Friday, 21 December 2012

Machining errors?

-SG- Viktor has been busy checking dimensions prior to machining (above) some replacement castings for his twenties Norton engines. He was as surprised as I was to find there is quite a big discrepancy in the dimensions from the timing side main bearing to the cam wheel and cam follower centres of his 1925 engine.  From the little I know about such manufacturing matters (mainly gleaned from a few years with AEC, the commercial vehicle manufacturers, in the sixties), Norton crankcases and timing covers would have been machined using a jig or fixture and all one can assume at this distance in time, is that it wasn't very accurately produced by the tool room. Whether the standard of work was in any way influenced by the fact that - reputedly - the neighbouring associate company Shelleys machined some of the Norton components, is anyone's guess!  Shelleys produced items for car owners like jacks and adjustable spanners where a high degree of accuracy was hardly paramount. Viktor would like to hear from anyone else who has input on this matter.

Dimensions of the openings for main bearing,
cam wheels and cam followers. Note the discrepancies.
Note the discrepancy in the dimensions from main bearing
to cam wheels