Fixed Gear vs. Freewheel
11-20-17, 02:58 PM
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Like you I'm convinced that the cycle from zero power to peak is more taxing than something steady in the middle, even though the same amount of work is done. But I can't actually prove it. I suspect that types of muscle recruitment will vary even at low power and low cadence, and I know that if so it will impact biomechanical efficiency.
Beginners often do that coast-pedal thing and usually grow out of it with enough training, looking for a more steady and higher paced cadence. I think the question of "why" would be worth investigating. Is it a relative strength deficiency in slow-twitch? Are they optimizing energy use, as might be suggested by related investigations? Something to do with their energy transport systems? Or is it just poor untrained technique? It is possible IMHO, that the answer would lead to the why of the perception (of some) that fixed gear riding is somehow "more ease" than the same ride with a freewheel.
11-20-17, 07:21 PM
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Keep in mind that, as I explained earlier, the rear wheel, sprocket and chain can't push the cranks around without the noticeable pop of the slack moving from the lower to upper loop. So, the rear wheel cannot be acting as a flywheel or in any other way helping the cranks turn more smoothly. It's all YOU using learned motion to keep the upper loop constantly tensioned to some degree.
I liken this flywheel effect (illusion) to descending a steep flight of stairs. We've all done this a number of times, and probably remember how using the banister helps. But do we actually use the banister, ie. grab it to steady ourselves, or do we simply keep our hand floating above it, and in doing so feel more secure and descend with more confidence?
I liken this flywheel effect (illusion) to descending a steep flight of stairs. We've all done this a number of times, and probably remember how using the banister helps. But do we actually use the banister, ie. grab it to steady ourselves, or do we simply keep our hand floating above it, and in doing so feel more secure and descend with more confidence?
As for descending steep stairs, well, I have a LOT of experience with that - or at least had. Spent the better part of four years going up and down ship's ladders several times a day - whole series of them, too, so I got very good at descending them VERY fast - for many of us, the sound of our feet on the treads was like a burst of a drum roll, and plenty of others would indeed slide down the handrails without their feet touching the treads. The handrails were crucial. There's a transition between relying on the handrails somewhat and relying on them completely. I felt that the most excellent way was to rely on the treads about the way most people rely on the handrails - you might be surprised how little of either you really have to rely on.
Doesn't matter anyway, since whatever "flywheel effect" the rear wheel has, it would be the same whether or not it's connected to the pedals.
In fact, if you feel it it's because the pedals are pushing against your feet and that has the opposite effect of a flywheel - slowing the bike down.
In fact, if you feel it it's because the pedals are pushing against your feet and that has the opposite effect of a flywheel - slowing the bike down.
11-20-17, 08:35 PM
#203
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I must be missing something here. Why is it necessary for the wheel to work both sides of the loop if our legs don't have to? I mean, we can't push the lower loop when we make the wheels turn, so why should the wheel have to push the upper loop to make our legs turn? Isn't the pulling sufficient in both cases? ......
BTW - while we're here and you bring it up, you were taught wrong. Properly tightening a chain means NOT putting it under tension, which increases friction, wear and bearing loads. Proper chain tension has the return loop slack, with roughly 1/2" vertical play at the center.
When I brought up slackening the chain more than normal, it was only increase the amount of backlash for demonstration purposes, so the transfer of tension top to bottom would be obvious, as would it's not happening when you rode normally.
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11-20-17, 08:43 PM
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Yes, you are missing something. While I said, "pushing" the cranks around, you're taking it too literally. Earlier in the thread I explicitly said the rear wheel can't push the cranks via the upper loop, and tension is transferred to the lower loop when the wheel drives the cranks.
BTW - while we're here and you bring it up, you were taught wrong. Properly tightening a chain means NOT putting it under tension, which increases friction, wear and bearing loads. Proper chain tension has the return loop slack, with roughly 1/2" vertical play at the center.
When I brought up slackening the chain more than normal, it was only increase the amount of backlash for demonstration purposes, so the transfer of tension top to bottom would be obvious, as would it's not happening when you rode normally.
BTW - while we're here and you bring it up, you were taught wrong. Properly tightening a chain means NOT putting it under tension, which increases friction, wear and bearing loads. Proper chain tension has the return loop slack, with roughly 1/2" vertical play at the center.
When I brought up slackening the chain more than normal, it was only increase the amount of backlash for demonstration purposes, so the transfer of tension top to bottom would be obvious, as would it's not happening when you rode normally.
