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  1. #1
    Senior Member rdtompki's Avatar
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    Pedal stroke differences, single versus tandem?

    Warning: I'm an engineer and I'm over-thinking things a bit here, but I'd like some advice in full recognition that free advice is worth what you pay for it

    Background: Wife and I have 10-12K miles on the tandem. We've been riding for 4-5 years. Wife only rides the tandem, while I've been putting in a good deal of miles on my single; have gotten a good deal stronger over the last 2-3 years. We do a bit of riding during the week, a longer (30-50 mile) ride on the weekends and 100K organized rides whenever we can. We both enjoy riding the tandem, but I'm finding it increasingly difficult to find a cadence on the tandem where I can "relax". Of course climbing is much harder on the tandem, but that's not really the issue.

    Single bike analogy: On the flat, no wind, working hard you can find a gear/cadence that feels comfortable, sort of a cyclic load on your leg muscles to which you are best adapted. Introduce a headwind - you decrease speed, but it becomes very difficult to find that sweet spot. The tandem feels like this unless we are a) headed downhill or b) have a tail wind. I'll shift down on the tandem, but continue to find the effort much more fatiguing than on a single.

    Theory #1: The headwind creates a condition where you can't match the conditions to which you're best adapted; same thing seems to happen on the tandem albeit for a much greater percentage of the time.

    Theory #2: I'm a grumpy old guy who should HTFU.

    Is this in my imagination? Anyone else experience this?

    Next Steps: I changed from 175mm to 180mm cranks on the tandem to lower my cadence. This worked, reducing my cadence 2-3 rpm, but I'm thinking of going back to 175 to match my single. I didn't really notice the change, but the additional 10mm of diameter could make enough of a difference in range of motion to be a contributor.
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  2. #2
    Senior Member swc7916's Avatar
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    Our situation is similar in that we have been riding a tandem for about the same length of time and my wife only rides the tandem, whereas I ride both the tandem and my single. My observation regarding the cadence/effort difference between the tandem and single is the same as yours. On the tandem I feel like I'm pushing all the time whereas on the single I feel as if my feet are "floating" across the top of each pedal stroke. I only get the "floating" feeling on the tandem when we're going downhill or with the wind.

    My explanation for this phenomenon is as follows:

    Because of various drag forces on the bicycle and the fact that the power input is cyclical, the bicycle will decelerate between pedal strokes. The power portion of the pedal stroke is used to accelerate the bike back to the desired steady speed. Cycling against an increased load, such as when you're going uphill or against the wind, exaggerates the momentum loss between pedal strokes and increases the force needed to maintain the desired speed. I believe that either the tandem does not maintain momentum as well as a single, that a tandem is harder to accelerate, or a combination of the two. Therefore, the tandem needs some “help” such as a tailwind or downward slope to lower the momentum loss or the power requirement in order for it to feel the same as the single.

    (I’m an engineer also, and have the same tendency to overthink things.)

    Additional thoughts:

    It occurs to me that there may be another reason that the tandem is more work than the single - The difference in cadence between you and your stoker. Typically, a person with a lower cadence will have more of a push-push (rather than circular) pedal stroke and will pause at the bottom. This means that they are actually resisting when the crankarms are vertical and can make it uncomfortable for you when it takes longer than you want for the pedal to come around.
    Last edited by swc7916; 01-29-13 at 01:56 PM. Reason: additional thoughts
    2011 Rodriguez Rohloff tandem
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  3. #3
    Senior Member waynesulak's Avatar
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    The OP's description of loss of momentum in head wind and uphill conditions is very familiar. Ironically when we road our first tandem it seemed to maintain momentum better than my single even when climbing. It appeared to me that the tandem being less stiff than my extremely stiff single might be the reason. I purchased an old flexible single frame, built it up and it road much more like my tandem. Now I have replaced both bikes with a fairly flexible single and tandem and life is good.

    I know many people will say frame flex looses energy. All I know is that it easier to ride up hill and in the wind. I can get in a grove and get the heart rate up much easier, and therefore go faster. I am not an engineer so don't know why this is the case. I am only 150 lbs and don't put out a lot of power so that may have something to do with it.

