# Re: Conrod force/acceleration

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Olesen, Allan wrote:

> Wrong again.
>
> Even if you do not understand the physics, you must be able to see the
> logic:
> Acceleration = velocity change over time.
> No acceleration = no velocity change.
> No velocity change = constant velocity.
> Constant zero velocity = engine not turning at all.
>
> Another lister have used the example of a ball throwed up in the air.
> From the time the ball leaves your hand until it hits the ground,
> acceleration is constant 1g (downwards), even though the ball moves
> upwards, stops, and then moves downwards. This also proves that
> velocity can be zero without acceleration being zero.

It seems the assumption is that velocity is zero for one instant, not two
instants - eg v never = 0 for two trillionths of a nanosecond. if it did, for
two trillionths of a nanosecond, then acceleration would be zero, as v is zero
for that length of time. What the scientific community would have is that zero
only exists for one trillionth-of-a-nanosecond during the reversal of travel.
I believe that for two trillionths of a nanosecond you might have zero
velocity as the crank swings by to pull the piston back down, owing to
IMPERFECT properties of the sytem upon which you are practicing perfect
theoretical trig.

You are praticing perfect math on an imperfect object. The math, if adhered to
by the motor, is correct. But the motor is not perfect. The behavior of the
parts/metal is not perfect. This is where this whole thread started, if I
recall correctly (conrod strectching/compacting - imperfect behavior fo engine
internals).

Yes, this is tedious and a little tenuous, but I'm speaking in terms of
absolutes. I follow the rest of it sine, cosine et al. The math is perfect,
the motor is not. That, again, is the basis for this whole question. I didn't
mention this as I thought, given the start of this thread, that an imperfect
sytem was a *given*. It seems you all are applying perfect math to an
imperfect system and expecting a perfectly agreeable answer.  The imperfect
nature of the system (engine) is what makes this question interesting to me.
The tolerances, though tight, lead me to believe that a zero figure can exist
for piston velocity for more than a single consecutive instant in time. It all
depends on the period of time over which you measure velocity.

As far as the ball and gravity go; yes, it's all relative. I am not speaking
in terms of balls and gravity. Piston relative to crank. Forget about the
center of the earth for a minute. The zero V point at the top and bottom of
piston travel is absolutely more than one instant during the reversal of
travel in an engine, an inherently *imperfect* object. In a perfect system,
you win: It is one instant, not two (according to conventional trig). But,
again, how much time do you NEED in order to measure dv? At reversal of
travel, there is, I speculate, more than one trillionth of a nanosecond where
v=0. Therefore you technically could have a=0 for one short instant. (gravity
and arguments of balls and relativity aside). Again, I'm talking about
absolute measurements in an imperfect mechanical device. Sorry. I am stubborn,
I know. But I have yet to understand how you can disprove that a=0 by applying
perfect math to an imperfect device. It is the imperfection that allows for a
brief span of time where v=0, ( 2 trillionths of a nanosecond, ok) relative to
the block (not the center of the earth).

Again, I jumped into this when the discussion was on behavior of conrods - and
the implications of the instability caused by compression. It's the
imperfections that raised this whole issue initially, and now those
imperfections are being ignored.

Thanks for putting up with my obstinance. Most of y'all certainly
out-credential me in this dept, so I am now anticipating another great