YOU WERE ASKING IS SPONSORED BY CASTROL CLASSIC OILS
OHC crankshaft end-float
Following publication of the February 2023 issue of TCM, with a YWA answer to Cliff Somers’ question seeking crankshaft end-float advice for his 350cc International Norton, friend Rob Drury, who has much experience with ohc Velocette engines, emailed the following ‘hands-on’ advice.
Rob writes: “On their road engines, Veloce fitted a lipped roller on the drive side mainshaft and a ball race on the timing side, a practice copied by Norton. The ball race was an interference fit both onto the shaft and into the crankcase, so provided a firm lateral location for the flywheels, there being little positive thrust in that axis.
“A small amount of theoretical end-float allows for expansion as the engine gets hot, but since the cases expand more than the flywheels, the tendency is to increase any clearance. The ball race on the timing side maintains the relationship between the bevels.
“Veloce adopted the practice of fitting two lipped bearings for the racing engines, with any lateral movement being limited by the two lips. Phil Irving did indeed suggest a .004 inch pre-load on these engines when cold, with the result that the flywheels were free to turn with no end-float when hot.
“A more general practice seems to be setting ‘free to turn, zero end-float’ when cold. The lip on the timing side bearing maintains the minimum clearance between bevels while its opposite
