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smoothness and power

Old 10-08-10, 09:48 AM
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Originally Posted by RChung
It might appear that way but
1. those one hour efforts are on a fixed gear bike in a velodrome.
2. those one hour efforts are not done at greatest efficiency. They don't give a rat's ass how few calories they have to burn -- they only care about how many kms they can cover in an hour.
If you are defining efficiency by the number of calories burned per watt, then this would be correct. But this being the racing forum that definition has no application here. No one cares how many calories they burn, the point is to cross the line first, or go furthest in an hour, or set the fastest time. I default to power/time vs. power/kcal as the more appropriate definition for our discussion.

Not all those efforts were done in a velodrome on a fixed gear BTW. I can't speak to all of them but Coppi's was done on an open road; the velodrome was in use for the war effort.

My experience shows almost no change on a fixed gear/drome effort compared to a freewheel/der equipped bike for efforts of the same distance, the wattage produced is also the same. Any drop in "average" recorded cadence on the road would be due to occasional freewheeling, which you can't do on a fixed gear bike without some ugly consequences. But that's just for me; I have a lot of data points from both disciplines, the pursuit and sprint data from the track overlays pretty seamlessly on my prologue and sprint stuff on the road.
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Old 10-08-10, 10:08 AM
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Another thing that in implicit with high cadences is the gearing that goes with it. The efficiency of a chain drivetrain is largely a component of the smallest gear. As you make the 'small' cog bigger, it's more efficient. Given the option of running a 25 rear cog or an 11 at the same power output, the 25 is on the order of 5% more efficient. More of the power produced by your legs gets to the rear tire. It's a pretty big deal. Now, if you're not able to make your legs move fast enough to support the necessary cadence, then you can lose efficiency that way, but the crossover point seems to be somewhat in excess of 100 rpm cadence for hour record holders.

Last edited by Fat Boy; 10-08-10 at 10:53 AM.
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Old 10-08-10, 10:28 AM
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Originally Posted by Fat Boy
As you make the 'small' cog bigger, it's more efficient.
Presuming the chain line stays the same.
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Old 10-08-10, 10:29 AM
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Originally Posted by Fat Boy
Another thing that in implicit with high cadences is the gearing that goes with it. The efficiency of a chain drivetrain is largely a component of the smallest gear. As you make the 'small' cog bigger, it's more efficient. Given the option of running a 25 rear cog or an 11 at the same power output, the 25 is on the order of 5% more efficient. More of the power produced by your legs gets to the rear tire. It's a pretty big deal. Now, if you're not able to make your legs move fast enough to support the necessary cadence, then you can loose efficiency that way, but the crossover point seems to be somewhat in excess of 100 rpm cadence for hour record holders.
Can you explain (as simply as possible) why this is?
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Old 10-08-10, 10:50 AM
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Originally Posted by Racer Ex
Presuming the chain line stays the same.
Logically, the chain line remaining the same helps (i.e. track bike), but in the data I've seen the chain line doesn't make a hell of a lot of difference. Whatever losses exist because of a cross-chain seem to be overshadowed by losses due to making the chain take a tighter radius.
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Old 10-08-10, 10:53 AM
  #56  
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Originally Posted by tombailey
Can you explain (as simply as possible) why this is?
The tighter you make the chain turn around a sprocket, the less efficient it is. You can get more involved than that, but that's the simple way of looking at it.
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Old 10-08-10, 11:15 AM
  #57  
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Originally Posted by Racer Ex
If you are defining efficiency by the number of calories burned per watt, then this would be correct.
That is the only definition that applies to DrWJODonnell's post.
But this being the racing forum that definition has no application here. No one cares how many calories they burn, the point is to cross the line first, or go furthest in an hour, or set the fastest time.
This is what I said.
I default to power/time vs. power/kcal as the more appropriate definition for our discussion.
Power/kcal is a red herring.

Not all those efforts were done in a velodrome on a fixed gear BTW. I can't speak to all of them but Coppi's was done on an open road; the velodrome was in use for the war effort.
Really? That's interesting. The UCI record book has it being set at the Vigorelli Velodrome in Milan.

My experience shows almost no change on a fixed gear/drome effort compared to a freewheel/der equipped bike for efforts of the same distance, the wattage produced is also the same. Any drop in "average" recorded cadence on the road would be due to occasional freewheeling, which you can't do on a fixed gear bike without some ugly consequences. But that's just for me; I have a lot of data points from both disciplines, the pursuit and sprint data from the track overlays pretty seamlessly on my prologue and sprint stuff on the road.
The comment about velodromes is that velodromes are flat. I have lots of data files from many different riders where I can see their moment-by-moment power, cadence, and the virtual slopes they're riding on. No one rides at a constant cadence of 101+ under all conditions.
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Old 10-08-10, 11:54 AM
  #58  
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Originally Posted by RChung
The UCI record book has it being set at the Vigorelli Velodrome in Milan.
According to Fothringham's pretty well researched biography of Coppi, the Vigorelli track was in use for troop mustering at the time, and if memory serves had been also hit by allied bombs, though that might have been later. Coppi supposedly did his ride on a long straight stretch of road in the Milan area. There was a fair amount of detail in the book about the effort and subsequent certification.

