Rod ratios

robs ss said:

A bit further to the above, there should be an "ideal" amount of Desaxe so that the rods are more vertical on the power/thrust stroke.
For a forward rotating crankshaft this would mean the crankshaft C/L should be forward of the barrel centreline. It would mean more rod angle on the exhaust stroke, but unlikely to be as important.

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Desaxe - Wikiwand

A desaxe engine, is one in which each cylinder is positioned with its exact center slightly offset from the center line of the crankshaft. "Désaxé", in French, ...

www.wikiwand.com

mdt-son said:

Rob. the crankshaft C/L needs to be positioned _behind_ the barrel centerline for the Desaxe concept to yield a positive effect.

Desaxe - Wikiwand

A desaxe engine, is one in which each cylinder is positioned with its exact center slightly offset from the center line of the crankshaft. "Désaxé", in French, ...

www.wikiwand.com

Having waded through threads here and at other sites, it seems the 750/850 engines have a negative Desaxe of 0.0425" or about 1mm. I think it was unintentional and the figure is too small to have a negative overall effect.
To make a difference, the Desaxe should have been a positive 15-18 mm. Did Kenny Dreer turn the idea into reality when he designed the 961?

In 1957/58, AMC designed the lightweight G2/G5 engines with a positive Desaxe of 6.35 mm vs. stroke of 64.84 mm (9.8%). Thanks in part to the cylinder offset, these engines (the G2 in particular) are very efficient engines,
and it's a pity that tooling costs prevented this concept to be applied across the model lineup.

- Knut

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