# Small Hybrid Electric Aircraft

Discussion in 'Electric Propulsion' started by litespeed, Aug 14, 2019.

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1. Aug 15, 2019

### litespeed

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The generator should as long as it has adequate cooling only ever need new bearings.

The model two stroke can be surprisingly reliable if treated right.
It will not be screaming its head off but at a fairly constant speed. No prop loads helps.
The big flat four has a much nicer balance than singles or twins and only runs 7.5 cr, it has a lowish mean piston speed and will not be run constantly at max output. This all helps for reliability. In actual use it would spend only a tiny %of time anywhere near max power and mostly be running at approx 50%.

If it is cooled well, fueled well and given quality oil, it should be good for 25 hour inspections and the rings at 50-100 hrs. That is real conservative. It will not be subject to the loads and g forces of a full aerobatic regime model aircraft. In operation it should be able to do 200hrs if done right.
For most of us that is a lot of flying.

Super long life is not the point, it is cheap and experimental. Easily fixed and part of a backup charging system. The fundamentals of the design are no different to a small rotax or any number of other small two strokes.

Sure a GX Honda can be reliable but the power and weight do not suit a hybrid application.
The extra weight is a lot of spare fuel and or battery capacity to overcome power loss in flight.

That extra mass of kg is a lot of battery to get you safely down if the hybrid dies mid flight.

Running a GX is only really viable as a standalone gas engine with prop attached.

Last edited: Aug 15, 2019
2. Aug 16, 2019

### henryk

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3. Aug 16, 2019

### RonL

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I think the gap between VW engine and model RC engine is just about to close, this looks to be a serious engine and priced close to three thousand $dollars US. I personally have an interest in electric-only and use the speed of an aircraft to supply some additional power through thermal energy extracted from the airflow. Sockmonkey and litespeed like this. 4. Aug 16, 2019 ### BJC ### BJC #### Well-Known Member Joined: Oct 7, 2013 Messages: 9,501 Likes Received: 6,262 Location: 97FL, Florida, USA Please explain. Thanks, BJC 5. Aug 16, 2019 ### RonL ### RonL #### Well-Known Member Joined: Jan 9, 2007 Messages: 456 Likes Received: 28 Location: Texas Basically a ducted fan system, but unlike a ducted fan design that draws air straight through a tube and thrust it out back, my thoughts are to pattern it similar to the mechanics of a vortex tube cooler design. Air enters the front and is diffused and diverged into a spinning vortex swirl, the majority of air and heat will be compressed into a thin band of very energetic and dense mass airflow, the friction will be designed to drag a thin shell stator of a generator as the air works its way spinning to the rear of the duct tube where an electrically powered fan thrusts it out. As in a vortex tube, the central core will be very cold and represent the majority of space in the tube. The mechanics of motors and generators will operate in this cooler area. The air spinning inside the tube is tangent to the direction of the plane and should have little or no negative effect on drag. I believe what is important is that for every foot forward the plane flys, the air inside the tube travel as much as ten times further in one complete spin, meaning a much greater heat transfer time is allowed. The air in has to equal air out, so the volume and time for energy exchange inside the tube will determine what the temperature of discharge will be. henryk likes this. 6. Aug 16, 2019 ### henryk ### henryk #### Well-Known Member Joined: Mar 8, 2010 Messages: 4,653 Likes Received: 441 Location: krakow,poland 7. Aug 16, 2019 ### BJC ### BJC #### Well-Known Member Joined: Oct 7, 2013 Messages: 9,501 Likes Received: 6,262 Location: 97FL, Florida, USA In the energy industry, we use a tool called an energy balance to assess different energy processes. Any system is represented by a series of blocks showing all energy exchanges and work input to the system or extracted from the system, with temperatures, pressures and enthalpies of the working fluids. Have you completed, and analyzed, an energy balance to validate your assumptions? Thanks, BJC 8. Aug 16, 2019 ### Tiger Tim ### Tiger Tim #### Well-Known Member Joined: Apr 26, 2013 Messages: 2,846 Likes Received: 1,588 Location: Thunder Bay And here I was innocently expecting the explanation to essentially be the Meredith effect. Sockmonkey likes this. 9. Aug 16, 2019 ### RonL ### RonL #### Well-Known Member Joined: Jan 9, 2007 Messages: 456 Likes Received: 28 Location: Texas Unfortunately no, it's theory based on things I have used and believe the engineering specs that are posted on the equipment, plus what I have studied and think I understand. If someone with the ability to carry out the analysis of what I'm saying and takes things to the next level and carries on, then I'll be proud to have been a help in reducing dependence on batteries in general aviation with regard to electric flight. 10. Aug 17, 2019 ### litespeed ### litespeed #### Well-Known Member Joined: May 21, 2008 Messages: 1,415 Likes Received: 262 Location: Sydney The Roto 170 fs sure is a nice engine. Only 4.65 kg and nice a quite compared to a two smoker. Pity it is a bit low on the power stakes 8.4 hp or 6.3 kw, but still a impressive power/weight for a four stroke- compared to big ones. TBO is 200hrs plus. Roto are in the UAV market but only do a version up to 2 kw for generation duties. However also acts as starter and you still get to put a prop on it. It could be a goer as a hybrid drive and under 8kg all packaged up and has the quiet factor. Pity it is a bit under powered though. But on the right machine 6.3 kw charging the batteries may be plenty for sustained level flight and some charge as spare power. Estimate cost approx$5000 as stand alone hybrid sustainer to power a electric aircraft. So not that bad really given what some all electric systems costs with batteries.

