There's a similar neat video, "Most People Don't Know How Bikes Work", where they fix the steering so the handlebars can only be turned left, and people then aren't able to turn left.
When I first started MTB in 2020... I tried to inflate my tubeless rear tire to 60psi once, because that was the "max pressure" written on the sidewall.
There are times you are incorrect, and wow, there are times you are very very wrong. They should make tubeless sealant in blood red just for fun.
Similarly, a Honda Fit with tires inflated to 90% ofthe sidewall's max pressure is /very/ fuel efficient, but you better plan on replacing tires pretty often. After a few potholes, usually.
You probably know this...but the song is not about a literal bicycle...it's about Freddie being "bi". I only say this because it took me too long to realize that.
This is the greatest explanation of two-wheeled vehicle dynamics I've ever seen. Anyone who rides a bicycle or motorcycle should read this whole thing!
> The further away that line is from the center of mass, the easier it is for the force to rotate the object. In the following demonstration, you can apply two forces of the same magnitude to two identical boxes. The only difference is the distance to the center of mass at which these forces act:
> When the distance between the force-line and the center of mass is large, the box spins faster as well. That distance doesn’t change the acceleration of the box to the right and both boxes move with the same linear speed. However, that distance affects the angular acceleration of a box – the longer that arm, the faster the box spins.
This does not make sense to me. If the two forces are truly of equal magnitude, then shouldn't the one that is in-line with the center of mass accelerate it faster, since 100% of the force is being converted to linear momentum, while the off-center force is being split between increasing linear momentum and rotational momentum?
This would appear to violate the conservation of energy.
> This does not make sense to me. If the two forces are truly of equal magnitude, then shouldn't the one that is in-line with the center of mass accelerate it faster, since 100% of the force is being converted to linear momentum, while the off-center force is being split between increasing linear momentum and rotational momentum?
Forces don't "split" that way. 100% of the force goes into creating linear acceleration, and 100% of the force goes into creating torque.
> This would appear to violate the conservation of energy.
It's not. The off-center force does more work, putting more energy into rotation.
First, there is no splitting between linear momentum and angular momentum per se. They have different units, you can't add them, and it makes no sense to say "this is 30% linear momentum and 70% angular momentum". But you can calculate how much energy is stored in linear motion and how much is stored in angular motion, and (at least at non-relativistic speeds), you can indeed add them. So you are on to something here.
But Newton's Laws don't lie. If you apply a force F, then a=m/F, and the fact that the object is spinning doesn't change the acceleration. Yet applying the force off-center does indeed seem to add more energy to the object: you're accelerating it just as much as if you applied the force on-center and you're also spinning it.
So how do you resolve this? A piece of general advice in physics (and math, and many other fields) is to state your assumptions and your questions precisely and unambiguously. The question is: if you apply an equal force to two objects of equal mass, and there are no other external forces involved, how can one accelerate faster? But just because the forces are equal doesn't mean that the work (energy applied) is the same. In fact:
W (work) = F (force) * d (distance)
Divide by a small unit of time:
P (power, which is work per unit time) = F * v (velocity, which is distance per unit time)
And that's the velocity of the point that receives the force. And if you look at the animation, you will see that the off-center force on the rotating box is applied to a (variable) spot on the box that is moving to the right. So the power needed to apply the force is larger, and more work is done.
(In fact, the excess velocity is ωr, so the excess power is Fωr = ωτ (angular velocity times torque), which is exactly the power needed to produce angular acceleration. So energy is conserved and all is well.)
I think in my head I was mixing up "force" and "power"; it's clear that with two cubes travelling linearly at the same velocity, the one that's also rapidly spinning has more energy.
That it can take varying amounts of energy to apply the same amount of force to the same object was the missing piece for me, since I was thinking of force as power.
It’s fairly easy to demonstrate this if you have a friend with a bicycle. Have someone on a bike stay still and hold the brakes, and press firmly on their back. It’s easy. Then have them bike at a slow jogging pace, run along with them, and try to apply the same force on their back. It will be hard work.
Also see the work of Jason Moore (referenced in that blog) for whom it seems modeling bicycle dynamics in open source scientific python has been a huge passion for him for more than ten years. I remember in the scientific python development in those days there were these guys from like the hubble optics correction division and like the asml metrology department and then this one weird bicycle guy lol.
This effect has a big play on motorcycles. Riding a bicycle is considered prerequisite knowledge for learning to ride a motorcycle, largely because of this counter steering. One thing that is more pronounced on a motorcycle is that counter steering only occurs while the bike is moving at speed. As in, you only counter steer a motorcycle above ~10mph (higher for some motorcycles). It's really cool to think about how intuitive this switch is, almost everyone picks it up quickly and it becomes second nature.
The debate is whether countersteering is something you have to consciously do by turning the steering column ("yaw"), or whether it's an automatic effect of pushing/leaning down on the side you want to turn toward ("roll").
"countersteering isn't real" because "steering isn't real", cycles at speed turn by leaning/rolling, not steering/yawing.
If you need to quickly swerve out of the way of an obstacle you push hard on the handle and you will immediately initiate a turn (you could just as easily say that your are initiating a lean). It's also well understood that handle bar input allows you to increase / adjust the lean mid-corner. I ride and never knew there was a debate about this.
Countersteering and roll are not mutually exclusive. The countersteer generally happens when steering whether you think about it or not. If you know about countersteering, you can practice it to make emergency turns.
For roll, Leaning in the direction of the bike is actually a bad habit (but it'll be fine on most road turns)
It turns out you want to lean the bike, and lean/shift your body in the opposite direction. This keeps center of mass above the wheels.
For example, the pro motorcycle racers with their knee an inch off the ground,they're leaning their body weight away from the turn, away from the ground. Meanwhile their bikes are leaning crazy hard.
That style of leaning is important for fast descents, or switchbacks, particularly switchbacks. Eg: "MOUNTAIN BIKE TIPS: CORNERING WITH CONFIDENCE" (start at 1:45) https://youtu.be/GFKPtEzE4xw
Ride a motorcycle for 5 minutes and you'll believe.
