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Tandem Cycling A bicycle built for two. Want to find out more about this wonderful world of tandems? Check out this forum to talk with other tandem enthusiasts. Captains and stokers welcome!

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Old 03-09-13, 12:58 PM   #26
VeganGraham
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I've got a Centre Track system on a solo mountain bike.
The Gates app is only for Iphone.
The ContiTech one for Android does pretty much the same thing.
https://play.google.com/store/apps/d...ptg.Tension2Go
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Old 03-09-13, 02:22 PM   #27
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For a low tech player, 83hz is pretty much Low E. Or, you can easily find a free tone player online and save the 83hz output.
An even lower tech test is the 1/2" belt deflection with a 10lb weight placed in the middle of the span.
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Old 03-09-13, 03:26 PM   #28
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okay, thanks. I'll check it out..
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Old 03-09-13, 05:43 PM   #29
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Recomended tension is about 60psi, down from gates original recommendation of 80psi. At those tensions the belt can not skip under any cyclist imposed load.

The original CDC sprockets came in both anodized and carbide anodized. There is no indication which one might have. Turned out we had the carbide anodized and had 15,000 miles on it with no sign of wear. We are in Colorado with dry, dust free riding for the most part. Others with the normal anodizing saw wear within 5,000 miles. Our carbide equipped bike in now owned by a WY team and I have not kept track of the miles since.

We now have a new bike with CDX front sprocket, CDC rear sprocket and I do not have data on whether the CDX has been carbide anodized. Why we have CDC rear is that the belt is on the right on a V2R Paketa designed for this installation, and the clearance in the back is very tight. So tight that because the DCX does not have that shallow recess normally in the face for the sprocket/ring, the bolt is 1mm closer to the frame and does not clear. Paketa is working on Gates to include that bolt recess in the face of the CDX as they do on the CDC. A couple picture below.

For alignment, it is worth noting that the construction of the belt is done on about a 4' wide drum with the carbon strands wound spiral from one end to the other. As each belt is cut it inherits a slight angle withint the threads of the belt. As a result, you may find that a well aligned belt still wanders off a CDC system. You might try flipping the belt 180 degrees / reversing the rotation of the belt.

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Old 03-09-13, 07:25 PM   #30
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Recomended tension is about 60psi, down from gates original recommendation of 80psi. At those tensions the belt can not skip under any cyclist imposed load.

The original CDC sprockets came in both anodized and carbide anodized. There is no indication which one might have. Turned out we had the carbide anodized and had 15,000 miles on it with no sign of wear. We are in Colorado with dry, dust free riding for the most part. Others with the normal anodizing saw wear within 5,000 miles. Our carbide equipped bike in now owned by a WY team and I have not kept track of the miles since.

We now have a new bike with CDX front sprocket, CDC rear sprocket and I do not have data on whether the CDX has been carbide anodized. Why we have CDC rear is that the belt is on the right on a V2R Paketa designed for this installation, and the clearance in the back is very tight. So tight that because the DCX does not have that shallow recess normally in the face for the sprocket/ring, the bolt is 1mm closer to the frame and does not clear. Paketa is working on Gates to include that bolt recess in the face of the CDX as they do on the CDC. A couple picture below.

For alignment, it is worth noting that the construction of the belt is done on about a 4' wide drum with the carbon strands wound spiral from one end to the other. As each belt is cut it inherits a slight angle withint the threads of the belt. As a result, you may find that a well aligned belt still wanders off a CDC system. You might try flipping the belt 180 degrees / reversing the rotation of the belt.
Just curious. Would there be any point in doing this every few years to even out any potential wear on the belt (like rotating car tires?). I'm not sure where or how these things wear out but flipping the belt would reverse which side of the belt teeth is engaging the sprocket.
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Old 03-09-13, 07:29 PM   #31
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yes, very true. Flipping the belt starts a new wear surface
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Old 03-10-13, 09:45 AM   #32
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I used the app and it just seems way to tight.
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Old 03-10-13, 09:57 AM   #33
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Recomended tension is about 60psi, down from gates original recommendation of 80psi. At those tensions the belt can not skip under any cyclist imposed load.

The original CDC sprockets came in both anodized and carbide anodized. There is no indication which one might have. Turned out we had the carbide anodized and had 15,000 miles on it with no sign of wear. We are in Colorado with dry, dust free riding for the most part. Others with the normal anodizing saw wear within 5,000 miles. Our carbide equipped bike in now owned by a WY team and I have not kept track of the miles since.