For the left field designers- could imagine a four engine Lazair- LOL.

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11. Aug 17, 2019

### pictsidhe

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So you have invented a revolutionary device that breaks the known laws of physics, but haven't built it or shown it to work in theory?

12. Aug 17, 2019

### RonL

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I guess it's an oversimplified description of a much-complicated design, what part confuses you and, breaks the known laws of physics, as you know them?

13. Aug 17, 2019

### RonL

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I have never heard of the Meredith effect, so I had to do a search, this one of the many things found (my thoughts seem to be on the right track)

https://history.nasa.gov/SP-445/ch5-5.htm

Taken from the text..........
"In our engineering analysis of the effects of heat in internal flow systems, the conversion of heat to thrust power was clearly the most [162] intriguing aspect. Thinking in terms of flight speeds of 550 mph, we calculated ideal thermal efficiencies of as much as 10 percent, and by Mach 1.5 the heated duct would have a thermal efficiency comparable to an internal combustion engine. Clearly, the insignificant "Meredith effect" had the potential to become a primary jet-propulsion system. (The term "ramjet" was not then in general use, and we were unaware that there were several discussions of propulsive ducts in the literature starting with Lorin in 1913 and including later treatments by Carter, V Leduc, Roy, and others.)"

14. Aug 17, 2019

### pictsidhe

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Breaking the second law of thermodynamics for starters.

15. Aug 18, 2019

### emir_82

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The price of installed battery is a little above 1000usd/kWh.
The price of the hybrid generator must include besides the engine and generator, the capacitor bank and another electric motor controller (used as inverter).

For some missions it will be cheaper to install hybrid.

16. Aug 18, 2019

### litespeed

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Yes,

I assumed these costs in the \$5000 for the Hybrid system. That is at cost for a DIY setup.

That will still need the electric engine, prop, controller and the small battery bank costs to be added for the motive power.

17. Aug 18, 2019

### RonL

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Ok, it's been almost two days now, so I need to ask again for an answer from you to my question " what did I say in my post that breaks the second law of thermodynamics as you understand them?"
@henryk seems to have picked up my intended thoughts and provided a link that helped me decide to call it a "Tornado Tube".
I won't say anymore unless someone is interested in what's in my mind.

18. Aug 18, 2019

### BJC

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It might help if you described the source of energy and the power input into the propulsion system, then the nature of the thrust and the power out of the system.

BJC

19. Aug 18, 2019

### pictsidhe

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You appear to be taking ambient air and generating work whilst cooling the air.

20. Aug 18, 2019

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