Upper Transfer Ports
Right Cylinder

BEAU de ROCHA FUNCTIONS / ATTRIBUTES 

The upper transfer ports are opened by the piston head/rings for 100 degrees of crankshaft travel (from 130 degrees before bottom dead center until 230 degrees after bottom dead center– black arrow and black degree compass on the animation) and the fresh air/fuel mixture (under pressure) from under the piston hits the turbulating fins on the piston head which puts that fresh air/fuel mixture into cyclonic motion in the top of the combustion chamber so it does not escape through the open exhaust ports. The following function that Beau de Rocha identified in 1862 has been accomplished: 

• Intake (from under the piston to the combustion chamber) 

RUSSELL BOURKE’S FORMULA 

• Port openings will always be computed from the degree of crankshaft travel.
• Upper transfer ports open 50 degrees before bottom dead center (130 degrees – black arrow and black degree compass on the animation) and close 50 degrees after bottom dead center (230 degrees – black arrow and black degree compass on the animation).
• The upper transfer ports are open for 100 degrees of crankshaft travel (from 130 degrees before bottom dead center until 230 degrees after bottom dead center – black arrow and black degree compass on the animation).
• Upper transfer port hole size is calculated from the stroke of the engine (see Table II for maximum and minimum hole sizes). There are four upper transfer port holes, two (2) holes are aligned with each section of the turbulating fins. When the piston is at bottom dead center, the top of the piston should be above the top of the upper transfer port holes to prevent fresh air/fuel mixture from being sucked out with the exhaust gasses (all fresh air/fuel mixture must be put into cyclonic motion in the top of the cylinder to avoid sweep out with the exhaust gasses). 

All of the volumes shown below for the 10.842 cubic inch (177.6748 cc) model were calculated using Solid Works:

• The volume under the piston when it is at Top Dead Center (TDC) is 166.478 cubic centimeters (cc), or 10.1591 cubic inches.
• The volume under the piston when it is at Bottom Dead Center (BDC) is 88.7875 cc, or 5.4181 cubic inches.
• The volume in the combustion area when the piston is at Bottom Dead Center (BDC) is 88.8374 cc, or 5.4212 cubic inches.
• The volume in the combustion area when the piston is at Top Dead Center (TDC) is 7.2358 cc, or 0.4416 cubic inches. 

The compression ratio for this model is calculated by dividing the volume at BDC by the volume at TDC (88.8374 cc/7.2358 cc =12.28:1 compression ratio).