ET: Engine (Twin) Camshaft design

O

oexing

Well Known and Active Forum User
VOC Member
Yes, that is the way to go ! You won´t have that pointy cam shape like with the flat followers and when you do some easy mods to get max oil supply into the camshafts all oil that is flung out the oil holes will easily prevent all this wear you see on flat drilled followers. Oil holes in the follower in an area at highest loads does NOT help here , simply stupid !
I was looking at my Horex parts, could almost fit in the Vincent engine ! There is NO oil supply , neither from within the camshaft nor from the pushrods into a hole in the follower contact pad !! All lubrication in this department is just oil mist. The curved followers were stellited standard in the factory and usually these engines have no real problem here, even less so with modern oil.
So big question: Where do we get these followers and more so who supplies the cams to go with them ???

Vic

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T

timetraveller

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You can't buy the cams or followers yet Vic. They are both my design and at the moment the cams, followers, ratioed rockers, modified valves with longer thick parts to the stems and beehive valve springs are with Mike Hawthorne to be built into his racing 500 engine and then to be tested on Ken Craven's brake. These cams were designed to replace Mk 1s. I have also lent Mike another cam, based upon the Picador cam, to give power at the 6,000+ rpm range and which will use the same follower as in the photograph. I don't want to claim anything for these cams yet until I have them tested in anger. Not knowing anything about cam design I designed them so that the acceleration while closing was the same as that while opening. Grey One has made me aware that this might be an error and that possibly the closing acceleration needs to be reduced in order to avoid valve bounce. We will see.
 
O

oexing

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I think you are quite right with symmetrical curves. The critical points are the quieting ramps that did not come until the sixties. So that is one of the reasons why the Vincents sound a bit like a can of screws. I have added curves from "The Apfelbeck", my bible. Curves no. 7 are my test cam for the Horex, upper types. The lowest curve is standard Horex, too little quieting ramps there, I added them by grinding the base circle a bit smaller, helped with our 30ies Guzzi a lot.
So I believe bouncing can be controlled by decent quieting ramps as used for long times. The curve below is a proper racing type, nevertheless real quieting ramps are essential.

Vic
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greg brillus

greg brillus

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I had to make up shorter than normal pushrods as well. I had new valves made using stainless ones from a big block Chev, like David says with the step on the valve moved further up the stem by 2 mm ( 80 thou). Hd to take a small amount off the top of the fork on the rockers.
 
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