Tuesday, June 23, 2009

Efficiency In Inefficiency

Cycling is said to be an efficient mode of transport, when compared to running or driving a motor vehicle. Agreed. Mile for mile, far lesser calories and energy is spent, far lesser pollution emitted. But might that idea topple upside down when the road heads uphill?

When road grade rises, there is a seesaw effect in the amount of resistance wind and gravity play. Wind drag now goes down resisting less, and gravity comes up slowing you considerably. All that matters now is how much weight you carry and what gearing you have on the bike. The same gearing that perhaps tripled your speed output on a given rotational crank input on flats will plunge on a steep climb. If you choose to go with a lower gearing, your speed drops. So there is an apparent tradeoff there.

But it stands out, I guess, that one of the obvious elements of cycling athleticism - this notion of how good a cyclist someone is - is by assessing how well they can climb steep roads. Some of us may have this thinking that we're a real cyclist if we climb, and climb steep. I think there's a certain attractiveness in this tiring act. It gives one a sense of accomplishment, and sets a certain level of worth among the people he or she rides with. Bragging rights, yeah that's what it is. Besides, there's always a great view or a downhill to be earned at the other end, isn't there?

Top races in the world are most often won on the steep climbs, when a competitor can easily put time on his rivals. Stars who often showoff their talent on the climbs gets us all motivated to climb, and do it without getting off the bike. Getting off the bike and walking is somehow regarded shameful, powerless. You're no good. You aren't born to do it. Now where a cyclist does show mettle and talent on high gradient climbs, I think more can be said about his physiology and mental faculties than about the efficiency of his activity.

Its interesting that throngs of cycling fans line up steep cobbled roads and alpine climbs in Europe to see their favorite hero drag along the climb at close to walking speeds. Say one casual observer stepped back for a moment and asked : 'How efficient is cycling uphill compared to doing the same on flatland?', what do you think he'd tell himself?

I think the above observer could determine that this cyclist, riding past him on such a steep hill at 3mph, heaving from side to side zigzagging across the road like a detracked choo-choo train, will be more efficient if he got off his bike and pushed it uphill. There's no shame in this. Its just the clever thing to do, for this observer could jog up faster than the cyclist dragging along uphill! I would think much lesser energy is wasted simply caressing the ground with your feet than having to go through the complex motion of pedaling in circles with a chain and derailleur system that ultimately transmits some power to the rear wheel after losses through friction and deformation of rubber tires.

But sporting activity wouldn't have that, would it? Its not considered sporting otherwise. There might be booing from the crowd. There's no athleticism is walking your bike uphill...c'mon now. You're a sissy. You lack mental prowess.

Cycling does have its inefficiencies (perhaps that is why our early ancestors didn't swim out of the ocean carrying bikes to land). But it is the level of efficiency inherent in the cyclist which he applies to get past the natural inefficiencies that come into play in this mechanical activity that ultimately determines his outcome in a race, a training goal or the worthiness and respect he has among his peers. But I'm not the guy is the white lab coat so I can't credibly tell you where this bodily efficiency lies or how to attain it.


Transport Efficiency

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Phil said...

Great post. About the sentence about our ancestors not born as bike riders..I think man is considered a tool making creature, which is what sets him apart from other creatures. Now this can apply even to a bike, if you would consider it a tool of transport. But like all tools have their disadvantages in places, the bike does too. That doesn't reduce my liking for cycling however! I save far more money on gas and putting lesser crap into the air through my bike.

Anonymous said...

damn why you think so deep? :)

Anonymous said...

Why do you think that slope has anything to do with efficiency? The work required to climb is just the vertical height of a climb, times the weight of you and your bicycle; slope is not a factor. Efficiency is just the amount of work you can do for a given metabolic input. Slope is not a factor there either. Things that rob your efficiency on a bicycle are wind and rolling resistance; those rob less power the slower you go, so for the same rate of vertical climb, the steeper slope, which is slower rolling, will be _more_ efficient (that's why climbing is viewed as such the test of athleticism-- it's all power to weight ratio and no aerodynamics or finesse). Climbing mainly becomes inefficient when you run out of gearing, and are not able to operate at a good cadence for your chosen rate of vertical climb; so get a lower gear, adn you get your efficiency back.

In one example, as you write you often see spectators running up alongside their heroes in the Tour de France. They can do this because they give up running after about ten meters! No one since the first year derailleurs were permitted on the bikes has ever run up the whole climb alongside the contestants.

In a second example, the road up Mount Washington in NH is raced by both cyclists and runners, and the cyclists post significantly better times.

In a third example, someone made a hundred ascents of Fargo Street in Los Angeles in eight hours. Another person established a Guinness record for most stairs climbed in 24 hours. Both made roughly the same vertical ascent, but the stair climber took three times as long to do it.

In a fourth example, after I take the ferry home after a day mountain biking, I am on a bike that offers a very low gear, so I just point the thing up James St, which exceeds 20% grade for several blocks, rather than the less direct route home. I pick an easy pace because I've throughoughly tired myself out and am out of food, and yet pass everyone walking up the same slope, and make it home sooner than if I'd detoured down to Jackson St.

Our ancestors were not born as bike climbers, _nor_ were they born to climb steep slopes on foot! As anthropologists have shown human's best claim to specialty evolved athletic ability is to be able to sweat away heat while pursuing prey for great distances over _flat_ terrain. Bipedal locomotion, especially our wierd flat-footed implementation of bipedalism, is really suited to flatland (ever see a mountain ostrich? Ever wonder why we have to build stairs to give our feet purchace on the same slopes that four-legged creatures just scramble up?)

Anonymous said...

Efficiency is a lot in genetics for sure. Back some while ago, I told my self I wasn't born with that extra gas power to do ridiculous things. Its interesting I say this, as I have wasted much time not doing the things I'm not good at while discovering what I am good at. And climbing hills is definitely not one of that. But I've won plenty of Master's time trials in the area.


Sanish Fernandez said...

Don't kill me... but I heard cycling increases the need for human food consumption to keep up with the expending of physical energy. In other words cycling to work may be "green" but it's actually building us up for a massive food shortage.

Crusher Joe said...

Based on the calculations and some heft assumptions - the maximum angle at which a bicycle can maintain forward motion - I think somewhere in the low 30% range is more likely from personal experience. When the runner takes over is when they can "scramble" by using their arms for an extra point of contact.

The logical next question is - over what distance?

Bill said...

There was a discussion of exactly the same topic on rec.bicycles.tech. Just search there.

Yokota Fritz said...

When I lived in Colorado we cyclists (who also liked to climb mountains) had this discussion often. Is it easier to walk or bike up Mount Evans ? The people who've done both say it's much easier to walk up and about as enjoyable.