen much use the bike was shifting as crisply as any bike that cost 5 times the price... albeit with a little more noise from the steel derailleur.
A fancier derailleur may have not survived the initial abuse and the corrections.
On the other hand, those TY20 SIS derailleurs are modelled on Shimano's derailleurs from the 60's and those worked well and just happened to index, which is why they have remained in production for so long.
They are cheap and effective at what they do and must be the most successful derailleur of all time since they have been built and copied for so long.
I straightened the hangar and then lined up the derailleur and had told her the shifting might not work properly (because things were really bent) but with grip shifts that did not seem to have seen much use the bike was shifting as crisply as any bike that cost 5 times the price... albeit with a little more noise from the steel derailleur.
A fancier derailleur may have not survived the initial abuse and the corrections.
On the other hand, those TY20 SIS derailleurs are modelled on Shimano's derailleurs from the 60's and those worked well and just happened to index, which is why they have remained in production for so long.
They are cheap and effective at what they do and must be the most successful derailleur of all time since they have been built and copied for so long.
06-14-14 | 07:19 AM
#106
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From: Melbourne, Oz
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I think you missed the reason Retro Grouch asked the question. He wasn't referring to the resulting gear ratios or chain angle. He was asking if the inner cage plate of the front derailleur would clear the inner chainring's teeth when shifted to the outer chainring given the small diameter difference between them. Unless the derailleur is set way too high to shift properly modern front derailleurs have rather deep inner plates and often require a 10T or larger chainring difference to work properly.
But after a lot of messing around with bastard chainring spacers, I was able to successfully space the rings to get nice chainlines with no chainring interference, and it looked like a normal FD would work.
Sure enough, when I swapped out the RED FD for a 7700 one, bingo
I had to run it a fraction high (about 3-4mm gap). Seems to shift nicely enough (I shouldn't need to program any overshift into the arduino), although I've yet to throw on some flat bars with thumbshifters to try it out under load... but I'm pretty optimistic. The 52t could be a plain ring, since the chain doesn't get to see any of its shift-assist from the 50t.
Spacing is 3mm inboard for the 38t, with the 50t 3mm from that (0.4mm less than the spider thickness), putting it inline with the spider. The 52t is 2.4mm outboard from the spider. So the gap between the 38t and the 50t is 0.4mm less than normal, and the 50-52t gap is similar to the gap between 6s cogs (around 5.5mm C-C). The chain can reach the first 8 cogs from the 38t without scraping the 50t, and I only need it to reach the first 7 for my setup. The chain will reach all cogs off either big ring without scraping. (It took a few goes before there was clearance for the 50t to small cog line without scraping the 52t.)
YMMV with frame clearance...
Oh yeah, 14mm chainring nuts required.
Last edited by Kimmo; 06-15-14 at 12:07 AM.
06-14-14 | 07:51 AM
#107
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From: Melbourne, Oz
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...And you can get an arduino for like $2.80. I bought three. Wasn't much fun getting my head around C++ to tell the thing what to do, but after a few days' struggle I have a basic program that'll do the job. Actually, once I had my test servo going through the motions, it was pretty fun (IT'S ALIVE), and I'm looking forward to learning more C++ and making my code pretty fancy... a sensor on the crank and wheel, and I can make it auto-shift, with the buttons being used to set a desired cadence. With a switch in the seat and maybe a gyro/accelerometer pair, maybe I can cook up some code to successfully guess my desired cadence for the most part...
There's a kind of servo, usually called wing or slim servos, in a ~30x30x10mm package that are pretty small, light and cheap (20-30g, $10-$100), and have a decent amount of torque... I found a waterproof model in digital (better holding torque) with metal gears and BBs, with about 5kg/cm torque, for $20 each; ordered a couple. 7.4V 1Ah LiPo battery, ~$10, a charger for it, $20.
It's shame there are no miniature linear actuators small enough... I keep fantasising about tiny 15x15x30mm stepper motors with eensy little ball screws... oh well. My derailers each need about 5kg of force on the cable to move through their throw, which isn't far off the stall torque of the servos, but I can simply pull on the end of the cable with 5kg of spring force, with the servo in between - that should easily lighten the servos' load by enough.