EDIT: To answer your question more directly, you are steering in one direction to initiate a lean in the opposite direction. E.g. if you are attempting to turn right, you first steer left which generates force in a left-sided contact patch in the front tire, which causes the bike to lean right. The bike then assumes a stable right lean angle (you have to do some work with your body, but the bike naturally wants to do this), and the front wheel comes back into alignment, and you are now turning right.
Yeah, but you quickly counteract with direct steering after you initiate the turn, so the overriding sensation is one of direct steering at low speeds, even through the physics is the same. This is what I think most people are referring to when they talk about high speed / low speed steering.
Countersteering applies at all speeds, it's just that balance plays a bigger role at lower speeds. The wikipedia article on countersteering goes into this a little bit.
Countersteering is convenient, but not required. A bicycle and rider are not a single rigid body. You can simply lean to one side and you'll have to steer in that direction to keep your bike under you -- no countersteer necessary.
I am not saying people don't countersteer, only that it isn't necessary to make a turn.
Also, bicycles aren't motorcycles where the weight ratio between rider and vehicle is swapped.
If you don't feel like clamping your handlebars so they only turn one direction, try this: coast along a straight line (and outdoor basketball court is great). Then pick a direction and just lean that way. You can absolutely keep your wheels on the line until you turn in the direction you picked, with no countersteering necessary.
This "fact" came about with a video of low skill riders who can't manipulate a bike very well, or don't know what it is they're doing when they do it.
He might be wrong, and just didn't know enough, but he is usually researching his videos very well and I would be surprised for him to be wrong about this.
just try it. roll perfectly straight and lean to a side. It accomplishes the same thing as countersteering, which is to put weight on one side of the bike, so when you turn that direction, the bike gets under you and you don't fall.
That's literally what they did in the video, I recommend you watch it. The issue is: you think you can just lean on the side you want, but you can't without counter-steering, so they devised a bike that literally does not allow counter-steering: you can't take a turn at all.
Because of the geometry of the front fork (rake and trail), if you lean to one side the bars will initially turn in the opposite direction. It's still countersteering. If you ever ride a bike where this geometry is wrong, which is difficult because it's so necessary, it's very different to ride, and you'll struggle to ride it non-handed.
What he demonstrated first of all is that you simply can't ride a bike that prevents the steer from turning in one direction. A bike continously falls to one side or the other, which gets corrected by steering in that direction to put the contact area back under the center of mass. This happens not necessarily through the rider's (conscious) action, even a bike with no rider does it to some extent, but in all cases it requires the ability to turn the wheel assembly freely around the steering axis.
IMO that means the bike in the video demonstrates failure to keep basic balance even before it gets a chance to demonstrate failure to turn properly.
I'm not sure your line method proves much since the countersteer could be very subtle. However I think you're still right. Countersteer makes you start to fall faster, but it clearly isn't necessary to make you fall because you do that anyway!
No it's not necessary in the strictest sense of the word, but counter steering achieves higher turn speeds, offers better control and precision, requires far less physical effort, and works at nearly every speed. I can't think of many pragmatic reasons not to use counter steering outside of just screwing around for fun.
I wish physics teachers start using geometric product of vectors, instead of the cross product. This allows forces and torques to be combined into a single concept "Forque". Really, translations are just rotations around infinity and rotations are just composition of two reflections. If we allow the algebra to take care of rotations, physics becomes a lot simpler.
Wait until (all) teachers start using AND SHARING really well crafted prompts for teaching aides /r/coolguides lesson material.
There should be a central repo for all subjects where topics can be looked up to find a guide like this one - and the prompt is public, with revision edit logs (like wikipedia) such that a standard agreed upon response can be adopted by acedmia for explaining a particle concept.
Let the acedemics expand upon, tangent from, deep dive into the sub components of each topic.
A much worse book on the science of bicycles is "The Third Policeman" from Flann O'Brien.
Some of its wisdom:
“The gross and net result of it is that people who spent most of their natural lives riding iron bicycles over the rocky roadsteads of this parish get their personalities mixed up with the personalities of their bicycle as a result of the interchanging of the atoms of each of them and you would be surprised at the number of people in these parts who are nearly half people and half bicycles...when a man lets things go so far that he is more than half a bicycle, you will not see him so much because he spends a lot of his time leaning with one elbow on walls or standing propped by one foot at kerbstones.”
Agreed. Bicycles are kind of a miracle of seeming simplicity hiding a ton of important developments of the industrial age. 99 Percent Invisible did a recent episode on just this topic: https://99percentinvisible.org/episode/the-safety-bicycle/.
Bikes benefit a lot from pneumatic tyres, pressure pumps, smooth asphalt (not cobbles), precision engineering of chains, chemistry of oils and lubricants, rust-proof steel, rubber brake pads with compounds that last long enough and resist rain, spring steel for suspension, cables that don't stretch. Without those things you get a wooden boneshaker hobby-horse, large, heavy, energy inefficient, incovenient: https://duckduckgo.com/?q=hobby+horse+victorian+bike&t=ffab&...
(And internal combustion engines; how are you going to distribute them around the Roman Empire by the tens of millions without trucks or ships?)
Yeah. Surfing is a great example of a Stone Age sport that has been radically changed by Space Age technology. Koa wood gets you a longboard that is hard to steer and can only surf long smooth waves. The modern surfboard is very much born out of California's aviation industry and its fixation on light, strong materials and aerodynamics. Surfing Pipeline is only possible with modern plastics, fins and shaping.
To expand on one of those things - bike chains get slightly longer as they wear out. Once it's about 1% longer than it started, it looks about the same as it always did, but it's starting to damage the drivechain and you need to replace it. An ancient Roman blacksmith has no hope of making a chain with anything like that level of precision.
