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stationary gear and rotor sizes

Detailed technical information. Norton Interpol 2. Classic. Commander. F1. F1 Sport.

All the Norton engines were built to very close tolerances so in order to do a good job when building or rebuilding a rotary engine you really need to refer to the charts and tables shown here to check component dimensions.These engines are too special to risk anything less!

The dimension tables are listed as a free download on the downloads page.

Stationary gears;

Stationary gears from water cooled engines have two holes through the side of the bearing holder to allow oil into the main bearings:

Stationary gears from air cooled engines do not need these holes because oil is fed into the centre of the engine instead of through the main bearings.

This means the later design stationary gear for water cooled engines can be used on Interpol, Classic , Commander or F1 type engines.

Early ones without the holes can only be used on air cooled motors but if you are really stuck for a matching stationary gear for a water cooled motor, it is possible to carefully grind a hole in the stat gear in the correct place. Keep the hole size to a minimum and keep the edges smooth to reduce any risk of cracking, though stationary gears are very strong and rarely break or crack up.

Sizing of stationary gears is done when new by resting 3.000mm steel pins into the gear at opposing sides and measuring the over pins size. A number is then engraved on the outside flange of the gear. The final number of the set of four or five is the grading number, it can be a positive or negative number.

Having measured the over pins size, the gear is then graded in order to match it to a rotor, thus providing the correct backlash.

A similar measurement has to be made to grade the rotor. ie between pins size. These two figures are then added together. Acceptable figures are 5, 6 or 7. 5 is tight, 7 is slack.

Stationary gear   Rotor
Dimension grading number Dimension grading number
53.105 to 53.082 -3 66.505 to 66.549 3
53.082 to 53.060 -2 66.549 to 66.593 4
53.060 to 53.035 -1 66.593 to 66.637 5
53.035 to 53.011 0 66.637 to 66.680 6
53.011 to 52.987 1 66.680 to 66.722 7
52.987 to 52.963 2 66.722 to 66.764 8
52.963 to 52.939 3 66.764 to 66.806 9
52.939 to 52.915 4    
52.915 to 52.891 5