ET: Engine (Twin) Camshaft design

[oexing]

Thanks for these pictures. Roller cam followers are quite common today but most of them are used on ohc designs, often for smaller four valve gear. In case of the Vincent engine they would operate not only the big valve but one pushrod and another rocker so dimensions matter here a lot. In my eyes the roller above looks not overly big so one will see if it is a durable proposition. There were numerous - plain bearing - roller followers for pushrods even prewar like Horex when I did a crowded needle roller mod like in the 1935 Guzzi we run like that since the eighties, no problems. The pinions are casehardened for the needles of course and punchlocked with carbide punch in the followers.
Maybe a curved contact pad on the near standard Vincent follower , no roller, would be tougher instead, lighter too. That would be very similar to the postwar Horex Regina with almost roller looking followers and certainly cam lobe shapes to go with the curved followers.

Vic

 

[Deleted member 3831]

Follower wear, whether on flat or curved pad, can be sucessfully managed through the use of DLC coating. Followers only may be coated, or both follower and cam, although if the latter it is advisable to not use the same DLC treatment on both items.

 

[greg brillus]

Ok so after all this talk about cams/followers which by the way is probably way over the top for most forum users to understand.........Where are we now.............Is one of you geniuses going to come up with some revolutionary new design that no one has ever thought up that will make a Vincent the most powerful V twin ever made with outstanding reliability.............Lets not forget the fact that these bikes have stood the test of time and will be around long after we are all gone. I'm all for improvement and sensible upgrades, but where is this all heading...................

 

[davidd]

A couple of questions David; What material was used as the pivot for the roller? That must have been a bit of good stuff. Secondly, that is a very interesting construction for the cam wheel. Are the threads in the holes in the camshaft part threaded for some sort of adjustment of the teeth to cam rotation? And why is it made in two parts, teeth plus pinion, unless that is to allow some rotational adjustment. Interesting posting that.

Norman,

I don't know about the materials. I have tested the stock followers and they are at 60 Rockwell, generally. I would think the roller might have to be near the same hardness and would be a good steel alloy that would perform.

And the cams are a vernier adjustment. I think of it like like setting up the cam indexer. You have to decide where you set the events and moving them to a tooth or the groove, or somewhere in between makes a difference. It may mean you are a bit off and with a vernier you can make finer adjustments.

I took the photo of the cam at Steve Hamel's shop and the follower, which Steve uses, was a Horner item, also. Steve uses Irving-Vincent cases on his bike.

David

 

[Chris Launders]

Ok so after all this talk about cams/followers which by the way is probably way over the top for most forum users to understand.........Where are we now.............Is one of you geniuses going to come up with some revolutionary new design that no one has ever thought up that will make a Vincent the most powerful V twin ever made with outstanding reliability.............Lets not forget the fact that these bikes have stood the test of time and will be around long after we are all gone. I'm all for improvement and sensible upgrades, but where is this all heading...................

Hi Greg
I've been following it just out of interest and the only outcome I can see that would benefit ordinary riders would be a roller follower cam design or two and followers to suit, these providing extra longevity and reduced wear and covering the same sort of range as mk1s and mk2s but with increased economy.

 

[greg brillus]

The main issue with the Vincent engine with regards to cam/follower design is lack of room. I've spoken to Ken Horner about this and that was the first thing he said to me. This is probably why the ratio rocker arms give good results, only the extra load on the valve train goes through the roof. If solid type followers were installed where the pushrod tubes locate in the upper timing chest, this would work well, but how many owners would go for that............ let alone the expense. I personally would do it to one of my engines but not for anyone else. People would not pay and would not want their engines altered that much. It's been hard enough to get people to change their front suspension............ And that was fundamentally a safety issue.

 

[Deleted member 3831]

Referring to Roger's original post, I'm assuming the type of drawing he's looking for is similar to the one attached here, which shows the dimensions per degree.
This was a type of drawing commonly used before computers and CAD software made drawing boards obsolete, but Nortons used a data table for the Manx cams.
In those days four places of decimals was the best they could do.
Today's CNC cam grinders need no masters to grind from, they will accept digital design data, provided it is in the appropriate format, and the finished item is a first class example of high precision engineering at it's best.
You just have to hope the designer did an equally proficient job.

 

[roy the mechanic]

Greg, I'm with you on the cam follower job. It has been done on at least two motors ,also had proper overhead rockers. The height penalty was not an issue as they were in a sidecar outfit, and a right quick one. Now if I had a bit more oil pressure I could use hydraulic followers with rollers.

 

[timetraveller]

I wonder about trying to get all the lift at the cam rather than using ratioed rockers. Is there enough clearance under the tappet adjustment covers to allow for extra lift? The only way I can find out for certain is by sacrificing one by cutting the top off to see exactly where the adjuster nut goes at maximum lift. I don't want to do that.
Regarding different cams and diamond like coated followers; here is a picture of one where the follower design allows the use of the valve lifter,

 

[davidd]

Norman,

I think that I found .100" up and down between the button on the shoulder of the valve and the roof, which is the top valve guide. To clear the guide you have to raise the shoulder on the valve about .080", which is eating into that .100". You also have to mill the top of the valve guide down and throw away the seal. This will get you around .500" lift. My cam makes .480" lift, but I think that is close to the max you can get reliably out of those tight quarters. I have also ground down the button by grinding the bevel off to get more clearance, but the rocker at full open can't be near the lower guide because grinding the button will lower the rocker arm.

The Vincent does well without hot rodding it, but if you want to hot rod it, it is very difficult.

The finished cam on the left, the prototype that I ran on the right.

David