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Comment by salmonellaeater | Hacker News Reader

The first bike is missing its chain stays, the bars connecting the bottom bracket to the rear axle and the ends of the seat stays. Wikipedia has a nice diagram with the names of all the parts of a bicycle [1].

There are real bike designs that have a monofork (a one-sided fork, e.g. the Cannondale "lefty"), a monostay, or a solid body instead of top & down tubes (e.g. many folding bikes or the extremely aero Ventum One [2]). The Giant Halfway [3] folding bike has all three features!

[1] https://en.wikipedia.org/wiki/File:Bicycle_diagram-en.svg

[2] http://www.slowtwitch.com/Products/First_look_at_the_elusive...

[3] http://www.giant-bicycles.com/en-in/bikes/model/halfway/1905...

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Another fun fact about chain stays is that modern bikes are not symmetrical on either side of the vertical plane. The drive-side chain stay is noticeably thicker on the right hand side (drive side) to deal with the very high stresses in this area.

This photo shows this asymmetry quite clearly: http://velonews.competitor.com/files/2010/09/IB2010_cervelo1...

That looks to me like the non-drive-side is thicker, rather than the drive side.

It also depends on the bicycle. I've got a '53 Schwinn three speed that's made out of what seems like gas pipe and it's perfectly symmetrical. A number of my old steel road frames look similarly, and so does my current titanium road frame.

That's a good point! I completely got it the wrong way around and didn't look at the image properly before posting it. The non drive side must be thicker because of the torsional force on the frame when pushing on the pedals. Too late to edit my post!

As another example, here's a 19th-century bicycle design without a chain stay. Not necessarily a good design, but it was actually built and ridden: https://commons.wikimedia.org/wiki/File:BicyclePlymouth.jpg

the first thing i noticed wrong with the first bike was 'oh my god that's a terrible placement for brake levers!' and only after I noticed the missing chain stays haha.

What is the purpose? To reduce torsion of the rear axle?

To form the triangle that locates the rear axle. Without it, the seat stays (?) would flex and break.

Most bicycle frames are two triangles sharing the seat tube, making it strong and rigid.

But at least that bike is theoretically possible if it was built rigidly enough that it didn't flex too bad.

The interesting thing was that many of the drawings were not physically possible at all, like connecting the chain to the front wheels, or some other bizarre mistakes.

> But at least that bike is theoretically possible if it was built rigidly enough that it didn't flex too bad.

True, but a construction would stand a good chance of being too brittle and subject to catastrophic failure during riding involving changing loads (or bumpy roads).

Connecting the chain to the front wheel is certainly possible. For example, take a look at the Cruzbike http://www.bentrideronline.com/wordpress/wp-content/uploads/...

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