  4. #4
    Santana Couple
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    OK I am a wannabe engineer so here is my story. I am a long time rider. My wife only rides tandem and never rode before. She has a bike computer on stoker bar and would slack off as we approached our target speed. I put a piece of black electric tape over the speed and asked her to focus on her heart rate. Not wanting to force anything on her I did not set a target. When I feel my work load getting higher I kindly ask her what her heart rate is. When she heasitates I have a clue that the number is real close to what she sees on the screen . Problem solved! FYI using CatEye V2 wireless, one sending unit with two head units.

  5. #5
    Santana Couple
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    Quote Originally Posted by apage4u View Post
    OK I am a wannabe engineer so here is my story. I am a long time rider. My wife only rides tandem and never rode before. She has a bike computer on stoker bar and would slack off as we approached our target speed. I put a piece of black electric tape over the speed and asked her to focus on her heart rate. Not wanting to force anything on her I did not set a target. When I feel my work load getting higher I kindly ask her what her heart rate is. When she heasitates I have a clue that the number is real close to what she sees on the screen . Problem solved! FYI using CatEye V2 wireless, one sending unit with two head units.
    Correction V3

  6. #6
    Senior Member rdtompki's Avatar
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    We did a relatively easy 24 mile ride today and I tried to focus more, grumble less. I'm pretty sure I know what's happening.

    I'm transferring the feel of shifting from single to tandem (both single and tandem have a 12-30 cassette). On the single my cadence probably ranges from 95 down to 85 except when climbing in extreme conditions. As I accelerate at a certain speed I'll shift up knowing that I have enough in reserve to overcome the drop in cadence and power which would usually accompany same.

    On the tandem I'm more in the 82-92 range - doesn't seem like much, but I'm shifting up, dropping cadence to the low 80's and in many cases can't accelerate the bike to a functional cadence, but overload my leg muscles trying. Solution seems simple; just tell the dummy up front not to shift in the first place. It isn't unusual to up shift and 10 seconds later have to down shift.

    So... I'm going to do two things: 1) go back to 175 mm cranks and 2) be more conscious of this coffin-corner situation. I don't think the 180 mm cranks are helping so might as well match the single. As far as avoiding the back side of the power curve - re-schedule all the various processing going on in my brain to pay more attention to when I'm shifting, at least until I've reprogrammed things.

    The funny thing is I'm so conscious of shifting when climbing, but someone on the flats I've fallen into bad habits.
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  7. #7
    Senior Member zonatandem's Avatar
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    Possibility:
    Stoker is not pedaling as hard/efficiently as pilot.
    Try pedaling 90 degrees OOP . . . always a powersroke going over the top compared to pedaling in-phase.
    Am not an engineering, but over 38 years tandeming experience.
    Pedal on!
    Rudy and Kay/zonatandem

  8. #8
    Senior Member rdtompki's Avatar
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    Quote Originally Posted by zonatandem View Post
    Possibility:
    Stoker is not pedaling as hard/efficiently as pilot.
    Try pedaling 90 degrees OOP . . . always a powersroke going over the top compared to pedaling in-phase.
    Am not an engineering, but over 38 years tandeming experience.
    Pedal on!
    Rudy and Kay/zonatandem
    Rudy, I have not doubt my dear stoker pedals less efficiently. Unfortunately, with the daVinci it's very difficult for her to get out of sync. We've tried to get OOP, but failed. I think your suggestion has a lot of merit; we will try again. The key would be finding a cue that the stoker can use to lock into OOP as she currently does IP.
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  9. #9
    Rod & Judy gracehowler's Avatar
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    Interesting thread, I will chime in and say I notice the same effects and we also have similar riding history. When I really want to get out and find that sweet spot, I really enjoy my single, when I really want to spend time with my girl, I ride tandem. And I will add, when we tour, the more days we ride the more together we become and I think we find that nervana! For us, that's about 5th or 6th day.
    R&J

  10. #10
    Blast from the Past Voodoo76's Avatar
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    Was just going to make the same observation as zonta. I don't have a lot of time on a tandem, but do have 30+ years on the road (and an engineering degree ). I noticed this same effect riding with my then 11 year old son. I think the OP was on the right track, but the root cause I believe has more to do with your stoker having a flat spot in his/her stroke that coincides with yours. My son actually grew out of this, funny I can feel a lot of push coming from the back now if I ask for it.

