Advertise on Bikeforums.net



User Tag List

Page 2 of 3 FirstFirst 123 LastLast
Results 26 to 50 of 57
  1. #26
    pan y agua merlinextraligh's Avatar
    Join Date
    Aug 2005
    Location
    Jacksonville
    My Bikes
    Wilier Zero 7; Merlin Extralight; Co-Motion Robusta; Schwinn Paramount; Motobecane Phantom Cross; Cervelo P2; Motebecane Ti Fly 29er
    Posts
    27,416
    Mentioned
    10 Post(s)
    Tagged
    0 Thread(s)
    We now have a number of rides on the new belt. I tried to follow the instructions as closely as possible in the installation.

    After a couple of rides, the belt started slipping under heavy pressure. It first did it on the same hill where the first belt broke. At first I wasn't sure that it was in fact the belt skipping, but when it became more frequent, you could see that the captain's crankset was advancing, and at the end of a ride where it skipped multiple times,the captains pedals were about 60 degrees advanced.

    The belt tension was reasonably snug, certainly tighter than you would typically run a timing chain. In talkin with Web Cyclerly they suggested upping the tension, so I tightend the belt pretty much as tight as I could.

    The tightening stopped the skipping, but lead to a substantial amount of noise. So I backed off the tension, noise disappeared, but it skipped again. Right now we're back to very tight, noisy, and no skipping.

    I'm going to try reversing the belt direction as suggested in another thread.

    I'm concerned at this point that the violent skipping under pressure may have damaged the belt (given that they can apparently break from just being rolled on the ring) And the noise level is really not acceptable.

    So for us the belt is an ongoing saga. And I'm beginning to see why Co-Motion does not reccomend retrofitting them.
    You could fall off a cliff and die.
    You could get lost and die.
    You could hit a tree and die.
    OR YOU COULD STAY HOME AND FALL OFF THE COUCH AND DIE.

  2. #27
    Tandem Mountain Climber
    Join Date
    Mar 2007
    Location
    San Mateo, CA
    My Bikes
    Calfee Tandem, Custom CAAD9 BB30, 90 Santana Arriva Tandem, 02 CAAD4 errand bike, 87 Cannondale "Black Lightning"
    Posts
    4,090
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Ever since I tried to put the power down on a belt-drive equipped Strida folding bike, and the thing just skipped like a slipping clutch in a car, I have been skeptical of the belt drive.

    I know it can work, AND I think it's a good idea... but man, everything has to be spot on.

  3. #28
    just another gosling Carbonfiberboy's Avatar
    Join Date
    Feb 2007
    Location
    Everett, WA
    My Bikes
    CoMo Speedster 2003, Trek 5200, CAAD 9, Fred 2004
    Posts
    8,584
    Mentioned
    6 Post(s)
    Tagged
    1 Thread(s)
    The skipping is alarming. I've read that these belts are being used by racing teams, so there must be some trick to it. The Gates website shows a special tensiometer in use, but I don't see it for sale or its cost. It looks very simple and inexpensive, though. By the look of the tensiometer, the distance between centers would effect tension, the greater the distance, the greater the tension. Which wouldn't make any sense if the belts stretched at all. But, since you are skipping teeth, they obviously do stretch! The Gates site instructs to have 1/2" deflection at 10 lbs., but all photos show a belt on a single bike, which is much shorter than a tandem belt. So this is all quite unclear to me.

    I'm friends with a very fast local tandem team, I would call the captain extremely strong, riding passes on a 90" fixie. They just got their newest racing tandem, with carbon belt. I'll talk to them about these issues.

  4. #29
    Senior Member
    Join Date
    Nov 2006
    Posts
    787
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    I was intrigued by the belt and heard many liked it.
    I think this nails it for me. I'm sticking with chains.
    What happens if you are a long from home and have a problem?
    Are you suppposed to carry an extra belt at all times?
    Just doesn't seem very practical.

  5. #30
    Senior Member
    Join Date
    Jun 2008
    Location
    Hamilton, Ontario, Canada
    Posts
    265
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    ^^ It's not *supposed* to be practical. Just profitable.

