We Still Don’t Know How Bicycles Work

as you can see today's video investigates a topic so complex we usually wait until children have reached preschool age before even attempting to teach them such a skill and if you're into learning about really advanced concepts such as bike riding or einstein roads and bridges you should check out today's sponsor curiosity stream curiosity stream is a subscription streaming service that offers thousands of documentaries and non-fiction titles from some of the world's best filmmakers including exclusive originals curiosity stream is available on many platforms and web apps including roku android xbox one smart tvs ios chromecast amazon fire amazon kindle and apple tv it's offered worldwide and it's constantly updated with awesome timely content right now for instance they have a popular new documentary series called the top science stories of 2020. 2020 obviously it features profiles on covert 19 but it also dives into crispr the mars rover fossilized dna and several other exciting news stories that you might have missed from last year and if you're really into bikes why not check out curiosity stream's 10-part series how to adventure which profiles adventurer ryan mansour as he circumnavigates all of africa on a bicycle really right now you can go to curiositystream.com forward slash brain food for unlimited access to the world's top documentaries and non-fiction series and it's just 2.99 a month it's a great way to support this show keeps us making more videos and it's a great fit and let's get into today's video [Music] it's as easy as riding a bicycle so the old saying goes and indeed in the wide world of transportation few vehicles are as mechanically elegant as the humble bicycle which at its most basic consists of little more than a tubular frame two wheels a steerable fork a seat pedals and a chain drive this basic configuration has remained essentially unchanged for more than 130 years so it's safe to assume that scientists and engineers know everything there is to know about bicycle design right well no actually but beneath the bicycle supposedly simple exterior lies a profound scientific mystery it's a phenomenon many of us have witnessed first hand let a riderless bicycle coast and it will remain upright resisting all efforts to topple it until it finally slows down and falls over yet incredibly despite more than a century of research we don't 100 understand why the first bicycle as we would recognize it today appeared in 1820 in the form of german inventor carl dreyer's dandy horse or dry scene unlike a modern bicycle the dry scene had no pedals and had to be propelled by kicking one's feet rather like a modern scooter over the next 70 years the bicycle would evolve into a multitude of weird and wonderful forms including the popular penny farthing of the 1870s and 1880s with its gigantic front wheel but it was not until the 1890s that the modern safety bicycle with wheels of equal size and a chain drive finally emerged this design would take the world by storm bringing affordable transport to the masses and spawning a global industry worth nearly 50 billion dollars today and aside from relatively minor improvements in shape materials and gear technology the basic design of the common bicycle has remained more or less unchanged for over a century making it one of the all-time design classics yet despite the mechanical elegance and success of the safety bicycle very little science or mathematics went into its design the configuration having been arrived at through trial and error it was not until the turn of the century that mathematicians began to seriously investigate the mysterious physics behind the bicycle's remarkable stability the most comprehensive early analyses were conducted in 1899 by english mathematician francis whipple and in 1910 by german mathematicians felix klein and fritz nother who using rigid body mechanics determined that a bicycle stability was mostly due to gyroscopic procession this is the tendency of rotating objects to remain rigidly fixed in space and resist changes in orientation and is responsible for example for keeping spinning tops upright thus according to whipple klein and nosa the wheels on a bicycle act as large gyroscopes their rotation keeping the vehicle upright this remained the accepted explanation for bicycle stability for nearly six decades until in 1970 british science writer david jones examined klein and nother's analysis and discovered a number of mathematical errors that effectively cancelled out the effects of gyroscopic precession furthermore the parameters of the analysis assumed that the bicycle was stationary even though a stationary bike is demonstrably not stable to previous point jones built a bicycle with extra counter-rotating wheels that canceled out the gyroscopic effects of the main wheels and found that it was just as stable as a regular bicycle something else had to be responsible for the bicycle's remarkable self-writing ability back in the 1860s scottish engineer william rankine had observed that when a coasting bicycle begins to topple over the front wheel automatically steers into the fall riding the bicycle once more indeed if a bicycle's handlebars are tied off so that the fork can no longer steer it immediately becomes unstable based on this countersteering phenomenon jones proposed a new model for bicycle steering which he called cast a theory casters such as those found on shopping carts are wheels where the steering axis and the ground contact point are not aligned the distance between the two being known as the trail this offset causes the caster to automatically align itself with the direction of travel allowing all four wheels on a shopping cart to steer once examining common bicycle designs jones realized that the standard 72 degree angle of the fork placed the steering axis the imaginary line extending along the fork and into the ground ahead of the wheel's ground contact point effectively turning it into a giant caster from this jones concluded that only bicycles with a positive trail could be stable and that the caster effect was the soul mechanism responsible for the bicycle's self-writing ability and there he left the matter even broadcasting in his memoir 30 years later that i am now hailed as the father of modern bicycle theory but jones was a little too quick to rest on his laurels for soon another researcher would arrive and blow the