How smooth can an IO360-M1A be?

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Rich
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Re: How smooth can an IO360-M1A be?

Post by Rich »

Pilot55 wrote:If your engine is running @ 2200 rpm you are turning 36.7 rps. on a 4 cylinder 4 stroke engine it has a power stroke every 180 degrees so the engines power frequency is 18 hz @ 2200 rpm.
Power stroke each 180 degrees means 2 power strokes per revolution, so the number of power strokes is double the rps (not half), or more like 73 Hz.

However, any given cylinder produces a power stroke every 2 revolutions, which would be about 18 Hz.
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Re: How smooth can an IO360-M1A be?

Post by Charles K »

Which Hartzell composite prop did you put on your DA40 - is there a service bulletin from Diamond or something else that allowed that? I was thinking of replacing my 2 blade metal Hartzell,

For what it is worth I have a 2004 DA40 about 1200 flight hours and a few dings in the prop (dressed) and my 6 cylinder flying buddy was amazed how smooth my 4 cylinder is.

Thanks
pietromarx wrote:I just had my DA40 dynamically balanced (engine running at 2200 RPM) from an IPS of 0.4 to essentially zero (unmeasurable).

This said, the Hartzell composite propeller has always felt smoother than the aluminum one I had on my previous DA40. This one is brand new (undisclosed lightning strike from previous seller) and it had been statically balanced, of course. The metal one on my old DA-40 simply rattled around a lot during startup and shutdown.

There are a lot of moving parts (literally) and I haven't found the DA40 to be much different than the other airplanes I've flown with a -360 motor (including wood Decathlons, metal C172s, and composite DA40s).

You might want to check the engine mounts and see if they've gotten stiff in the last fourteen years (assuming they weren't replaced during your overhauls). The vibration issue was certainly one that made the whole exhaust system crack on early DA40s (I had one that broke multiple times on a 2004).
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Re: How smooth can an IO360-M1A be?

Post by pietromarx »

This one: https://hartzellprop.com/diamond-da-40- ... c-options/

It came out after your plane (and my old one, too).

Expensive ... but definitely a nice propeller. Would be interested to hear what your impressions are if/when you switch and whether it makes a difference in speed.

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Re: How smooth can an IO360-M1A be?

Post by Pilot55 »

"Power stroke each 180 degrees means 2 power strokes per revolution, so the number of power strokes is double the rps (not half), or more like 73 Hz."

Sorry your math is wrong. A 4 stroke engine takes 720 degrees to complete a cycle. 180 degrees for intake,180 degrees for compression, 180 degrees for power and 180 degrees for exhaust. simple math divide 720 degrees by the number of cylinders and you get the phase angle of each cycle.
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Re: How smooth can an IO360-M1A be?

Post by Rich »

Pilot55 wrote:"Power stroke each 180 degrees means 2 power strokes per revolution, so the number of power strokes is double the rps (not half), or more like 73 Hz."

Sorry your math is wrong. A 4 stroke engine takes 720 degrees to complete a cycle. 180 degrees for intake,180 degrees for compression, 180 degrees for power and 180 degrees for exhaust. simple math divide 720 degrees by the number of cylinders and you get the phase angle of each cycle.
Which is 180 degrees, which means 2 power strokes per 360 degrees and every cylinder has delivered 1 power stroke every 720 degrees.
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Re: How smooth can an IO360-M1A be?

Post by pietromarx »

Either way, the measured vibration corresponds to *something* timed to the engine's rotational speed.

Cylinders or crankshaft ... or ... ?
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Re: How smooth can an IO360-M1A be?

Post by Pilot55 »

The power stroke frequency is 73.3hz but the harmonics at the crank when measured will produce a frequency 95% of the time of 25% of the power stroke which would be 18 hz. I have been designing and manufacturing high performance engines for Ford Motorsports Racing for 40 years. The other forces acting on the crank at the same time as the power stroke of one cylinder with the compression of another and so on.
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Re: How smooth can an IO360-M1A be?

Post by Charles K »

My understanding is that the M1A has some kind of counter weights on the crank that should make it a very smooth 360. I cannot complain about my 2004.
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Re: How smooth can an IO360-M1A be?

Post by Rich »

Charles K wrote:My understanding is that the M1A has some kind of counter weights on the crank that should make it a very smooth 360. I cannot complain about my 2004.
Some variants of Lyoming engines have counterweights. The M1A is not one of them. I also have no complaints.
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Re: How smooth can an IO360-M1A be?

Post by Charles K »

This is a direct copy and paste from the IO360 M1A Operators Manual from Lycoming's Site....

Crankshaft -
The crankshaft is made from a chrome nickel molybdenum steel forging and all journal
surfaces are nitrided. A system of dynamic counterweights eliminates torsional vibration.
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