Inventors discovered oval chain rings shortly after the safety bicycle
appeared, but you may not have seen oval technology applied to
inch-pitch, shaft drive, double drive, treadle drive, or tandems.
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Here's a charming early lady's version with a wavy ring representing
the teeth:
http://www.google.com/patents?id=3CBVAAAAEBAJ&pg=PA1&dq=431529
Note the adjustable-height front suspension
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The most aggressive oval ever seen:
http://www.google.com/patents?id=bGRcAAAAEBAJ&pg=PA43&dq=513589
Look carefully--the oval will trick you into thinking that it's a
three-quarter view of the bicycle from the rear.
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Stubby teeth make these oval chain rings look cruder than they were:
http://www.google.com/patents?id=ZFZgAAAAEBAJ&pg=PP1&dq=515449
http://www.google.com/patents?id=_ZNUAAAAEBAJ&pg=PP1&dq=530058
Note how seat-stay design hadn't settled down yet.
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Who thought that oval shaft drives existed?
http://www.google.com/patents?id=hdpnAAAAEBAJ&pg=PA44&dq=518970
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You can get the same oval effect by having a round chain ring and a
crank arm that extends and retracts for more or less leverage:
http://www.google.com/patents?id=budhAAAAEBAJ&pg=PA1&dq=516137
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The silly double-chain, oval gears front-and-rear design mentioned in
an earlier thread:
http://www.google.com/patents?id=Pj5HAAAAEBAJ&pg=PP1&dq=528145
The inventor got lost in dreams of efficiency, but at leasthe
realized that his chains would have slack lower runs during part of
the cycle.
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Treadle drive with oval chain ring:
http://www.google.com/patents?id=VyJAAAAAEBAJ&pg=PP1&dq=547612
The seat-stays still haven't settled down into their modern position.
***
Tandem with treadle rear connecting to oval front:
http://www.google.com/patents?id=qUZtAAAAEBAJ&pg=PP1&dq=568862#PPP1,M1
Note the odd front seat-post.
Cheers,
Carl Fogel