  6. #31
    pan y agua merlinextraligh's Avatar
    Join Date
    Aug 2005
    Location
    Jacksonville
    My Bikes
    Wilier Zero 7; Merlin Extralight; Co-Motion Robusta; Schwinn Paramount; Motobecane Phantom Cross; Cervelo P2; Motebecane Ti Fly 29er
    Posts
    27,416
    Mentioned
    10 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by jnbrown View Post
    I was intrigued by the belt and heard many liked it.
    I think this nails it for me. I'm sticking with chains.
    What happens if you are a long from home and have a problem?
    Are you suppposed to carry an extra belt at all times?
    Just doesn't seem very practical.
    I still want the thing to work. Also I don't want to be overly negative and discourage others, particularly if my experience is unique, or the result of my installation, or maintenence.

    But personally, I would think twice about retrofitting one again, until there is some more experience out there about their long term results. And also, hopefully allowing the price to drop in the interim.
    You could fall off a cliff and die.
    You could get lost and die.
    You could hit a tree and die.
    OR YOU COULD STAY HOME AND FALL OFF THE COUCH AND DIE.

  7. #32
    Senior Member
    Join Date
    Nov 2006
    Location
    Lafayette, Colorado
    My Bikes
    1998 Co-Motion Co-Pilot
    Posts
    577
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    All hail the early adopters (I'm not one of them). Without them, technology wouldn't advance.

    Gates does market a tensionometer. It treats the belt span like a guitar string. The inputs to the device are the unit mass of the belt (like gm/cm) and the belt span. You then pluck the belt like a guitar string and a microphone on the device listens for the fundemental frequency. This translates into tension. The higher the tension, the higher the frequency.

    These devices aren't cheap (many hundreds of dollars).

    Where I work we use timing belts all the time but mostly for precision motion transfer - not for power transmission. However, Harley Davidson uses timing belts for power transmission on their motorcycles so it is obviously possible. I wonder if the belt was sized correctly for this application.

    I would think that if the belt were slipping, the captain would feel a distinct clunk as the belt slipped one tooth & caught on the next - not a clutch like slip. But for the belt to slip, all the teeth on 180 degrees of wrap around the pulley would have to disengage all at once until the belt teeth advanced one pitch. I think someone would have to watch carefully as the captain pushed hard on the pedals with the bike in a stationary mode.

  8. #33
    pan y agua merlinextraligh's Avatar
    Join Date
    Aug 2005
    Location
    Jacksonville
    My Bikes
    Wilier Zero 7; Merlin Extralight; Co-Motion Robusta; Schwinn Paramount; Motobecane Phantom Cross; Cervelo P2; Motebecane Ti Fly 29er
    Posts
    27,416
    Mentioned
    10 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by oldacura View Post
    I would think that if the belt were slipping, the captain would feel a distinct clunk as the belt slipped one tooth & caught on the next - not a clutch like slip. But for the belt to slip, all the teeth on 180 degrees of wrap around the pulley would have to disengage all at once until the belt teeth advanced one pitch. I think someone would have to watch carefully as the captain pushed hard on the pedals with the bike in a stationary mode.
    It's a hell of a clunk, not a smooth slipping. You can hear it and feel it. Loud enough that people around us go WTF?

    At first I questioned whether something else in the drivetrain was making the noise. However, it doesn't do it when we put the timing chain back on, and you can see where the captain's cranks have advanced after it does it, so I'm pretty certain it was in fact skipping.

    To put this in context, it only does it with a lot of torque being put on the pedals. It happened doing stomp drills (accelerating from 10mph in a 53/12 as hard as you can.) and climbing out of the saddle in the big ring.

    If it were just under the load of doing stomps, I wouldn't be concerned, but racing and competitive group rides, there are going to be times where we're going to be doing short power climbs in the big ring, and skipping in that situation isn't acceptable.
    You could fall off a cliff and die.
    You could get lost and die.
    You could hit a tree and die.
    OR YOU COULD STAY HOME AND FALL OFF THE COUCH AND DIE.

