1:7 Friday to week ratio stinks.
2014-02-28 15:29:41
27
The F-ratio
In the light of my experiments riding single speed, I propose to add a new term to the cycling lexicon, the F-ratio.
The F, naturally, is force, and it's taken in ratio to body weight, although other F words may also come to mind.
The ratio could be computed as follows: ((formula for calculating power)/(2*PI*crank length*cadence)). Many sites will take care of the first part for you. And cadence meters are cheap, there's accelerometer based cell phone apps, or for one off sampling or you could just look at your watch and count pedal turns.
Or simpler, in Pittsburgh, we're lucky enough to have many hills that allow a relatively simpler, but probably accurate enough calculation... at low, steady speed: gradient * gain ratio * (rider weight + bicycle weight + stuff)/ rider weight.
Now, I'm assuming the audience here, with love for all things shelton brown, will be familiar with gain ratio. For anyone who is not, it's just the inverse of mechanical advantage, or (rear wheel with tire radius/crank length) * (teeth in front ring / teeth in back ring).
If a term for equivalent to F-ratio already exists, please educate me. But if it doesn't, I think it's useful to add to the lexicon.
Now, I've defined in it here terms of gain ratio, but I don't think people really talk about gain ratio much. Would this fare better? I don't know, but suspect people don't talk about gain ratio much because it's too close to gear inches and fairly few change their crank length (or if they do, it's only once, to fit their leg length better, and then it's not worth thinking about afterward). Also because gear inches is proportionate to something riders see, movement forward per one pedal turn.
F-ratio expresses how that turn feels, and, at a limit, how much you have to smooth out power deliver over the whole stroke or yoink down on the handlebars to avoid stalling. Seems useful.
F-ratio is, perhaps unsurprisingly, an overloaded term. http://en.wikipedia.org/wiki/F-ratio_(disambiguation). But I think statistics, optics, and oceanography are far enough afield so as not to cause any confusion here (though nerd bonus points for someone who manages to construct a decent joke to prove me wrong). That will also be how I'll know whether the proposed term has stuck, if (by someone other than me) it gets put on that wikipedia disambiguation page and actually sticks.
I think it might, not in any way due to me, but because it's expressing a primitive sensation, but is doing it in a cycling context where some of us (myself included) have a self measuring naval gazing streak. Also it relates to riding style, gearing choices, and that whole stupid mini culture war. And people like saying F words.
Speaking of which, let's hear it for Fridays!
Cheers
2014-02-28 15:04:40
F=ma
2014-02-28 15:39:57
At last summer's Try-A-Bike Jamboree, the unicycling folks from Butler Wobble switched out cranks for a couple of their wheels, depending on whether they were climbing or trying for speed. That was the first and only time I've seen that done. Choices were 110 or 150 mm cranks.
2014-02-28 16:14:35
sorry, but I fail to see how these two equations are equal. please show us your math.
gradient * gain ratio * (rider weight + bicycle weight + stuff) is not equal to power. and show me an accurate web calculator for power.
how is watts/kg unsatisfactory?
2014-02-28 21:11:26
steve k wrote: how is watts/kg unsatisfactory?Fails to capture 50289134 different potential excuses.
2014-03-01 15:02:11
Neither equation is power to weight, that's all very much part of the cyclng lexicon already, nothing to add.
I'm talking about force to weight. As the closest to universal (people's strength to weight ratio varies obviously) way of talking about liklehood of pain.
I think it's also useful to talk about in terms of changes to positioning, pedal retention, and overall technique that become necessary as the ratio goes up.
It's probably also a useful marker, looking at the worst grade you want to be able to get up, and make bike gearing (or lack thereof) decision in those terms.
2014-03-01 19:25:04
I don't assume power calculators are accurate generally btw. In particular, no way to do wind resistance frontal area or drag coefficient, it's VERY loose guesses that go into those calculators .
I prefer the slow hill climbing scenarios where the work is overwhelmingly just to raise your altitude as a result.
