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Long Rides on a Tandem

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Old 06-29-18, 07:05 AM
  #51  
Yamato72
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Originally Posted by Carbonfiberboy View Post
If your toes hurt, it's probably because your saddle is too high and you're pedaling toes-down. Better to have the foot level at the bottom of the stroke, heel-down on the power stroke and heel-up on the backstroke. I start setting my saddle height using the heel-on-pedal method....
Interesting that you say that, as I definitely feel like I am pedaling toes-down, even though I set (checked) my saddle height with my heel on the pedal. I'll check out the video and investigate further.

Originally Posted by Alcanbrad View Post
...take care of your most important cycling interface and don’t ignore foot pain.
Thank you for the warning based on your experience, yes I'm way too active to risk messing up my feet!
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Old 06-29-18, 06:34 PM
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Originally Posted by DeadGrandpa View Post
I'm early in a relationship with a lady bicyclist and we've ridden a few times on my tandem. Maybe it's because I'm more of a higher cadence, lower pedal pressure kind of rider than she is used to on her single bikes, but she feels she doesn't really get the workout on the tandem that she does on her single. For sure, I seem to be working harder. I think maybe the dual HR monitor might help. What brand/model do you recommend?
Brand/model doesn't much matter as long as they have coded transmitters or are a different brand. We use two Garmins for navigation and my HR and then Stoker has a Polar watch for her HR. All ANT+ units that I know of have to be paired with their receivers, so anything ANT+ should work for both positions. Or one ANT+ and one Polar for the stoker's position like we have, however one wants to arrange that. Stoker also has to have some idea of LTHR and cruising HR, etc., for both people. Our team works best if Stoker usually runs ~5 beats ahead of me. Most women have higher HRs than men.

We go by breathing for a rough guide. If I hear her panting and I'm not, I tell her to back it off. If I'm panting and she's chatting I ask her for a little more power or I just say, "Are you with me?" Starting a hill using HR, Stoker will always lag my effort because my HR takes a while to come up. OTOH, after my effort her power stays high a little too long. So it's not perfect, but kindness and understanding helps, as always. Following another bike, she holds steady power and I vary mine to keep the right distance. That works pretty well.
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Old 06-29-18, 06:48 PM
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Originally Posted by merlinextraligh View Post
While I generally agree with your point that a tandem team is going to climb at the rate dictated by the sum of their w/kg, I think you're overstating the case a bit in this example.

Unless we're talking a very shallow grade, the tandem team in this example is going to be a bit slower. The captain's power out put on a tandem is going to have about a 7% efficiency loss in the drive train, compared to a 2% loss for both the stoker and the single rider. At most climbing speeds on a steep grade the loss of efficiency would outweigh any minute aero advantage.

Additionally, most tandem teams typically would lose a bit more than just the captain's drive train loss due to less than perfect coordination between the two riders, such as standing.
You may remember the tandem team we used to have on here composed of M-F track racers. Their tandem time on Mt. Diablo was the average of their single bike times. I don't know where you got the efficiencies for captain and stoker, but whereas a tandem (with the exception of BBs) has one of everything, 2 singles have 2 of everything. So I don't get that a tandem is less mechanically efficient than the sum of 2 singles. I do get that a team that isn't well synched will definitely suffer power losses. Even after lots of practice, we still don't climb well out of the saddle. OTOH, my stoker can't ride out of the saddle at all on her single. So we are definitely better on the tandem than on 2 singles.
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Old 06-29-18, 06:51 PM
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Originally Posted by Yamato72 View Post
Interesting that you say that, as I definitely feel like I am pedaling toes-down, even though I set (checked) my saddle height with my heel on the pedal. I'll check out the video and investigate further.
Just feel for that heel cup all the time. You could be pointing your toes even if your saddle is at the perfect height, whatever that is. It's an easy habit to fall into. I do it myself when I'm distracted. We climb stairs toe-down, after all.
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Old 06-30-18, 06:02 AM
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Originally Posted by Carbonfiberboy View Post
You may remember the tandem team we used to have on here composed of M-F track racers. Their tandem time on Mt. Diablo was the average of their single bike times. I don't know where you got the efficiencies for captain and stoker, but whereas a tandem (with the exception of BBs) has one of everything, 2 singles have 2 of everything. So I don't get that a tandem is less mechanically efficient than the sum of 2 singles. I do get that a team that isn't well synched will definitely suffer power losses. Even after lots of practice, we still don't climb well out of the saddle. OTOH, my stoker can't ride out of the saddle at all on her single. So we are definitely better on the tandem than on 2 singles.
the 7% power loss for the captain has been referenced on several previous BF threads. IIRC it comes from one or more studies. The explanation for the loss is the captain's power has to be transferred through 2 bb's and two chains to get to the hub. It's one of the arguments for making the stronger rider the stoker.

