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-   -   Who leads (stoker or Captain) when pedalling in-phase (http://www.bikeforums.net/tandem-cycling/751089-who-leads-stoker-captain-when-pedalling-phase.html)

barkersoldbean 07-12-11 05:22 PM

Who leads (stoker or Captain) when pedalling in-phase
 
A question when pedalling in-phase.

When i set up my Tandem "in-phase" I had it exact - but have subsequently been told that the correct set up is to adjust the crank phasing by a few degrees so that the stoker leads the captain through the stroke (i.e. the stoker goes through TDC just before the captain).

I'd like to know whether this is the case and not the reverse (i.e. the Captain goes through TDC before the stoker?).

(By the way - i did as told and set it up this way and have just done a pretty brutal climb from Bellagio to Madonna del Ghisallo - but intrigued as to why its good?)

steve53mg 07-13-11 01:42 PM

I've never heard this. We ride in phase, but those who don't seem to favor 90 degrees out of phase. If you are 1 tooth out, assuming 40 teeth, puts you almost 10 degrees out.

JanMM 07-13-11 01:58 PM

Quote:

Originally Posted by steve53mg (Post 12923408)
I've never heard this.

Ditto. We ride in phase.

PMK 07-13-11 03:19 PM

We run out of phase with Captain leading by two teeth. Not sure if it is correct or incorrect. For us it smoothed out our spin and seemed to help our speed slightly.

PK

waynesulak 07-13-11 03:31 PM

We ride in phase, however setting it up with the stoker one or two teeth ahead of the captain helps in cases where the stoker has a little trouble keeping as high a cadence as the captain. Since the stoker gets to the power stroke just a little ahead of the captain the stoker can always feel resistance in the pedals. This avoids the stoker sometimes feeling the pedals drop away where the captain is a touch quicker and the cranks are exactly in phase.

No right or wrong answer. Try different approaches and choose what works well for you.

diabloridr 07-13-11 04:58 PM

We ride in phase with captain leading stoker by either 1 or 2 teeth (I can't remember which). For us there is a noticeable improvement in smoothness/net power transmission vs. having no offset

My advice is to experiment and find what works for you.

zonatandem 07-13-11 10:15 PM

1 Attachment(s)
Pedaling 'in phase' means exactly that.
If capt or stoker is 1 or 2 teeth, or more off, then you are technically out-of-phase.
We have been pedaling 90 degrees out-of-phase (with capt.leading) http://bikeforums.net/attachment.php...hmentid=210490 for over 230,000 miles.
Yeah, guess we like it that way!
Pedal on TWOgether!
Rudy and Kay/zonatandem

diabloridr 07-14-11 10:14 AM

Quote:

Originally Posted by zonatandem (Post 12925965)
Pedaling 'in phase' means exactly that.
If capt or stoker is 1 or 2 teeth, or more off, then you are technically out-of-phase.

I look at it differently:

OOP implies a 90-degree, or near 90-degree, offset to maximize smoothing of power delivery. Teams which can stand using OOP are rare and the ability to quickly surge is hampered. For these reasons OOP is almost never used by competitive teams.

IP maximizes available peak power, though offsets to accommodate team pedaling dynamics are OK provided they are small enough to not compromise the ability to stand or surge.

akexpress 07-14-11 11:13 AM

in phase captain ahead by one tooth

bgross 07-14-11 11:14 AM

We ride in phase.

Since we have different fitness levels and different cycling experience, it helps as an 'equalizer'. That is, I select the gear based upon perceived pedal effort & terrain, the stoker just pedals at a level of exertion that she's comfortable with and I lead with cadence.
When we stop & start we do the usual: I straddle & steady while she mounts & clips in, she rotates the pedals to the position that I like to start, I clip in and say "pedal". I pedal with one foot while she pedals a couple strokes and after we're moving I say 'coast' and then clip in my other foot.

From then on, she matches my cadence at an effort that she's comfortable with and I shift as necessary.

Tandem: The great equalizer!

Caveat: While we might not be matched if riding singles, my bride is a perfect stoker. She doesn't 'steer', she lets me know when she needs to adjust her position, and she doesn't whine. YSMV.

tredlodz 07-14-11 12:15 PM

You've stumbled on IP/OOP, one of the great tandem controversies. We try to be as perfectly IP as possible, occasionally get a tooth or two out due to sloppy maintenance - I can't say I've really detected much difference although I correct it as soon as I notice. I saw a tandem 90 degs OOP last week and it looked like the Captain and Stoker were going in different directions, would have driven me nuts, but this was a low end bike that looked pretty noodly, nothing like Zona's stiff carbon frame.

