MolaKule
Staff member
An ICE engine of 3.5" stroke is running at 3,000 RPM.
What is the piston's average linear speed in ft./second?
What is the piston's average linear speed in ft./second?
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Piston Speed
- Thread starter MolaKule
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I can't answer that question, but doesn't rod length alter it somewhat?
MolaKule
Staff member
What is its average linear speed in ft./second?
29.167 ft/second
29.166666.... ft/sec.
Rod length doesn't matter for the average since it's a factor of time. What impact a change in rod length has on one end of the stroke is made up for on the other.
Rod length doesn't matter for the average since it's a factor of time. What impact a change in rod length has on one end of the stroke is made up for on the other.
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0 ft/second. Answered as written. HAHAHA
Is just an engine running on a stand for example. Are we talking pistons?
MolaKule
Staff member
We're talking pistons and it should have stated:
An ICE engine of 3.5" stroke is running at 3,000 RPM.
What is the "piston's" average linear speed in ft./second?
An ICE engine of 3.5" stroke is running at 3,000 RPM.
What is the "piston's" average linear speed in ft./second?
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Swag (7" * 3000) / 60 = 350" per minute
350" / 12" per foot = 29.17 ft per second
350" / 12" per foot = 29.17 ft per second
Four or two stroke? 
It affects the dwell time at TDC and BDC and hence they should offset. However the overall distance and time for one full stroke remains constant - so the acceleration is higher but average should be same? The old "Long rod, short stroke = more torque" theory.
^^ This would be my guess as well.
MolaKule
Staff member
That's one way to solve the problem.
Always use units to make sure certain units cancel when making any calculation.
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Of course you are correct; my SWAG was incomplete.
You sound like all my Math and Computer Science teachers. Just getting the answer may work but is not good enough.
Oh yeah, and then there's code documentation... Sheesh.
Documentation helps find errors (and bugs).
Personally, I do not generally believe in code documentation; well written code is self documenting.
All good.
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3000 RPM, assuming 4 stroke, means up/down twice per revolution. 3.5” X 4 strokes=14” per revolution. 3000 RPM X 14” per revolution=42000”/12” per foot=3500/60 seconds per minute=58.333 feet/minute(?) Sound right?? Unless we factor in the deceleration & acceleration at the top & bottom of the bore, but those should cancel out.
I think you mean twice per cycle? RPM is measured at the crankshaft regardless of cycle (2 or 4 stroke), right?
Back in the late fifties early sixties Dodge searched for the slowest piston speed and came up with 1700 ft per min IIRC. Anything less than that caused problems. Testing done on a V8.
ok....Ill show my work for credit right or wrong.....
3000 rpm / 2 = 1500 rpm, since the stroke is the same up and down, for simplification/cancellation....so the piston is moving up 1500 times per minute and down 1500.....so we are really talking 1500 strokes per minute........
1500x3.5 inches per/min= 5250 in/min
5250/12 inches= 437.5 ft/min
437.5/60 seconds
7.291 ft per second?
thanks to @Molekule for getting our brains going on something other than thick vs thin!
3000 rpm / 2 = 1500 rpm, since the stroke is the same up and down, for simplification/cancellation....so the piston is moving up 1500 times per minute and down 1500.....so we are really talking 1500 strokes per minute........
1500x3.5 inches per/min= 5250 in/min
5250/12 inches= 437.5 ft/min
437.5/60 seconds
7.291 ft per second?
thanks to @Molekule for getting our brains going on something other than thick vs thin!
