Cam shaft and timing case gears

This image shows setting the position of the cams on the table of the mill. The shaft is held in the chuck of the dividing head and supported by the centre at the other. The dividing plate has 3300 holes for direct indexing  clock wheels. For this application I choose the outer row which has 288 holes. The plate was first marked in quarters, then marked 92 holes either side of these marks. A "Y" shaped tool which comes out of a battery drill kit for driving cup hooks was used to locate each cam in the correct location by the index plate. Care was needed to not only have the firing order correct (1-2-4-3) but also set the cams for the right sequence as the exhausts are on the outside of the engine on 1 and 4 but in the centre together on 2 and 3. The cams were locked in position by 3mm grub screws and loctite.

Hobbing the crankshaft gear from silver steel. This gear has a keyway for location and will be oil hardend.











This image shows the camshaft gear being hobbed.

Here the gears are mounted in position. The small 13 tooth gear, which is driven from the large cam shaft gear, drives the fan. In the prototype the gear train is 38, 76 ,38 and 16  on the fan. I have selected 30, 60, 30 and 13 which fit the centre distances in the model with availiable hobs. The fan shaft is 6mm in diameter and runs in a 6mm by 13mm ball race next to the gear. The missing gear to the top left drives the water pump and magneto (on the model it will be a distributor).