    Like the idea of trying OOP.

  11. #11
    Senior Member rdtompki's Avatar
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    I almost sprung for the adapter to convert the daVinci (temporarily) to non-ICS. I think it's worth a try, but starting and stopping will be a bit hazardous.
    Rick T
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  12. #12
    Senior Member waynesulak's Avatar
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    I agree that lower cadence could be contributing to the problem.

  13. #13
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    Quote Originally Posted by rdtompki View Post
    I almost sprung for the adapter to convert the daVinci (temporarily) to non-ICS. I think it's worth a try, but starting and stopping will be a bit hazardous.
    After twenty-five years OOP, I'm wondering why you think starting and stopping is more hazardous OOP relative to IP. If anything, since there is less time between power strokes, it is easier to start, particularly on hills.

  14. #14
    Senior Member rdtompki's Avatar
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    Quote Originally Posted by B. Carfree View Post
    After twenty-five years OOP, I'm wondering why you think starting and stopping is more hazardous OOP relative to IP. If anything, since there is less time between power strokes, it is easier to start, particularly on hills.
    My concern has nothing to do with OOP. The daVinci is ICS. We have no experience with the coordination required to start/stop when we're locked together. We're both coordinated and intelligent so we can pull it off. Our first go at OOP will be with ICS, but my wife may have trouble being consistent.
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  15. #15
    just another gosling Carbonfiberboy's Avatar
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    The OP's OP and swc have it right IMO. When we first started riding the tandem in 2007 it slaughtered my legs, and I was a strong single rider. My take on it is that on a single, when you push hard on the pedals, the bike accelerates - it "gets out of the way." The tandem does not accelerate, or at least not nearly as much. Thus the contraction is more isometric. You push hard but nothing happens.

    I think there's a period of adaptation. We can't captain a tandem like we ride a single. We have to be much smoother, macro in acceleration and micro in the pedal stroke. After 5 years of tandeming, I'm riding more hours to exhaustion that I rode on my single 5 years ago. Of course we don't go as far per hour as I once did. IOW a 70 mile hilly ride takes us about 1.5 hours longer than it took me on my single. So doing the same rides as I used to is actually a lot harder and finishing them at the same exhaustion level is good progress.

    I pretty much no longer ride my single outdoors, riding it only on my rollers. I think that "tandem only" riding helps, because I don't pick up my "bad" single riding habits again.

    Other things that have helped: weight training seems to help keep me from blowing out my legs as easily when pushing against that tandem weight. Stoker and I both do one-legged pedaling drills, me on my rollers, her on her trainer. I think they help us smooth up our stroke. When we're training together indoors, we both pedal the same cadence.

    Just plain miles has helped. We try to get in a 100k or so ride every weekend, weather permitting, shooting for at least 50'/mile of climbing. We both work out during the week. In the winter, we lift and do a spin class, obviously both at the same cadence. Stoker has gradually worked up to being able to pedal 120 on a spin bike. Stoker rides dressage, I downhill ski. We hike together in the summer, snowshoe together when it's unsafe to ride.

    I don't think cadence or crank length is that big a deal, except that one gets used to a particular thing. I'm 5-6" and run a 172.5 crank on the tandem. I used to be a 90+ pedaler on my single, now I'm perfectly comfortable as an 85+ pedaler on the tandem. I could get comfortable pedaling even more slowly. The strongest tandem team I know pedals about a 60 cadence. They can drop us pedaling one-legged.

    I think it's just about doing it more and training to do it more, realizing that if your stoker puts out fewer watts per kilogram than you do, you're going to be slower than you were on your single.