2014-03-01 19:45:02
I have always wondered what the difference is between wet and dry roads due to surface tension from water between the tire and roadway.
There must be other small factors like that to add up also.....
2014-03-03 19:40:26
I calculated my greenfield F-ratio.
http://www.bikecalc.com/wheel_size_math
(155+30 (weight of bike) + 10 (weight of stuff))/155 *
48 teeth (front)/18 teeth (rear) *
349mm /170mm *
(349 is radius based off diameter from http://www.bikecalc.com/wheel_size_math)
.08 (from veloroutes, looks like 8% is the grade at the worst part of the greenfield climb)
=~
.57
Even two digits precision here is a bit much, as numerous posters have pointed out, there's a lot of inefficiencies to consider that probably add up to at least few percent in the best case. Still, I think it's probably a useful shortcut for me to look at that number, think about what it entails and wince slightly.
Also got me curious what that might mean in terms of projection for peak grade on my geared bike at the rock bottom granny gear 24 (front) / 28 (rear). Basically, it says 25% grade equivalent there.
That number was honestly pretty disappointing, I think this feels worse than that honestly, maybe resistance increasing a bit with speed. I think a more significant factor may be the length at that or near that gradient. I've never had to ride for long at that gradient. Anyways, it's true-ish to my experience, the major difference in the feel being, I think, just that it's more possible to accelerate the pedals on the steeps with lower geering since you accelerate yourself so little by doing so whereas here it's more a wind up, wind down kind of thing. Not sure in terms of biomechanics or psychology which is better... may be an individual thing.
2014-03-04 12:54:28
I think one interesting marker here actually is the F ratio of a cyclist relying on body weight only (well, and the magical ability to lift their body weight instantaneously from a position at the bottom of pedal stroke to top of the alternate pedal stroke).
Basically, then, the force ratio is the average of the absolute value of a sine function over a full revolution, or 2/PI.
With perfect efficiency (no resistance other than gravity and an infinitely light bike), this is also equivalent to climbing stairs 2 X the size of the crank arm length.
So, all very amusing and silly, but seriously, for those that ride with an F ratio approaching or above .637 for more than a short stretch, what's your technique? Pulling up on the pedals, down on the handlebars, ankling through the stroke? Some wacky maneuvering with the hips? Some combo? What works? I'd like to survey the field.
2014-03-04 13:19:33
This is satire, right?
2014-03-07 18:20:53
I'm seriously semi-serious here.
If the F-ratio exceeds your strength to weight ratio over a turn of the pedals the gear is on top of you there and you'll be bogging down, that the gear is on top of you. That to me means it's a useful measure.
Was hoping to get more physics geek/bike racing geek type responses. Bonus if there were a kinesthesiologist in the house. Anyways, looks like this all went kinda pffft. Unless someone wants to prove me wrong now, which would be great.
I can easily see why taking a survey of "wacky maneuvering with the hips" might not be taken all that seriously.
2014-03-09 00:03:49
Being "on top of/under the gear" speaks to me. I get that. You're trying to identify and quantify that moment most of us recognize but can't put our finger on. That some crazy sh*t. But that's also why I try and avoid power meters and the like. I'll be interested to see where this goes.
2014-03-09 10:29:43
I've stayed out of the discussion so far, but taking the 10,000-foot view, it seems to me you're trying to objectivize a subjective measure. To me, it's a deeper topic than mere force-to-mass ratios and other simple measures of physics. More variables, more complexity, perhaps some principles of artificial intelligence involved.
Taking a different approach, I had a friendly argument a few days ago about why one would want to deal with East Carson St out past Hot Metal St to Becks Run Rd. To use a specific example, if you were starting at Zenith Antiques at Sarah and 26th, and headed to Colteryahn Dairy on Brownsville Rd just north of Agnew Ave in Carrick, whether you would go 18th St or Becks Run? The latter is longer by about a quarter mile but has an easier grade. And the easier grade might make up for the suckier traffic situation on that half mile of Carson. And the main point of input in making that decision would be what you are trying to quantify with your F ratio.
