On Wednesday, June 15, 2011 12:40:32 PM andy pugh did opine: > On 15 June 2011 17:07, Viesturs Lācis <[email protected]> wrote: > > And, if the required CAM profile is offset by the radius of the > > grinding wheel, then moving the center of grinding wheel along that > > line will produce the required profile. > > I don't think that this is true for all shapes of cam. If you consider > a cam with a flat or near-flat face, the wheel will often be grinding > a part of the cam significantly above or below the centreline.
That effect also has to be accounted for, along with the face profile of the tappet, with the rate of lift or close being constrained by the diameter and face profile of the tappet. This can make a powerful argument in favor of mushroom faced tappets with a spherical face profile. One of the better, precomputer designs was in the big 6 Nash engines after WW-II. Using valves that were double sprung and deeply tuliped, a mushroom tappet whose face was about a 3 foot sphere and nearly 2" in diameter, allowed that engine to breath well and produce race winning horsepower at engine speeds that rather handily exceeded the accepted 4000 feet a minute in piston speeds. With a 4 & 3/8" stroke, nearly 8 grand was on tap for a block or so, but it needed a set of pistons and rings when you did it as it even broke the oil rings at that rpms. I think by sheer luck, the Nash folks hit a winner. Its too bad they didn't swap the bore and stroke measurements so the rest of the engine could survive the performance that valve train gave them. I had one for a couple of years, and I still remember tuning tricks that made that old bathtub a giant killer. How I managed to outlive its lack of brakes is another wonder but I did. Cheers, gene -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) You definitely intend to start living sometime soon. ------------------------------------------------------------------------------ EditLive Enterprise is the world's most technically advanced content authoring tool. Experience the power of Track Changes, Inline Image Editing and ensure content is compliant with Accessibility Checking. http://p.sf.net/sfu/ephox-dev2dev _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
