Variable pitch prop design for electric

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Dan Thomas

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The early IVOs had issues with non-knurled squash plates and bushings causing blade shifting. Zero problems with mine and I have dozens of customers flying IVOs, also with no issues. Mine has the knurled plates and no bushings.
Those bushings were part of the problem, I think. They prevented the plates from grabbing the blade itself, but those blades were 95% foam with a really thin carbon skin on them. Some of the props threw blades, the centrifugal force tearing them right off the bushings. Are the IVO blades more substantial at the root now?

The other thing I didn't like about the IVO was that all the pitch change was in the outboard sections, exactly the opposite of what is needed. Even a variable-pitch/CS prop rotates the entire blade the same amount, when what is really needed is a blade that rotates more near the root and less at the tips, to maintain an even AoA across the span. Trigonometry.
 

Vigilant1

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Does anyone have a link to an example layup schedule for a 1.2m ish carbon prop?
This is from the Paul Lamar site that henryk linked to in Post #20. It shows an Ivoprop blade cross section with its built in metal rod for adjusting the blade twist (in flight or on the ground, depending on model of prop). That metal tube has an L on the end ( about 75% radius??) that twists the composite blade from that location as the tube twists. FG and gel coat skin with CF spar caps. Fabric thicknesses aren't shown. A regular fixed pitch composite prop might be very different.

1610223461985.png
 

rv6ejguy

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Those bushings were part of the problem, I think. They prevented the plates from grabbing the blade itself, but those blades were 95% foam with a really thin carbon skin on them. Some of the props threw blades, the centrifugal force tearing them right off the bushings. Are the IVO blades more substantial at the root now?

The other thing I didn't like about the IVO was that all the pitch change was in the outboard sections, exactly the opposite of what is needed. Even a variable-pitch/CS prop rotates the entire blade the same amount, when what is really needed is a blade that rotates more near the root and less at the tips, to maintain an even AoA across the span. Trigonometry.
The root is quite substantial on mine but I've never seen an early blade to compare. My blades are over 20 years old now.

Most of the thrust on any prop is generated in the outer 3/4 of the blade. Look as most conventional metal props whether FP or CS at the root- not much of any airfoil section there so no way to generate much thrust.

I don't think the IVO is as good as an MT for cruise speeds but TO and climb is comparable or better. They cost about 1/4 of what an electric MT costs and they are much lighter. These were the main reasons why I chose the IVO.
 

henryk

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the IVO is as good as an MT for cruise speeds
-in case of motor-glider it is good,iff FATHERING possibility exist...IVOPROP do not !

BUT=a variable-pitch IVOPROP will be optimal=for every PITCH proper
TWIST !

=simple Variable Pitch on base of conical gear=
 

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Vigilant1

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[The inflight adjustable IVOprop] cost about 1/4 of what an electric MT costs and they are much lighter. These were the main reasons why I chose the IVO.
For cases where wood props are normally favored due to MOI or resonance reasons (e.g. VWs, industrial engines using direct drive), I wonder if these light inflight adjustable IVOprops might be okay. They probably do put more stress on the crankshaft than a wood prop (heavier, less self-damping of torque pulses). The Remasters successfully used custom hydraulic variable pitch props many years ago.
 
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Speedboat100

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This is from the Paul Lamar site that henryk linked to in Post #20. It shows an Ivoprop blade cross section with its built in metal rod for adjusting the blade twist (in flight or on the ground, depending on model of prop). That metal tube has an L on the end ( about 75% radius??) that twists the composite blade from that location as the tube twists. FG and gel coat skin with CF spar caps. Fabric thicknesses aren't shown. A regular fixed pitch composite prop might be very different.

View attachment 106119

The measure 5 has to be 4.
 

Vigilant1

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The measure 5 has to be 4.
I don't think so. Note that the arrow shows that the "1" is for the leading edge part and "2.2" is for the trailing edge portion. If the whole chord is 5, then the remaining middle portion is 1.8. That looks consistent with the drawing.
 

blane.c

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This has (had) a extensive documentation to the process of Paul Lipps building a propeller. My saved links no longer work (the one's I tried quickly I haven't time to get deep into it at the moment). Many of my saved links no longer work and further searches result in a place to purchase the information. Purchase for information on the web and worse "censorship" seems to me to become increasingly the "new normal".

Paul Lipps (designed) "elippse" propellers | HomeBuiltAirplanes.com
 

Speedboat100

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I don't think so. Note that the arrow shows that the "1" is for the leading edge part and "2.2" is for the trailing edge portion. If the whole chord is 5, then the remaining middle portion is 1.8. That looks consistent with the drawing.
Sorry... Yes Autocad oddity.
 

Foundationer

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These guys would be my choice for a fixed pitch prop for electric. Very light. I like the idea of the sock over a foam core as i can mill foam so this can work for me to make light bespoke blades for variable pitch system. Have to get designing...

 

Foundationer

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The gaz'aile designer did try to do a DIY electric variable pitch prop, here his attempt: Blanc 01
E-props custom-designed a prop for the project, with some aero-elastic effects? It's lighter, simpler and perform about the same, if not better: https://aircraft.e-props.fr/DOCS/HEP_gazaile_nov2015F.pdf
That is a great link! Thank you. I'll have a hollow prop shaft so shouldn't need the slip ring and the actuator can be nice and stationary on the fuselage side.
 

TLAR

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Thanks Blane.c
Why don’t we see a pointed tip prop?
This is just the ticket for the electric folks. Near silent flight. Listen to Pink Floyd through 6x9 jbl speakers.
The emg6 powered by the Poloni sure had a funky looking prop and now I understand why

oh btw, that is one bad ass lookin biplane!
 
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TLAR

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Thanks Dan
I just read the article, why don’t we see more of those?
 

Vigilant1

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If they work, I wonder why we don't see more Lipps-style props. Racers would sell their mothers for 5 mph, GA aircraft manufacturers are in a competitive market, there's pressure for quieter aircraft, and homebuilders have freedom to go this route without the headache and costs of certification. Are they just too exotic? Is there an IP embargo or patent bill ? Hamilton-Standard, Sensinech, MT, Prince - all too stuck in their ways to adopt a better approach? Did the magic die with Paul Lipps? Just seems odd, if there was something to it, that they haven't proliferated.
 
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