This video is a practical demonstration to show the problem that is encountered when using a diaphragm instead of a conventional piston, there is no leakage from a diaphragm.
You will notice that as the pressure builds up the power output drops this is due to the diaphram being pushed too far up resulting in the magnets of the alternator hitting the laminated pole pieces.
When the balance valve is fitted the mean pressure is equal on both sides of the diaphragm.
When the water levels on the manometer are 12 inches apart the pressure is approx .434 of a pound per square inch, the diaphragm working diameter is approx 4 inches which is an area of 12.5 square inches which means that there is an upward force of approx 5.4 pounds pushing the diaphragm up.
