Hi Mark, I read a bit on these engines in my younger day in the 1970's. I read that the main reason for their poor success was the conflicting engineering requirements caused by the design. There was a need for very tight clearances between the rotating valve cone and the head casting to ensure good compression and to minimise loss of oil (on the cutaway pictures you can see a compression spring fitted to the spindle forcing the cone up into place). This resulted in a very thin film of oil above the cone exposed to very high heat stress because of the close proximity to the combustion area. Because it was a thin film it didn't flow well around the system. The oil therefore tended to overheat, "cook off" and couldn't provide sufficient lubrication to allow good reliability. Perhaps with synthetic oils or even ceramic components it might be made to work more reliably.
Hi Mark, I read a bit on these engines in my younger day in the 1970's. I read that the main reason for their poor success was the conflicting engineering requirements caused by the design. There was a need for very tight clearances between the rotating valve cone and the head casting to ensure good compression and to minimise loss of oil (on the cutaway pictures you can see a compression spring fitted to the spindle forcing the cone up into place). This resulted in a very thin film of oil above the cone exposed to very high heat stress because of the close proximity to the combustion area. Because it was a thin film it didn't flow well around the system. The oil therefore tended to overheat, "cook off" and couldn't provide sufficient lubrication to allow good reliability. Perhaps with synthetic oils or even ceramic components it might be made to work more reliably.
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