TECH-LINE

DESIGN GEOMETRY 101

Rocker "geometry" is "angles" of motion. Specifically, it is the angles between the pushrod and the valve center-lines. The YELLOW circle represents the pushrod's radial, and is shown at a 90 degree relationship with the pushrod at the same time this is being achieved on the valve side of the rocker. The inclined angle of the rocker stud on this SB Chevy illustration can easily be seen. Raising the rocker unnecessarily will push the roller tip farther across the valve tip. Choose valve lengths carefully. CLICK to see: VALVE TIP HEIGHT

For 30 years, this has been the only way we've ever designed a rocker arm. The entire engine's critical angles are precisely laid out. In MID-LIFT, everything balances at the MID-LIFT point of the NET valve lift. Both sides of the rocker arm are perpendicular at MID-LIFT, so the very least amount of in and out motion occurs on BOTH sides. A very well known rocker company, promotes an over-arcing geometry that he put his own name to. The brand is probably the most well recognized name in "shaft" systems. His argument implies that reaching a 90 degree relationship with the valve when it's closer to full lift (about 2/3) has less loading on the valve train. There is no merit to this argument since the loads are compounded and dynamic throughout the lift cycle. There is never a benefit to trading excessive motion during the conversion between radial to linear process, for shuffled loads at various valve lift points.