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which IO-360? My head hurts!

Go German

My logic was simple: Germans make better stuff! So I went with Thielert-owned Superior Air Parts engine. Thierlert also did most of the design work for for their roller lifters, etc.

Hans
 
nucleus said:
My logic was simple: Germans make better stuff! So I went with Thielert-owned Superior Air Parts engine. Thierlert also did most of the design work for for their roller lifters, etc.

Hans
... they still had Cylinder recalls.
 
gmcjetpilot said:
All the angle valve 360's or 390 200/210HP are counter weight cranks. So if you want non-counter weight than you will be looking at a parrellel valve 180Hp engine. Non-counter weight is a good choice if you want to save weight and are going to do formation flying (rapid throttle movements which can de-tune counter weights)...
My partner and I are looking at a RV with a 0-360 that has a counter weighted crank. We were both impressed with how smooth and quiet the plane was. We'll be using the plane for mostly for x-country so we'd like that feature. Are there any other down sides to flying with a counter weighted crank? What happens exactly when they get 'de-tuned'? And I assume it takes a re-build to 're-tune'?
 
<<What happens exactly when they get 'de-tuned'?>>

Both the crank and the weight have two sets of hollow bushings with precise internal diameters. Rollers with precise external diameters pass through the bushings. The weight thus hangs on the rollers. The rollers ("pins") are not tight fits in the bushings; they have significant clearance, which is why the pins roll when the weight rocks side to side. The clearance is the mechanical equal to a short pendulum arm. The tuned order is dependent on the precise length of that pendulum arm dimension, and the ability of the pin to roll in the bushings. The pendumum is thus detuned by wear that changes the precise relative dimensions, or by damage that disrupts the ability of the pin to roll in the bushings.

<<And I assume it takes a re-build to 're-tune'?>>

Yes, bushing and pin replacements.
 
nucleus said:
My logic was simple: Germans make better stuff! So I went with Thielert-owned Superior Air Parts engine. Thierlert also did most of the design work for for their roller lifters, etc.

Hans

At Airventure last year I took a look at the superior (Thielert) roller lifters and also the Lycoming roller lifters. They are quite different in their design. Intuitively I like the Lycoming design better. It looks more failsafe to me. Just my opinion (but also the opinion of a couple of major engine builders as well).
 
Smooth throttle!!

Low n Slow said:
My partner and I are looking at a RV with a 0-360 that has a counter weighted crank. We were both impressed with how smooth and quiet the plane was. We'll be using the plane for mostly for x-country so we'd like that feature. Are there any other down sides to flying with a counter weighted crank? What happens exactly when they get 'de-tuned'? And I assume it takes a re-build to 're-tune'?



One disadvantage with having a pendulum/counterweighted crank is rapid throttle movement which is hard on the pins, bushings, etc. :( From what I've learned is to be very smooth and not jerk the throttle back from high power setting or make rapid RPM increases or reductions, not good on the piston rings either. Longevity and not wearing these parts out is all in the pilots throttle movements. Make small RPM changes and just don't yank the throttle back when you approach pattern as an example or doing aerobatics where throttle movement is quick and abrupt at times.

The way I fly my plane which is mostly cross country at a set RPM / C/S prop and being smooth with the throttle should not cause any problems down the road, but at TBO there will be a few $$$$ spent on this style of crank to get the parts back up to spec.

Hope this helps with your decision. :)

"The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information provided responsibly and at your own risk."
 
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DanH said:
<<What happens exactly when they get 'de-tuned'?>>

Both the crank and the weight have two sets of hollow bushings with precise internal diameters. Rollers with precise external diameters pass through the bushings. The weight thus hangs on the rollers. The rollers ("pins") are not tight fits in the bushings; they have significant clearance, which is why the pins roll when the weight rocks side to side. The clearance is the mechanical equal to a short pendulum arm. The tuned order is dependent on the precise length of that pendulum arm dimension, and the ability of the pin to roll in the bushings. The pendumum is thus detuned by wear that changes the precise relative dimensions, or by damage that disrupts the ability of the pin to roll in the bushings.

<<And I assume it takes a re-build to 're-tune'?>>

Yes, bushing and pin replacements.
Thanks Dan! How easily can they be de-tuned, one rapid throttle movement, or hundreds? Can they be de-tuned any other way, besides abusing the throttle? How can you tell when it's happened, just a general increase in vibration?

Thanks AJ!
 
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Hummm

Low n Slow said:
Thanks Dan! How easily can they be de-tuned, one rapid throttle movement, or hundreds? Can they be de-tuned any other way, besides abusing the throttle? How can you tell when it's happened, just a general increase in vibration?

Thanks AJ!

I'd be telling you a lie if I knew best answer, but I'm guessing with any moving engine part that it takes time for something to wear out or get out of tolerance if abused.
 
<<How easily can they be de-tuned>>

How easily? I don't know. As Alan said, rapid throttle movement is usually considered the culprit. Who keeps count of (or admits to) details like "how often and how rapid?"

You can walk through theory and get some ideas. Normal operation is a rolling contact. Assuming that materials meet spec and no foreign matter is introduced, rolling contact should be low wear. Because the pin has inertia it can't start and stop rolling instantly; some skidding is enevitable. This is probably the root cause of normal wear, and you should be able to minimize it with good lubrication. Wear lowers the order for which the pendulum is tuned (like from 6th order to perhaps 5.9); it simply becomes less effective. This much shift only requires .002" or .003" of wear. Even so, there is no gross "failure".

I suspect most severe detuning is the result of crank motion that allows the pin to get out of contact with the bushing surface. The result would be severe skidding or impact damage. Conventional wisdom says these things happen with gross, rapid throttle movements. I have not had reason to consider the actual mechanics.
 
XP-400 uses counterweighted crank

rv969wf said:
I have no idea what crank Superior is using in the XP-400. I guess a phone call to them might answer the question. I'm like you Dan, it'd be nice to know what parts / crank they're putting in those monsters.

I called Superior yesterday and asked: the XP-400 uses a counterweighted crank. It's not in production yet, as you probably know. This summer, they said.

Another fact: I was told the XP-400 uses a front governor mount. Do any of you know if it'll fit under an RV cowl?

Regards,
Martin
 
Pros/cons of counterweighted crankshaft

Non-counter weight is a good choice if you want to save weight and are going to do formation flying (rapid throttle movements which can de-tune counter weights).

Until I read this, I thought the only drawback to a counterweighted crankshaft was just the weight that it adds to the airplane.

I am trying to weigh occasional rapid throttle changes against less dampening on continuous basis.

What mechanism can cause this “de-tuning” ? Is there risk of the weights moving somehow? Any other potential disadvantages of a counterweighted crank?
 
Don’t the Extras and Edge aircraft have counterweighted IO-540s and they smash their throttles in and out like crazy?
 
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