  9. #34
    just another gosling Carbonfiberboy's Avatar
    Join Date
    Feb 2007
    Location
    Everett, WA
    My Bikes
    CoMo Speedster 2003, Trek 5200, CAAD 9, Fred 2004
    Posts
    8,584
    Mentioned
    6 Post(s)
    Tagged
    1 Thread(s)
    Quote Originally Posted by oldacura View Post
    All hail the early adopters (I'm not one of them). Without them, technology wouldn't advance.

    Gates does market a tensionometer. It treats the belt span like a guitar string. The inputs to the device are the unit mass of the belt (like gm/cm) and the belt span. You then pluck the belt like a guitar string and a microphone on the device listens for the fundemental frequency. This translates into tension. The higher the tension, the higher the frequency.

    These devices aren't cheap (many hundreds of dollars).
    <snip>
    Then what is this?
    http://www.carbondrivesystems.com/im...1231907551.pdf

    I don't see any other tensiometers on their website. This one looks very simple and cheap, and as you say of the other device, it also takes span into account.

    And I used to run OS/2 Warp on all my machines.

  10. #35
    Senior Member
    Join Date
    Nov 2006
    Location
    Lafayette, Colorado
    My Bikes
    1998 Co-Motion Co-Pilot
    Posts
    577
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    This is the one we use at work:

    http://www.gates.com/brochure.cfm?br...cation_id=3539

    Again - it treats the belt span as a guitar string that will oscillate at different frequencies based on the belt mass, span & tension. May not be practical for bike owners.

    Increasing the belt tension to prevent it from skipping is probably not a good solution. This will likely increase the friction in the system, cause premature belt wear and/or failure, accelerate BB bearing wear and put a lot of bending force on the bike frame.

    Some belt tooth profiles (curved -vs- trapazoidal) are better for transmitting power. I would assume that Gates and the bike designers would have optimized this already. Since you already have ~20 teeth of engagement on each pulley, it is hard to imagine how one could reduce the skipping problem some other way.

  11. #36
    just another gosling Carbonfiberboy's Avatar
    Join Date
    Feb 2007
    Location
    Everett, WA
    My Bikes
    CoMo Speedster 2003, Trek 5200, CAAD 9, Fred 2004
    Posts
    8,584
    Mentioned
    6 Post(s)
    Tagged
    1 Thread(s)
    My tandem racer friend got back to me with the following:

    "We have about 1100 miles of trouble free use so far. Much of it has been under extreme racing conditions. Our experience so far: quiet, clean, maintainance free, and light weight. It is essentially a smaller version of the kevlar belts they use on Harleys and Buells successfully on their motorcycles. Generally on the motorcycles the belt can last the life of the motorcycle.

    If you are considering the upgrade I would certainly go for it . . ."

  12. #37
    Senior Member
    Join Date
    May 2005
    Posts
    569
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by jnbrown View Post
    I was intrigued by the belt and heard many liked it.
    I think this nails it for me. I'm sticking with chains.
    What happens if you are a long from home and have a problem?
    Are you suppposed to carry an extra belt at all times?
    Just doesn't seem very practical.

    Quote Originally Posted by Carbonfiberboy View Post
    My tandem racer friend got back to me with the following:

    "We have about 1100 miles of trouble free use so far. Much of it has been under extreme racing conditions. Our experience so far: quiet, clean, maintainance free, and light weight. It is essentially a smaller version of the kevlar belts they use on Harleys and Buells successfully on their motorcycles. Generally on the motorcycles the belt can last the life of the motorcycle.

    If you are considering the upgrade I would certainly go for it . . ."
    Maybe they are not designed to break unless damage and we are too used to having chains that break every so often. I don't think people on motorcycles carry an extra belt.

    However, if the belts last the life of a motorcycle, why does Gates say they "only" last twice the life of a bike chain?