We now have a new bike with CDX front sprocket, CDC rear sprocket and I do not have data on whether the CDX has been carbide anodized. Why we have CDC rear is that the belt is on the right on a V2R Paketa designed for this installation, and the clearance in the back is very tight. So tight that because the DCX does not have that shallow recess normally in the face for the sprocket/ring, the bolt is 1mm closer to the frame and does not clear. Paketa is working on Gates to include that bolt recess in the face of the CDX as they do on the CDC. A couple picture below.

For alignment, it is worth noting that the construction of the belt is done on about a 4' wide drum with the carbon strands wound spiral from one end to the other. As each belt is cut it inherits a slight angle withint the threads of the belt. As a result, you may find that a well aligned belt still wanders off a CDC system. You might try flipping the belt 180 degrees / reversing the rotation of the belt.

Interesting solution. I never would have thought that the CT belt was compatible with the old CDC rings.

I imagine you considered each of these, so maybe you could comment on them and why they didn't work out:
- drill your own bolt recesses in the CDX ring
- look for chainring bolts that have a flatter/thinner head
- spacing the Lightning cranks differently to provide a bit more clearance room on the drive side

Last edited by twocicle; 03-10-13 at 10:06 AM.
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Old 03-10-13, 10:02 AM   #34
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I used the app and it just seems way to tight.
It is tempting to do a test ride at some point to find the loosest setting the belt can run without skipping. Assuming loose = best, all things being considered like BB wear and friction.

We are currently running the CT belt with more like 1" deflection rather than 1/2" and it is working just fine at that looser tension. Our setup is using a more standard crossover/timing ring configuration with the 2012 Ultegra R601/603 tandem cranks. So far, we have not detected any flex in our new S&S Calfee frame, so having a super stable inter-BB span may aid in maintaining tension uniformity under load.

With the belt being perfectly quiet and no vibration as I always felt with tha timing chain, our impression of the Gates CT is very much thumbs up. Bonus I don't have to clean or oil the sucker either

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Old 03-10-13, 10:35 AM   #35
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Twocicle, I also backed mine off to about what you set yours at and I think I'm happier with that tension. But the real test will be when we get out on the road with it.
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Old 03-10-13, 12:19 PM   #36
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Twocicle, I also backed mine off to about what you set yours at and I think I'm happier with that tension. But the real test will be when we get out on the road with it.
I see you mounted the ring on the inside of the spider. To do that on our setup would require cheating the crank spacing to the timing side, and the drive side chainline would have suffered. With the chainline set at 50mm, there wasn't enough room for mounting the CDX ring on the inside. On the front, I added 2mm chainring spacers (and 9mm bolts) to move the ring further out and align it with the rear, without requiring offsetting the captain's cranks to the timing side.

Pretty nice & new cranks there I can't tell if it's the carbon weave or protective tape in your photo. If they don't have some kind of "frame-saver" tape on the crank arms yet, you might want to add that to keep scuffs off. I use: ISC Helicopter-OG Surface Guard Tape (8 mil Outdoor Grade)

Last edited by twocicle; 03-10-13 at 09:44 PM.
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Old 03-10-13, 09:09 PM   #37
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I used the app and it just seems way to tight.
pushing the middle of the belt down should be no more than 1/2" deflection under pretty good force. Yes, very tight. For the teeth to interact with the sprocket correctly it needs to be tight. If the teeth squirm up in the sproket they wear incorrectly. The teeth of the belt are not meant to ride high on the sproket as they would under low tension.

Reducing the tension does not help. The tension from the captains pedal stroke is higher than 60psi, so you are not really inducing any more load on the frame by running the belt at the proper tension.

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Old 03-10-13, 09:56 PM   #38
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pushing the middle of the belt down should be no more than 1/2" deflection under pretty good force. Yes, very tight. For the teeth to interact with the sprocket correctly it needs to be tight. If the teeth squirm up in the sproket they wear incorrectly. The teeth of the belt are not meant to ride high on the sproket as they would under low tension.

Reducing the tension does not help. The tension from the captains pedal stroke is higher than 60psi, so you are not really inducing any more load on the frame by running the belt at the proper tension.
The belt teeth and ring sprockets are quite different between the new CDX and the earlier CDC. The CDC does not work well at all when the belt tension was not tight up to spec, whereas the new system does appear to work fine with less. This seems to indicate a substantial tollerance difference between the two systems. We aren't talking about running with a very loose CT belt to the point where it is sagging - which would be extreme, but suggesting that a little less than spec may be sufficient and perhaps preferable to getting it too tight which would induce excess wear on other components.