One snag is the short amount of cable pull for the FD; with 160-180° of servo movement (and I'd be nuts not to use it all), we're talking a pulley about 7mm in diameter or so... obviously that's not something a gear cable is going to handle well. So after looking at various flavours of kevlar, I'm gonna give that 1mm survival cord they sell in camping shops a shot. I'm a bit worried about how I'm going to get the cord through any housing (hope I don't have to break out the vacuum pump), and clamping it effectively might prove a challenge... hopefully it won't tear up my housing liner too. But I couldn't come up with anything else as elegant...
But it's all coming together fairly easily so far. The hardest part (aside from the coding) will be to make the servo brackets, pulleys and counterspring setup, and making it sexy enough.
DIY roboshift actually seems to be a piece of piss.
I'm gonna be super-generous and post my arduino code:
Weird bug: every closing curly bracket is being replaced by a double asterisk for some reason. If you use this code, just replace every double asterisk with a closing curly bracket.
The degrees for servo positions are just arbitrary for now, until I've built the rig. This code can be easily modified to suit any drivetrain.
There's a kind of servo, usually called wing or slim servos, in a ~30x30x10mm package that are pretty small, light and cheap (20-30g, $10-$100), and have a decent amount of torque... I found a waterproof model in digital (better holding torque) with metal gears and BBs, with about 5kg/cm torque, for $20 each; ordered a couple. 7.4V 1Ah LiPo battery, ~$10, a charger for it, $20.
It's shame there are no miniature linear actuators small enough... I keep fantasising about tiny 15x15x30mm stepper motors with eensy little ball screws... oh well. My derailers each need about 5kg of force on the cable to move through their throw, which isn't far off the stall torque of the servos, but I can simply pull on the end of the cable with 5kg of spring force, with the servo in between - that should easily lighten the servos' load by enough.
One snag is the short amount of cable pull for the FD; with 160-180° of servo movement (and I'd be nuts not to use it all), we're talking a pulley about 7mm in diameter or so... obviously that's not something a gear cable is going to handle well. So after looking at various flavours of kevlar, I'm gonna give that 1mm survival cord they sell in camping shops a shot. I'm a bit worried about how I'm going to get the cord through any housing (hope I don't have to break out the vacuum pump), and clamping it effectively might prove a challenge... hopefully it won't tear up my housing liner too. But I couldn't come up with anything else as elegant...
But it's all coming together fairly easily so far. The hardest part (aside from the coding) will be to make the servo brackets, pulleys and counterspring setup, and making it sexy enough.
DIY roboshift actually seems to be a piece of piss.
I'm gonna be super-generous and post my arduino code:
Code:
#include <Servo.h>
Servo frntservo; // 3 positions: X,Y,Z
Servo rearservo; // 10 positions: A-J
byte mpin=5; // mode button
byte upin=6; // gear up
byte dpin=7; // gear down
byte X=20; byte Y=100; byte Z=160; // angles in °
byte A=20; byte B=35; byte C=50; byte D=65; byte E=80; byte F=95; byte G=110; byte H=125; byte I=140; byte J=155;
byte fpos[24]={0,X,X,X,X,X,X,X,Y,Z,Y,Z,Y,Z,Y,Z,Y,Z,Y,Z,Y,Z,Y,Z**; // first position of array not used
byte rpos[24]={0,A,B,C,D,E,F,G,C,C,D,D,E,E,F,F,G,G,H,H,I,I,J,J**; // arrays for linking positions and gear #
byte gear=3; // gear number
boolean ss=false; // ss mode flag
byte lpin=13; // ss mode indicator
void setup() {
Serial.begin(9600); // diagnostic
frntservo.attach(9); rearservo.attach(10);
pinMode(mpin,INPUT_PULLUP); pinMode(upin,INPUT_PULLUP); pinMode(dpin,INPUT_PULLUP);
pinMode(lpin,OUTPUT);
**
int normal() { // normal gear selection
if(digitalRead(upin)==LOW) {delay(10); gear=gear+1; gear=constrain(gear, 1, 23); diag();
**
if(digitalRead(dpin)==LOW) {delay(10); gear=gear-1; gear=constrain(gear, 1, 23); diag();
**
return gear;
**
int ssmode() { // ss gear selection
if(digitalRead(upin)==LOW) {delay(10); gear=gear+1; gear=constrain(gear, 1, 23);
if (gear==9||gear==11||gear==13||gear==15||gear==17||gear==20||gear==22) {gear=gear+1;
** // skip extra gears
diag();
**
if(digitalRead(dpin)==LOW) {delay(10); gear=gear-1; gear=constrain(gear, 1, 23);
if (gear==22||gear==20||gear==17||gear==15||gear==13||gear==11||gear==9) {gear=gear-1;
** // skip extra gears
diag();
**
return gear;
**
void diag() { // serial print diagnostic
Serial.print(gear); Serial.print("\t"); Serial.print(rpos[gear]); Serial.print("\t"); Serial.println(fpos[gear]);
**
void loop() {
if(digitalRead(mpin)==LOW) {delay(10); ss=!ss;
** // toggle ss mode
if (ss==false) {digitalWrite(lpin,LOW); normal();
** else {digitalWrite(lpin,HIGH); ssmode();
**
rearservo.write(rpos[gear]); delay(150);
frntservo.write(fpos[gear]); delay(350);
**
The degrees for servo positions are just arbitrary for now, until I've built the rig. This code can be easily modified to suit any drivetrain.