mystery of bicycle stability wide open in 1975 american engineer jim papadopoulos working at cornell university began reviewing nearly a century's worth of academic papers on bicycle theory and was unimpressed by what he found like the original kleiner nother analysis the papers either made overly simplistic assumptions or mathematical errors and very few referenced each other or built upon previous studies after years of work papadopoulos managed to combine all of these disparate analyses into a single unified set of equations which immediately revealed that jones was wrong it was in fact possible to build a stable bicycle with a negative trail provided the weight distribution was moved far forward together with fellow engineer andy rooney papadopoulos launched the cornell bicycle research project with the goal of better understanding bicycle dynamics and passing on that understanding to the industry so that better more efficient bicycles could be produced based on papadopoulos's calculations the team built an experimental device that barely resembled a bicycle with small wheels and counter-rotating wheels to cancel out the gyroscopic effect a negative trail to counteract the caster effect and a long-weighted boom extending ahead of the front wheels amazingly this strange contraption proved perfectly stable demonstrating that neither gyroscopic procession nor the caster effect was solely responsible for the counter-steering phenomenon further research with a model featuring a small front and a large rear wheel suggested a possible alternate explanation when the bicycle begins to fall the front end being shorter falls over faster than the rear end however as the two ends are rigidly connected the front end pulls the rear with it causing the fork to immediately steer into the fall and right the vehicle despite this great leap forward the cornell bicycle research project was short-lived not only had it failed to attract sponsorship from more than a handful of small bicycle companies but papadopoulos was slow to publish their findings later admitting i find much more joy discovering the new and working out the details and of course it's boring to write it up in any event with few published papers to show for their work the project dissolved and papadopoulos drifted away from bicycle research moving to illinois where he ended up as an engineer for a toilet paper manufacturing company in 2001 david wilson an engineer at mit and the inventor of the recumbent bicycle invited papadopoulos to co-author the third edition of the book bicycling science but beset by a divorce large debts and other personal responsibilities papadopoulos took a full two years longer than anticipated to complete the work much to wilson's frustration meanwhile andy rooney continued to carry the torch of bicycle research teaming up with fellow scientist aaron schwab in 2001 to establish a bicycle research center in where else than the netherlands in 2003 papadopoulos joined the team and together with jdg kugeman and j.p mayard from the university of delft t rooner and schwab confirmed their results from the 1970s while carrying their research forward into a new more high-tech domain for example by building a cycling robot that could keep a bicycle upright through steering alone without any weight shifting or stabilizing gyroscopes this research culminated in a groundbreaking 2011 paper titled bicycles can be self-stable without gyroscopic or caster effects the delft research center has also produced a variety of unconventional bicycle designs such as a stable rear wheel steering bike a rear-wheel drive recumbent a steer by wire bike that decouples the active steering from that balancing and a powered steer assist bike that will automatically stabilize itself at low speeds while these odd creations may seem like mere mechanical novelties runa sees in them great potential to benefit the world given the millions of people who depend on bicycles for daily transport stating with these changes of appearance one might have bicycles that are easier for old people to ride bicycles that are easier to maneuver but still feel stable when riding straight bicycles that have more comfortable sitting arrangement or bicycles that have more convenient places for storage or carrying kids but while the delft team sees endless possibilities for evolution and bicycle design the bicycle industry has been slow to adopt their findings part of this reluctance is practical despite being born of trial and error the classic bicycle design is simple robust and just plain works but another factor is organizational the uci the international governing body for cycling sports has standardized the design of road race bikes along the traditional lines forcing the industry to conform to its guidelines but renschwab is optimistic stating in a tedx talk that my vision is that with careful experiments and validated computer models we can move past this 19th century bicycle evolution into a 21st century bicycle revolution and despite the great strides made by the delft team and other researchers much about the dynamics of bicycle stability remains as poorly understood a mystery both frustrating and exciting for researchers such as mont hubbard at uc davis everybody knows how to ride a bike but nobody knows how we ride bikes the study of bicycles is interesting from a purely intellectual point of view but it also has practical implications because of their ability to get people around we are all stuck in the 19th century when there wasn't such a difference between math and physics and engineering bicycles are a math problem that happens to relate to something you can see if nothing else the fact that the bicycle still manages to stump the world's leading mathematicians and engineers 130 years after its invention is a humbling lesson in how little we know about the workings of the universe the lesson perhaps best expressed by quantum physicist michael brooks in 2013. forget mysterious dark matter and the inescapable accelerating expansion of the universe the bicycle represents a far more embarrassing hole in the accomplishments of physics so i really hope you found that video interesting if you did please do hit that thumbs up button below don't forget to subscribe and as always thank you for watching

Channel: Today I Found Out

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Length: 11min 38sec (698 seconds)

Published: Wed Jan 20 2021