Norman,
you may think the roller changed its direction around the lobe, but in fact the lobe shape would be very different for a roller follower. So the rotation will never reverse. There are loads of roller followers, even prewar, that operate quite reliably - provided you modify for crowded needle bearings inside. Traditionally you´ll find a simple bush or nothing and that does not wear well.
In Vincent engines I see a problem with space for roller followers and some extra weight from them but it has been done? In car engines roller followers are applied as well today but for 4 valve heads mainly so small valves in there and small rollers with not so high loads. So maybe a curved follower in a Vincent engine is better for racing and rollers for road use if ever.
Vic
you may think the roller changed its direction around the lobe, but in fact the lobe shape would be very different for a roller follower. So the rotation will never reverse. There are loads of roller followers, even prewar, that operate quite reliably - provided you modify for crowded needle bearings inside. Traditionally you´ll find a simple bush or nothing and that does not wear well.
In Vincent engines I see a problem with space for roller followers and some extra weight from them but it has been done? In car engines roller followers are applied as well today but for 4 valve heads mainly so small valves in there and small rollers with not so high loads. So maybe a curved follower in a Vincent engine is better for racing and rollers for road use if ever.
Vic
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