I believe you only have this problem if your bike has gears based on a set of sprockets (different size chainwheels and a derailleur to move the chain from one to the other).
In Europe (Holland in particular), people ride single gear city bikes (or internally geared hubs) for decades without replacing chains or cogs. When you only have one chainring and one cog, they wear along with the chain, and it takes a very very long time to encounter problems.
It's when you have the sprocket cluster with multiple cogs that are not all wearing equally, that you get problems. Or often the problem on geared bikes doesn't appear until you replace your worn chain and the new chain no longer meshes well with the cogs worn to match the old chain.
Wouldn't the chain still need to be quite intricate and pretty hard to make even then? Though now that I think about it, you could probably make it in a way similar to chainmail, since tight tolerances aren't actually that crucial (the results would suck, but only compared to modern bikes). Though the other parts might be just as hard to make and especially to fit together (the bearings, the gearing for the chains...)
Bronze bushes work for bearings (still needs a lathe/ but not ball bearings). Chains can be belts of horsehair (or any civilisation with wire, tube and sheet metal can make a modern chain) or a treadle works okay. Spokes can be wooden.
The main limiting factor is probably the pnuematic tyre and smooth roads.
Nope, with single speed/hub gears chain wear is still a problem, it's just that they're less sensitive to it and there's fewer parts to replace. When the chain gets longer it gets loose, but it has to be very loose indeed to fall off or skip on a single speed. With a derailleur setup there's a tension arm with a weak spring so when the chain wants to skip that tension arm lets it. Derailleur setups commonly have some cogs with fewer teeth than single speeds so the problem is more obvious. Also, often derailleur cogs are aluminium while single speed ones are steel (not always!).
Typically a safety bike will get through 3-5 chains before needing to replace the rear cog, and many more before replacing the chainring(s). But Pinion gearboxes in the bottom bracket often run small chainrings that are similar in size to the rear cog, and I suspect they need to replace both rather than just the rear one.
I ride a bicycle with a hub gear as my main form of transport. About two years ago, I noticed the sprocket (rear cog) was getting very worn, so I removed it so I could reverse it and let it wear on the other side of the teeth (standard procedure for this sprocket to extend the wear life). But I accidentally put it back the same way as before and didn't notice until recently when I changed the hub oil. I had no problems with the chain skipping, despite the heavy sprocket wear (although it's now worn to the point that I no longer feel comfortable letting it wear on the other side of the teeth, so I'll have to buy a new sprocket). But you are correct that the chain wears more than the sprocket; I've already replaced the chain a few times.
You don't have to use chains though, you can have pedals on the front wheel, like the original bikes(velocipedes), or not pedal at all, just push yourself on the ground (balance bicycles)
Penny farthing bikes are death traps. Bikes that have similarly sized wheels with pedals on the front wheel aren't practical enough to be better than walking. Bikes without pedals are also not practical.
They were both more efficient than walking. Humans will put up with death traps if it means more efficiency in transportation (just look at car fatalities). The only reason they didn't took off faster was the lack of roads. And by the time we had tarmac roads bikes already evolved to have chains and read drive.
Watch a kid on a balance bike and tell me how it's not practical, lol. A 4 year old can bike around a whole park in seconds.
Chains don't stretch, they wear down. When measuring a chain, you measure the distance between links to see how much material has worn away. The links don't actually get longer from stretching.
The key invention that made them possible was ball bearings. This is why the modern bicycle and the modern car were invented within a year or two of each other.
And now of course some of the most prestigious races in the professional cycling world are across predominantly cobbled roads as a form of torture for those racing.
Well, I've got a bike from the 30s and it's perfectly fine for everyday riding. While I agree that most of those things you listed are valuable and convenient, good enough is often just good enough. Like I've got no use for any cables and I don't need precision engineered chains.
Don't even get me started on airplanes though - there was only 66 years between the first airplane (Wright Flyer in 1903) and the moon landing (1969).
Disclaimer: that's of course a cool anecdote on the surface, but rockets have been around since the 13th century so they're two mostly different technologies.
Key development for flight: Wings which carry the plane. First planes didn't even have an engine (besides human)
Key development for rockets: Strong powerful engines to escape gravity. Aerodynamics matter relatively little, mostly for heat control.
I don't know how related the development of jet engines and rocket engines was. Of course things like the Space Shuttle, which has some airplane-like aerodynamic steering tie both together ...
We're playing a bit fast and loose with our phrasing here if we want to split hairs about the development of these technologies.
Powered, navigable, human flight existed before the development of wings.
The early rockets mentioned above weren't for human flight, nor for spaceflight. Rockets were developed to be terrestrial weapons, not to propel humans.
Rocket engines and turbine engines are both a type of jet engine. These engine technologies themselves weren't developed together because one was developed to make airplanes go higher and faster, and the other was developed to stab people with arrows better. If what we're really talking about is "human flight", then rockets and turbine engines were both used to propel humans on airplanes before anyone started considering spaceflight.
And then when humans did consider spaceflight, humans were developing space planes and tubular orbital rockets at the exact same time. The space shuttle was far from the first plane to operate at heights where the control surfaces no longer work. The X15 actually flew 2 years before Vostok 1.
The people developing human flight were always interested in going faster and higher. The technologies they experimented with were intermixed the whole time.
You will be amazed to know that the Ball Brothers, who invested the Mason Jar/Atlas Jar, and perfected canning and soups... is also Ball Aerospace - who makes super-high end space components for the MIC, black projects, skunkworks, NASA etc...
The invention of the bicycle came at a similar time like engine driven vehicles. Before those became popular, the direct competitor for bicycles (one person transportation) were horses.
There might have literally not been a need to invent a bicycle as horses fulfilled the same purpose and had the advantage that they fared better on the back then nearly non-existent infrastructure.
Also: a single person transportation vehicle was not something a lot of people needed in their lives. You needed something to move stuff, but the demand to move single people daily came into existence with the dawn of big cities.
There's a reason that horses were the fancy sports car/military tool of the animal transport world. They eat a lot, break easily, and don't last long.
