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-   -   Right-side timing chain (http://www.bikeforums.net/tandem-cycling/930231-right-side-timing-chain.html)

LongVehicle 01-17-14 11:22 AM

Right-side timing chain
 
Full of questions today... Is anyone using single bike triple cranks front and rear and using the inner most ring as the timing gear? As everyone probably knows, Stages has come out with a crank arm based power unit, but the only works on the non-drive side and is only available for a select listing of cranksets. One available set up if for the Shimano 6700 series, and I am wondering if you could swap the 6700/6750 right arm for a 6703 and use the inner ring for timing? Dumb idea, probably, but the Stages units seem to be the most cost effective option for collecting individualized power readings.
Thank you

Bezalel 01-17-14 12:45 PM

The 6703 spider is a double and it uses a triplizer middle ring so you can't mount the inner ring without the middle one. Regarding the crank arm, the 6700 and 6703 use the same left crank arm.

The Garmin Vector looks better but it costs almost twice as much (but it measures both legs).

waynesulak 01-17-14 02:40 PM

Very possible to set up and some here have it. I would avoid any nonstandard crank with BCDs other than 130mm, 110mm and 74mm. Lots of triple cranks out there that do not tie you to one manufacturer.

fietsbob 01-17-14 03:32 PM

Rohloff Rear Hub , and you only need a double crank on the right side.. single up front.

Chris_W 01-17-14 05:24 PM

We're using a pair of 5603 single-bike triple cranks on our tandem. We have 26-42 in the inner and middle drive rings and a CDX belt drive in the outer ring position for the timing drive. The 5603 cranks have slightly more clearance behind the crank-arm for the belt ring, which is why I got those instead of the newer 5703, but if you're running a chain instead of a belt then this difference wouldn't matter. As mentioned above, 6703 uses an odd mounting and BCD for the inner ring, so I would avoid it. Stages cranks are available for the 5703 cranks, one of their cheapest options, and the left-hand crank mounting interface is the same on many Shimano cranks (at least it is for 66xx, 56xx, 57xx, probably 67xx and others), so it would be pretty universal and easy to switch between bikes; only the styling and finishing differs between the models - I've been considering getting one of their LH cranks for my single bike.

merlinextraligh 01-20-14 07:10 AM

Quote:

Originally Posted by Bezalel (Post 16419214)
The 6703 spider is a double and it uses a triplizer middle ring so you can't mount the inner ring without the middle one. Regarding the crank arm, the 6700 and 6703 use the same left crank arm.

The Garmin Vector looks better but it costs almost twice as much (but it measures both legs).

I've been using Vector on the Captain's crank for about 3 months now. Other than a couple of setup glitches, it's worked fine. I can't see any difference in the data from the Quarq on my single bike.

The Stages Power meter is supposed to be improved with its second generation of software ( see DCrainmakers review).

I'd prefer the garmin over the Stages because:

1) Vector appears to be a more mature product from a mature company, wheras Stages is a startup. Virtually every new power meter design released has had some initial problems. All the testing and delays Garmin went through bringing Vector to market gives them an edge in that department;

2) Vector gives you actual power from both legs, not an extrapolation from 1 leg.

Obviously cost is an issue, but if you're going to have to make changes in the drivetrain to utilize a Stages crank, the cost savings get smaller.

LongVehicle 01-20-14 10:03 AM

Sorry, I didn't know the 6700 was a change over what I currently use (2000ish Ultegra tandem cranks of unknown numerology).

As for the Vectors, they were an option, but being blind I couldn't get my head unit through the calibration process every time I sneeze on the units. Plus, while Garmin swears up and down that you can't strike when your pilot enters a corner inside pedal down, they won't warranty the repairs when your pilot starts pedaling on the upside of a curb while you are still on the down side (shoud have opted for the set of wheels I wanted).

Thanks for your input.

LongVehicle 01-20-14 10:06 AM

Can't give up my DI2, so I need (like an addiction) my FD.

LongVehicle 01-20-14 10:14 AM

A 26/36 low gear on my tandem??? I could bike the north face of the Eiger... Used to live in the Lauterbrunnen/Wegen area. Loved the climb to Grindelwald when the tourists weren't hammering the road.

This area doesn't quite hav those climbs, I (and my pilots) would hate to lose the 53/11 high gear, but your solution is under consideration for a tandem cyclocross bike.

"A train pass and no car..." Ah, we miss those days!

