The Norton rotary engine design has an excellent power to weight ratio. This light weight was achieved by using aluminium for the housings and endplates.
The coating for the housings is elnisil (developed by Mr Wankel himself for the rotary engine) and it does an excellent job.
The endplates fare remarkably well considering they are not coated but just aluminium, etched to help with oil retention.
The rotor, side, corner and apex seals all press on to the endplates with varying forces. Under ideal circumstances all the seals run flat on the endplates in a film of oil creating a gas tight seal.
Finding the exact reason why the cast iron seals or rotor sometimes damage the endplate would take the kind of extensive testing I cannot afford to do. Bikes most likely to have trouble are those stood for some time, especially in damp conditions.
For the time being I have decided not to try and find out why damage occurs (though I do have many theories) but concentrate instead on an effective preventive measure – make the endplates so tough that they will stand greater strain without sustaining damage.
Norton developed Molybdenum coating for the endplates in the early 1990s but it was not considered necessary for all engines –just for those which came back under warranty having smeared or scored. I think prevention is better than cure.
Moly coating involves grooving out a track about 1cm wide at the perimeter of the working surface of the endplate and metal spraying pure molybdenum into the track.
The endplate is then ground back smooth.
Graham Wilshaw (Startright)