People used oxen, donkeys, llama etc way more than horses. And the Chinese invented wheelbarrows and used them extensively rather than using draft animals. They often use bicycles much the same way as wheelbarrows now, and rich people often find that amusing (possibly because a KMart bike is a toy, a Chinese bike is a workhorse).
A parallel thought is that the first airplane is the product of bicycle mechanics and not railway or automotive mechanics.
As others pointed out, there are a lot of necessary technologies like rubber, bearings, lubricants, sprockets and chains that need to be developed, but there is also something very elegant about bicycles. If you start to mess around with a 70's era road bikes you get a sense of just how perfectly everything needs to fit together and how everything affects everything else. (You see it more clearly in older bikes because you need to deal with non-standard parts). I think I learned more about bicycles from the royal pain of a 1982 Peugeot than anything else. This is not to say that a car doesn't have similar complexity, but the use of chemical fuel and 4 wheels masks how the tunings fit together. With my current bike there is a serious difference when it is perfectly tuned.
The production of quality steel isnt thousands of years old.
Yeah they could produce small items - but to make the steel of the quality needed for bicycles is pretty new - the past 150-200 years with the Bessemer process
Bicycles are a relatively new invention because they require roads/flat paths which are also a relatively new occurance, and came about due to the widepread use of horses and then carraiges for transportation.
A bike at any other point in human history would have been completely useless trying to traverse natural terrain.
Mountain bikes do not require roads or flat paths; they work fine on trails (hence the name "mountain bike"), which have existed since large animals evolved.
However, mountain bikes arguably require even more technologies than other bicycles, especially for suspension and brakes (MTBs pioneered the use of disc brakes on bicycles).
The safety bicycle (chain, pedals in the middle) is about a decade newer than the car (under 150 years), although they hit mass production within a year either side of each other depending in how you define it.
> Bikes seem like such a primitive technology, and yet as this article demonstrates, it takes a lot of engineering to design even primitive products.
Very strange. I get that we take things for granted if they've been around forever (ie. since before we were born). But I never considered bicycles "primitive". What makes you think that? Is it because they don't need electronics? What is a non-primitive transport technology?
He settles on general economic and cultural factors. Experimentation requires there to be enough people with spare time and resources to play around with things with no immediately obvious payback.
Bicycles are truly beautiful machines. They are the most energy efficient form of transportation. You can travel pretty long distances with not that many calories.
At equal diet, the bicycle always win. You don't eat significantly more meat because you are using a bicycle to move vs a total couch potato that would use a Prius and eat the same.
I disagree with this. On days I cycle 100km+ in a day I do eat vastly more than if I drive 100km and don't exercise.
The energy does have to come from somewhere. If you're only cycling 5km in a day the reason you don't notice the difference in food quantity is because the amount of energy used for that small amount of cycling does not really exceed the amount of energy your body uses in a day for everything else. When you're cycling 100km, it's a different story.
It's an interesting question, and in fact the conversion of food to mechanical energy isn't actually very carbon-efficient compared to electricity generation or even gasoline.
Cars are actually very efficient at what they do, it's just that what they do (hauling around a 1000kg metal box) is an inefficient way to transport a human, and that's where the inefficiency comes from.
If you fill up a large car with full occupancy and go on a long road trip, I'd venture to say it's carbon-wise likely to be more efficient than all of the occupants cycling, regardless of diet.
Part of the problem is that the former number is wildly variable depending on the type of food, the type of production and the amount of transportation to get it to where it is eaten.
Whereas oil-derived fuels are ... well, they vary but not as much. Certainly some food production models (e.g. alfalfa-raised cattle eating for meet thousands of miles from where they are raised) are truly horrible, and may indeed be worse than using fossil fuels.
That said, plant-centric, reasonably local food systems that don't use much in the way of synthetic fertilizer generate massively less carbon than any sort of oil production in terms of distance-travelled-per-unit-of-carbon.
Part of the problem is that people consider that the driver are some aliens that do not eat anything, or stay fit by just following a strict diet and without doing any exercise.
But the true reality is most people eat more, make reserves and a huge fraction of the population is either overweight or do physical activities in the purpose of burning those reserves and feel better. Mixing transportation with the later is quite efficient.
- 2000kcal from food = how much CO2 including all the energy needed to farm it?
If it's 2000kcal from beef, you're looking at about 72.88 kg [1]
If it's 2000kcal from fish, you're looking at about 15.21 kg [1]
If it's 2000kcal from brassicas, you're looking at about 6 kg [1]
- 35000kcal from gasoline emits how much CO2?
35000 kcal is 140440 kJ, which would consume about 4.36 liters of gasoline, which would be about 10 kg of CO2 emissions [2].
So the CO2 efficiency of a car isn't that much different, and falls somewhere in-between a biker on a fully meat and biker on a fully vegetable diet. Biking isn't vastly more efficient than a car, CO2-wise.
That said, a motorized bike is hellishly efficient, CO2-wise, and trumps almost everything else.
If you're going to do that, what about the CO2 (gasoline) emitted to collect the gasoline? Given you need oil to extract oil, it's still far, far, far less efficient.
It's miniscule compared to burning the gas, or the oil industry wouldn't exist, considering a lot of the oil extraction and refinement industry is powered by oil itself.
You could have also Googled that number instead of trying to make a comeback for the sake of it.
I used to be an elite racing cyclist, I know what it is to need fuel in a 200km bike race
Besides, riding at conversational slower pace only need a fraction of that energy. When I was commuting 75km a day myy food intake may be at worst marginally higher than a day off.
Correct, I wasn't trying to make a statement about specific diets, just that diet does make a huge difference in evaluating the carbon efficiency of cycling.