Well, I never managed to get it tight, so I guess that's a good thing. I just checked, and I can lift and press the chain about 1/2" on both the upper and lower. Is that totally screwed up?
Still, I don't understand how the slack would prevent energy transfer in one direction when it doesn't prevent it in the other. Are you saying that because it's slack only on the lower side, the wheel can't effectively pull? Of course it doesn't work to push a chain - regardless of which side it's on. Do I have that much right?
By the way, why is it "proper" to have slack?
Last edited by kbarch; 11-20-17 at 08:47 PM.
11-20-17, 08:48 PM
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Huh.
Well, I never managed to get it tight, so I guess that's a good thing.
Still, I don't understand how the slack would prevent energy transfer in one direction when it doesn't prevent it in the other. Are you saying that because it's slack only on the lower side, the wheel can't effectively pull? Of course it doesn't work to push a chain - regardless of which side it's on. Do I have that much right?
Well, I never managed to get it tight, so I guess that's a good thing.
Still, I don't understand how the slack would prevent energy transfer in one direction when it doesn't prevent it in the other. Are you saying that because it's slack only on the lower side, the wheel can't effectively pull? Of course it doesn't work to push a chain - regardless of which side it's on. Do I have that much right?
The free play you get when the slack transfers between the two loops is called backlash.
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11-20-17, 09:02 PM
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Yes, the chain can ONLY pull. So when you pedal the upper loop is tight, and the lower is slack. When you back pedal or if the wheel is "pushing" (idiomatic English, it's actually pulling the crank by the lower loop which is now the tight one and the upper slack.
The free play you get when the slack transfers between the two loops is called backlash.
The free play you get when the slack transfers between the two loops is called backlash.
So backlash occurs whenever we transition between slowing the bike and speeding it up AND vice versa? After it has occurred once we get back underway and start pulling the bike along, everything works fine, right? So wouldn't everything work fine after the backlash occurred once we started letting the wheel take over, pulling our legs along? The loss from backlash would be the same in either case, wouldn't it? I'll concede there's only loss once we let the wheel take over - I mean, the wheel would be just as capable of moving our legs as our legs are capable of moving the wheel, except the wheel is incapable of bringing anything new to the party the way our legs can; our legs would just be bringing it down, the way the wheels usually do.
11-21-17, 12:56 AM
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There are tons of research papers concerned with the efficiency of muscles, and many of them discuss the "internal friction" of muscles. Unfortunately, you have to pay to get the full text of most journal articles today. I have copied and pasted a few paragraphs from one I have a copy of: Mechanical Muscular Power Output and Work During Ergometer Cycling at Different Work Loads and Speeds, M. Ericson, European Journal of Applied Physiology (1998)57; 382-387.
So, what's the punchline? There are no free lunches - it takes a fair amount of power to move those pesky legs, even when there is no external resistance, i.e. even if you're soft pedaling.
(Again, there are lots of research papers that echo this conclusion.)
Summary:
The aim of the study was to calculate the magnitude of the instantaneous muscular power output at the hip, knee and ankle joints during ergometer cycling at different work loads and speeds. Six healthy subjects pedaled a weight-braked cycle ergometer at 0, 120 and 240 W at a constant speed of 60 rpm. The subjects also pedalled at 40, 60, 80 and 100 rpm against the same resistance, giving power outputs of 80, 120, 160 and 200 W respectively.
Introduction:
The cycle ergometer has been used extensively in applied human physiology. One use has been in attempts to determine human mechanical efficiency (e. g. Benedict and Cathcart 1913; Dickinsson 1929; Garry and Wishart 1931; Whipp and Wasserman 1969; Gaesser and Brooks 1975; McCann and Gliner 1982). In most of these studies the total amount of muscular work done has been assumed to equal the external work dissipated in the ergometer braking system.
Some investigations have aimed at determining "internal friction" (Benedict and Cathcart 1913; Garry and Wishart 1931; Bigland-Ritchie et al. 1973; L611gen et al. 1980) or "internal mechanical work" (Kaneko and Yamazaki 1978; Wells et al. 1986). Internal mechanical work (W-int) is regarded as the work that is necessary just to move the limbs and that cannot be measured at the ergometer braking system. Work efficiency has been defined as the ratio of work accomplished to energy expended above that in cycling without a load (Benedict and Cathcart 1913; Dickinsson 1929; Garry and Wishart 1931; Bal et al. 1953; Gaesser and Brooks 1975). These authors also questioned whether "no-load" cycling really represents the work necessary just to move the limbs ("internal friction" or "internal mechanical work"). Using quantified and normalized EMGs to study the electromyographic activity in eleven lower limb muscles during cycling at different work loads and speeds, Ericson et al. (1985) showed that the recorded full-wave rectified EMG during no-load cycling ranged between 2 and 118% of the activity recorded during cycling at 120 W. The highest activities were in biceps femoris (44% of the activity recorded during 120 W cycling), medial hamstring (64%) and medial gastrocnemius (118%).