Last edited by Kimmo; 06-14-14 at 10:09 AM.
06-15-14 | 05:28 PM
#108
Senior Member
Joined: Dec 2009
Posts: 9,563
Likes: 736
From: Melbourne, Oz
Bikes: https://weightweenies.starbike.com/forum/viewtopic.php?f=10&t=152015&p=1404231
I was having a hard time finding chainring bolts long enough, but then I saw the 15mm Thorn SS chainring sleeves at SJS Cycles - neat idea, bolt in each end.
I know, I should start another thread about this... I'll get around to it at some point
I know, I should start another thread about this... I'll get around to it at some point
06-16-14 | 01:21 AM
#109
Strong Walker
Joined: May 2007
Posts: 1,407
Likes: 616
From: Black Forest, Germany
Bikes: too many
Some of the 9- and 10-speed Ultegra parts are known to wear down or malfunction pretty fast, while there are few things as durable as, say, an 8-spd DA train - i know one that has 120.000+ km on the clock.
Also, there is a distinct difference in function between my XT and my XTR gear.
06-16-14 | 11:23 AM
#110
Hmmm
I use XTR and XT components interchangeably
Now I prefer XTR components-prettier and lighter-
but 2x to 2.5x the price of XT,so....
I have some XTR hubbed wheels-lasting for EVER
but I haven't managed to wear out any XT stuff either.
My XTR caliper brakes-do seem to "work better" than LX and XT brakes-but it is a small difference.
Frankly I rarely wear ANY components out-other than chains pads occasional chainring
my derailleurs and hubs-last forever- at 2000 easy street and levee miles per year.
NOLA metro- is flat-so I really don't shift a lot-and OLD habit-never shift under load-so I'm pretty gentle on equipment
Maybe that is why I never noticed any durability difference- XT vs XTR
I'm guessing-most folks are pretty easy on gear-
true MTB riding-shifting under load-pounding on rough trails-yeah durability would be important
But I still have my doubts about the heavier XT components being less durable than XTR
XTR -very pretty of course-frequently that is worth the 2X charge
I use XTR and XT components interchangeably
Now I prefer XTR components-prettier and lighter-
but 2x to 2.5x the price of XT,so....
I have some XTR hubbed wheels-lasting for EVER
but I haven't managed to wear out any XT stuff either.
My XTR caliper brakes-do seem to "work better" than LX and XT brakes-but it is a small difference.
Frankly I rarely wear ANY components out-other than chains pads occasional chainring
my derailleurs and hubs-last forever- at 2000 easy street and levee miles per year.
NOLA metro- is flat-so I really don't shift a lot-and OLD habit-never shift under load-so I'm pretty gentle on equipment
Maybe that is why I never noticed any durability difference- XT vs XTR
I'm guessing-most folks are pretty easy on gear-
true MTB riding-shifting under load-pounding on rough trails-yeah durability would be important
But I still have my doubts about the heavier XT components being less durable than XTR
XTR -very pretty of course-frequently that is worth the 2X charge