Perhaps more carbon efficient, but 15x less energy efficient:
> Biking takes around 25 kcal/km [iii] above basal metabolism, which is equivalent to .11 MJ/km. A typical car in the US gets 25 mpg, or 9.5L/100 km, which is equivalent to 3.3 MJ/km. The Toyota Prius takes only 5 L/100km, or 1.7 MJ/km. So a typical car takes 30x more energy per kilometer than biking, and a Prius takes 15x more. This is what we expect given how much heavier cars are than bikes.
Not even close to true. I can ride 60-70 miles on reasonably hilly terrain on about 2000kcal. There’s no car that can come close to that. And that’s assuming drivers don’t eat (the McDonald’s wrappers I see by the side of the road proves that they do).
2000 kcal worth of food takes somewhere in the range of 6 kg (for vegetables) to 72 kg (for beef) of CO2 emissions to farm.
If you assume a gas car needs 35000 kcal to make the same journey it's about 10 kg of CO2 emissions.
You're making a kcal-to-kcal comparison, which is apples-to-oranges in terms of climate change. Climate change doesn't care about kcal, it's greenhouse gases like CO2 that do matter.
I know internet forum people are going to come back with a retort about how drivers also eat, but the fact is that cyclists do need to eat more than drivers to make the same journey, and the math puts the answer somewhere in the middle, you need to do the interpolation.
Your numbers are absolute nonsense. You excluded the CO2 to extract the oil and refine it into petrol/diesel. Nobody eats 2000kcal of beef: that's 6 whole burgers!
On top of that, your numbers assume that drivers don't eat, which is self-evidently not true!
This is miniscule compared to the amount emitted by burning it. It sort of has to be, or the industry wouldn't exist.
Congratulations, you're now deliberately fishing at the opposite and and nitpicking at the opposite end just to argue, at this point, when you could be looking at the entire pond.
Of course nobody eats 2000kcal of beef, I never said that. I was providing an extremum of all-brassica and all-beef so that you can interpolate somewhere between them, but evidently you're more interested in taking the endpoints and call it nonsense instead of doing the interpolation.
So go ahead and assume drivers eat. Bikers eat more. Again, do the interpolation. You get some data, you do the math, then argue. You will still find that it's within the same order of magnitude. CO2 from food production is a thing, and it's hugely variable depending on diet, that's the point.
> So go ahead and assume drivers eat. Bikers eat more.
Not that much more, and you're being disgustingly disingenuous by just grabbing the mid-point. To get 2000kcal, you're going to be eating more rice, potatoes and raw sugar i.e. carb-dense foods to fuel the ride. That's more like 2kg of CO2, so vastly below the 10kg of CO2.
I can safely exclude the beef, pork, etc. because that's food I'd eat "outside" of fuelling the ride. To spell it out for you: I won't eat more meat because I rode 65 miles, I'd eat more potatoes and cane sugar. Thus, that's what we measure in terms of excess CO2 produced vs just sitting on my couch.
Also, I'm being very generous to cars here. Most don't come close to achieving 65mpg, and certainly not on the route I measured with the steep climbs it involves.
Modern fat bikes will be more efficient than walking in the scrub desert where I live, in grasslands, in not too dense woodlands, on any kind of open dirt/sand.
I've done 100 mile MTB races, and while it's not as efficient as riding a flat smooth road on a road bike, it's probably still more efficient than walking.
Obviously at some point there's a line, where you can't ride a bike, but for most roads and trails, the bike is going to win.
I think that the comment I was responding to was about scenarios where are no human-created pathways, trails or roads. As I mentioned in some of these, modern fat (tire) bikes are still great; in others, it is true that walking would be the best choice (unless you're at the level of, say, Danny MacAskill).
But yeah, in some natural environments, with some kinds of bikes, you can beat walking. The Burning Man festival is a great example, but it is also a terrible place to live.
That's why in most cases, without smooth roads, bikes are not practical.
I think it's fair to point out that you should be referencing road bikes then when you say bikes are not practical. Advancements in tubeless technology, suspension, MTB groupsets with dinner plate low gears, derailleur clutches, and hubs/rims designed to take a beating while supporting wide tires can definitely make a bike more efficient than walking on most terrain.
- Fat bikes are more efficient than snowshoeing or breaking trail on XC skis.
- CX bikes are more efficient than walking in mud.
- Fatter tire gravel bikes are more efficient than hiking through sand.
- A bike with a 51T cog and 28T ring will be more efficient than hiking up steep grades until balance at low speed becomes an issue.
They don't require a flat and smooth surface, but do benefit from a road of some sort. How do you make a road? You ride on it over and over again. Ever seen a sheep track? Is that not natural?
A smooth and flat road, while not necessary, is better and does make things a lot more efficient. The same is true for any wheeled vehicle but cyclists appreciate it a lot more than motorists.
They are the pinnacle of personal transportation technology. Not aware of anything that comes close. I'm not sure how anyone can use a car, keep filling it with more and more fossil fuel and think "yeah, this is good technology".
ciechanow.ski pages are usually super performant for me, but this one is super laggy, especially widgets with the bicycle man/mesh. Anyone else experiencing this?
This is a really impressive article -- he went quite far into the physics of bikes and wheels and didn't say anything that I could point to as being wrong.
Nice demo of countersteering. When you jerk the slider quickly to the right, you can see that the right handlebar briefly lunges forward (left steer) before the steering recovers to the right. It's still noticeable with smaller/slower movements of the slider, but not as much.
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[ 3.2 ms ] story [ 275 ms ] threadThere's a similar neat video, "Most People Don't Know How Bikes Work", where they fix the steering so the handlebars can only be turned left, and people then aren't able to turn left.
https://www.youtube.com/watch?v=9cNmUNHSBac
Holy moly!! I didn't realize I didn't know how I actually ride a bicycle!!
Obligatory sound track for this excellent post:
https://youtu.be/KwvWtZl2ICY
https://youtu.be/skW_Ysew3zw
There are times you are incorrect, and wow, there are times you are very very wrong. They should make tubeless sealant in blood red just for fun.
https://en.wikipedia.org/wiki/Countersteering
> When the distance between the force-line and the center of mass is large, the box spins faster as well. That distance doesn’t change the acceleration of the box to the right and both boxes move with the same linear speed. However, that distance affects the angular acceleration of a box – the longer that arm, the faster the box spins.