Am I on topic here, or going off on a useless tangent?
2014-03-10 06:17:14
No one number is going to tell you everything. The question to me is whether that number tells you one useful thing. I think this does... how hard it is to turn the crank. Arguably I could have left it exactly there, units in (shudder) pounds, or newtons.
It's normalized to body weight because I believe it's a more reasonable measure of strength, would get a tighter dispersion and more comparability. And by dividing by body weight you get something very specific, a measure of strength requirements at gearing and grade.
Normally, nobody cares whether it's force or cadence that gets you there, if you have the power, you have the speed. That's true as long as there's always another gear. Most of the time that's true. But not always.
As with power, a single number doesn't tell the whole tale. I (just) managed to make it up my driveway on Friday, where, while I freely admit over first 3, 25% grade slabs I was loosing speed rapidly. But where it leveled to 13-15% I was (just) managing to keep the 5 or 6 mph I had left.
Does that mean I could've kept going at 13-15%? Hell no. I can only do so many one legged deadlifts. I imagine like with power to weight you could easily make up an F-ratio chart like this one for power to weight : http://www.bicycling.com/training-nutrition/training-fitness/trainingpeaks-power-profiles-cyclists. That would be a really useful resource, actually.
2014-03-10 08:19:21
As a singlespeeder on flat pedals, there are a some confounding factors that spring to mind.
There are optimal pedal cadences depending on if you are standing or sitting as well as the grade. This is related to how much force is applied to the pedals during various parts of each stroke. Certain muscle groups are better to use than others so optimal power is variable throughout the stroke. Standing on the pedals means that the optimum cadence changes as compared to sitting, etc.
To help acheive the most power when in the body position to deliver it efficiently from the optimal muscle groups, it is pretty typical to sway the bike from side to side. This makes part of each pedal stroke easier and part of each pedal stroke harder. When the slope gets really tough, I augment this with a forward/backward body motion that accentuates that effect.
Another observation as a singlespeeder is climbing strength can be measured in different ways. Riding a singlespeed means that you're typically climbing in too high a gear. It forces you develop muscles and a riding technique for that. I am extremely fast at most of the hills around here. Yet my hill climbing endurance is not as good as geared riders.
What's it all mean? Beats the hell out of me. But my take is that it is impossible to derive broad conclusions from such an isolated measure.
I know downhillers on the UCI circuit are now doing practice runs with crank-based power meters before races. The data from this is combined with GPS data and suspension monitoring sensors... mind blown.
2014-03-10 10:41:06
Can you dumb this down so I can tell you why its not needed?
I think so much of this has to do with efficiency that it is relative to
the user. some people are crazy efficient out of the saddle. Others
not so much.
Power to weight
VAM
If you want to geek out individual physical ability you can use wko.
If you have a power meter and wko you can look at the quadrant graphs.
http://support.trainingpeaks.com/trainingpeaks-wko/wko-user-guide/workout-data/quadrant-analysis.aspx
2014-03-10 21:34:59
Everything you sent was power focused. Which makes sense, you want to go fast. It's based on the assumption that you always have all the gears you need to optimize that and are just trying to zero in on the right trade-offs. I have no doubt that's 100% correct in your case.
Most others, like myself, do not approach that level of fitness. I'm also fed up enough with winter destruction to chuck the sensible gearing mentality, loose a little time (bad), and force a little more dietary and mental discipline (good) by making even a basic climb a bit of a test.
The F in the F ratio looks like AEPF. So, that perhaps is why this is not necessary. But I still think it's more useful normalized to body weight and I think this is a catchier name.
People can geek out with power meters and quadrant analysis. People could geek out to F-ratios. But I think F-ratio can also be less on the geek out of the spectrum than most measures.
Where did it feel like the gear was on top of you and you were bogging down on a stern hill climb? Get the gradient, weight of a couple things, do a little math and you've got a number that's a reminder of that suckiness. Remember it, avoid it, or depending on your inclination, attack it.