I didn't find the reference in a quick google search, but it's somewhere in BF archives.
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Old 06-30-18, 06:13 AM
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Found the reference. Testing by BF's own ASU_GT, found a 6% loss for the captain, and a 1.8% loss for the stoker. So I was off by a percent.

Power loss in transmission
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Old 06-30-18, 10:58 AM
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Originally Posted by merlinextraligh View Post
the 7% power loss for the captain has been referenced on several previous BF threads. IIRC it comes from one or more studies. The explanation for the loss is the captain's power has to be transferred through 2 bb's and two chains to get to the hub. It's one of the arguments for making the stronger rider the stoker.

I didn't find the reference in a quick google search, but it's somewhere in BF archives.
And also two chains. This is a good argument for putting the stronger rider in the back. Too bad it doesn't work most of the time. Often, the weaker rider isn't strong enough to hold the bike up.
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Old 07-02-18, 09:06 AM
  #58  
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For a conventional tandem drivetrain that does not have IPS, it should not be the assumption that the Captain's power is anymore impacted by the drivetrain components than the Stoker. Even if a tandem were locked in a trainer and the Stoker assessed separately for power output they would still activate the Captains bottom bracket and the timing chain. The only explanation for the measured difference in the combined power of a tandem team vs the Captain and Stoker separately is due to the difficulty of synchronizing independent powerplants. Triples are worse, Quads even worse. That's why 8 man tandem craft have never taken off. 8 man rowed shells compete with a non-rowing Coxswain who functions mainly to coordinate the efforts of the Crew. Even so, the primary benefit of pairing, trebling and more of individual efforts is social vs performance. An 8 man rowed shell is not 8x faster than a single scull, not even close to that. The aerodynamics of the close drafting position of the Stoker behind the Captain should outweigh all of the drivetrain inefficiencies. What is left is Companionship and Sociability. A fair trade, I think.
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Old 07-02-18, 11:43 AM
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Originally Posted by Leisesturm View Post
For a conventional tandem drivetrain that does not have IPS, it should not be the assumption that the Captain's power is anymore impacted by the drivetrain components than the Stoker. Even if a tandem were locked in a trainer and the Stoker assessed separately for power output they would still activate the Captains bottom bracket and the timing chain. The only explanation for the measured difference in the combined power of a tandem team vs the Captain and Stoker separately is due to the difficulty of synchronizing independent powerplants. .
There is the loss of efficiency (of the captains power) thru the timing chain and drive chain, plus the (loss) flexing of a longer frame, and the flex of the boom tube as the captain pedals. These things rob some of the captains power before it gets to the rear wheel and not in play (other than the drive chain) for the stoker's power delivery.

I am not an engineer, so if I am missing something here, please comment.

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Old 07-02-18, 01:57 PM
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Originally Posted by Chancy View Post
There is the loss of efficiency (of the captains power) thru the timing chain and drive chain, plus the (loss) flexing of a longer frame, and the flex of the boom tube as the captain pedals. These things rob some of the captains power before it gets to the rear wheel and not in play (other than the drive chain) for the stoker's power delivery.

I am not an engineer, so if I am missing something here, please comment.
I am not an engineer either but it is obvious to me that things aren't as neat and tidy as "the Captains power flows through the total drivetrain but the Stokers power just flows through the drive-chain". There are times when my Stoker does not get the memo to cease pedaling(!) and tries for a quarter revolution or so to keep going. Why only a quarter revolution? Because her efforts are quickly resisted by the uncooperative timing chain and if we are going to go there then boom stiffness is a factor in exactly what is felt at the Stoker cranks. Even if the more powerful person is at the Stoker position they can only do what is 'allowed' by the weaker rider otherwise they waste energy trying to drive the Captains feet around. Clearly the Stokers power, rather than flowing entirely and directly into the drivechain must of necessity interact with the power (or lack) generated by the Captain.
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Old 07-02-18, 04:20 PM
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Originally Posted by OneIsAllYouNeed View Post
My wife and I are admittedly far younger, but we find the tandem is the best tool for long rides. Inevitably on a really long ride, there will be times that each person isn't feeling their best. By sharing a bike, you'll be able to ride through those situations without having without having to meter your efforts. Even if one person bonks or cramps, the other can help in a meaningful way. There's little more demoralizing than riding separate single bikes with someone who doesn't have the energy to keep going -- and not being able to help.
My wife also finds it easier to eat, drink, and take pictures from the back of the tandem. As captain, I enjoy having unwrapped snacks handed to me. You'll both get that feeling of accomplishment by working together.
Totally agree with you.

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Old 07-02-18, 05:02 PM
  #62  
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All the above said, yesterday a steel CoMo tandem in our group with a well-trained but ordinary 50's team knocked out a 5800', 55 mile ride with no problems. They had a great time.
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