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*To*: "Quattro mailing list" <quattro@coimbra.ans.net>*Subject*: Re: Conrod force/acceleration*From*: "John Torset" <johnt@borre.mail.telia.com>*Date*: 27 Jan 98 01:05:49 +0100*Sender*: owner-quattro@coimbra.ans.net

>> If both acceleration and velocity are 0 at the same time, it is a >> clear indication that the engine isn't running at all. Absolutly correct. :) >Come again? Is there not a point in time where acceleration and >velocity are zero? I certainly think so. When there is no velocity, >there is no acceleration. Acceleration can be zero while velocity is >constant, but if velocity = 0, acceleration = 0; >acceleration is nothing more than the rate of change in velocity. Right, and the acceleration is highest at TDC. >At TDC velocity is >zero, and therefore acceleration is zero, too. Yet the engine is most >definitely running. If velocity is ZERO and acceleration (rate of change in velocity) is ZERO, then the velocity will remain at ZERO, and It's IMPOSSIBLE for the engine to be running. >Are you suggesting a perfectly parabolic acceleration curve with no >zero point? (1) There will be a time when acceleration is zero; (2) >You have massive acceleration/deceleration approaching/leaving TDC, >as a function of rapid reversal of travel. You also have zero >velocity, and therefore zero acceleration, at one micor-instant in >time (at TDC). Acceleration curve as an function of the crankshaft angle. A 7 -! ! 7 A C 6 -!* *! 6 C C 5 -! * * ! 5 C E 4 -! ! 4 E L 3 -! * * ! 3 L E 2 -! ! 2 E R 1 -! * * ! 1 R A 0 ---!---------*---------------------------*---------!--- 0 A T -1 -! * _ * ! -1 T I -2 -! * * * * ! -2 I O -3 -! * * ! -3 O N -4 -! ! -4 N -5 -!-----------!-----------!-----------!-----------! -5 0 90 180 270 360 DEGREE CRANKSHAFT ANGLE DEGREE >Additional question: additional cylinders = more rapid acceleration, >more constant crank velocity, lower piston velocity overall? Eg in a >I-4 vs. I-5 vs. V8 vs. V12? The piston acceleration and velocity is an function of crankshaft/pistonrod lenght and the crankshafts angular velocity. and is the same for 4,6,8 and 12 cyl. engines. The 4 cyl. has an higher oscillating peak to peak value (difference in angular velocity at a constant RPM during one revolution) than an 6,8 and 12 cyl. who have a higher oscillating frequencies but lower peak to peak values. => running smoother with less viberations. BRGS -- John Torset johnt@borre.mail.telia.com Amiga 4000

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