Or, you climbed hill A in this gear, what about hill B in another gear? Again, assuming all this is slow moderate or high gradient stuff, do a tiny bit of math and you've got a number that tells you something about the way B will feel.
Obviously only partly... how long you're going matters here as much as with power (maybe more when we're talking high forces and suboptimal cadence?). I'd really like to see a chart produced like the one I linked earlier for power to weight. I think it would be useful in telling you whether, for instanced, fixed/single speed makes any sense given your fitness and where you want to ride that bike or if it's just foolishness. Also might help people choosing between road/compact crank or triple when considering steeper hills.
That's the theory anyways.
2014-03-10 23:29:42
Or you could, you know, just ride up the hill and find out if you want a different gearing. ;-)
It's an interesting exercise so I don't to discourage your theorizing. At the same time, it is doubtful that anyone would choose between a compact and a triple via calculations. If you know enough about biking to do that kind of work, you already know what size gear you can push.
And that's assuming that the calculation is valid for such a purpose anyway. While measurements can be performed, it isn't clear if they can be used to predict performance in a different scenario. Each person has their own optimal cadences for standing, spinning, or standing and swaying, etc. And then there is muscle types, height to weight ratios and more. All of these contribute to everyone having a different performance curve based upon gearing, grade, altitude, available traction, etc.
I too like to geek out and ponder the science of bicycling. In particular, I'm fascinated by platform pedal performance vs clipped in. My take is that the efficiency difference is far less than widely believed.
Yet when I've looked for research, it seems there is a massive jump required between fuzzy heuristics and meaningful, empirical data. Attempting to simplify bicycling performance modeling leads to inaccurate generalizations. In my opinion, the f-ratio described in this thread is of no use other than an exercise in contemplating a few factors that influence cycling.
For the record, my favorite 29er gearing for singletrack around Pittsburgh is 28x17. For road riding, I've tried figuring out a good single speed ratio for my cross bike. Yet at my preferred gearing, the frame twists a scary amount under heavy acceleration and occasionally causes the right crank to hit the chainstay. That bike has a max f-power limit. ;)
2014-03-11 08:00:59
Oh . . . And here I thought is was the ratio of the use of the F-bomb to the remaining words in sentences uttered by passing SUV owners.
Never mind. ;-{)}
2014-03-11 09:58:15
It's a number in the stew.
Just ride and see how it goes is never the wrong answer.
There are other numbers or combinations of numbers that are more important in terms of performance in most scenarios, unless I think when you're riding fixed or single speed on hills, where it looms large (at least to me).
In any case I think I can somewhat tie to a feel and one that creates a need to change technique to compensate. Would like to hear more from that angle.
Thanks for starting into that discussing standing (which I do often), standing and swaying (which I rarely but sometimes do, though not sure if it's really makes part of the stroke easier and part harder, main mental image is clearing a path for the power of a downstroke), and front to back motion (which I don't think I do at all).
Would like to understand the "feel" to drive for better when feeling near my sustainable limit on pedal effort and needing to eek out that little bit extra, but preferably before getting into full one legged deadlift mode. In terms of the visual, would watching some dirty dozen videos basically give the idea? Seems like at the bottom of the stroke there's a little kick forward basically??
I'm just a touch wary of trying to do forward/backward shifting because I'm worried about slipping from the platforms. I'm not sure if you're saying because the efficiency difference doesn't feel all that great that means the technique is also pretty much the same clipped vs unclipped?
BTW, that's crazy that the bike flexes that much! I've been getting annoyed about occasionally hitting the kickstand on hard efforts... wasn't sure if that was my foot just getting in a weird position, a more minor case of frame flex, or what. Will pay more attention to it.