Kaneko and Yamazaki (1978) tried to estimate the W-int necessary to just move the limbs during cycling. They estimated that W-int was equal to the sum of the kinetic energy of the limb. Wells et al. (1986) calculated the internal mechanical work, including not only the kinetic energy but also the changes in potential energy of the limb. They found that the internal work rates obtained during cycling at 30, 60 and 90 rpm were 11.5, 20 and 62 W respectively.
The aim of the study was to calculate the magnitude of the instantaneous muscular power output at the hip, knee and ankle joints during ergometer cycling at different work loads and speeds. Six healthy subjects pedaled a weight-braked cycle ergometer at 0, 120 and 240 W at a constant speed of 60 rpm. The subjects also pedalled at 40, 60, 80 and 100 rpm against the same resistance, giving power outputs of 80, 120, 160 and 200 W respectively.
Introduction:
The cycle ergometer has been used extensively in applied human physiology. One use has been in attempts to determine human mechanical efficiency (e. g. Benedict and Cathcart 1913; Dickinsson 1929; Garry and Wishart 1931; Whipp and Wasserman 1969; Gaesser and Brooks 1975; McCann and Gliner 1982). In most of these studies the total amount of muscular work done has been assumed to equal the external work dissipated in the ergometer braking system.
Some investigations have aimed at determining "internal friction" (Benedict and Cathcart 1913; Garry and Wishart 1931; Bigland-Ritchie et al. 1973; L611gen et al. 1980) or "internal mechanical work" (Kaneko and Yamazaki 1978; Wells et al. 1986). Internal mechanical work (W-int) is regarded as the work that is necessary just to move the limbs and that cannot be measured at the ergometer braking system. Work efficiency has been defined as the ratio of work accomplished to energy expended above that in cycling without a load (Benedict and Cathcart 1913; Dickinsson 1929; Garry and Wishart 1931; Bal et al. 1953; Gaesser and Brooks 1975). These authors also questioned whether "no-load" cycling really represents the work necessary just to move the limbs ("internal friction" or "internal mechanical work"). Using quantified and normalized EMGs to study the electromyographic activity in eleven lower limb muscles during cycling at different work loads and speeds, Ericson et al. (1985) showed that the recorded full-wave rectified EMG during no-load cycling ranged between 2 and 118% of the activity recorded during cycling at 120 W. The highest activities were in biceps femoris (44% of the activity recorded during 120 W cycling), medial hamstring (64%) and medial gastrocnemius (118%).
Kaneko and Yamazaki (1978) tried to estimate the W-int necessary to just move the limbs during cycling. They estimated that W-int was equal to the sum of the kinetic energy of the limb. Wells et al. (1986) calculated the internal mechanical work, including not only the kinetic energy but also the changes in potential energy of the limb. They found that the internal work rates obtained during cycling at 30, 60 and 90 rpm were 11.5, 20 and 62 W respectively.
(Again, there are lots of research papers that echo this conclusion.)
11-21-17, 05:52 AM
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There are tons of research papers concerned with the efficiency of muscles, and many of them discuss the "internal friction" of muscles. Unfortunately, you have to pay to get the full text of most journal articles today. I have copied and pasted a few paragraphs from one I have a copy of: Mechanical Muscular Power Output and Work During Ergometer Cycling at Different Work Loads and Speeds, M. Ericson, European Journal of Applied Physiology (1998)57; 382-387.
So, what's the punchline? There are no free lunches - it takes a fair amount of power to move those pesky legs, even when there is no external resistance, i.e. even if you're soft pedaling.
(Again, there are lots of research papers that echo this conclusion.)
So, what's the punchline? There are no free lunches - it takes a fair amount of power to move those pesky legs, even when there is no external resistance, i.e. even if you're soft pedaling.
(Again, there are lots of research papers that echo this conclusion.)
What we want to know here is: how many of the extra watts we crank out come back at us when we stop providing the power and the pedals start pushing on our feet, and how much good does it do us?