Do you have photos, data or other information that proves the CT/CDX system would wear improperly when less tension is used?
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Old 03-11-13, 03:24 AM   #39
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For a low tech player, 83hz is pretty much Low E. Or, you can easily find a free tone player online and save the 83hz output.
An even lower tech test is the 1/2" belt deflection with a 10lb weight placed in the middle of the span.
The Gates Belt App calls for 60-65hz, where did you see 83hz as a setting?
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Old 03-11-13, 09:11 AM   #40
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The Gates Belt App calls for 60-65hz, where did you see 83hz as a setting?
According to the following doc, 60-65hz is for "a Lightweight Speedster". Does your team fall into that category?
see: http://www.carbondrivesystems.com/im...endations1.pdf

Also, from the Gates FAQ section, they indicate approximately 1/2" deflection with 5-10lbs of force. To me this indicates there is a window of tollerance. Absent sufficient reason otherwise, I choose to run on the "less force" side.
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How much tension is needed, and how do I know when I have enough?

The best way to tension the Carbon Drive belt is to use our tension gauge. If you don’t have a gauge, you can use the “force/deflection” method. Press down in the center of the belt span. The belt should move approximately inch with 5-10 lbs of force.
...
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Old 03-11-13, 09:25 AM   #41
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According to the following doc, 60-65hz is for "a Lightweight Speedster". Does your team fall into that catagory?
The app has the same catagories listed, but also lists a tandem catagory:

Tandem Drives
Lightweight Speedster: 60hz
Big and Powerful: 65hz
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Old 03-11-13, 09:56 AM   #42
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The app has the same catagories listed, but also lists a tandem catagory:

Tandem Drives
Lightweight Speedster: 60hz
Big and Powerful: 65hz
What isn't clear from the Nov/11 doc I cited, is whether or not the CDC and newer CDX systems have different tensioning ranges. That doc is from Nov/11 which means it predates the CDX system.

I picked up the phone and called Gates (720-524-7206)... again, to discuss all this with their tech guy "Ian". Unfortunately they do not have any docs or FAQS discussing the possible installation differences between the CDX vs CDC (the latter may require the higher tension to prevent the belt from walking), or between single bikes vs tandem setups.

Ian confirmed that although the CDX/CT system can be tensioned up to 85hz (even higher than 83hz), there is no requirement to do so. He also confirmed that "less tension is always better because there is less friction", and that there is no wear issue that would be caused by running a looser tension - logically the reverse would be true.

Final recommendation point is to run the system just tight enough to prevent the belt from slipping/jumping sprocket teeth.
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Old 03-11-13, 12:12 PM   #43
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What isn't clear from the Nov/11 doc I cited, is whether or not the CDC and newer CDX systems have different tensioning ranges. That doc is from Nov/11 which means it predates the CDX system.

I picked up the phone and called Gates (720-524-7206)... again, to discuss all this with their tech guy "Ian". Unfortunately they do not have any docs or FAQS discussing the possible installation differences between the CDX vs CDC (the latter may require the higher tension to prevent the belt from walking), or between single bikes vs tandem setups.

Ian confirmed that although the CDX/CT system can be tensioned up to 85hz (even higher than 83hz), there is no requirement to do so. He also confirmed that "less tension is always better because there is less friction", and that there is no wear issue that would be caused by running a looser tension - logically the reverse would be true.

Final recommendation point is to run the system just tight enough to prevent the belt from slipping/jumping sprocket teeth.
I just got off of the phone with the Sales guy, Steve, who I bought my system from. His comment is that twocicle may have loosely interpreted what Ian said. The issue is that if you do run the belt too loose and it skips, you can damage the fiber in the belts. He said there is not a good reason to run the belt loose. So there you have it! LOL I will run mine at around 50hz.

Wayne
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Old 03-11-13, 01:28 PM   #44
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I just got off of the phone with the Sales guy, Steve, who I bought my system from. His comment is that twocicle may have loosely interpreted what Ian said. The issue is that if you do run the belt too loose and it skips, you can damage the fiber in the belts. He said there is not a good reason to run the belt loose. So there you have it! LOL I will run mine at around 50hz.

Wayne
My post here was not a lame interpretation of the earlier conversation and although I do not have an actual transcript it pretty much quoted what was said on that call. FWIW, my wife sitting in the same room heard the entire thing too.

Perhaps Steve misinterpreted what I said, or didn't actually participate in the call (bingo!). Nobody said to run the belt so loose that it would skip, but that it may not be necessary to run it at the top end of the tension specification. If Gates is worried people will start riding around with floppy loose belts and poke their eye out (A Christmas Story), then that is quite laughable.

50hz sounds (pun) about right, Wayne. Glad you got the gist of it, unlike Steve.

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Old 03-11-13, 01:51 PM   #45
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My post here was not a lame interpretation of the earlier conversation and although I do not have an actual transcript it pretty much quoted what was said on that call. FWIW, my wife sitting in the same room heard the entire thing too.