This does not make sense to me. If the two forces are truly of equal magnitude, then shouldn't the one that is in-line with the center of mass accelerate it faster, since 100% of the force is being converted to linear momentum, while the off-center force is being split between increasing linear momentum and rotational momentum?
This would appear to violate the conservation of energy.
Forces don't "split" that way. 100% of the force goes into creating linear acceleration, and 100% of the force goes into creating torque.
> This would appear to violate the conservation of energy.
It's not. The off-center force does more work, putting more energy into rotation.
First, there is no splitting between linear momentum and angular momentum per se. They have different units, you can't add them, and it makes no sense to say "this is 30% linear momentum and 70% angular momentum". But you can calculate how much energy is stored in linear motion and how much is stored in angular motion, and (at least at non-relativistic speeds), you can indeed add them. So you are on to something here.
But Newton's Laws don't lie. If you apply a force F, then a=m/F, and the fact that the object is spinning doesn't change the acceleration. Yet applying the force off-center does indeed seem to add more energy to the object: you're accelerating it just as much as if you applied the force on-center and you're also spinning it.
So how do you resolve this? A piece of general advice in physics (and math, and many other fields) is to state your assumptions and your questions precisely and unambiguously. The question is: if you apply an equal force to two objects of equal mass, and there are no other external forces involved, how can one accelerate faster? But just because the forces are equal doesn't mean that the work (energy applied) is the same. In fact:
W (work) = F (force) * d (distance)
Divide by a small unit of time:
P (power, which is work per unit time) = F * v (velocity, which is distance per unit time)
And that's the velocity of the point that receives the force. And if you look at the animation, you will see that the off-center force on the rotating box is applied to a (variable) spot on the box that is moving to the right. So the power needed to apply the force is larger, and more work is done.
(In fact, the excess velocity is ωr, so the excess power is Fωr = ωτ (angular velocity times torque), which is exactly the power needed to produce angular acceleration. So energy is conserved and all is well.)
I think in my head I was mixing up "force" and "power"; it's clear that with two cubes travelling linearly at the same velocity, the one that's also rapidly spinning has more energy.
That it can take varying amounts of energy to apply the same amount of force to the same object was the missing piece for me, since I was thinking of force as power.
https://moorepants.github.io/dissertation/
https://github.com/moorepants
It's pretty much impossible to believe without thinking it through, and yet everyone naturally intuits it.
It's one of my favourite examples of how the brain can just 'feel' forces and make the right adjustments incredibly fast. So amazing.
I don’t believe that this is true. Can you explain the physics?
"countersteering isn't real" because "steering isn't real", cycles at speed turn by leaning/rolling, not steering/yawing.
For roll, Leaning in the direction of the bike is actually a bad habit (but it'll be fine on most road turns)
It turns out you want to lean the bike, and lean/shift your body in the opposite direction. This keeps center of mass above the wheels.
For example, the pro motorcycle racers with their knee an inch off the ground,they're leaning their body weight away from the turn, away from the ground. Meanwhile their bikes are leaning crazy hard.
That style of leaning is important for fast descents, or switchbacks, particularly switchbacks. Eg: "MOUNTAIN BIKE TIPS: CORNERING WITH CONFIDENCE" (start at 1:45) https://youtu.be/GFKPtEzE4xw
> In this next demonstration, the wheel is spinning around the red axis, and you can also apply a torque that rotates the wheel around the green axis:
At highway speeds on a motorcycle, this effect is very strong.
But at low speeds in a parking lot, any gyroscopic effect of the slow wheels is nothing compared to a 250lb+ motorcycle.
Bicycles work the same way when you're moving very slow.
EDIT: To answer your question more directly, you are steering in one direction to initiate a lean in the opposite direction. E.g. if you are attempting to turn right, you first steer left which generates force in a left-sided contact patch in the front tire, which causes the bike to lean right. The bike then assumes a stable right lean angle (you have to do some work with your body, but the bike naturally wants to do this), and the front wheel comes back into alignment, and you are now turning right.
A good explanation: https://www.youtube.com/watch?v=PgUOOwnZcDU Some more detail: https://en.wikipedia.org/wiki/Countersteering
EDIT 2: I misread your point. You are correct, counter-steering still applies at low speeds but the "feeling" is masked by lack of momentum.
I am not saying people don't countersteer, only that it isn't necessary to make a turn.
Also, bicycles aren't motorcycles where the weight ratio between rider and vehicle is swapped.
If you don't feel like clamping your handlebars so they only turn one direction, try this: coast along a straight line (and outdoor basketball court is great). Then pick a direction and just lean that way. You can absolutely keep your wheels on the line until you turn in the direction you picked, with no countersteering necessary.
This "fact" came about with a video of low skill riders who can't manipulate a bike very well, or don't know what it is they're doing when they do it.
He might be wrong, and just didn't know enough, but he is usually researching his videos very well and I would be surprised for him to be wrong about this.
IMO that means the bike in the video demonstrates failure to keep basic balance even before it gets a chance to demonstrate failure to turn properly.
Next time I'm on my bike I will try it anyway.
I wish physics teachers start using geometric product of vectors, instead of the cross product. This allows forces and torques to be combined into a single concept "Forque". Really, translations are just rotations around infinity and rotations are just composition of two reflections. If we allow the algebra to take care of rotations, physics becomes a lot simpler.
There should be a central repo for all subjects where topics can be looked up to find a guide like this one - and the prompt is public, with revision edit logs (like wikipedia) such that a standard agreed upon response can be adopted by acedmia for explaining a particle concept.
Let the acedemics expand upon, tangent from, deep dive into the sub components of each topic.
The University.ai
Some of its wisdom:
Compare bicycles with steel making, for example. Steel making happened thousands of years ago. The modern bicycle was what - under 200 years ago?
