Ok ....... here are the areas - with some assumptions.
1. Cylinder diameter = 3.550 inches. Given
2. Piston diameter = 3.45 inches. Assumed
3. Depth of ring groove in piston 0.125 inches. Assumed
4. Ring outer diameter = 3.550 inches. Given
5. Ring inner diameter = 3.250 inches. Assumed
6. Ring end gap 0.030 inches. Given
7. Ring end faces are parallel when ring is in cylinder. Assumed
These numbers allow for the piston to move 0.025 inches either side of the centerline of the cylinder. Then the inner diameter of the ring is against the bottom of the piston ring groove.
This means that the area for blow-by varies. It will be a minimum when the piston moves toward the cylinder wall in a direction exactly in line with the location of the end gap.
The shape of the area is per that attached bmp image earlier. The outer arc is the cylinder wall, the parallel lines are the ring end faces and the inner arc is the piston. Note that the 2 arcs do not have a common center due to the pistons movement. They will only have a common center IF the piston is sitting exactly in the center of the cylinder.
The minimum area for blow-by using the figures above is 0.00075002 sq. in., the maximum is 0.00225002 and if the piston is perfectly centered the area is 0.00150002 sq. in. If the piston moves toward the cylinder wall in a direction exacly 90 degrees to the end gap location the area is 0.00150545 sq.in.
What I do not know is ....
1. How much blow-by is from gases getting in behind the rings.
2. How much blow-by gets through the first ring end gap AND then gets through the second ring end gap.
Is it always assumed that there is never any blow-by from gases going in between the piston and rings ?
As the end gaps do not line up vertically is it assumed that what gets past the first ring will always get past the second ?
regards
Doug I
PS If someone could given me the real world numbers for those that I assumed, I can give you the real world areas