Next up, ask about crank length, gearing and tires - you will get a "range" of opinions

barkersoldbean 07-14-11 03:27 PM

waynesulak comments make sense - it's a cadence thing and that's why it has worked for us - my cadence is naturally higher than my wife (stoker) and this has smoothed out the stroke in high cadence flat terrain situations. Presumably the opposite is true if the stoker has a naturally higher cadence (which might be the case for female spinning devotees).
Tony

dwmckee 07-28-11 09:43 PM

By accident wE started riding two teeth out captain leading a year ago. It is much smoother for us and helps especially when standing. We rode six months this way thinking we had reached a new level of competence before we figured out it was the OOP magic instead!

bjjoondo 07-29-11 04:06 PM

Newbie here, how do you "SET" the phase of a tandem?? I take it ours in IP as we ride it in the stock set up but what do you adjust to make it 1 or 2 teeth OOP or 90% OOP?? Whew, there is a lot of new terms to learn going to a tandem ;)

PMK 07-29-11 04:14 PM

Quote:

Originally Posted by bjjoondo (Post 13006775)
Newbie here, how do you "SET" the phase of a tandem?? I take it ours in IP as we ride it in the stock set up but what do you adjust to make it 1 or 2 teeth OOP or 90% OOP?? Whew, there is a lot of new terms to learn going to a tandem ;)

To have the same phase angle or truly be in phase, the forward crankset and aft crankset will match on all clocking angles. As an example, both cranks will be dead vertical simultaneously.

To phase with the captain leading, the forward crankset would be adjusted so the captain will cross the 12:00 position first. This could be any number of teeth difference.

90 out of phase is just that and it too could have the captain crossing 12:00 first or not.

I think I got it explained correctly, if not I'm sure someone else will get you dialed in.

PK

nfmisso 07-29-11 08:16 PM

Quote:

Originally Posted by bjjoondo (Post 13006775)
........what do you adjust to make it 1 or 2 teeth OOP or 90 OOP?? ........

Derail the sync chain, and put it back on, one or two or 10 teeth offset - 10T = 90 for 40T chainrings.

diabloridr 08-01-11 08:30 AM

Quote:

Originally Posted by nfmisso (Post 13007741)
Derail the sync chain, and put it back on, one or two or 10 teeth offset - 10T = 90 for 40T chainrings.

Prior to derailing, I place a mark on the chain and the matching tooth at both rings.

This greatly simplifies verifying the appropriate offset during reinstallation of the chain.

A magic marker works fine this.

Open Lateral 08-02-11 08:35 AM

Also the eccentric will tighten the timing chain in two positions, and know which position you are using.
We ride exactly in phase, and only get a dead spot when we get tired. -someone is not spinning a circle!

Hermes 08-02-11 05:44 PM

I love phasing threads. We started riding tandem in 1981 and it was OOP. We took delivery of the tandem and it was setup OOP. We asked the shop to change it and the owner said to try it. Once we got used to OOP, we liked it. We have been riding that way every since. We started racing our tandem and noted that the other racers typically rode IP. However, this was in time trials which do not require accelerations such as in crits or road races. The standing start does not have to be explosive. So we stuck with OOP.

We purchased another tandem in 2006 and this one was set up IP. We tried riding IP for a few hundred miles but ultimately changed back to OOP. We prefer OOP for climbing and standing.

Besides road racing, we are both track racers. We would love to try a pursuit on a track tandem. In that case, we would definitely use IP to get the tandem off the line in a big gear for a standing start. We just got back from Nationals at Trexlertown and I think next week or so is the tandem Nationals. That would be a total rush.

I think many racing tandem teams are ad hoc. One racer has a tandem and finds a race where he/she has a competitive advantage and gets another to stoke. In that case, OOP is out of the question. I would not invite a stoker and try to explain the virtues of OOP v IP. I would set up the tandem IP and get on with it.

I think tweaking the phase by a couple of teeth could work. If you believe something works, then there is a good chance that it will. YMMV.

twilkins9076 08-05-11 05:14 PM

We've been riding OOP with the captain leading by 45 degrees for quite a while. Gives us most of the perceived benefits (smoother stroke, better hill climbing) without the difficulty starting and stopping that 90 degrees OOP gave us.

JanMM 08-05-11 08:23 PM

Quote:

Originally Posted by diabloridr (Post 13017071)
Prior to derailing, I place a mark on the chain and the matching tooth at both rings.

This greatly simplifies verifying the appropriate offset during reinstallation of the chain.

A magic marker works fine this.

Good plan. If you don't have a plan/system/technique, you can go nuts getting the cranks oriented exactly the way you want them.

JanMM 08-05-11 08:25 PM

Quote:

Originally Posted by Hermes (Post 13025048)
If you believe something works, then there is a good chance that it will. .

The strength of a self-fulfilling prophecy.


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