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Discussion Starter #1
Aloha Mike and Insighters: I've been lurking on various Insight sites seekingn background data that could be relevant to powering a homebuilt aircraft (which I already have-a flying boat) with an insight motor/IMA. Most aircraft
require twice as much power for take off as they require in cruise flight.
Obviously the MIMA is a step in the right direction, if it could be "overboosted" to say 20KW for 10-20 seconds. Flying power settings are much more steady-state than in autos, starting at 100% for take off (20 seconds), then 75-85% for climb (<5 minutes) and finally 65% or below for cruise. The MIMA or a similar manual control device could make this feasible.
The Insight engine is about the lightest one litre engine around, with the Suzuki 3 cyl. Metro engine a close second. The new sport pilot regs are going to encourage the design and construction of two seater aircraft weighing <1300 lbs. It may even be possible to use the Insight without a speed reduction unit for the propeller, but the bearings required to isolate gyroscopic forces from the crankshaft may be just as heavy as a reduction drive.
I apologize in advance for my lack of technical Insight comprehension, but
the MIMA discussion caught my attention. I would like to eliminate the fuel injection (carburators are reliable and good for constant power settings), install a magento (reliable) and eliminate all of the black boxes if possible. If not possible, then at least simplify the circuits/boxes to save weight. Can the Insight IMA ever be simplified to this point? Please direct me to any past posts that might help. Mahalo and Aloha. David
 

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The biggest problem I foresee is a battery recal where all IMA assist is lost. The complexities of aircraft engines, or should I say simplicities make such a conversion a serious engineering challenge. The Insight is much more complex and potentially much less reliable, nor suitable for use in all orientations. Oil starvation at angles "X" (?) beyond vertical is the first the comes to mind.

Since this is essentially a different topic from the MIMA project I am splitting this into its own topic. There are a few other Insight / aircraft pilots (private pilot myself) that may also reply to your post.

HTH! :)
 

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Dumbing down the Insight engine for use in an aircraft would not make sense. The high efficiency of the engine depends on the very things you would want to remove for "reliability". Furthermore, in a calculation of the power to weight of an Insight engine, you must consider the weight of all the IMA batteries and support electronics.
 

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I've had occasional late-night thoughts about using the Insight engine in a small homebuilt - like I'd ever have the time to really do it :-( - but always concluded that 1) the weight of batteries &c would outweigh the gains; and 2) the hidden charging would kill your cruise.

With MIMA objection #2 would go away, so it might be doable, even possibly practical. If it were me, though, I'd re-think changing the electronic & fuel injection, as that's what gives the engine a lot of its efficiency. Reliablity doesn't seem to be an issue. I have a Piper Cherokee, and over maybe 10 years & 1500 hours have had 2 or 3 carb problems (one requiring replacement), and had to install new mags due to an AD. Have had zero problems in 2 years / 20K miles of Insight driving, and don't recall seeing much of anything related in the problems section.

What I would do, though, is look seriously at the turbo kit. Not just for power gains, but to keep the power at altitude. And maybe you could get lean burn in cruise :)

Anyway, keep us posted.
 

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To supply 20kW additional for 10 minutes (take off and climb plus a bit of reserve) would require a bigger assist motor (the existing motor is 10kW). 20kW for 10 minutes also adds up to 3.3 kWh, which is quite a lot of battery energy storage, at least 5 Insight battery packs would be required to provide that at 80% DOD which, including the casings and electronics, would add up to about 5 x 35 = 175 kg.

It might be worth checking out AC-Propulsion, who are quite advanced in the whole electric aircraft thing. They use 220 Wh/kg Lithium-Ion cells which are about one fifth the weight of the same amount of energy storage in Insight style NiMH, and obviously when it comes to aircraft, weight is everything. A 3.3kWh pack of these could therefore weigh in at only 15kg (3300/220), though electronics and casings would add substantially to this.
 

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Discussion Starter #7
MIMA Aircraft engine

