Turbotandem

NEAT tool!
If I enter our Old La Honda HC, 390W, 280# riders, 23# bike, 17# gear-water-shoes-etc. 3.0 mi climb at 8.1%, it comes right out at our sub-26 minute time. And compare that to a chain tandem at 1W more power considering the belt is NOT at 80 psi, and 100g heavier for chain, I'd save 2 seconds (a full 2w loss comes to 6 seconds). 1/10th to 3/10ths of 1% saved. I think I would call that vanishingly small. Maybe not equal to 50g, but equal to the gains in responsiveness of the belt when we stand, and far less than, say, a good pair of cycling shoes or tires. We agree, the report is making much ado about nothing.

waynesulak

Since we rarely coast that would be 2 watts on 95+% plus of our ride not only while climbing. Purely insignificant when dealing with motorcycles due to the large amount of power available. If either the belt or chain could be conclusively shown to save us 2% I would use that system to gain that 2%. This like most of what we discuss here about tires, inflation ect. is probably to small to really matter but heh that is what we worry about.

Points on cleanliness are a valid and there the belt has a clear advantage.

It would seem to me that the more responsive feeling of the belt is due to tension. I have tried running a chain at higher tension and it felt very responsive with a locked in feeling with the stoker. I would expect that if a belt was run a normal chain tensions so as to be most efficient, it would loose the edge in responsiveness. I know if the chain is preloaded with tension then I cannot stretch the chain any additional amount.

Turbotandem

The things we worry about...
The belt is carbon and has little or no stretch. It feels more like ceramic than a belt. I believe chain and belt both have negligible stretch under load, although the chain stretches over time and the belt does not.
A belt run at 40 to 60 psi per more recent recommendations and on a 69t sprocket will not unload the bottom as the report postulates, and at 40-60psi it will reduce the results from the friction labs report down from 2 watts in 200w to, say, 1w in 200w. Or in my case, 1W in 300-400w considering the team output. I also conclude from the report that loads in the belt over 208w induced by the rider result in less loss than a chain when it's loaded over 208w or if the chain were to be unduly tensions when set up. Maybe the conclusion is that really hard riders come out ahead with a belt where the losses drop below those of a chain when highly loaded, and more recreational tandem come out ahead with a chain.

Turbotandem

To that point of pedaling 95% of the time, worth considering so I ran another one. Cripple Creek Double, 204 miles, 20,000 feet of climbing took us just under 16 hours in motion, average 230w. I can match that in the low key calculator assuming 100 miles of climbing at 4% and 100 miles of flat. You can see in the link it is not that simple, but lets go with it! Let's also forget the 4 hours of rain, happy to forget that. And let's be conservative and forget the downhills when we did not pedal. I get the 1 to 2 watts reported lost in the belt would affect the time by 1 to 3 minutes of climbing and 30 to 60 seconds on the flat. So not more than 1.5 to 4 minutes in a 16 hour effort is 1/10th to 4/10th of 1%. Vanishingly small, even when pedaling 95% of the time. Compared to wind, rain, no drafting, etc that probably affected the time by some 10-15%.
That said, we were shaving every ounce off the bike for that race knowing it would be tough to beat the time cutoffs. I am kind of with you on every bit helps. The gram shaving was more of a psychological thing with all that climbing in mind, since keeping your head on square in this sort of race is the biggest challenge.

merlinextraligh

We've used the Vector 5-6 times now. After a few setup hiccups, it seems to be working well. ( More detail in the Road forum thread)

Here's a file for the warm up ride up Hogpen, the day before Six Gap:

https://www.trainingpeaks.com/av/CMHH...EEWFW7MGIRFS2E

Ritterview

We got the Vectors to work on our captain's crank, but not the stoker's. The Lightning's 16.9 mm crank arm depth proved a challenge. Eventually the stoker's would have worked, probably, with more filing of the carbon around the crank arm.

The insurmountable problem wasn't the Vector, but the Look Keo style pedals. Mrs. R is a skittish and inveterate clipper-outer. The one-sided Keo style pedals made it too difficult to repeatedly clip back in. She had used Crank Bros. mountain Candy's before the Keo's, which were two-sided but weren't the greatest.

We returned the stoker's Vectors and purchased Speedplay Light Action pedals. Mrs. R's joy at finally having easy clip-in/out road pedals far exceeds any interest she had in power measurement. Eventually Garmin will make a Vector version in Speedplay, and we will be back in the stoker power business.

Turbotandem

[QUOTE=Ritterview;16121745]We returned the stoker's Vectors and purchased Speedplay Light Action pedals. Mrs. R's joy at finally having easy clip-in/out road pedals far exceeds any interest she had in power measurement. /QUOTE]

SPeedplay LA are a good choice. Ms Turbo was not big enough to engage the normal Speedplay, she could not get in to them and out was a problem as well. The LA are good for her. Some suggest they are too easy to pop out of inadvertently, so you might keep an eye on that potential.
PS, if you want the float restricted on the speedplay LA you can swap out the plastic plate in the cleat with one from the X which has the set screws in it. Or you can just tap a set screw into the LA platic plate to match the X, which is what I have done. Let me know if you need a picture.

Hermes

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We purchased Vector Power meters a few months ago and have used them on road, time trial and track bikes plus we did a cycling camp and rented bikes and installed the Vectors on the rental bikes. The Vectors worked perfectly in all instances. Having said that, there were a couple of hiccups that was principally battery issues, installation and calibration. However, with some practice, swapping the Vectors around between bikes is really easy especially after it has been done the first time on that bike.