2014-03-11 10:37:51
PghDragonMan wrote:Oh . . . And here I thought is was the ratio of the use of the F-bomb to the remaining words in sentences uttered by passing SUV owners. Never mind. ;-{)}I called it F-ratio and not force ratio to invite stuff like this. I was thinking of F-bombs on the part of the rider mind you, but I think there's a reasonably strong correlation between stuff that requires hard effort on the part of the rider, stuff that makes a rider slow, and stuff that motorists curse riders for. You could go on another tangent and make F-ratio a sub-in for "fixie" and correlate with both high required forces and a whole cluster of cursable behaviors. It's fun that way.
2014-03-11 11:11:32
Keep in mind, much of what i've been spouting off is from the perspective of a single speed mountain biker. At least some of it is transferable though. The point is that climbing ability/optimization is extremely complicated.
Frame flex is something I feel on every bike under heavy acceleration. But that's probably because I start from a stop in a higher gear than most people. That is a factor of using platform pedals on a singlespeed mountain bike.
At first, carbon bars were scary because they reaaally flex with hard pedaling. Each downward stroke exerts enough pressure on that side of the bike that you have to pull up on that side of the handlebar and push down on the other. They visibly deform when being used to prevent the frame from swaying.
Pedaling up steep grades on a single speed is a fairly good upper body workout. Just resisting the twisting of the bike takes a lot of strength. Add on top of that, extra swaying for easier climbing, and it's even more of a workout.
What that does is use downward leg motion/momentum on a greater portion of the entire pedaling stroke, which is precisely the opposite of what road cyclists try to achieve when pedaling long distance seated with clipless pedals. Yet it is also a technique common to mountain biking in particular, especially for riders who ride shorter distances more aggressively rather than fixating on long distance efficiency.
The forward backward motion that I referred to mostly is useful when climbing really steep slippery surfaces on a singlespeed. It can be used as a ratcheting mechanism to move your weight forward without losing traction. It isn't an extended climbing technique.
If worried about slipping off of the pedals, try some platform pedal specific shoes. There is zero slipping with those.
Here's an interesting read on platform pedals:
http://www.bikejames.com/wp-content/uploads/2012/12/ManifestowithLinks2.pdf
2014-03-11 11:52:40
Thanks for that link. A good read I should have gotten to earlier.
I'm at least not doubting if I can make the climb any given day or having as much discomfort so I'm on track to making this really work, just need to find out how.
The main implication I think I'm drawing from this and some recent experience to my situation is that stand and mash is natural, probably more natural than seated climbs at high force and low cadence, and not to necessarily plop my butt down the moment I think I can get away with it without risking stopping entirely.
In retrospect the climbs that hurt the most THE NEXT DAY are the ones where I tried to be in the saddle more to save energy. Need to work on the mental discipline and conditioning so I can tap what energy I do have more deeply and build it up to a better level. Put those demands on my system, not torque on my back at an acute angle.
Never really thought of platform pedal shoes as a category. Do they loose grippiness quickly if used as a general purpose shoe?
2014-03-19 11:44:23
Platform pedal shoes aren't too unusual but do differ in important ways from normal shoes. With the right shoe, your foot feels glued to the pedal and slipping off is pretty much impossible.
They tend to be a bit stiffer in the sole, which is important when you're standing on something smaller than your foot.
The sole rubber is strangely hard but maluable. It feels hard but if you press your fingernail in, the nail will slowly sink deeper and deeper. The rubber molds itself to the shape of the pedal.
The bottoms of these shoes are mostly flat. This allows variable foot placement without having to worry about where the pedal pins are in relation to tread pattern.
The most popular brand is Five Ten. They started out making climbing shoes but now most of their business is probably bike shoes.
http://fiveten.com/products/bike
But back to pedaling...
Here's an expensive toy if you want to really geek out on pedaling. Pioneer is making a crank based power meter that displays pedaling force and direction throughout the entire pedal stroke, independently for left and right leg!
http://www.bikerumor.com/2013/03/21/in-depth-look-at-pioneer-crank-based-power-measurement-cycling-computer/
2014-03-19 12:27:18
dfiler wrote:Platform pedal shoesThis concept is useful to me.
2014-03-19 15:11:36