Perhaps Steve misinterpreted what I said, or didn't actually participate in the call (bingo!). Nobody said to run the belt so loose that it would skip, but that it may not be necessary to run it at the top end of the tension specification. If Gates is worried people will start riding around with floppy loose belts and poke their eye out (A Christmas Story), then that is quite laughable.

50hz sounds (pun) about right, Wayne. Glad you got the gist of it, unlike Steve.
You know how sales guys can be! LOL
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Old 03-11-13, 04:26 PM   #46
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Hitting the 60-65 Hz range is not so easy when you're on tour, reassembling the bike in a coach parking lot or beside a grass airstrip, and don't have a nice pin spanner to rotate the eccentric precisely, and are instead relying on the needle-nose pliers from a Leatherman multi-tool braced against the crank (which I became quite adept at). In addition, the tension varies a little with the position of the two cranks since the belt rings are not perfectly centered on the crank axles, which for us results in a variation of about 5 to 8 Hz between the loosest and tightest spots in the cranks' rotation.

Therefore, if there is no point in the crank rotation that gives a reading below 50 Hz or above 65 Hz, then I am happy enough, and I lock it in place there (hopefully, as long as I remember this final step). So I'd certainly agree on the guidelines that others above have given.
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Old 03-11-13, 08:04 PM   #47
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Hitting the 60-65 Hz range is not so easy when you're on tour, reassembling the bike in a coach parking lot or beside a grass airstrip, and don't have a nice pin spanner to rotate the eccentric precisely, and are instead relying on the needle-nose pliers from a Leatherman multi-tool braced against the crank (which I became quite adept at). In addition, the tension varies a little with the position of the two cranks since the belt rings are not perfectly centered on the crank axles, which for us results in a variation of about 5 to 8 Hz between the loosest and tightest spots in the cranks' rotation.

Therefore, if there is no point in the crank rotation that gives a reading below 50 Hz or above 65 Hz, then I am happy enough, and I lock it in place there (hopefully, as long as I remember this final step). So I'd certainly agree on the guidelines that others above have given.
Perhaps some of the schwagoholics here might consider bagging a titanium mouth harp (PC name) if one were available in the correct pitch to use as a belt tuning aid. Having a Ti harp in your seatbag would be oh so cool. Gates, you missed out on selling at least one of those trinkets. LOL.
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Old 03-11-13, 10:11 PM   #48
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I imagine you considered each of these, so maybe you could comment on them and why they didn't work out:
- drill your own bolt recesses in the CDX ring
- look for chainring bolts that have a flatter/thinner head
- spacing the Lightning cranks differently to provide a bit more clearance room on the drive side
A recess could be drilled. Pretty touchy work to get the recess centered on the existing holes. We have a shop that could do it. But in the mean time, odd that Gates included them on the CDC and not on the CDX. There is no real down side to the CDC on the rear.

The chain ring bolts are a specialty item, very long to get this configuration. I didn't procure them, but I suspect options are limited in this length. If I could those bolts would be ti, but they are not available in the length needed.

I did not do the assembly, but I know Dave worked the configuration over and over again including shim options with the Lightning cranks. He was not happy with any of those configurations. He's thinking about chain line as well as keeping the belt center close to the bottom tube center which makes the tandem ride more stiff/responsive.

For now, the solution is to use the CDC ring. For the day when CDC rings are no longer supported or available, we'll have to work another solution. Gates says they will continue to support and manufacture the CDC, but in case not there are solutions as you suggest.
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Old 03-12-13, 09:59 AM   #49
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Makes sense. I agree it seems odd Gates did not provide bolt recesses in these new rings.

I looked at putting our rear CDX ring on the inside of the spider, but that would leave only about 1mm clearance to the chainstay with the belt on. That is a bit too close for my comfort level and I didn't want to mess up the chainline by shifting the rear Ultegra cranks more to the timing side. These cranks have a fairly low Q-factor (159mm), but along with that comes less wiggle room for spacers, etc. So, I stayed with outboard ring mountings for now, until I come up with something better.
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Old 03-12-13, 01:21 PM   #50
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I looked at putting our rear CDX ring on the inside of the spider, but that would leave only about 1mm clearance to the chainstay with the belt on.
If you go with the inboard mounting you will gain some stiffeness / responsiveness in the frame bottom tube. The closer to the centerline of the frame the less bending stresses are induced. If you have only 1mm, the sprocket and axle do deflect a bit so it is tight. I would put one of those clear 8mm protective film/dots on the stay right where the belt might rub, just in case.

PS. When I used the term "inboard" in prior posts to refer to our bike, that is to mean inboard of the chain rings. A few makers have attempeted a belt installation outboard of the chain rings, but this induces so much bending in the frame so far from the center line. Better to put the belt on the left than to put it outboard of the chainrings on the right.
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