The UCI probably went with the location of convenience.

Originally Posted by RChung
No one rides at a constant cadence of 101+ under all conditions.
I do. I'm that good.

Seriously though, it's something I've worked on. I can take my TT files apart and there's little difference between the out and back legs, or from TT to TT. At our State TT this year on a rolling course with several snappy climbs and variable winds I was at 99 RPM on the out leg and 100 on the return leg. That's pretty typical for me. Even at Gila my cadence was within a couple of RPM average and that's a major up and down course with nasty winds.

But there certainly are peaks and valleys in there.

Much less so for my pursuit efforts; and even in the Team Sprint I ended up much closer to my "best practices" TT cadence for my leg; much higher gearing than most track guys thought would work.
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Old 10-08-10, 12:05 PM
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Originally Posted by Fat Boy
Logically, the chain line remaining the same helps (i.e. track bike), but in the data I've seen the chain line doesn't make a hell of a lot of difference. Whatever losses exist because of a cross-chain seem to be overshadowed by losses due to making the chain take a tighter radius.
I'm skeptical that 53/27 cross chain, given the amount of noise it makes, creates little difference.
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Old 10-08-10, 01:46 PM
  #60  
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Originally Posted by Racer Ex
I'm skeptical that 53/27 cross chain, given the amount of noise it makes, creates little difference.
Fair enough. I'm going off of _Bicycling Science_ 3rd Ed. pg. 342

Noise is a type of transmission loss, so there is that. I guess what shows up in standard tests is that the loss in efficiency due to the cross-chaining is offset or more than offset by the gain in sprocket size. Interestingly enough, they also found to transmission efficiency differences due to lubrication or the lack thereof. A dry, rusty chain, however, does show an efficiency loss, so at least _that_ makes sense.
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Old 10-08-10, 06:34 PM
  #61  
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Originally Posted by dbikingman
I've read that thread I have purposely left out what my candence is to avoid such arguements. I'm not trying to get to some magical candence number. I'm just trying to figure out how much effort/power others feel they are putting out at higher candences.
I will try to answer this for me personally. I fatigue as I drop below 95rpm. That is to say, my muscular endurance is not as good, because higher torques are draining on my muscular system. From 95 to roughly 104 is my "wheelhouse." I develop a sustainable power that equally taxes my muscular endurance and my cardiovascular and gas exchange systems. Above 105 I find that my HR and PE climb without any increase in power and in fact, my sustainable power takes a nosedive as I spin much beyond this. I say sustainable power because I always sprint in this range, and have run a few, short, track races at very high average cadence. For me, every TT in the past 4 years (hill climbs, rolling, or flat) have nailed either 100 or 101 for a cadence. Just where my balance lies.

Is this what you were looking for?
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Old 10-08-10, 06:42 PM
  #62  
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Originally Posted by RChung
No one rides at a constant cadence of 101+ under all conditions.
Since I assume you are here to be argumentative rather than helpful to the OP, I will try to satisfy you.

You are the king. You are correct on all counts. You are in line with the greatest of all coaches and gods.

And hopefully that satisfies you. Unless it doesn't, in which case, I would still ask you to be unsatisfied but at least TRY to help the OP with the might of your knowledge.
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Old 10-08-10, 08:51 PM
  #63  
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DrWJO that is helpful. Reading this thread and others here have been helpful. I am amazed at those that pedal above 120, or state they do. I'd look like a match if I tried to go above 120. Maybe I need to figure out a training program. I feel I've got a base, but just haven't worked towards improving speed. My improvements in speed have come from JRA. i push myself on these rides, but I'm trying to get to a whole new level. I am now finding, or feeling, I'm inefficient when I try to push myself to new levels.

As was suggested above I've been doing one legged pedaling. Sprints during my rides and just a faster pace for shorter rides (TT efforts). I guess it is like many things there are so many different areas to work on, once you get something down, there is something else, repeat ad nausuem.

I will say some of this discussion seems to be over my head, but hey I got nothing but time to learn.
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Old 10-09-10, 04:57 AM
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dbikingman, what you may be experiencing as "efficiency" may have to do with smoothness. What happens a lot is when people start to increase their cadence, is they get more and more sloppy. The variations between peak & minimum pedal-pressure increase and you may end up with a situation where power drops. This could be due to the upstroke-leg getting lazier and requires more wasted power from the downstroke-leg to push it up. It could also be due to continually pushing down on the pedal at the bottom of the stroke (foot should actually be moving backwards). These effects aren't as noticeable at lower cadences, but gets multiplied at higher RPMs.

