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Counterbalanced crank and constant speed prop question.

What is your combination?


  • Total voters
    38

AX-O

Well Known Member
All,
I am trying to collect data on how many folks are running a constant speed prop with a counterbalanced crank and without a counterbalance crank. depending on the results, I may be working on a project for a constant speed prop (flight test). If you care to provide feedback, reply with one of the answers below. If you care to ellaborate on #3 (if that is your selection), that will deeply appreciated.

1. Counterbalanced crank and constant speed prop.

2. Non-counterbalanced crank and constant speed prop. No prop issues/failure.

3. Non-counterbalanced crank and constant speed prop. Some prop issues/failure.

Thank you for the feedback.
 
Engine/Prop Combo

Constant speed (Hartzell) and counter-balanced crank.

Skylor
 
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2. Non-counterbalanced crank and constant speed prop. No prop issues/failure.

Titan IO-360 Parallel valve. 9:1 compression.

Hartzell metal blended airfoil with B-hub.

Approximately 800 hours on prop engine combo.
 
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2. (Stroked) non-counterbalanced crank and constant speed prop. No prop issues/failure.

Aerosport IO-375/Hartzell.
 
Not a lot of time on it so far, only 260 hours, but non-counterbalanced and Whirlwind C/S here, no problems.
 
The questions are much too superficial.

Blade failure is a function of vibration, i.e. number of cycles and amplitude. The blade is a victim. Whack it at one of its natural frequencies, and it will resonate. If the resonant vibration exists for enough cycles (think operating hours), or has high amplitude (meaning high stress), the blade will fail eventually. If run at a engine RPM which does not result in significant blade vibration, the blade will be fine.

Mere knowledge of the crank type is useless without also knowing the operating condition. That's why prop manufacturers who actually instrument and test their blades using strain gauge arrays may insist on operating restrictions...an RPM range, or RPM/MP combination, at which operation is to be transitory only. The measured stresses were high in those ranges, so they wish to limit the number of cycles.

In general, plain crank engines result in more prop restrictions. However, the presence of pendulum absorbers does not guarantee a happy prop across the entire operating range. The IO360-A3B6D/McCauley is an example.

Nor is the issue restricted to constant speed props.

In addition, the questions say "constant speed" but do not specify a blade material. Aluminum, composite, and wood blades are very different.
 
Thanks Dan for the info. I was trying to make a quick poll and a small post so i could actually get data. If someone said ?i have had issues?, then i was going to contact the person individually. We have instrumented data for some combos of cranks/props. Just trying to get some feedback from users vice only from a test stand.
 
Crank and prop info

Non-counterbalanced crank with WW200 RV constant speed prop. 1805 hours with no problems. Very smooth, fast combination.

IO-360M1 with 9.2 to 1 pistons and Lightspeed electronic ignition. Carbon fiber prop blades.

Dan Miller
RV-8
Battle Ground, WA
 
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