## Formula for peak piston acceleration at top/bottom of stroke?

## Formula for peak piston acceleration at top/bottom of stroke?

(OP)

I found the formula for mean piston speed on this forum, and that was useful. But I want to be able to figure out how much more stress I'm putting on a piston (due to rapid change in acceleration) if I shorten the rods.

I remember a formula from Physics class:

Final velocity =(Initial velocity)+((acceleration)x(time)^2)

Should I be using some from of this equation? If so, how do I find the max velocity of the piston (is it always in the middle of the stroke?)

Lots of questions...trying to learn.

Thanks,

MazdaJim

I remember a formula from Physics class:

Final velocity =(Initial velocity)+((acceleration)x(time)^2)

Should I be using some from of this equation? If so, how do I find the max velocity of the piston (is it always in the middle of the stroke?)

Lots of questions...trying to learn.

Thanks,

MazdaJim

## RE: Formula for peak piston acceleration at top/bottom of stroke?

The instantaneous speed of the piston at a given crank angle (q)is as follows: Sp=pi/2*sin(q)[1+cos(q)/((R^2-sin^2(q))^.5)*ave. piston speed. (R is the ratio of con. rod length to crank radius) If you know the speed of the engine, you can calculate the time required to slow the piston from max velocity to zero (at TDC or BDC), which will be 1/2 stroke. Your ave acceleration should be (Sp(max)-Sp(TDC))/T(1/2 stroke) or you can take the derivative of the speed eqn w.r.t (q) and calculate instantaneous accleration.

You might want to pick up a copy of Internal Combustion Engine Fundamentals by John Heywood, it has alot of useful information regarding basic engine design.

## RE: Formula for peak piston acceleration at top/bottom of stroke?

and what rpm ranges are you looking for ?

Bore in inches

Stroke in inches

Rod C-C length

Pin offset ..

Larry Meaux (meauxrace2@aol.com)

Meaux Racing Heads

MaxRace Software

ET_Analyst for DragRacers

## RE: Formula for peak piston acceleration at top/bottom of stroke?

## RE: Formula for peak piston acceleration at top/bottom of stroke?

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Larry Meaux (meauxrace2@aol.com)

Meaux Racing Heads

MaxRace Software

ET_Analyst for DragRacers

## RE: Formula for peak piston acceleration at top/bottom of stroke?

## RE: Formula for peak piston acceleration at top/bottom of stroke?

Thanks, Larry

Larry Meaux (meauxrace2@aol.com)

Meaux Racing Heads

MaxRace Software

ET_Analyst for DragRacers

## RE: Formula for peak piston acceleration at top/bottom of stroke?