A4 scale = 70%
| | A4 scale = 70% |
EGGring Ovals page 7
52t Durham chainring (USA, 1970's)
Here are some examples of Oval chainrings that have been made during the past 110 years:
| decade introduced | name | origin | shape* | size* | ovality* | crank offset* |
|---|---|---|---|---|---|---|
| 1890 | Linley + Biggs ? | joined semicircles ellipse | adjustable 30% | 0° | ||
| 1920 | Lantier | rough ellipse | 48 | 40% | ||
| 1930 | Elan Thétic van Deuren | France Belgium | rough ellipse ellipse ellipse | 48 46 | 40% 15% 11% | 0° -37° |
| 1940 | Larsen | trimmed rhombus | 50 | 54% | 0° | |
| 1960 | Bridgestone | Japan | ellipse | 6% | +24° | |
| 1970 | Daniel Durham Polchlopek | France USA France/NL | ellipse joined semicircles | 52 48 | 28% 65% 23% | +30° +15° -12° |
| 1980 | Biopace types* Shimano Biopace Miche Ofmega SIO SR Ovaltech Stronglight Sugino Cycloid | Japan Italy Italy Japan France Japan | rounded rhombus rounded rhombus ellipse ellipse ellipse ellipse | 28 28 28 48 | 16% 16% 17% 8% | +50° +50° +74° +90° |
| 1980 | Mavic | France | skewed ellipse | 26 | 13% | adjustable |
| 1990 | EGGring Harmonic MPS | UK Monaco Ukraine | ellipse bi-radial ellipse | custom 54 40 | custom 21% 31% | custom -3° -35° |
| 2000 | Osymetric Rotor Q-ring | France Spain | bi-radial ellipse | 52 53 | 21% 11% | -3° adjustable |
*Shape: The different shapes have little effect on how the chainrings work in practice. An ellipse is the purest shape from a mathematical point-of-view and, arguably, gives the smoothest transition between major and minor axes, but some of the other shapes are easier to design and make. It has been suggested that the shape of Biopace chainrings owes more to its patentability than to any performance benefits.
*Size, ovality and crank offset: Most types were also made in other sizes. The quoted ovality and crank offset relate to the particular example given.
*Biopace-type rings: These gave Ovals a bad name in the 1980's because their crank offsets orientated them back-to-front on upright bicycles. This gave a higher gear to push through the dead-spots instead of a lower one, making matters worse, not better, than with round chainrings!
| © Chris Bell, 2007 |
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