There’s no point to it anyway, because you lose ability to balance at about that speed. The slowest I can pedal a bicycle is in the neighborhood of about 3 miles an hour, which is, as has been pointed out, a moderate-to-brisk walking pace on flat ground. If you’re on a hill that you’d have a hard time riding a bicycle up, you’d have to walk it much slower, maybe 1.5 to 2 mph.
What does happen on a bicycle (if the road and traffic allow) is that you might tackle a really steep hill by swinging back and forth across the road in order to reduce the slope as much as possible. In that way, someone on foot might keep up at a similar level of effort. But of course the bicycle would be traveling much further.
Which basically means that while walking, you’re having to accelerate constantly to maintain any forward progress at all. There are obviously a lot of situations while, when riding a bike, you keep going a considerable distance without having to accelerate, or (going downhill) the acceleration is provided by gravity.
So to borrow that F=ma equation from earlier in the thread, your mass may be slightly bigger while cycling, due to the addition of the bicycle, but the acceleration required to move you a particular distance is a lot less under most circumstances. So the force required to move yourself by foot is a lot greater.
True enough. But the reality is that most countries are covered with a network of smooth paved surfaces that go pretty close to practically all of the places you would want to go.
But friction is proportional to the normal force and the normal force here is weight. So it is relevant. Otherwise, traveling at a constant speed would take no force at all.
Yes. And I’ll point out how efficient that process of paving is. Once done, many wheeled vehicles can take advantage of it. It probably helps a little with walking, but not much more than the well beaten path would.
Being the sort of nutcase who was unafraid, in his younger days, to ride a road bike on beaten paths, I’ll take that a step further: the path has to be rough indeed for the walker to have the advantage. Rocks, tree roots, or other obstructions maybe every 40-50 feet that are big enough that one has to lift the bike over or all but stop to maneuver one’s bike around would even things up, I’d expect. But if I can go 10 mph for 200 feet at a stretch between obstructions, I’m going to go a lot faster on wheels than on foot.
I’m not sure that’s a great description of efficient cycling. Raising your body and lowering it is very inefficient – you only do it when you want a lot of power (sprinting, starting). Muscles get less efficient when they’re putting out a lot of power; they’re most efficient when lightly loaded (for cyclists, high power also means creating oxygen debt, so there are two reasons to avoid it). Efficient cyclists don’t come near to using their full leg strength; they’re sitting down and spinning fairly quickly and lightly.
Recumbent bicycles might be a little more mechanically efficient because the rider’s body isn’t bent, and so forth, but lower wind resistance is really why they’re faster than upright cycles. Again, except for very short periods, cyclists aren’t using their maximum leg strength (any more than runners going farther than 200m are).
Another thing to think about is the concept of an ungeared wheeled vehicle, like a scooter or skateboard. You push with one foot, and the wheels allow you to retain most of your kinetic energy, without having to do anything else. When you walk, if you stop moving your legs back and forth, you fall on your face and stop.
Go up a hill, and you can still use the scooter, but each push will get you less and less far the steeper the hill is. Eventually, you get to the point where you get about 1 step higher each time you push, and you have to stop yourself from rolling back down the hill, so it’s easier to walk.
I’ll grant that most cyclists are “gradual” peddlers - rather than lifting their body and litting it fall with the crank, they slowly straighten their leg as the crank turns, but the effect is the same - the pull of gravity on your body is turning the pedals.
However, on a recumbent, you are doing the equivalent of the “leg press” one leg at a time. This is more efficient; your leg is capable of lifting more than your body weight.
Yes, at higher speeds wind resistance in the dominant factor in limiting cycle speed.
The answer is that a bicycle takes advantage of both muscular and mechanical efficiency. There is a very good article that explains this (Tucker, V.A. The Energetic Cost of Moving About. American Scientist, July-August 1975.) I can’t seem to find this online, but I do have a copy that I just scanned. If anyone wants it, just send a PM with your e-mail address and I’ll be happy to send a copy. The very first paragraph of this paper reads much like the OP, and the explanation is quite interesting.
The lowest granny gear on a decent mountain bike will let you sit in the saddle and pedal up just about any slope - the limiting factor is usually finding the balance point between stopping the front wheel lifting off the ground and keeping enough weight over the back wheel to maintain traction if you’re on a loose surface. On a paved road it’s easier, of course.
It only really becomes tiring when you get fed up of going at about 2mph and try to go faster.
Worth pointing out that a human walking is actually astoundingly efficient, and one of the most efficient animals on the planet. (Energy per unit mass by distance.) A human on a bike is way more efficient than anything else out there. A human on a bike starts from a very high base in the efficiency stakes.
I was under the impression that humans were nothing special in terms of efficiency, since I saw this clip where Steve Jobs describes the computer as a “bicycle for the mind.”
Perhaps the figures he referred to didn’t adjust for weight?
This is what I was getting at. What do you mean by ‘more efficient’? Because, in general, if you’re talking about energy produced per unit of fuel or oxygen, muscles get much less efficient at their maximum force. Like gasoline engines, muscles get better mileage at medium speeds and torques, rather than low speed max torque.
If you’re talking about maximum possible power, regardless of efficiency, then sure, a recumbent with a solid seat and back could allow slightly higher max power. For short-term power applications, this could make a difference. But a person can only put out max power for less than a minute, so for actual bicycle riding to get anywhere, theoretical max power is pretty irrelevant.
What really sets us apart from most land animals is our endurance: Very few critters could run a marathon or longer in anything like a human time. I guess you could consider that a form of efficiency, though it’s slippery to define.
When sprinting on a conventional bike, an experienced rider will pull upward on the handlebars, allowing them to press on the pedal with significantly more than their own weight. It is not uncommon to break/bend handlebars in this way. I have done it a couple times with cheap bars, and I have never entered a race.
As has been mentioned, though, this is only when sprinting, as it is possible for even a very fit athlete to exhaust themselves in a few minutes without lifting off the saddle. A trained rider can sustain their absolute peak sprinting power for only around 20 seconds, IIRC from my reading of this book. The author of that book is a big fan of streamlined recumbents, by the way.
The case for them is all in the aerodynamics though…a young, fit, healthy rider can put out about the same sustained power on a 'bent as a conventional bike. When hills limit the speed, rather than air resistance, the advantage of the 'bent vanishes, and conventional bikes typically climb as well or better than most 'bents. Weight has a lot to do with it, but a short wheel-base with the riders weight near the rear axle helps a lot too. The less aerodynamic riding position might allow for a bit of improvement in heat-shedding.
Bikes require a prepared surface, or at least one smooth enough for travel by bike, so the range of terrain one can access via bike is a fraction of what can be gotten to by foot.
More like a car with 2 main gears, walking and running. Some animals have multiple various different modes such horses which walk, trot, canter?, & gallop.
Also cyclists will clip their feet in to the pedals which allows them to apply power throughout the entire pedal cycle. While one leg is pushing down the other can be pulling up, thus you are not limited by gravity as to how much power you can output.
I haven’t seen many recumbents, but the ones I have seen, on organised bike rides, get easily overtaken by conventional bicycles going up hill. A big disadvantage of a recumbent is that you always have to push with the same leg muscles on every stroke, you don’t have another position to go to. If I get tired on my diamond frame bike going up a hill, I can stand up and use different muscles in my legs. This gives parts of me a rest that a recumbent cyclist doesn’t get. The other issue is that although you can push more than your body weight with a leg, you can’t do it for hours on end. This means that for the length of time a cyclist typically rides for, it is not gravity that is limiting the power they can output, but rather the time spent riding.