How much of the extra power that we put out in order to move more than our legs but the bike also is counter-productive? That is, to what extent are we applying force in the wrong direction relative to the pedal's position? I suspect this varies greatly with effort and cadence, not to mention the rider's physiology and approach. Aren't some peoples' pedaling styles more counter-productive than others'? Aren't some people's legs more resistant to being pushed around than others'? Would a light yet powerful rider be more likely to enjoy relaxing on a fixie than a heavier-legged one? Also, we apply the force in a very irregular fashion, but the wheel will pull the chain in a very regular fashion, so even though it's much less effective, wouldn't the rolling wheel be more efficient at moving our legs than we are?
And by the way, do we know how many watts it takes to cause freehub pawls to clatter at various speeds?
Add: I'm wondering exactly what those estimated wattages represent. Wouldn't it be dependent on the size and weight of the legs?
Also, it sounds like some people have researched the questions I was asking, but it's not clear what this study, which you only gave us some introduction to, was after, other than some data. What value is there in knowing "the magnitude of the instantaneous muscular power output" at various parts of our legs, anyhow?
Last edited by kbarch; 11-21-17 at 06:12 AM.
11-21-17, 07:20 AM
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For the purposes of the discussion in the past couple of hundred posts, the relevant point is this: when a rolling wheel is moving a rider's legs (i.e., when the legs represent a load on the wheel), those legs are slowing that wheel.
11-21-17, 07:54 AM
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That's a fact that has been acknowledged and taken into consideration, and hardly the point at all. The wheels slow the legs, too, but neither prevents the other from working altogether. It is the extent to which they do continue that matters in both cases.
11-21-17, 10:17 AM
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It pretty much is the point because we're asking what you gain or lose from it. If you let a pedal push your foot around, the work came originally from you pushing the pedal. You would get the same effect just by keeping heavy pressure on both pedals and having your power stroke push the other foot up. It's easy to see that it doesn't help anything to do that - the missing idea here is that you have the same result ultimately if it's the bike's momentum that pushes the pedal. You still had to push that momentum earlier, and opposing it later, working against yourself.
11-21-17, 10:33 AM
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It also suggests another reason someone might perceive "more ease" from the fixed gear compared to a multi-gear bike. Riding at low effort, their 70 gear inches or so would have them in the neighborhood of 60 rpm whereas with gears they may be riding at 80-90. It IS more ease, one third of overhead of moving your legs.
11-21-17, 11:17 AM
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Originally Posted by kbarch
... we never doubted that it takes some energy to move the legs.
11-21-17, 01:00 PM
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Oh, I remember. I also remember the difference between transitive and intransitive verbs, and that "move" is used both ways. In the first instance, I should have said "for the legs to move."
Last edited by kbarch; 11-21-17 at 01:04 PM.
11-21-17, 01:09 PM
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I don't know if it's more appropriate to say you're trying to move the goal line or make smoke and zig zag. Either way, I'm tapping out.
11-21-17, 01:09 PM
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so pedaling a few times at 60 rpm then resting would save them a little energy compared to pedaling steady at 30 rpm, but pedaling 90 and resting will cost them energy. This leads me lean to the idea new riders are optimizing energy when they pedal-coast because untrained riders usually self-select at the lower ranges of cadence.
It also suggests another reason someone might perceive "more ease" from the fixed gear compared to a multi-gear bike. Riding at low effort, their 70 gear inches or so would have them in the neighborhood of 60 rpm whereas with gears they may be riding at 80-90. It IS more ease, one third of overhead of moving your legs.
It also suggests another reason someone might perceive "more ease" from the fixed gear compared to a multi-gear bike. Riding at low effort, their 70 gear inches or so would have them in the neighborhood of 60 rpm whereas with gears they may be riding at 80-90. It IS more ease, one third of overhead of moving your legs.
11-21-17, 01:26 PM
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I'm sorry if your focus on this slight misunderstanding has been so exhausting; I was hoping your expertise would provide some insight, instead, into what causes the FG experience that people get so worked up about - what's actually happening, in mechanical terms, that makes it so perceptibly different. But if you don't think it's an important question, or if you're convinced that those of us who appreciate what happens when the bike and rider cooperate with each other are all deluded, then yes, by all means, you're excused.
11-21-17, 01:34 PM
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I guess I'm glad I discovered this thread late. It would have been frustrating to try to explain stuff to people who tenaciously hold belief in falsehoods.
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11-21-17, 01:41 PM
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11-21-17, 01:57 PM
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I'm sorry if your focus on this slight misunderstanding has been so exhausting; I was hoping your expertise would provide some insight, instead, into what causes the FG experience that people get so worked up about - what's actually happening, in mechanical terms, that makes it so perceptibly different. But if you don't think it's an important question, or if you're convinced that those of us who appreciate what happens when the bike and rider cooperate with each other are all deluded, then yes, by all means, you're excused.