  13. #38
    Senior Member
    Join Date
    Jun 2005
    Posts
    274
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    You may be surprised by the amount of torque a heavy bike rider can exert on a drive train while standing and putting all the force they can into the pedals. It's more than a Harley, and may rival a V8 car. Don't ask me to prove it, but this was argued out on rec bikes tech years ago and the concensus was stunning. Small chain rings increase the burden.
    no signature

  14. #39
    Senior Member
    Join Date
    Nov 2006
    Location
    Lafayette, Colorado
    My Bikes
    1998 Co-Motion Co-Pilot
    Posts
    577
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    I don't see how even the strongest rider could develop as much torque as a V8 car engine.

    Conservatively, a V8 can develop 300 lb*ft of torque. A 175mm crank arm on a bike is .57 ft long.

    300 lb*ft/.57 ft = 526 lbs. I don't see how any rider could apply that much force to the pedals and if they could, many things on the bike would fail.

    If a bike were designed to withstand that much torque, you wouldn't want to ride it - it would be far too heavy.

  15. #40
    Senior Member
    Join Date
    Oct 2007
    Location
    SoCal
    Posts
    1,144
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    I'm at 195lbs. and if you drop me from .57 ft. and I land on one foot how much weight is the impact point?

  16. #41
    pan y agua merlinextraligh's Avatar
    Join Date
    Aug 2005
    Location
    Jacksonville
    My Bikes
    Wilier Zero 7; Merlin Extralight; Co-Motion Robusta; Schwinn Paramount; Motobecane Phantom Cross; Cervelo P2; Motebecane Ti Fly 29er
    Posts
    27,416
    Mentioned
    10 Post(s)
    Tagged
    0 Thread(s)
    FWIW,

    I went back and looked at a couple of old Powertap files from races, on my single bike. The highest tourque I saw was 1633 lb/in. Converting that to foot pounds yields 136 foot pounds of torque.

    I'm betting that when we broke the belt we were putting out more torque than that because we were in a very big gear, on a steep grade, and pretty much giving it 100% to keep the pedals turning over.

    Nonetheless, I don't think it would have broken without some preexisting damge in the installation.
    You could fall off a cliff and die.
    You could get lost and die.
    You could hit a tree and die.
    OR YOU COULD STAY HOME AND FALL OFF THE COUCH AND DIE.

  17. #42
    Senior Member
    Join Date
    Nov 2006
    Location
    Lafayette, Colorado
    My Bikes
    1998 Co-Motion Co-Pilot
    Posts
    577
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    dvs - torque = force x distance from the axis of rotation - not weight x the height of the drop.

    The only way you could increase the force put on the pedals above your weight would be to pull down on the bars. Then maybe you could briefly apply 150% or so of your weight.

  18. #43
    Senior Member
    Join Date
    Jun 2005
    Posts
    274
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    The number I remember was about 200 ft lbs on a mtb crank with a 22 tooth ring. I suspect a 200 pound rider could exert over 400 pounds of force on a pedal by collapsing wieght, extending the driving leg, pulling up on the other side, and pulling up on the bars.

    In any event, its more than a Harley can develop. Too bad we are limited to such low RPM's.

    EDIT I just googled and I saw the torque rating on a Harley is 81 ft/lb's.

    Another edit- I had a 5.0 high performance Mustang, which was a very fast car. It was rated at 300 ft/lbs of torque.

    This whole discussion on rec bikes tech came about over a discussion of chains breaking more often on mtb's compared to road bikes. The small chainrings allow cyclists to test the limits of chains
    Last edited by dfcas; 07-27-09 at 11:41 AM.
    no signature

  19. #44
    Senior Member rdtompki's Avatar
    Join Date
    Nov 2008
    Location
    Hollister, CA
    My Bikes
    Volagi, daVinci Joint Venture
    Posts
    3,963
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    The Harley belt is considerably wider than the Gates tandem timing belt and I would think the alignment of the motorcycle belt to be essentially perfect so a comparison of the torque doesn't necessarily go to the heart of the problem, but does emphasize the load on these belts.

