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Old 07-12-18, 08:51 PM
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Originally Posted by jethro00 View Post
Leisesturm, I agree with you that da Vinci confirms your assessment, and also adds a factor.
So, now I have some questions for you and others about IPS versus traditional tandems.
Let's start with my da Vinci.
If captain (C) and stoker (S) pedal at different rates, then the total power = 100% of the rider spinning faster, right?
If C and S spin in sync, then is the total power 100% C + 100% S?
Do the C & S have to be perfectly in sync to combine power or just close to the same rate?
If one person slacks off so that they are pedaling at a slower rate they will immediately feel no significant resistance in the pedals. It would be the same as if you were coasting down a hill and decide to slowly turn the crank - sure you can pedal at a lower cadence, but it'll feel completely different from normal pedaling where you are pushing against a resistance force from the pedals.

When pedaling normally, i.e. each pushing against a resisting force, the two riders will always be in perfect sync.
Now, let's go to a traditional tandem, like the Trek T900 we both have.
If C and stoker pedal at different rates (with C faster), then the total power = 100% C - some factor for C pulling Ss pedals + 100% S?
If C and S spin at equal rates/power, then is the total power 100% C + 100% S?

I am finding this thread educational.
C and S can't pedal at different rates on a typical tandem since their cranks are connected by the cross-over chain between their cranks and therefore the cranks turn at exactly the same speed as long as the rings on each are the same. If one of them (say C) decides that the cadence is impossibly high and tries to actively resist the motion then I suppose you could say the total power = 100% S - 100% C, but I can almost guarantee that situation won't last long.
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