Aloha Hana hou: The Insight technology and its possible application to aircraft was first proposed by no less than Burt Rutan himself, when asked to review the Insight by Road and Track (Rutan's EV-1 had been reppoed by GM the day prior to the interview.
Q by R & T:
"Does he see any application of hybrid propulsion for airplanes? An innocent question, although it leaves Rutan unusually silent. "Gee, maybe I shouldn't disclose this in Road & Track. But at the risk of someone else doing this first, let me tell you about an airplane that would be really interesting to do. This is fascinating...."
Rutan leans back and stares into middle distance. "Visualize an electric airplane with enough batteries to climb to about 500 feet. Actually, it would have several small electric motors with small propellers scattered all around the airplane—some on the tail, some on the wings—so if one motor seized, it's just a nuisance. Plus, there's a phenomenal advantage here: You wouldn't need control surfaces. Put a motor on a high part,one on a low part and give the first power and the other negative thrust or regen, and you pitch down, for instance.No elevator, no ailerons, no rudder. "Okay. Now after climbing to 500 or 600 feet, the batteries are pretty much puked. However, onboard would be this gas-powered generator that would produce 10 to 20 percent more [electrical] power than you need to cruise. The climb from 500 feet would be slow, but, the most important part to climbing is the initial part, getting over the trees.
For landing, or even if something bad happens like the generator seizes or you run out of gas, all the way down the props would be doing regen,charging the batteries up for a controlled landing (altitude being equivalent to potential energy). During the last part coming down, you actually want drag anyway; a very efficient airplane needs flaps or speed brakes to slow it down. "Here's a prediction: You may find that within the next few years Burt Rutan will go off and build one of
these."
I assume Rutan was thinking more of a RPV or UCV, but the concept makes sense but without Lipoly batteries and their fire issues. Gold Peak and other Nimh cells are now capable of 100 amp discharge rates without dropping below one volt at 68 grams apiece. An aircraft would require only brief power bursts, not power density. High tech electric motors for models are reaching 4KW at 2kg. weight again only for 30 second bursts. Rutan's idea of eliminating flight controls is interesting, but is probably designed to simpify the control system computer design.
Getting back to the Insight and flying, most successful aircraft conversons from auto engines have been engines which were run on their limits while in cars, for a high percentage of power duty cycle. Two examples are the VW and the Suzuki (metro); both cars require a substantial fraction of the max avaiable power to run on the street. The Insight is the same, and is designed with this high power fraction in mind. Yes, it has complicated valve gear, fuel injection/ignition mapping, idle-taming software, etc., but it's basically an engine that runs nearly flat out at Interstate speeds, particularly when no IMA power is available.
there are other reasons on flying boats to have a substantial amount of electric power generation or electric boost (not to mention engine starting) would be very handy. Every time I get on my Yamaha Waverider (1200cc) and accelerate to 50+ I think how a flying boat could get off the water instantly if it had an electric-powered jet pump or pumps rather than an air propeller (usually cavitating) during its take off run. More importantly, takintg Rutan a step further, bury the ICE in the hull and power all the propellers electrically. The loss of efficiency in the ICE-to-electrical conversion and re-conversion back to propeller rotation is more than compensted for by the increase in propeller efficiency with multiple propellers (not in the water spray), lighter weight, lower G.G. (no ICE motor high on a pylon). Some of the ICE power could be mechanically transferred to a pylon mounted propeller.
My same questions remain about the ability to boost IMA power for short periods; is this possible, and can the multiple control systems be reduced in complexity or hard-wired to reduce risk off single-point failures? More later and mahalo to this who replied. David.
 

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Re: MIMA Aircraft engine

Manuiwahi2005 said:
is this possible, and can the multiple control systems be reduced in complexity or hard-wired to reduce risk off single-point failures? More later and mahalo to this who replied. David.
Really short answer: no.

Slightly longer answer: Yes, but you would need to simulate all the sensor inputs with a computer (microcontroller), or make a totally new ECM that ignores these inputs.

There are several failure mods that will turn off the IMA system, and these failure modes are common (O2/LAF sensors, for example). This would be bad in an aircraft.
 

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Gasoline engine only?

It sounds like the safest way to do this might be to just use the Insight gasoline engine and remove all the IMA components. Then you would just have the lightweight 124 lb. engine without all of the IMA control boxes and battery pack, and you would not have to worry about the IMA system failing. Of course, that would only work if the engine could supply enough power to take off. The gasoline engine alone has 67 hp @ 5700 rpm, and more if you turbocharged it. The IMA motor does not add much horsepower, mostly just torque. If my understanding of that is correct (it may not be), it may not make much difference on a propeller once it is up to speed.

This would still be a difficult project with many other things to consider, for example, you might need to add an alternator or a large battery supply to keep the engine running without the IMA system and its 12V DC-DC converter.
 

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Aaron, I believe that the rotary conversions are already being done for high performance kit planes.

Low end torque for a propeller would be almost useless!

The IMA motor is essentially a huge alternator. Just store the 144 volts in a large capacitor and down convert to 12 volts. Use the 12 volt starter to crank the engine. simple!

The advantage of the Insight motor would be that it sips gas, effectively increasing cruising range.
 