    Does anyone have information as to Gates intended market for this product? Someone had earlier mentioned that a version of belt drive was appearing on lower end, cruiser bicycles. Tandem applications will range from cruiser types to racers and it's possible the stress on the belt over this range of applications would vary by a significant factor. Has Gates really designed this product (belt plus hardware) for the severe application represented by really strong go-fast tandem teams?
    Rick T
    --------
    Volagi - Triple"ized" and Tubeless
    daVinci Joint Venture

  20. #45
    pan y agua merlinextraligh's Avatar
    Join Date
    Aug 2005
    Location
    Jacksonville
    My Bikes
    Wilier Zero 7; Merlin Extralight; Co-Motion Robusta; Schwinn Paramount; Motobecane Phantom Cross; Cervelo P2; Motebecane Ti Fly 29er
    Posts
    27,416
    Mentioned
    10 Post(s)
    Tagged
    0 Thread(s)
    ^ They were being raced in the Co-Motion Classic Tandem Race last year, apparently without any problems.
    You could fall off a cliff and die.
    You could get lost and die.
    You could hit a tree and die.
    OR YOU COULD STAY HOME AND FALL OFF THE COUCH AND DIE.

  21. #46
    Certifiable Bike "Expert"
    Join Date
    May 2005
    Posts
    5,632
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    You armchair physicists are confused if you are comparing crankshaft torque on a motorcycle with crank torque on a bike.

    IF you wanted to make a comparison (engineering by analogy is an awfully imprecise science!), you should compare belt tension on the bicycle vs. belt tension on the moto. Ignoring preload, belt tension on the motorcycle will come from crankshaft torque multiplied by transmission gear reduction and divided by output pulley radius. But it seems like a totally pointless comparison.
    I don't even use the offensive term "Fred." -- Sheldon "All Cyclists Are My Friends" Brown (1944-2008)

  22. #47
    pan y agua merlinextraligh's Avatar
    Join Date
    Aug 2005
    Location
    Jacksonville
    My Bikes
    Wilier Zero 7; Merlin Extralight; Co-Motion Robusta; Schwinn Paramount; Motobecane Phantom Cross; Cervelo P2; Motebecane Ti Fly 29er
    Posts
    27,416
    Mentioned
    10 Post(s)
    Tagged
    0 Thread(s)
    Just to update how the belt is working, after playing around with the tension, we've gotten to the point where it is basically quiet, with occassionally a little noise, and we can't make it skip.

    Now, my question is whether when it was skipping it damaged the belt. Gate's literature says that skipping can break the carbon fibers, so I'm pretty sure I know what they're going to say when I talk to them.
    You could fall off a cliff and die.
    You could get lost and die.
    You could hit a tree and die.
    OR YOU COULD STAY HOME AND FALL OFF THE COUCH AND DIE.

  23. #48
    hors category TandemGeek's Avatar
    Join Date
    Jan 2002
    Posts
    7,162
    Mentioned
    0 Post(s)
    Tagged
    1 Thread(s)
    Quote Originally Posted by merlinextraligh View Post
    I'm pretty sure I know what they're going to say when I talk to them.
    No Belt For You!!! Come back one year...


  24. #49
    Senior Member
    Join Date
    Nov 2006
    Location
    Lafayette, Colorado
    My Bikes
    1998 Co-Motion Co-Pilot
    Posts
    577
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    The smaller the pulley (or chainring), the higher the tensile load on the belt (or chain) for a given force input by the rider.

    If a rider can exert 200# (at 3 o'clock) on a 175mm crank arm, the belt (or chain) will see about 577 pounds on a 30 tooth (~61mm radius) chainring.

  25. #50
    Senior Member
    Join Date
    Nov 2006
    Location
    Lafayette, Colorado
    My Bikes
    1998 Co-Motion Co-Pilot
    Posts
    577
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    If the noise were caused by the belt momentarily coming out of engagement with the pulley teeth - either by overload or by friction with the flanges or something else, the belt path would also momentarily (and periodically) be increased - stretching the belt. This could very easily break the tensile cords - espeacially if the stretch were not uniform along the length of the belt.

    It would make me very wary of standing up. Sounds like you were lucky that you weren't badly hurt the 1st time.

Page 2 of 3 FirstFirst 123 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •