Member postings for Wayne Ward

Cam design is a really complex job if you are going to look into all aspects of the problem. I can recommend the book by Rothbart "Cams: Design, Dynamics and Accuracy" if you like maths. It's available second-hand and the price has fallen in recent years, presumably because a lot of old boys are retiring and the young pups just rely on incredibly expensive programs to do the calculation for them.

It depends what you are doing. A new engine where you can leave yourself lots of space, where performance is not an issue and where speeds are modest is easier than designing a cam for a racing engine which runs at high speed and where maintaining valve to piston clearances and control of the valve and spring are significant problems.

I wrote a huge spreadsheet in excel many years ago for flat-faced followers where you played with the shape of the acceleration profile until you got an acceptable maximum opening angular velocity (which dictates the size of the follower you need), sufficient oil film thickness between cam and follower, sufficiently low contact stresses between cam and follower (always at the nose at the lowest engine speed), sufficient spring force to maintain a safety margin at max lift / max engine speed etc, all whilst having tangency in the acceleration curve. It took many weeks of work, but it played a significant part in landing me a couple of good jobs.

Curved followers, finger followers, pushrods etc all make the problem more difficult.

To top it all off, every bit of the system is elastic: the camshaft twists and bends, the valve compresses and stretches etc. Designing a desired valve lift profile is one thing, but making the valve do what you expect it to do in a high-speed engine is quite another. Thankfully most people are blissfully ignorant that their valves are not following the designed profile until they get on a valvetrain rig where valve position can be measured with a laser at high speed.

None of this is meant to put you off, just to point out some of the things that you might need to consider.

Edited By Wayne Ward on 11/06/2017 10:52:45

Edited By Wayne Ward on 25/03/2017 18:54:00