Ok Pete. I had better start at the beginning.
Radial engines have a problem in that only the number one cylinder is coupled directly to the crank by the master rod, all the other pistons have slave rods that connect to the master. If the pins in the rod are at equal angles around the big end
the secondary pistons do not arrive at TDC at the correct angle spacing of 72° for a 5 cylinder engine.
Now ( normal radial engines ) only have one cam and one ignition system so timing is never correct, my OHC allows me to correct these errors. I did not worry about the power pulses being not quite right on the basis that V twins and split vertical twins run quite happily with power pulses Waaay out.
This problem is corrected by repositioning the pins in the rod ( if you look at the drawing you will see that the pins are radially positioned around the lower part of the rod. not at 72° spacing ) the pistons now arrive at TDC on time at 72°
Problem solved.
But we have another problem with this system. only the master rod big end follows a perfect circle around the crank,
the pins follow an elliptical path caused by the master rod rocking as it turns, this causes the timing for number one cylinder to be slightly out compared with the others Now on most engines this is simply ignored. but on some of the high powered ones the magnetos had the cams made to correct this, on my engine the ignition is independently set for each cylinder.
Many model engine designs choose to totally ignore these problems and seem to run perfectly well, but as it was commented on I felt I must put things right.
I hope this answers your question if not feel free to ask.
Brian
Radial engines have a problem in that only the number one cylinder is coupled directly to the crank by the master rod, all the other pistons have slave rods that connect to the master. If the pins in the rod are at equal angles around the big end
the secondary pistons do not arrive at TDC at the correct angle spacing of 72° for a 5 cylinder engine.
Now ( normal radial engines ) only have one cam and one ignition system so timing is never correct, my OHC allows me to correct these errors. I did not worry about the power pulses being not quite right on the basis that V twins and split vertical twins run quite happily with power pulses Waaay out.
This problem is corrected by repositioning the pins in the rod ( if you look at the drawing you will see that the pins are radially positioned around the lower part of the rod. not at 72° spacing ) the pistons now arrive at TDC on time at 72°
Problem solved.
But we have another problem with this system. only the master rod big end follows a perfect circle around the crank,
the pins follow an elliptical path caused by the master rod rocking as it turns, this causes the timing for number one cylinder to be slightly out compared with the others Now on most engines this is simply ignored. but on some of the high powered ones the magnetos had the cams made to correct this, on my engine the ignition is independently set for each cylinder.
Many model engine designs choose to totally ignore these problems and seem to run perfectly well, but as it was commented on I felt I must put things right.
I hope this answers your question if not feel free to ask.
Brian