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An other alternative would be a hayabusa powerplant with a turbo 250hp (up to 300 if you really wanted that risk) and less weight than the Insight's powerplant.
(Suzuki GSXR1300) :D

As for the idea of a hybrid aircraft it is a cool idea but I don' think the Insight''s IMA is the proper powertrain to use.

--Ash
 

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Discussion Starter #13
Aloha hana hou: I guess that I didn't scare up enough interest in a hybrid aircraft. We did look at other engine/motor combinations, but none (not even the Hayabusa) are as light as the Insight. Many small high RPM motors from motorcycles or scooters look great on paper, but once you hook a large diameter propeller to them they break crankshafts due to tortional resonance in the drive train. Any propeller is a huge flywheel, and cannot be accellerated/decellerated several times a rotation as easily as the crankshaft.I'm told that some geared WWII engines had spur gears that were designed to take 1300% of the expected load (torque) even though they had 9, 18, 27 or 36 cylinders and thus smaller power pulses.
Another reason a hybrid makes sense (particuarly for a flying boat) is that the IMA electrical power generated could be directed to a motor-jet ski pump to power the plane on the water. We looked at whether a Rotax C or D gearbox could take the torque of an Insight motor and provide gear reduction. These gearboxes have a clutch that allows the engine to reach about 2500 RPM before it engages the propeller drive, thus allowing the IMA to generate its power low down without turning the propeller, which most non-flying observers consider a large Cusinart.
I can't believe nobody responded to Burt Rutan's ideas about a hybrid aircraft with no control surrfaces and multiple motors. Any interest?? Aloha ka kou. David Bettencourt
 

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Not really a hybrid, but you might look at the "Solar Impulse" project for ideas on an electrically-powered plane.

To be honest, though, I can see few benefits from a hybrid general-purpose airplane. The main benefits of a hybrid are that you can A) recapture power lost in braking; and B) use a much smaller engine, since cruising at highway speeds uses only a fraction of the power that acceleration does.

But with a plane the situation's a lot different. A) You don't HAVE stop & go driving: you (generally) accelerate once, on takeoff & climb, then decelerate once, maybe hours later, for landing. B) You usually use a large fraction of the engine power, maybe 70-80%, in cruise, so you can't make your engine all that much smaller.

A hybrid concept might be useful for special purposes. For instance a spy plane that cruises to its target on IC power, then shuts down and runs off batteries to foil infrared & acoustic detection. Or maybe a self-launching sailplane...
 

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I agree with Jerry (the newbie) you wouldn't want to try to use the IMI part of the Insight's powertrain. If it were me I would ditch it and just the ICE and try to convert it to use a single small aircraft carb. I might could live with electronic ignition if it was very simple. For takeoff power you might be able to use nitrous oxide as alterative to a turbo. With this said I have always thought that an Insight engine would make a great touring motorcyle engine. It is of simlar size as a lot of other motorcycle engine's. Most bike engines are made more for power than for frugalness. You could have an 8 gallon tank and go at least 500 miles everytime you filled up. Which would be longer in the saddle than most riders would want to be but for those who wanted to they could do it. Just my 2c worth.
 

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Discussion Starter #16
Aloha hana hou:
I agree that most flight missions would not work with hybrid; the two exceptions are motorgliders and seaplanes. Electric flight generally makes no sense. Both motorgliders and seaplanes require a large amount of power for short periods of time. Now that fuel is so expensive (I pay nearly $4.00 per gallon her in Hawaii) most people are cruisingmuch slower, about 50-60 per cent power, unless they are renting the plane wet, in which case they fly and "rental power" or as much as they can get away with.

Many seaplanes require about twice the power to get on the step as their cruise power; the first ten knots of water speed needed to get up on the float's step require much more power than the rest of the take-off run. You can actually decrease power once on the step and still take off. Because the floats are so draggy, you cruise and 50% power if you want to get any reasonable range. You can go with a constant speed prop to get more RPM (power) at the start of the take off run, but you pay a large weight penalty and they are complex and expensive

I agree that the Insight might work alone, but then you still need (at last for a seaplane) both a starter and an alternator. Most turboprops use starter-generators to combine the two functions. Even for a small engine they weigh a minimum of 5 kilos total.