Bikes seem like such a primitive technology, and yet as this article demonstrates, it takes a lot of engineering to design even primitive products.
It makes me wonder how many other simple or primitive products are out there which have yet to be discovered.
(And internal combustion engines; how are you going to distribute them around the Roman Empire by the tens of millions without trucks or ships?)
Very little of the "modern stuff the ancients didn't figure out" could be done without modern materials.
If dumped back in time, maybe you could make rent teaching swimming or doing accounting. Medicine would probably be too dangerous.
Romans might have been able to do shaft-drive. Or Penny-farthings (direct pedal-wheel drive).
In Europe (Holland in particular), people ride single gear city bikes (or internally geared hubs) for decades without replacing chains or cogs. When you only have one chainring and one cog, they wear along with the chain, and it takes a very very long time to encounter problems.
It's when you have the sprocket cluster with multiple cogs that are not all wearing equally, that you get problems. Or often the problem on geared bikes doesn't appear until you replace your worn chain and the new chain no longer meshes well with the cogs worn to match the old chain.
I ride my single speed (not fixed) every day. It’s my most beloved possession.
The main limiting factor is probably the pnuematic tyre and smooth roads.
Typically a safety bike will get through 3-5 chains before needing to replace the rear cog, and many more before replacing the chainring(s). But Pinion gearboxes in the bottom bracket often run small chainrings that are similar in size to the rear cog, and I suspect they need to replace both rather than just the rear one.
I'm not saying you should do this. And Rohloff strongly suggest you don't do this I'm just saying that you can do this.
Watch a kid on a balance bike and tell me how it's not practical, lol. A 4 year old can bike around a whole park in seconds.
https://youtu.be/gXd-3UnqoaM
Bicycle riding societies were some of the more vocal proponents on paved roads (predating the automobile):
* https://www.vox.com/2015/3/19/8253035/roads-cyclists-cars-hi...
* https://www.theguardian.com/environment/bike-blog/2011/aug/1...
* https://www.smithsonianmag.com/travel/american-drivers-thank...
https://cdn.mos.cms.futurecdn.net/hD4Vtdmow7B4Jf4XiWPH5g.jpg
* https://en.wikipedia.org/wiki/Cyclo-cross
(Kidding, of course, it's a wildly entertaining form of racing)
Disclaimer: that's of course a cool anecdote on the surface, but rockets have been around since the 13th century so they're two mostly different technologies.
Key development for flight: Wings which carry the plane. First planes didn't even have an engine (besides human)
Key development for rockets: Strong powerful engines to escape gravity. Aerodynamics matter relatively little, mostly for heat control.
I don't know how related the development of jet engines and rocket engines was. Of course things like the Space Shuttle, which has some airplane-like aerodynamic steering tie both together ...
Powered, navigable, human flight existed before the development of wings.
The early rockets mentioned above weren't for human flight, nor for spaceflight. Rockets were developed to be terrestrial weapons, not to propel humans.
Rocket engines and turbine engines are both a type of jet engine. These engine technologies themselves weren't developed together because one was developed to make airplanes go higher and faster, and the other was developed to stab people with arrows better. If what we're really talking about is "human flight", then rockets and turbine engines were both used to propel humans on airplanes before anyone started considering spaceflight.
And then when humans did consider spaceflight, humans were developing space planes and tubular orbital rockets at the exact same time. The space shuttle was far from the first plane to operate at heights where the control surfaces no longer work. The X15 actually flew 2 years before Vostok 1.
The people developing human flight were always interested in going faster and higher. The technologies they experimented with were intermixed the whole time.
All from the Mason Jar.
https://www.visitmuncie.org/a-legacy-etched-in-glass-the-bal...
(also "Aliens")
The invention of the bicycle came at a similar time like engine driven vehicles. Before those became popular, the direct competitor for bicycles (one person transportation) were horses.
There might have literally not been a need to invent a bicycle as horses fulfilled the same purpose and had the advantage that they fared better on the back then nearly non-existent infrastructure.
Also: a single person transportation vehicle was not something a lot of people needed in their lives. You needed something to move stuff, but the demand to move single people daily came into existence with the dawn of big cities.
People used oxen, donkeys, llama etc way more than horses. And the Chinese invented wheelbarrows and used them extensively rather than using draft animals. They often use bicycles much the same way as wheelbarrows now, and rich people often find that amusing (possibly because a KMart bike is a toy, a Chinese bike is a workhorse).
Yeah they could produce small items - but to make the steel of the quality needed for bicycles is pretty new - the past 150-200 years with the Bessemer process
A bike at any other point in human history would have been completely useless trying to traverse natural terrain.
. o O ( Now if only 18.8 MPH were enough to activate the flux capacitor. )
However, mountain bikes arguably require even more technologies than other bicycles, especially for suspension and brakes (MTBs pioneered the use of disc brakes on bicycles).
Very strange. I get that we take things for granted if they've been around forever (ie. since before we were born). But I never considered bicycles "primitive". What makes you think that? Is it because they don't need electronics? What is a non-primitive transport technology?
He settles on general economic and cultural factors. Experimentation requires there to be enough people with spare time and resources to play around with things with no immediately obvious payback.
If the cyclist is vegan or even an average diet, yes. If the cyclist is paleo, a Prius with 2-person occupancy may actually be more carbon-efficient:
https://keith.seas.harvard.edu/blog/climate-impacts-biking-v...
The energy does have to come from somewhere. If you're only cycling 5km in a day the reason you don't notice the difference in food quantity is because the amount of energy used for that small amount of cycling does not really exceed the amount of energy your body uses in a day for everything else. When you're cycling 100km, it's a different story.
It's an interesting question, and in fact the conversion of food to mechanical energy isn't actually very carbon-efficient compared to electricity generation or even gasoline.
Cars are actually very efficient at what they do, it's just that what they do (hauling around a 1000kg metal box) is an inefficient way to transport a human, and that's where the inefficiency comes from.
