IVO prop installation

[Capt. Art]

I need information on installing an IVO electric propeller on a Lycoming Engine

[Mike Busch]

Wow, Art, this one's above my pay grade! Can anyone help Art with this?

[teknosmurf]

The only info I have is that I removed my IVO in liu of an old wood prop. Be careful when you handle that thing (edges can be very sharp and pokey), and if you are attaching it directly (no gear box) make sure you are aware of the "retorque every 10 hours" bulletin. That was kind of a PITA for me, but every time I did retorque, it desparately needed it (usually at least one bolt was loose)! As a matter of fact, I might even caution to fudge it earlier than 10 hours, but don't go longer!

[WLIU]

This season there has been quite a bit of discussion in the aerobatic community about installing very light weight 2 blade props on 4 cylinder Lyco engines. The short version is that the engine needs mass to absorb the power pulses. This mass can be in the form of 6th order crankshaft counterweights, or a propeller that is heavy enough, or made of the right materials, to absorb the energy pulses. I know of at least one owner who discovered that a carbon fiber 2 blade propeller was bad for his un-counterweighted Lyco. The engine was discovered to be internally destructing. Gears coming apart and other very expensive problems.

The bolt loosening described in the previous post is a symptom of the prop (and the engine) getting beat up by the lack of dampening of the engine power pulses.

Interestingly, 6 cylinder engines have much lower amplitude power pulses so they don't have this problem. 3 blade propellers absorbe the energy differently than 2 blade props (different phase relationships) also, so the 3 blade MT's (wood core blades) seem to work well.

Hope this info helps. My guess is that you should not do that installation.

Best of luck,

Wes
N78PS

[Bill Berson]

The science of prop/engine interaction is quite complex and every combination is different.
The aerobatic prop is probably the worst situation, so the particular use needs to be specified.
I would not say that a light weight prop is a problem, since wood props are very light, yet still have enough mass to act as a flywheel. It is more about the vibration frequency and destructive interactions.
And wood also absorbs vibration better than metal or carbon fiber.*

A carbon or metal prop should probably have more vibration testing than wood.
A common modern experimental prop is made with wood core and fiberglass or carbon sheath (Catto prop, for example). This may be a good compromise.

*ref. Fred Weick, AIRCRAFT PROPELLER DESIGN (1930)

[WLIU]

You are correct that wood has vibration dampening properties. But the other factor is the size of the engine that is delivering power to that prop. In the aerobatic community you see the larger 4 cylinder engines and as you note, we see issues that a 100hp installation might not.

I will note again though, that the report of prop bolts loosening after 10 hours or so of operation, is a very bad symptom. I assume that the reporter had torqued the bolts to the recommended spec and there are no elves sneaking into the hangar at night messing with those bolts. So the data is telling us that the prop-engine combination is a bad one.

The experimental world is wonderful, but if you have seen even a photo of what happens when a prop comes loose in flight, you might decide to approach that part of your airplane very conservatively.

Hey, I just had a novel idea. You could give IVO Prop a call and see if the prop that you are talking about is compatible with the engine that you are looking at. After all Ivo Zdarsky is the authority on his props. Historical trivia - Ivo Z was once a young, Czech I think, aeronautical engineering student who decided that life in a communist country was not very promising. So he engineered his very first ultralight aircraft and built the parts in his mother's basement. When he had all of the parts done, he borrowed his mother's car, and drove in the night as close to the border as he probably dared. He assembled his new aircraft in the dark, and made his first flight across the border to freedom. Not too many builders get shot at on their first flight. A great true homebuilding story and Ivo Z is another great immigrant success story.

Best of luck,

Wes
N78PS

[teknosmurf]

I should probably clarify my setup a little, because I don't want to give any false impressions. I agree that one should do their own research as far as engine/prop combinations. What I had was:
Continental 0-200 Engine
IVO 2-blade, ground adjustable prop
64" long

And yes, I did make darn sure the torques were correct, and I am pretty positive, after about 30 hours of flying, that gremlins weren't doing anything because it was very consistently loose.

Also, the service bulletins are online about using direct drive engines with the props. The website is: http://www.ivoprop.com/

Here is the SB regarding the torquing and tape-checking of the prop: http://www.ivoprop.com/servicebul2.htm. Again, my humble advise is to not rely on the tape breaking to know when to retorque the bolts...my tape only broke one time (I went 11 hours) but the bolts needed attention every time.

[WLIU]

Thanks a lot for posting the link! Very informative.

I find the low prop bolt torque used very interesting though. 200 inch lbs (16.6 ft lbs) vs Hartzell using 70 ft lbs. Seems hardly enough to keep the prop in place.

There are lots of alternatives for fixed pitch props for your O-200. Twisted Composites and Catto come to mind. The F-1 guys at Reno who run their O-200's at 4100 RPM do well with carbon fiber units that do not have bulletins like the IVO.

Best of luck,

Wes