You should also have sufficient overhead to ensure smoothness. I prefer to have a 100% overhead for my cruising cadence. So if I want to target 90-rpms as my cadence for 25mph in 40k TT, I want to be able to spin 180rpms. This ensures that I"m smooth at 90rpms. However, as others implied, there is a balance between muscles and lungs when it comes to selecting optimum cadence. The general rule-of-thumb is legs face more stress at low-RPMs, while the heart & lungs are stressed more at high-RPMs. For me, 90-rpms for 25mph is way too low, my legs get fatigued and cramp up within 30-minutes at that pace. However, 100-105 rpms lowers the leg stress and balances it out nicely with my cardio system.

That's assuming you're after steady-state TT power and efficiency. If you want to improve interval and sprint speeds, you may need to increase RPMs even more. That's because power = pedal force * RPM. If you are already at the point where you're pushing down on the pedals as hard as you can, the only way to increase power is to spin faster (while not lose efficiency). Two equally-strong sprinters can face off in a finishing sprint. If one slams it into top-gear and slugs it out at 65rpms and the other uses a lower gear for 130rpms, they can both push with equal force on the pedals. However, the guy using 130rpms will generate TWICE as much power and end up going faster and winning the race. Many track sprinters practice spinning at 200rpms+ just for this reason.
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Old 10-09-10, 08:34 AM
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Originally Posted by DrWJODonnell
Since I assume you are here to be argumentative rather than helpful to the OP, I will try to satisfy you.

You are the king. You are correct on all counts. You are in line with the greatest of all coaches and gods.

And hopefully that satisfies you. Unless it doesn't, in which case, I would still ask you to be unsatisfied but at least TRY to help the OP with the might of your knowledge.
Dude, the OP won't benefit from reading wrong and misleading things no matter how genteel the phrasing nor civil the tone. You've been posting wrong and misleading things. You know, if you're sensitive about having your errors pointed out, you could either cut down on the wrong info or else grow a pair. Just sayin'.
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Old 10-09-10, 08:50 AM
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incorrect
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Old 10-09-10, 11:04 AM
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Originally Posted by Fat Boy
incorrect
1. My English ain't bad for a non-native speaker.
2. Speaking softly and well doesn't make the words right; being a dick doesn't mean I'm wrong.
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Old 10-09-10, 11:13 AM
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this is going in circles
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Old 10-09-10, 12:55 PM
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Originally Posted by Grumpy McTrumpy
this is going in circles
At what rpm?
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Old 10-09-10, 01:05 PM
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Originally Posted by RChung
1. My English ain't bad for a non-native speaker.
2. Speaking softly and well doesn't make the words right; being a dick doesn't mean I'm wrong.
Can't you be right and not be a dick?

Why not teach us something in a way that we'd actually learn instead of calling everyone on here stupid and being abrasive. Seriously, we like having a discussion on here and we're all ears to what you really think minus the rhetoric.

So, tell us how you really feel without the feeling...
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Old 10-09-10, 01:11 PM
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Originally Posted by RChung
At what rpm?
Cadence is a red herring.

As far as the cross chain vs. 53/11 goes, my simple bench test shows greater drag going 53/27....takes more pedal weight to cause drive train movement. Not sure how bike science ran their test rig. Granted the test is biased towards static vs. dynamic, but for this model there shouldn't be a great divergence.
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Old 10-09-10, 02:49 PM
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Originally Posted by ridethecliche
Can't you be right and not be a dick?
1. What's the fun in that?
Why not teach us something in a way that we'd actually learn instead of calling everyone on here stupid and being abrasive. Seriously, we like having a discussion on here and we're all ears to what you really think minus the rhetoric.
2. I didn't call anyone here stupid. I said DrWJODonnell was wrong.
3. I stayed out of this discussion until DrWJODonnell started to lead the OP down the wrong path with bad facts. Bad facts make bad learning.
4. If you were really all ears and open to learning, you would've paid attention to this:
https://www.bikeforums.net/showthread...1#post11575913
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Old 10-09-10, 03:32 PM
  #73  
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Originally Posted by RChung
Bad facts make bad learning.
Then you shouldn't argue for points you believe to be invalid.

Originally Posted by RChung
those one hour efforts are not done at greatest efficiency. They don't give a rat's ass how few calories they have to burn -- they only care about how many kms they can cover in an hour.
Originally Posted by RChung
Power/kcal is a red herring.
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Old 10-09-10, 03:32 PM
  #74  
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I read this thread and thought I was in the 41.
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Old 10-09-10, 03:35 PM
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Originally Posted by mollusk
I read this thread and thought I was in the 41.
How do I get my dork disc off without removing the rear wheel?
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