If you fill up a large car with full occupancy and go on a long road trip, I'd venture to say it's carbon-wise likely to be more efficient than all of the occupants cycling, regardless of diet.
Whereas oil-derived fuels are ... well, they vary but not as much. Certainly some food production models (e.g. alfalfa-raised cattle eating for meet thousands of miles from where they are raised) are truly horrible, and may indeed be worse than using fossil fuels.
That said, plant-centric, reasonably local food systems that don't use much in the way of synthetic fertilizer generate massively less carbon than any sort of oil production in terms of distance-travelled-per-unit-of-carbon.
But the true reality is most people eat more, make reserves and a huge fraction of the population is either overweight or do physical activities in the purpose of burning those reserves and feel better. Mixing transportation with the later is quite efficient.
- 2000kcal from food = how much CO2 including all the energy needed to farm it?
If it's 2000kcal from beef, you're looking at about 72.88 kg [1]
If it's 2000kcal from fish, you're looking at about 15.21 kg [1]
If it's 2000kcal from brassicas, you're looking at about 6 kg [1]
- 35000kcal from gasoline emits how much CO2?
35000 kcal is 140440 kJ, which would consume about 4.36 liters of gasoline, which would be about 10 kg of CO2 emissions [2].
So the CO2 efficiency of a car isn't that much different, and falls somewhere in-between a biker on a fully meat and biker on a fully vegetable diet. Biking isn't vastly more efficient than a car, CO2-wise.
That said, a motorized bike is hellishly efficient, CO2-wise, and trumps almost everything else.
[1] https://ourworldindata.org/grapher/ghg-kcal-poore
[2] https://natural-resources.canada.ca/sites/www.nrcan.gc.ca/fi...
If you're going to do that, what about the CO2 (gasoline) emitted to collect the gasoline? Given you need oil to extract oil, it's still far, far, far less efficient.
You could have also Googled that number instead of trying to make a comeback for the sake of it.
I used to be an elite racing cyclist, I know what it is to need fuel in a 200km bike race
Besides, riding at conversational slower pace only need a fraction of that energy. When I was commuting 75km a day myy food intake may be at worst marginally higher than a day off.
> Biking takes around 25 kcal/km [iii] above basal metabolism, which is equivalent to .11 MJ/km. A typical car in the US gets 25 mpg, or 9.5L/100 km, which is equivalent to 3.3 MJ/km. The Toyota Prius takes only 5 L/100km, or 1.7 MJ/km. So a typical car takes 30x more energy per kilometer than biking, and a Prius takes 15x more. This is what we expect given how much heavier cars are than bikes.
2000 kcal worth of food takes somewhere in the range of 6 kg (for vegetables) to 72 kg (for beef) of CO2 emissions to farm.
If you assume a gas car needs 35000 kcal to make the same journey it's about 10 kg of CO2 emissions.
You're making a kcal-to-kcal comparison, which is apples-to-oranges in terms of climate change. Climate change doesn't care about kcal, it's greenhouse gases like CO2 that do matter.
I know internet forum people are going to come back with a retort about how drivers also eat, but the fact is that cyclists do need to eat more than drivers to make the same journey, and the math puts the answer somewhere in the middle, you need to do the interpolation.
On top of that, your numbers assume that drivers don't eat, which is self-evidently not true!
This is miniscule compared to the amount emitted by burning it. It sort of has to be, or the industry wouldn't exist.
Congratulations, you're now deliberately fishing at the opposite and and nitpicking at the opposite end just to argue, at this point, when you could be looking at the entire pond.
Of course nobody eats 2000kcal of beef, I never said that. I was providing an extremum of all-brassica and all-beef so that you can interpolate somewhere between them, but evidently you're more interested in taking the endpoints and call it nonsense instead of doing the interpolation.
So go ahead and assume drivers eat. Bikers eat more. Again, do the interpolation. You get some data, you do the math, then argue. You will still find that it's within the same order of magnitude. CO2 from food production is a thing, and it's hugely variable depending on diet, that's the point.
Not that much more, and you're being disgustingly disingenuous by just grabbing the mid-point. To get 2000kcal, you're going to be eating more rice, potatoes and raw sugar i.e. carb-dense foods to fuel the ride. That's more like 2kg of CO2, so vastly below the 10kg of CO2.
I can safely exclude the beef, pork, etc. because that's food I'd eat "outside" of fuelling the ride. To spell it out for you: I won't eat more meat because I rode 65 miles, I'd eat more potatoes and cane sugar. Thus, that's what we measure in terms of excess CO2 produced vs just sitting on my couch.
Also, I'm being very generous to cars here. Most don't come close to achieving 65mpg, and certainly not on the route I measured with the steep climbs it involves.
...On flat smooth surfaces. On any natural environment or terrain they are nowhere near as efficient as walking.
Modern fat bikes will be more efficient than walking in the scrub desert where I live, in grasslands, in not too dense woodlands, on any kind of open dirt/sand.
Obviously at some point there's a line, where you can't ride a bike, but for most roads and trails, the bike is going to win.
I wonder how many calories MacAskill burns. He makes it seem pretty effortless.
https://worldbicyclerelief.org
But yeah, in some natural environments, with some kinds of bikes, you can beat walking. The Burning Man festival is a great example, but it is also a terrible place to live.
That's why in most cases, without smooth roads, bikes are not practical.
- Fat bikes are more efficient than snowshoeing or breaking trail on XC skis.
- CX bikes are more efficient than walking in mud.
- Fatter tire gravel bikes are more efficient than hiking through sand.
- A bike with a 51T cog and 28T ring will be more efficient than hiking up steep grades until balance at low speed becomes an issue.
A smooth and flat road, while not necessary, is better and does make things a lot more efficient. The same is true for any wheeled vehicle but cyclists appreciate it a lot more than motorists.
Be careful if you have deadlines for today though, you may be there for a long and awesome time.