With respect to the fixed gear track bikes, the Vector reads zero with negative torque.

Since we switched to racing and training with power, we have not ridden the tandem very much. We are going on a tandem rally in May so we thought we better do a shakedown ride. I put the Vectors on the tandem. It is a little tricky getting the Garmins not to detect multiple power meters but with a little thought, that issue was solved and I was able to produce power and calibrate each PM on the bike. There was a couple of watts shown on the captain's garmin when pedaling the stoker's pedals and vice versa. However, on the bike, we felt that the power being shown was accurate and post ride analysis also confirmed it seemed to be correct.

My wife loved having power and said it was the most fun she has had on the tandem and it was definitely our best ride since we started riding tandems in 1980.

twocicle

I've heard the pedal pods (the part next to the crank) being made of AL are susceptable to breaking off. Any problems with that?

Interesting about the track "fixie" tandem being different with zero readings. Assume you spaced the pod plates and torqued appropriately. Wonder why the issue when AFAIK these work ok with normal track bikes?

Adding the pod plates (and maybe washers behind to keep the plates off the crank arms) adds to the Q-Factor... not something we want to do with our setup. Hoping the next version (whenever) streamlines the components.

Hermes

We do not have a track tandem. We have individual track bikes and the Vector works on them and records negative torque as zero. On our geared tandem, I did record a small offset on the captains power when applying power from the stoker's pedals and vice versa.

Hermes

My pedal pods are fine but I suspect if I hit something with them they may break or get damaged at which case, I would buy a replacement.

merlinextraligh

This is similar to our experience. A few glitches in setup. A bit tricky to get the two vectors linked to two different head units the first time.

Also have the phantom couple of watts for the captain, just from the stoker moving the cranks around.

Otherwise it's working we'll for us.

merlinextraligh

I broke one pod plate installing it, even though I was very careful to use a spacer, not have the pedal touch anywhere but where it's supposed to, and used a torque wrench to spec. So they are prone to break.

Garmin sent me two new pods by overnight delivery under warranty, so I've got an extra.

Jus t riding around, It would be hard to break one, but leaning the bike against a curb, getting it out of car etc, I think you could potentially break one.

Supposedly there's a redesign to make them a little more robust, but I can't see a change with the replacement pod.

As for Q factor, the pod moves the pedal out perhaps 1mm. A spacer another mm. And you don't need to use a spacer as long as the pod only contacts the crank around the circle on the pod. So if there's no recess in your crank arm the total increase in Q factor would be 1 mm a side.

Using a crank with narrower crank arms would more than offset the increase in Q factor.

LastKraftWagen

There was a couple of watts shown on the captain's garmin when pedaling the stoker's pedals and vice versa. However, on the bike, we felt that the power being shown was accurate and post ride analysis also confirmed it seemed to be correct.

Think the 1-2 watts from one set while pedaling the second set should be expected. Don't these units use accelerometers? Then, the unladen set would sense movement and you don't get movement without work (watts). Probably a condition Garmin didn't really consider, or consider frequent enough to warrant a software change like "0" readings for negative torque.

colotandem

Power meters? I think we'll just sit on your wheel and enjoy the draft!

Chris_W

I recently got a Stages Power Meter left-hand crank. Since I have 165mm-long Shimano 105 cranks on 4 different bikes and use SPD pedals on them all, it's easy to move one power meter between all the bikes, and the unit costs less than US$1000. This works on the tandem because the bike is setup as a single-side drive with 105 triple cranks (26-42 drive rings plus a Gates timing belt). I won't bother to move the power meter for every ride, but because we went away for a 4-day weekend on the tandem, I put the Stages crank on the front of the tandem for the first time (it probably took about 3 minutes to get it off of my race bike and onto the tandem).

If you like having lots of information, then you'll like what a power meter gives you. Whether it's taught me anything useful about how I ride or how I should change my riding is debatable, but I'm not too concerned about that. It is nice to see how efforts on the tandem compare to efforts on the single bike in an objective way. Pushing hard on the tandem has a different feel to it than on a single bike, so it's interesting to have some solid numbers. I'm not yet familiar enough with the system, my abilities, and the analysis tools to make any strong conclusions, but I'm starting to get an idea and understand everything that this new tool/toy can tell me.

My wife/stoker is not too interested, so I doubt that we'll be getting a second Stages crank for her, but that would be very easy to do if we wanted. I told her that she could have her Garmin also display my power readings if she wanted, but we haven't done that yet.

Also, for anyone wanting to put Garmin Vector pedals on Lightning cranks - Garmin have finally just released a pod unit with a long enough cable to reach around larger crank arms like the Lightnings (and FSA SL-Ks).

Hermes

That is what we were planning to do.

LastKraftWagen

Hey now! You'll be saving anywhere between 15 and 1500% power based on which Paul and Phil commentary you are watching and how much they adore the drafter [wheel sucker] they are fawning over.

So, if watts are joules per second, and a joule is approximately 0.238 calories, can I measure power by how many Big Macs I eat after a ride... I could "produce" pro-level numbers.

merlinextraligh

Buy Training and Racing with Power by Coggan and Allen. It will help you get more out of your power meter

Team Fab

Judging by that I should have won the TdF every year for the last 20 years. Unless of course someone cheated and used EPO. Oh wait they all did. Bazinga.

swiss_toni

Powertap have just announced their new pedal based power meter - and it doesn't have the hanging pods that the vecotrs have. PowerTap announces P1 Power Meter Pedals, also PowerTap C1 chainring unit | DC Rainmaker