<VV> Valve rocker arm ratio
chartzel at comcast.net
Mon Oct 10 20:31:13 EDT 2005
As CPF museum curator, I just happen to have the engineering drawing for a
Corvair rocker arm here. The dimension for centerline of rocker ball to
centerline of pushrod is .90.
The centerline of ball to centerline of tip radius is 1.328. Dividing those
numbers, I get a ratio of 1.476. Disclaimer: The centerpoint of the radius
of the pushrod tip, rocker ball and valve stem contact surface are not in
line, therefore, the ratio CHANGES as you rotate the arm about the ball.
The pushrod moves closer to the pivot at full lift where the valve doesn't.
The surface of the valve stem and rocker contact point slides back and forth
as the rocker pivots. This is what causes wear and worn guides. Hence the
auto companies now all use roller rockers to reduce the sliding friction to
rolling friction in their holy grail to reduce fuel consumption.
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