I got this book from the library and was not expecting how serious it would be... it's a lot of diagrams and hard math and physics explanations for how bicycles work. Seems pretty interesting but definitely not casual reading or close to a priority right now.

...Buuuut I did still skim through, particularly the section on the science of bicycle balancing, which was really the part I was most interested in. And it's interesting!! That and some of the information on relatives of the bike made me happy I got the book, even if I will return it not having read 99% of it.

Bike Relatives

There were tons of these actually but I'm just sharing the ones that tickled me most.

Sociable Monocycle

Behold:

Unfortunately, there was basically no information on this; the picture is shared without context, and the citation also seems to have no context. I couldn't find any information on it when I searched online either... I'm so curious if this was really a thing and if so, how many there were??

Quardacycle/Quadricycle

Apparently nowadays this is also getting applied to pseudo-cars like this, but it can refer to the equivalent of a bike but with 4 wheels. Here's one I found for sale. What the hell... I wanna ride in one!!!

Velomobile

Basically a bike or trike where the vehicle is encased so it's more car-like from the outside. Apparently this makes the vehicle more aerodynamic. Here's a top-tier video from 2011 where someone shows off his:

Bicycles: How Do They Work?

I've been repeatedly going like: "How the hell do people manage to ride bikes all the time and have it be second nature?? Shouldn't it be really hard to keep the bike balanced? But it seems everyone can do it, even tiny kids!" Obviously the human capacity to learn is amazing, but the bicycle has achieved a level of ubiquity that is unusual for vehicles.

There were three pages in the book that completely addressed this, in a section called "How Bicycles Balance." To quote a bit of it:

It was and often still is widely believed that the angular (gyroscopic) momentum of a bicycle's spinning wheels somehow supports it in the manner of a spinning top. This belief is absolutely inaccurate. [...] Locked steering on a forward-rolling bicycle does not permit any wheel reorientation, and the bicycle will fall over exactly like a bicycle at rest, no matter how fast it travels or how much mass is in the wheels.

[...] Still, there is an extremely interesting gyroscopic aspect to bicycle balance: the angular momentum of a bicycle's front wheel urges it to steer (i.e., to precess) toward the side on which the bicycle leans, as can be demonstrated by lifting a bicycle off the ground, spinning the front wheel, and briefly tilting the frame. In other words, the gyroscopic action of the front wheel is one part of a system that automatically assists the rider in balancing the bicycle. [...]

The basic means by which bicycles are balanced and controlled involves vehicle supports that travel only in the direction in which they are pointed [...] For this, at least one wheel must be steerable, usually the front one. This balancing-by-steering function can be performed not only by conventional large-diameter bicycle wheels [...] but also by small-diameter wheels, as on a foldable scooter, by skates on ice, by skis or runners on snow, and by fins or foils in water.

I ended up watching a video that goes over this, IMO extremely well and clearly:

(Honestly I think you can skip the first 4 minutes if you're impatient.)

Watching the bike ride by itself made me feel like... damn, what am I so nervous for?? Not only can 5 year olds ride bikes, bikes can ride with nobody on them at all! All I gotta do is get it going and then sit there!

Interesting to me about all this (expressed in both the book and video) is that research into bicycle physics is ongoing, and previously it seems even scientists thought gyroscopic action was "essential", only to have this be disproven in 1970. I usually think of inventions as something that you make after you come up with a very clear idea in which you know how all the pieces work... I forgot that people can just make whatever, tweak it and iterate on it, and then be surprised at how well it works. And yeah, the design of the bicycle is just incredible!!

I'll end with a paragraph from the intro to the "Steering, Balancing, and Stability" chapter that made me chuckle:

The most visible wonder in balancing a bicycle is that the bicycle can be balanced on just two points of support. Indeed, above a minimum speed, it appears impossible to fall down even if one were to try! This is of course not so; it would be easy to crash a fast-moving bicycle, but riders obey an unconscious compulsion not to do so.