funny

Peter Dohm wrote:

I am a little curious about the specifics of how the 2:1 reduction ratios
are acheived on both the belt and hy-vo chain drives, as I learned a
number of years ago that evenly divisible ratios (such as 2.0:1, 1.50:1,
3.0:1, etc.) should be avoided in spur gear type reduction drives as
they will wear unevenly and require more frequent overhaul. The problem
occurs when the same gear teeth consistently transmit the power or
compression strokes of the engine, and can be mitigated by slightly
hanging the ratios; usually by one tooth on either the drive gear or
the driven gear. However, since the drive gear is fixed to the crank
shaft, the uneven wear problem can not be eliminated in a spur geared
system.

Peter Dohm

Actually it has been found that exactly 2:1 ratio with a cog belt PSRU
runs trouble free whereas one tooth above or below that ratio caused a
very noisy unit. (Dave Blanton's original development work)
--
Bruce A. Frank, Editor "Ford 3.8/4.2L Engine and V-6 STOL
Homebuilt Aircraft Newsletter"
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