Hyd Roller vs Hyd Flat tappet on SM heads
Here's another drawing to illustrate ONE effect of roller tip diameter. I made this drawing so I could understand a little more about rocker geometry. I'm not interested in who is right and who is wrong. You guys are bringing up some fascinating topics that I want to understand.
So here's the point of this drawing. IF the rocker geometry is set up for minimum sweep (and I'm not saying it always should be) then roller tip diameter does not change the valve motion. The total sweep angle to achieve 1" of lift is the same for both roller tips and the valve lifts after 10 degrees of rocker rotation are identical. Roller tip diameter does affect optimum location of the 7/8" shaft centerline with respect to the top of the valve.
In this example we are looking at one half of the rocker arm and we are designing that half of the rocker arm the way we want it. It the real word we would be choosing parts that are already being manufactured and installing them on a rocker pedestal that may not be in the proper location. In that case the other half of the rocker arm, the rocker shaft location and the roller diameter would start affecting valve motion because geometry is not optimum.
The way I see it, the most important dimension for minimizing sweep is the distance from valve tip to rocker shaft centerline measured parallel to the valve.
Not saying I'm right, just stating things the way I see them. This is good stuff. I'm interested in other points of view.
Apologies to the OP if this is turning into a hijack. We can continue this elsewhere if need be.
Here's another drawing to illustrate ONE effect of roller tip diameter. I made this drawing so I could understand a little more about rocker geometry. I'm not interested in who is right and who is wrong. You guys are bringing up some fascinating topics that I want to understand.
So here's the point of this drawing. IF the rocker geometry is set up for minimum sweep (and I'm not saying it always should be) then roller tip diameter does not change the valve motion. The total sweep angle to achieve 1" of lift is the same for both roller tips and the valve lifts after 10 degrees of rocker rotation are identical. Roller tip diameter does affect optimum location of the 7/8" shaft centerline with respect to the top of the valve.
In this example we are looking at one half of the rocker arm and we are designing that half of the rocker arm the way we want it. It the real word we would be choosing parts that are already being manufactured and installing them on a rocker pedestal that may not be in the proper location. In that case the other half of the rocker arm, the rocker shaft location and the roller diameter would start affecting valve motion because geometry is not optimum.
The way I see it, the most important dimension for minimizing sweep is the distance from valve tip to rocker shaft centerline measured parallel to the valve.
Not saying I'm right, just stating things the way I see them. This is good stuff. I'm interested in other points of view.
Apologies to the OP if this is turning into a hijack. We can continue this elsewhere if need be.