Intellectual engine questionnnnn...

[10Toes]

You have to stop going forward before you can go backwards.

[evandael]

i would figure that, in theory (no main/rod bearing/wrist pin slop), the piston will instantaneously stop as it reverses direction. it's velocity changes so it must, at one point, experience a velocity of 0.

[fannman]

You have to stop going forward before you can go backwards.

^this. I believe people are putting more thought into this than is necessary. It is impossible for something to be in a upward or any direction, then without stopping even for a billionth of a second go into the opposite direction it was traveling. I understand the argument is there is some potential "side to side" play with the oil between the piston and the block, but that is such a small amount of travel it will still have to stop for and incredibly short time to change direction. Thats my t

[TwoJ's]

^this. I believe people are putting more thought into this than is necessary. It is impossible for something to be in a upward or any direction, then without stopping even for a billionth of a second go into the opposite direction it was traveling. I understand the argument is there is some potential "side to side" play with the oil between the piston and the block, but that is such a small amount of travel it will still have to stop for and incredibly short time to change direction. Thats my t

There are no forces acting on the rod/piston (from the crank) at bottom and top dead center.

[pandaboo911]

if you're asking whether is stops moving in 1 dimension (parallel relative to the cylinder walls) then yes it does, even if only for an infinitely small duration of time

[kronus]

actually TDC and BDC are where the piston experiences the most force during crank rotation. F = ma, etc.

[travish325]

How many people saying the same thing does it take to get an answer. Holy crap

[Wh33lhop]

actually TDC and BDC are where the piston experiences the most force during crank rotation. F = ma, etc.

Pistons don't move in a perfect sine function due to rod angle variation so this may not be true depending on the rod ratio of the motor, but net force at tdc/bdc is definitely not zero.

The issue has been gone over a few times in the thread already, people just get hung up over the definition of "stopped.". Pick your definition and you have an answer.

[Holland]

How many people saying the same thing does it take to get an answer. Holy crap

Why I walked away.

/thread

[Pac1373]

I feel like this thread is only missing a picture of an aircraft on a treadmill at this point.

[E-Thirty]

Even on a "roller based moving belt exercise apparatus"?

Exactly

[Xat1cZ]

Why do you guys always have to go and make EVERYTHING so fucking complicated!?


Does it stop? is that what you're saying? or does it only stop for 1 millisecond? or does it stop as in seize to move? or does it stop as in "fuck this I'm going this way" *brake* *goes other way*? or does it stop because the aliens push it in opposite direction? or is the stopping only an illusion?

look how fucking confused I am!!!

[frankenbeemer]

but net force at tdc/bdc is definitely not zero.

Seems like by F=ma, the force must be zero at some point. Not that it matters. :twisted:

[TwoJ's]

actually TDC and BDC are where the piston experiences the most force during crank rotation. F = ma, etc.

Pistons don't move in a perfect sine function due to rod angle variation so this may not be true depending on the rod ratio of the motor, but net force at tdc/bdc is definitely not zero.

Guys... come on guys.

Thank you for reminding us of Newton's second law. So in a sine-like wave form, TDC and BDC still have a derivitave of zero, yes? So what's the acceleration of an object with zero velocity? Mr. Newton's second law makes it pretty clear what the net force is when something isn't accelerating.

[LEANE30]

I fail to see anything in this thread yet that would constitute an "intellectual engine question". I am thoroughly disappointed, this thread fails. I had hopes for a topic like harmonic resonance tuning for ideal peak placements or something.

Rod ratio has nothing to do with the vertical loads placed on the piston at the wrist pin.