    Our solution to the equal effort dilemma is simple: Stoker navigates with a Garmin Edge 800 plus a cue sheet. I wear an ANT+ transmitter and have a Bontrager Node computer. Her Garmin and my Node pick up my HR. She wears a Polar transmitter and has her own HRM. She simply matches my HR. There's always a little lag time. She can't know to pick it up until my HR reacts, and then she'll overshoot when I ease off, but that works out fairly well. I try to pick it up slowly and ease off slowly. In a paceline I'll have to ask her to ease up occasionally. Her LT and MHR are probably higher than mine, but so what? She's hurting about the same as me at the end of the ride. If she were a lifetime athlete, we could figure HR percentages, but that's not necessary. We do well enough and are both comfortable with our system. If she gets whupped, she'll lag me a little and I won't have to know it. If she's fresh, she'll be ahead of me a little, same. I like her having the control of that.

  16. #16
    Senior Member rdtompki's Avatar
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    CFB, the isometric analogy is excellent. That's exactly what it feels like. Love my stoker, but no way she is going to work at this more than just getting on the bike, but I think we can figure out a way to experiment with OOP which might provide some relief. Regardless, I'll work at managing gear selection and expectations.

    I don't think we're riding the tandem as much as past years and this winter has been a bit wet. I think the natural course of things, more frequent, longer rides, will improve things as we get into the season.
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  17. #17
    just another gosling Carbonfiberboy's Avatar
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    Quote Originally Posted by rdtompki View Post
    CFB, the isometric analogy is excellent. That's exactly what it feels like. Love my stoker, but no way she is going to work at this more than just getting on the bike, but I think we can figure out a way to experiment with OOP which might provide some relief. Regardless, I'll work at managing gear selection and expectations.

    I don't think we're riding the tandem as much as past years and this winter has been a bit wet. I think the natural course of things, more frequent, longer rides, will improve things as we get into the season.
    I think you can change the way you ride a little without involving your stoker. Do you have a trainer? You do the OLP and muscle tension intervals on it. How frequently can you get out on the tandem? My observation over the years is that frequency makes a big difference. My stoker was quite suspicious of wet weather riding originally, but with proper clothing now doesn't mind it. We'd rather bike in the sun, of course, but it's still fun for us in the rain.

  18. #18
    Senior Member waynesulak's Avatar
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    Stoker motivation (and captain's too) is an interesting problem with individual answers. My stoker at times looses motivation until we see someone roughly our ability on the road to chase. Then she is very motivated. Unfortunately due to our schedule we usually ride alone. I find that it is my job to try to schedule our rides so that we happen to find some likely candidate on our route. After that I just have to worry about holding up my end.

  19. #19
    Uber Goober StephenH's Avatar
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    A while back, I was noticing how hard it was to ride into the wind, and then my speedometer lost the connection, and all the sudden it got easier. The thing was, I just couldnt happily ride into a headwind at 10 mph, but if I didn't know how slow I was going, it was okay.

    My theory: I think your stoker is a weaker rider than you, and instead of relaxing and and using a compromise pace, you're trying to maintain your single-bike pace and working too hard to do it. Try turning your speedometer off for a few rides and see if it's any more fun.
    "be careful this rando stuff is addictive and dan's the 'pusher'."

  20. #20
    Senior Member
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    It takes X amount of horsepower to move Y amount of mass. Your horsepower moves your single bike mass at a certain speed. Can your stoker match your horsepower / speed if she rides a single bike.

    i am guessing that she might be weaker than you are and in order to maintain the same speed that you ride on your single you have to attempt to produce more horsepower, thus the harder effort. You are attempting to move a 2Y mass with maybe 1.75X horsepower.

    Just a thought.

    Wayne

  21. #21
    Senior Member
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    Quote Originally Posted by DubT View Post
    It takes X amount of horsepower to move Y amount of mass. Your horsepower moves your single bike mass at a certain speed. Can your stoker match your horsepower / speed if she rides a single bike.

    i am guessing that she might be weaker than you are and in order to maintain the same speed that you ride on your single you have to attempt to produce more horsepower, thus the harder effort. You are attempting to move a 2Y mass with maybe 1.75X horsepower.

    Just a thought.

    Wayne
    +1; Power to weight ratio, innit?

  22. #22
    Santana Couple
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    I agree, our club does a just for fun time trial and I taped over the speed so I could focus on heart rate. I knew that if I focused on keeping my speed above our usual average I would blowup on heart rate.

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