E: Engine Camshaft

oexing

Well Known and Active Forum User
VOC Member
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
 
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D

Deleted member 3831

Guest
TT
whatever skiddding may occur, in some very famous and indeed strenuous applications it seems not to have been a problem. The ILMOR 265E engine which I have previously mentioned, was a pushrod engine with roller followers. This won the 1994 Indy 500 race, running over 10000 rpm.
Steve Hamel has run with roller followers, and to my knowledge two others also.
A similar situation exists with the rollers in the valve arms of rockers, as used in the American V8's. The roller cannot reverse at part valve lift, it must skid to some extent, but despite this they seem to be remarkably reliable.
 
D

Deleted member 3831

Guest
roller tipped rocker on a Vincent ........ Now I'd like to see that............:)
For anyone having gone this far with modifications, to produce a roller tipped rocker would present few difficulties
 

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timetraveller

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VOC Member
OK Vic, I can see that the roller would have to be a lot smaller than the 1.5" diameter that I used for my design. In that case, if the roller was very small, then the cam would certainly be a different shape so perhaps the roller would not have to change direction. I did know that many people use roller followers but I've never seen any analysis of the design of both cam and follower. Perhaps it is obvious if one sees it in the metal, so to speak.
 
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