They hybrid idea is to extract a fair percentage of the power out of the engine other than by driving the propeller, in order to make the cranshaft last longer. A fixed pitch propeller that that is fine enough to let the engine wind up with zero airspeed will overspeed in flight. You are limited as to where you put it, normally on a pylon, to keep the prop out of the water spray; drawback is an high thrust line which requies trim (drag) to correct. If you could use the IMA in motor mode at first (adding to the ICE power) and then go to generate mode after lift off, you have electricity to continuously drive smaller motor/propellers mounted below the center of effort to equalize the thust vectors. You also have that same power avaialble from the same motors to drive small (1/4 scale) jet ski pumps to help the plane get on the step and off the water quickly, before they drive the propellers after lift-off.
Still no comments on Burt Rutan's ideas? I am assuming that he is talking about an unmanned craft that requires periods of dash speed and high electrical demands part of the time for sensors, radar, transmissions, etc. He sized his ICE to provide slightly more power than all the motors he envisioned, so as to have excess electricity to recharge the batteries used for the first five minutes of flight, but the Honda IMA is not nearly large enought to absorb 80% or 90% of the Insights ICE power and generate electricity on a continuous basis. Mahalo for the comments and keep them coming. Aloha. David Bettencourt
 

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"Now that fuel is so expensive (I pay nearly $4.00 per gallon her in Hawaii)..."

That's for 100LL Avgas, right? Not autogas. Don't know what it runs around Reno these days. I've been gone since March, plus we have an autogas STC on the Cherokee.

As to Burt Rutan's ideas, if I understand them I don't really like them. Mechanical control surfaces seem to me to be the simplest & most elegant solution, short of feathers :)
 

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Discussion Starter #18
Aloha: I have the autgas STC, but the State of Hawaii is now mandating ethenol in the gas, which the STC specifically prohibits, but that hasn't been put into effect yet. More importantly, the last time I drove down Lagoon drive to my hanger with 4 5-Gallon cans of 87 octane in the back of my Suzuki it was urged, in no uncertain terms, to "assume the position" by numerous M-16 toting reservists. 87 octane on Oahu is $2.49 Gal, and over $3.00 on Molokai and Lanai. It is nice to have the STC, as it lets me weekend at locations which don't have AVGAS (Hana, Kamuela, Molokai, Lanai) and get fuel without having to stop at big airports (Kona, Hilo, Kahului) for fuel.

As to Rutan, I can only surmise as to the basis for his idea, but here is what I think. Rutan has already explained in his quote why his concept will minimize the risk of loss of the craft from an engine failure, as the "motors" work in reverse to trade potential energy (altitude) into watts, to be expended again at low altitude for final flight path control.

I assume he's taking about a UAV because that is where the DARPA money is now. It is well known that the junctions from control surfaces on wings and tails are non-stealthy and show up on radar much more than a solid structure.

The use of multiple motor/propeller pods for propulsion and manuevering means that differential thrust rather than drag changes the flight path. This in and of itself is probably not that significant, but it also allows a given KW of power to be converted to thrust more effeciently through multiple propellers. Just as the Hueys I flew some 35 years ago derive their lift from a large rotor disk for efficiency at accellerating air downward for lift, (ie, low "disk loading" of a 40 foot rotor compared to a 6 foot propeller), so do multiple propellers with low "disk loading" convert available watts to thrust more efficiently than a more highly loaded single propeller. Moller Sky Car, Solo Trek and other flying car idiots notwithstanding, this is a basic rule of the physics of moving air to generate thrust. Other factors, such as disk solidarity and motor effficiency (large motors make more KW's of energy per kilo than multiple small motors) may negate any increase in efficiency in real life.

My own ideas about hyrbrids arose back in the 60's while attending Berkeley long before the Insight was developed. Someone on campus had built a hybrid from a design he saw on the cover of (I think) Popular Mechanics which used a B & S generator and an aircraft starter motor on an discarded Dune Buggy. I was always a helium head from smal kid time, as there were many blimps based at Moffit field. Use of an aircraft turbine APU (which generate watts and airflow for engine starting) seemed the perfect solution to blimp handling at low speeds and take off/landing, as numerous motors could be placed at the extreme ends of a blimp to provide maneuvering leverage at low speed or zero speeds. Now several companies are working on such designs, some even using exhaust gas heat to super heat the lifting gas.

Our first project were working on is to convert an old rigid wing hangglider (Easy Riser) to a hybrid power ultralight motorglider. The two power pods will consist of a Honda 31cc ICE motors coupled direct drive to model aircraft electric motors, probably the simple brushed motor Astro 90 for simplicity of switching between starter/motor to generator. It takes only about 65 lbs of thurst to keep an Easy Riser in level flight at 20 knots, but it takes about 100 lbs of thrust to do a foot launched (no wheels) running take off on flat ground and initial climb. Because of out trade winds, in many spots only 100 to 200 feet of altitude gain is needed to get up into ridge lift.
I need to get out and do some real surfing, as a large south swell is about to arive for the next 24 hours. Aloha. David Bettencourt.
 
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