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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Twin Valve Timing
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<blockquote data-quote="timetraveller" data-source="post: 55881" data-attributes="member: 456"><p>Gentlemen. some years ago I published an article in MPH about cams. I am away from home at the moment so cannot give you the reference. The thing about flat lever followers is that, it is my belief, that one cannot get a symmetrical lift with such a system. Now that MartyG has his measurements in a spread sheet it is relatively straight forwards to go ahead and calculate the velocity and acceleration of the valve. Take the difference from measurement one to measurement two and divide by the number of degrees between those measurements. Then do the same for measurement two to three and so on. That will give you a graph of the velocity of the cam. Then do the same with the velocity calculations. Plot those values out and you will have a graph of the acceleration. It is the acceleration which knocks the stuffing out of the bits and pieces. What you will find is that first of all there is a lot of noise which is due to measurement errors but more importantly the lower part of the acceleration curve, which should be flat, has a slope. What this means is that the valve springs, which control that part of the curve, have to be much too strong as they are only working for about half of the time that they should be. If one designs a cam for use with a curved base lever follower then one can get a symmetrical lift curve etc. and the valve springs can do their job for the whole of the duration that is available to them. Additionally there is no need for a ramp at the start or end of the lift as that happens automatically with the curve based followers. </p><p>The value for the lift of about 0.45 inches was also independently determined by John Emmanuel when he worked with a chum who had a modern tuning shop with a lot of good gas flow instrumentation. John and his chum also developed a new shape for the inside of the cylinder head which to the naked eye looks to be identical to that developed by Terry Prince so it is encouraging that two independent routes have lead to the same shape.</p></blockquote><p></p>
[QUOTE="timetraveller, post: 55881, member: 456"] Gentlemen. some years ago I published an article in MPH about cams. I am away from home at the moment so cannot give you the reference. The thing about flat lever followers is that, it is my belief, that one cannot get a symmetrical lift with such a system. Now that MartyG has his measurements in a spread sheet it is relatively straight forwards to go ahead and calculate the velocity and acceleration of the valve. Take the difference from measurement one to measurement two and divide by the number of degrees between those measurements. Then do the same for measurement two to three and so on. That will give you a graph of the velocity of the cam. Then do the same with the velocity calculations. Plot those values out and you will have a graph of the acceleration. It is the acceleration which knocks the stuffing out of the bits and pieces. What you will find is that first of all there is a lot of noise which is due to measurement errors but more importantly the lower part of the acceleration curve, which should be flat, has a slope. What this means is that the valve springs, which control that part of the curve, have to be much too strong as they are only working for about half of the time that they should be. If one designs a cam for use with a curved base lever follower then one can get a symmetrical lift curve etc. and the valve springs can do their job for the whole of the duration that is available to them. Additionally there is no need for a ramp at the start or end of the lift as that happens automatically with the curve based followers. The value for the lift of about 0.45 inches was also independently determined by John Emmanuel when he worked with a chum who had a modern tuning shop with a lot of good gas flow instrumentation. John and his chum also developed a new shape for the inside of the cylinder head which to the naked eye looks to be identical to that developed by Terry Prince so it is encouraging that two independent routes have lead to the same shape. [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Twin Valve Timing
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