[zb]
anorak:
Fascinating stuff^^^
- You would have thought that simply offseting the centreline of the cam, axially down the shaft, from the centre of the follower, would promote the desired rotation. Not so, apparently.
- The wear on the knackered follower shown in the photograph looks excessive, even without the desired rotation. Maybe there was an issue with high lobe-follower contact loads, or bad material/heat treatment?
- The issue of the plate/pushrod fouling reminds me of a comment (credit gingerfold, possibly) mentioning AEC factory practice being that the shopfloor staff would solve problems themselves, unrecorded, without informing the engineers. This looks like an inevitable failure of that “system”.
As an aside, I once worked, as a sub-contract designer, on a system which required the follower to be kept in the same orientation, for a reason irrelevant to this discussion. IIRC, the thing that I drew had a pin stuffed into a groove, to stop it rotating. This tells us that non-rotating followers is not the end of the world. Of course, the ones I worked on might have been harder than usual material, or someone had found out that modern oils allowed the condition, or maybe the thing never made it to production!
I’ll see if I can find one of the worst old followers to photo, but they were horrendous.
Getting on for a 2 mm deep groove worn in the surface.
This is another one of those cases where correcting the underlying simple problem is impossible without making major component changes, but it is the general consensus of opinion that modern oils will reduce the effects significantly, as you say.