I suspect that it's a bit of a placebo effect, caused by the reminder to keep pedaling that fixed gearing provides.
On a freewheel bike you tire a bit and coast, then as the bike slows you need to start pedaling and work harder because you're bringing the bike back up to speed. Depending on your habits and conditions, this may only be a small change, ie from 15mph to 16, any increase in speed is work.
On a fixed gear bike, the moment you start to coast, the bike reminds you that you can't, so you continue pedaling, maybe at lower effort, and the bike little or no speed, meaning you don't have to work as hard to bring it back to speed.
There's also the impossibility of shifting to a higher gear and moving faster, which would be more tiring. Most of us ride fixed in a gear lower than we might cruise in on a multigear bike. We do so because we know we canb't climb otherwise. So, since we're riding lower gears, possibly at a higher cadence it's easier to pedal. We forget that we'd upshift if this were our road bike, and give the fixed bike more credtit than it's due.
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11-21-17, 02:03 PM
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Case in point, it has come up that it takes some 62 watts just to spin the cranks at 90 rpm. Downhill fast on a fixed gear you aren't expending that 62 watts, the bike does it. The drag from your legs being dragged around won't make all that much difference in the top downhill speed either. Certainly whatever extra energy you do expend is more than you would with a freewheel, but that's beside the point, his point - it's less effort than you'd have just spinning at that speed, because the pedals are pushing his feet. Who cares if he incorrectly describes it as a "flywheel" or attempts to cite Newton's Laws inappropriately, the bike is still pushing the pedals pushing his feet. And incidentally, anyone telling him that that's impossible is also wrong. So I'd personally rather get at what someone is describing, instead of attacking his reasoning for why something happens, and then the ramifications aren't quite what he may have expected, and then go on from there.
11-21-17, 02:56 PM
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I think that what was being held against him was the smug manner in which he attributed any disagreement with his position to inexperience/lack of technique. Most are okay with someone being wrong, but the inclination to kumbaya is considerably diminished when attempts at correction/clarification are met with said wrong person shooting back, "yeah, well I guess you're just not accomplished enough to understand [this magical nonsense]" YMMV.
11-21-17, 03:26 PM
#223
Senior Member
why is this thread 9 pages long.
I thought I was going to see pics of fixies and good times it brings, not page upon page of navel gazing about bio-metrics or some crap.
I thought I was going to see pics of fixies and good times it brings, not page upon page of navel gazing about bio-metrics or some crap.
11-21-17, 03:55 PM
#224
Senior Member
Audible sounds really don't take much energy at all to produce. Actually, in many cases, loudness is even indicative of efficiency because the sounds aren't being damped away. A good example in cycling would be road tires; most are silent, but the really fast and supple ones hum on good roads, drummed by the surface irregularities.
Last edited by HTupolev; 11-21-17 at 06:31 PM.
11-21-17, 06:03 PM
#225
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Thanks, @FBinNY and @wphamilton
For me, the take-away here is that whatever mechanical advantages the FG arrangement may have, we know they are short-lived and insignificant, energy-wise, in the long run; the net result may be a disadvantage. Because of this, they are generally not considered worthy of study or explanation. And as a result of THAT, poor, often "mystical" explanations abound.
However, the reason these bad explanations arise is because the experience of being driven by the bike is extraordinary and highly enjoyable to many.
The various experiences have material causes, and for me, the most interest in one is the transition between the two states (pedaling and being pedaled) but perhaps that delightful feeling is more like a color, a flavor or a fragrance rather than the carbs, protein and fat that we normally concern ourselves with, but I suspect it is more substantial than a flavor, because it IS all about movement, after all.
For me, the take-away here is that whatever mechanical advantages the FG arrangement may have, we know they are short-lived and insignificant, energy-wise, in the long run; the net result may be a disadvantage. Because of this, they are generally not considered worthy of study or explanation. And as a result of THAT, poor, often "mystical" explanations abound.
However, the reason these bad explanations arise is because the experience of being driven by the bike is extraordinary and highly enjoyable to many.
The various experiences have material causes, and for me, the most interest in one is the transition between the two states (pedaling and being pedaled) but perhaps that delightful feeling is more like a color, a flavor or a fragrance rather than the carbs, protein and fat that we normally concern ourselves with, but I suspect it is more substantial than a flavor, because it IS all about movement, after all.