LongVehicle 01-20-14 10:36 AM

While I generally like Garmin products, and normally tech support is top notch, they wouldn't cover my Vectors after a pedal strike climbing a curb (while the pod won't hit the ground in a corner, it can with an inexperienced pilot climbing a hefty curb). Plus, to get both pilot and stoker power, I would need two Vector units... I like the Stages because (1) I can use whatever pedals I like including my road and CX shoes; (2) Pedals wear out, where as I've never personally worn out a crank arm, there could be a longevity issue over time; and (3) As I mentioned before, the "spin backwards," "enter your crankarm length" setup it seemed to need every time the wind blew not being, and never will be, blind accessible on Garmin headunits wasn't worth the hype I fell for. While Stages is up and coming, the design is simple (yes, it extrapolates from one leg, but I can live with that), have already been picked up by Sky racing. Inside scoop is that they are seriously considering tandem options (they've had far more inquires for tandem applications than for track bike options), possibly when they can catch up on current demand. I think that by time they get there, there will be far fewer bugs.

merlinextraligh 01-20-14 11:39 AM

Quote:

Originally Posted by LongVehicle (Post 16425737)
As for the Vectors, they were an option, but being blind I couldn't get my head unit through the calibration process every time I sneeze on the units. Plus, while Garmin swears up and down that you can't strike when your pilot enters a corner inside pedal down, they won't warranty the repairs when your pilot starts pedaling on the upside of a curb while you are still on the down side (shoud have opted for the set of wheels I wanted).

Not to argue with your choice of power meters, but just to put out some more data points for anyone else considering Vectors.

As for calibration to the head unit, there are acouple of related concepts here. Just getting the Vector initially calibrated isn't a big deal. It took me awhile, mostly because the documentation is for a Garmin 810, and I was using an 800 and had to do a firmware update.

It's only a one time process to get it set up with the head unit. Once the intial setup is done, all you have to do to calibrate it for future rides is set the zero offset, which happens automatically when you pedal backwards 4 revolutions. That can't be anymore difficult than setting the zero offset for a stages power meter at the beginning of a ride.

The more complicated issue of calibration is determing the slope of the power meter is correct. Here Vector has an advantage over Stages. You can test to see the slope is correct and the unit is reading accurately by doing a static torque test with a known weight. My understanding is Stages does not currently allow for a static torque test.

Admittedly most users will never calibrate slope, so it doesn't much matter, but all said ease of calibration is a Vector advantage, not a weakness.

As for banging the pod unit, 3 months in it hasn't been an issue. We ride pretty aggressively (we've raced crits on the tandem) and I can tell you from experience, you can bang a pedal on the pavement without touching the pod to the ground.

I don't get the curb issue, unless your riding the bike over curbs which doesn't seem to be a good idea anyway. You can bang the pod on curbs moving the bike with you off it, such as leaning the bike on a sidewalk curb to hold it up. We've done it, without any damage. Also, the pod is replaceable, so if you broke one pod, its not like you're out the price of the whole system.

LongVehicle 01-20-14 12:23 PM

Every time I swapped the Vectors between bikes, which was one reason why I wanted them in the first place, I had to get someone to go through the whole set up over again. Even zeroing it out was difficult and required sighted assistance because my headunit(s) didn't audibly alert as to when to perform the reverse rotation, and the timing was not consistant.

As for the curb strikes, yes it was while riding. My CX pilot and I pull this off all the time, and the "new" pilot who is typically a mountain biker got the front wheel up just fine, then started pedaling before I cleared causingthe strike. The impact actually smashed (not just broke, but nearly pulverized) the pod, bent the spindle, and cracked the carbon sole of my shoe. Luckly the landing zone was grass 'cause it wasn't pretty (the landing). Otherwise, while I'm sure they work, they just aren't blind accessible.

merlinextraligh 01-20-14 01:16 PM

I agree that they're not all that easy to switch between bikes. They're slightly more involved to install than a pedal; you've got to use a torque wrench to get the torque right, and you've got to calibrate.

I would not recommend to anyone buying Vectors for the purpose of being able to swap them between bikes. Its quicker and easier to swap a Quarq or a SRM than it is to swap Vectors. I used to swap my Quarq from road bike to TT bike. It's a 3 minute job, and can be done easily between stages in a stage race when road stage and the tt stage are close together.

As for bashing the pods doing cyclocross or Mountain biking, your experience definitely would indicate that Vector may not be a great choice for those uses, and that certainly makes sense.

I do think there's a pretty good case that they're the best option right now for a tandem, albeit a pricey one.

Chris_W 01-21-14 02:04 AM

Quote:

Originally Posted by merlinextraligh (Post 16426255)
They're slightly more involved to install than a pedal; you've got to use a torque wrench to get the torque right, and you've got to calibrate.

Our local importer did some tests using different torque levels for tightening the Vectors. Apparently they found that as long the two pedals were torqued roughly evenly, the exact level of torque was not very important once it was above a certain level. He recommends torquing a bit more than for a regular pedal, using about the same torque on both sides, but beyond that not worrying about being too precise because in all of their tests they could find no difference in performance.

jleslie 01-21-14 05:09 PM

We just picked up a used 2008 Trek T2000 that is set up single side drive with Ultegra 10 spd., though not 6700. The timing chain is on the inner ring which is a 39, and then the drive is set up as a 53/39 double on the outer two, with a 11/32 XO cassette. Both crank sets are single bike cranks. Whole bike weighs 32 lbs.


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