crankshaft front bearing type

[steve davidson]

Some other makes with 2 bearing cranks got by with a single bearing at each end, one a ball to locate and one a roller to allow for expansion. The fatigue life of rolling races was hard to predict in automotive applications and the Seven errs on the side of caution. The ratings of modern bearings are much higher than 1920s, hence the meagre  bearings in moderns. I am sure two ball races in the front would do fine, at reduced cost.

Thanks Bob

---

Radial, not axial Bob - but basically correct. At least that's the theory, but crankshaft whip among other things clouds the picture slightly. There's quite a bit on alternative bearing configurations in the 750 companion. Two rollers would have little capacity to support end load. A pair of self-aligning ball races can and indeed does replace the ball and roller set up successfully as they are designed to take both axial and radial loads (also a degree of misalignment which a roller race can't handle so well). n.b. It's rather early in the morning so I'll probably realise I've written something stupid later...

Thanks for the reply, now that you mention it I do remember some notes in the companion, I'll have a read and learn some more!