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*To*: "Quattro mailing list" <quattro@coimbra.ans.net>*Subject*: RE: interference fit*From*: "John Torset" <johnt@borre.mail.telia.com>*Date*: 25 Jan 98 00:13:19 +0100*In-Reply-To*: <2546.329T1611T94172@borre.mail.telia.com>*Sender*: owner-quattro@coimbra.ans.net

>>> <snip> >>> Quite simply, the acceleration of the piston is at its greatest >>> at TDC and BDT. Right. >>> Is not piston acceleration zero *at TDC and *at BDC as the piston >>> is at a dead stop at that instant in time? Perhaps >>> de/acceleration is highest immediately TDC/BDC? [Snip.....] >The piston is moving up toward TDC. >At some instant in time it will be at rest at TDC. >For it to achieve the state of rest or 'no motion' the piston must >decelerate to 0. At this instant in time it has no motion and no >acceleration. The piston then must accelerate from 0 to proceed to >move back down. So, in my primitive and prolly wrong analysis, the >piston decelerates to 0 as it approaches TDC, @ TDC it has no motion >and no acceleration, it then reverses direction and accelerates >downward, so at some instant in time when upward deceleration is >zero and the piston is motionless in space, downward acceleration is >also zero, or it could not be motionless. There must be an instant >in time between upward motion and downward motion where both speed >and acceleration are both zero. (?) >Mebbe I am wrong because it may be possible for the piston to go >from upward deceleration to downward deceleration without reaching >zero acceleration at TDC while it is instantaneously at rest at TDC >and before downward deceleration Some formulas to calculate piston acceleration, speed and distance. Metric system. c = Piston speed ..................................... m/s R = Crankshaft radius ................................ m w = Crankshaft angular velocity ...................... rad/s a = Piston acceleration .............................. m/s^2 s = Distance the piston has moved from TDC ........... m A = Crankshaft angle relative to crankshaft at TDC ... Degree L = Piston rod lenght ................................ m n = Revolutions pr. second ........................... s^-1 S = Piston stroke .................................... m y = Crankshaft/pistonrod relation .................... 1 n = RPM/60 w = 2*PI*n S = 2*R y = R/L c = R*w*(sin(A)+y/2*sin(2*A)) a = R*w^2*(cos(A)+y*cos(2*A)) s = R*(1-cos(A)+y/2*sin(A)^2) aTDC = R*w^2(1-y) aBDC = -R*w^2(1-y) As an example, if you set R=0.1_m, L=0.2_m and w=1_rad/s. The piston acceleration will be ZERO at approx. A=68,5 Degrees, and piston speed will be maximum. Distance the piston has moved from TDC => s=0.042_m The piston acceleration will be maximum at TDC and BDC, and piston speed will be ZERO. -- John Torset johnt@borre.mail.telia.com Amiga 4000

**Follow-Ups**:**RE: interference fit***From:*"John Torset" <johnt@borre.mail.telia.com>

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