[Sportsandrec] Tandeming out of phase

[Lisamaria Martinez, NOMC]

I am finding that when Joe and I are perfectly in phase, the bike moves so 
much quicker and the pedaling is so easy, it feels as if we've shifted down 
a few gears. Because I am finding us pedaling more in phase than out, I 
really need to get my feet clipped in. In fact, when we are pedaling in 
phase, and all is smooth with the world, my feet slip off because the 
pedaling dynamics and energy has changed.

I finally figured this out last night. We chose to go to a restaurant for 
dinner. So, we hopped on the bike and went. We were both relaxed and geared 
up for a very short ride. But, in riding for a short time with no stress 
involved, I finally realized why my feet slip and when.

Clips here I come.

LM
 ----- Original Message ----- 
From: "Thornbury, Kelly" <kthornbury at bresnan.net>
To: <sportsandrec at nfbnet.org>
Sent: Monday, July 20, 2009 11:12 AM
Subject: [Sportsandrec] Tandeming out of phase


> Hi Keith,
> When you say "at opposite angles," are you putting the captain's right 
> foot forward and the stoker's left, or is one crank horizontal while the 
> other is vertical (90 degrees out of phase)? Placing the cranks 180 
> degrees apart still has both riders in a power phase of the stroke at the 
> same time, only with opposite feet. This can cause a lot of problems with 
> bike balance and coordinating stops and starts. Unless you both have 
> strong enough legs to not rock your upper body at all, or you use a really 
> low gear ratio, you will get a lot of wobbling as you are applying power 
> on opposite sides.
> If the pedals are slightly out of phase, instead of sharing the energy 
> both riders have to put out to keep the bike moving, you are alternating 
> between riders. Defined simply, power is strength (weight moved) times the 
> time it takes to move it. It takes a certain amount of power to move a 
> bike at a certain speed. If a bike is traveling at a given speed, and both 
> riders are entering a power phase at the same time, they share the 
> strength it takes to produce that power. If you are out of phase, one 
> rider must produce all that strength, then the other. Its like going for a 
> ride, having the captain pedal alone for the ride out, then the stoker 
> doing the work all the way home. You end up using different muscle energy 
> stores, designed for strength and not endurance, and you tire more 
> quickly. The power equation is more complicated than that on a bike, but 
> that's it in a simplified form.
> Another consideration is the "force/velocity" curve. Simply, the more 
> force a muscle has to produce, the slower it will contract. Imagine 
> lifting weights, when you are near your max, you lift the weight more 
> slowly, but if you are only lifting half your max, you can move it much 
> faster...that's the inverse relationship between force and velocity of 
> muscle contraction.
> I've read about some racers pedaling slightly out of phase in biomechanics 
> research literature, but I've never read of this being successful at more 
> than 45 degrees.
> A better way to eliminate the "dead spots" in pedaling is to practice 
> pedaling in a circle rather than a square. Learning to pull up on the 
> pedals and applying power across the tops and bottoms of the pedal cycle. 
> One reason most tandem manufacturers/builders set the pedals "in phase" is 
> because for the majority of the population that provides the most comfort 
> and ease of operation.
> If the bike and the components are as old as you think, there shouldn't be 
> much, if any, difference in repacking the bearings as you remember. Newer 
> hubs and bottom brackets may be sealed, and once they go bad they are 
> pretty much toast.
> The derailleur are usually pretty easy to adjust, and even sighted 
> mechanics use an audible approach (listening to the gears instead of 
> looking at the alignments). Something better described off list if you 
> want to do it yourself, and there are a few people here who I'm sure would 
> gladly help out.
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