Electric Hybrid

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John.Roo

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Very optimistic.
Yes, I know...
Reason was to show how large difference between "what you get from batteries" and "what you get on propeller".
Even if I use very optimistic efficiency koeficients I finally get only 65% of power.

You are also right with Elfin - so far is more "marketing".
However is interesting that it is not new idea.
e-Genius really did some flight test with similar configuration.
However - it was not succefull testing.
Now they follow a bit different way....
e-genius_hybrid.jpg
egenius-pod_0-862x485.jpg
egenius-pod_1-528x296.png
egenius-pod_2-528x297.png
 

Sockmonkey

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Flint, Mi, USA
I’ve never seen a commercial version of a free piston linear generator. Can you point out one for me?

Thanks,


BJC
I've checked, but I think it's not available yet. They've been used in the past as air compressors, but I don't know what's stalling the generators.
It's a giant PITA to bring a new engine to market though, so it's not surprising that it takes a while regardless.
The tricky bit is apparently controlling the motion of the pistons by finely adjusting the fuel input and electrical output resistance.
The crowbar solution would be adding a mechanical link between the pistons, but that costs some weight and adds a couple extra moving bits. It would be completely reliable though.
 

BJC

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I've checked, but I think it's not available yet. They've been used in the past as air compressors, but I don't know what's stalling the generators.
It's a giant PITA to bring a new engine to market though, so it's not surprising that it takes a while regardless.
The tricky bit is apparently controlling the motion of the pistons by finely adjusting the fuel input and electrical output resistance.
The crowbar solution would be adding a mechanical link between the pistons, but that costs some weight and adds a couple extra moving bits. It would be completely reliable though.
Thanks. First displayed 85 years ago, used for air compression in WW II, looked at by Worthington later, ...

I would expect that, if it were beneficial, it would be widely used today.


BJC
 

Sockmonkey

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Thanks. First displayed 85 years ago, used for air compression in WW II, looked at by Worthington later, ...

I would expect that, if it were beneficial, it would be widely used today.


BJC
They're good, but very niche. Until they decided to use them as generators, the only use for them was for applications where you needed a gasoline-powered air compressor as a standalone unit.
 

Dan Thomas

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The crowbar solution would be adding a mechanical link between the pistons, but that costs some weight and adds a couple extra moving bits. It would be completely reliable though.
No such thing as a completely reliable manmade device.
 

EzyBuildWing

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Sep 23, 2009
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Sydney NSW Australia
Electric-helicopter (converted Mosquito) with Emrax 228 motor (capable of 60 kW continuous) flies brilliantly.
Pilot says in comments below the vid : "This is the best and most fun machine I've ever flown"!
There are lots of other interesting comments and technical info below the vid.
Check out the pilot's channel also for more of his e-Heli vids.
Seems the new aluminium Mazda Wankel "range-extender" is small and light enough enough to fit under the floor of the Mazda SUV's trunk. Just Google for more info/pics etc.
(Note: Pipistrel electric foxed-wing trainer cruises at 90 knots on 20 kW with pilot and passenger, straight and level).

 

vhhjr

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Yeah, but you all know what I mean, and it's tedious to keep typing things like "a reasonable level of reliability under normal operating conditions" every time.
As part of a DARPA project I designed and built a small FPE about 20 years ago. It ran for 30 seconds and seized because I didn't have enough cooling. I never ran it long enough to change the bounce cylinder pressure or throttle the incoming fuel and air. FPEs are very hard to control especially if you are trying to throttle them. They are also very noisy and need a turbocharger to capture the energy going out in the exhaust. They are a natural for a linear alternator as the alternator bits can also be used by the control system and as the starter.

The engine shown in the attached article would vibrate like crazy. The are configurations with opposite moving pistons with a center, common combustion chamber.
or with combustion chambers at each end and a common bounce cylinder.. These engines can be balanced.

Vince Homer
 

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Sockmonkey

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As part of a DARPA project I designed and built a small FPE about 20 years ago. It ran for 30 seconds and seized because I didn't have enough cooling. I never ran it long enough to change the bounce cylinder pressure or throttle the incoming fuel and air. FPEs are very hard to control especially if you are trying to throttle them. They are also very noisy and need a turbocharger to capture the energy going out in the exhaust. They are a natural for a linear alternator as the alternator bits can also be used by the control system and as the starter.

The engine shown in the attached article would vibrate like crazy. The are configurations with opposite moving pistons with a center, common combustion chamber.
or with combustion chambers at each end and a common bounce cylinder.. These engines can be balanced.

Vince Homer
Oh of course. I was assuming opposing pistons. You can get away with not using a turbo if you use a chamber under each piston for your scavenging charge as regular two-strokes do.
 

Aesquire

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Rochester, NY, USA
The Human Cuisinart machines with the propeller plane intersecting the pilots terrify me.

Doesn't mean I wouldn't try one. ;)

I do have to ask if there is a tumble button on the controller like on the palm sized one I got for Christmas. I'd want that disconnected, I think.
 

Sockmonkey

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Why does nobody just stick two large diameter co-axial counter-rotating rotors on top and steer the thing hang-glider style by mounting the assembly on a gimbal?
 

vhhjr

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I've checked, but I think it's not available yet. They've been used in the past as air compressors, but I don't know what's stalling the generators.
It's a giant PITA to bring a new engine to market though, so it's not surprising that it takes a while regardless.
The tricky bit is apparently controlling the motion of the pistons by finely adjusting the fuel input and electrical output resistance.
The crowbar solution would be adding a mechanical link between the pistons, but that costs some weight and adds a couple extra moving bits. It would be completely reliable though.
How about a series system where the motor drives through an electric clutch to the prop. That way the motor can also be the alternator saving that weight. If you look at the power curve for most IC engines they flatten out at the top and if no more HP is demanded can run up an additional several hundred RPM. If you look at the power required to drive a prop that several hundred RPM can require considerable power that could be delivered by the electric motor. With a modest battery pack this extra HP could be available for take-off and climb out. Once cruise speed is established a small amount of IC engine HP is diverted to the electric motor, which is then operating as an alternator to recharge the battery pack. This all could be seamless with a FADEC like single throttle control and appropriate electronics.

Using an Excell prop design spread sheet I have let's look at a 48 x 54 prop spinning at 3500 rpm absorbing 75 HP. If we run the same prop to 4000 RPM it absorbs 112 HP. That's 37 HP more or 50% increase. That 37 HP could be provided by the electric motor. This is also a situation where an in-flight adjustable prop would be a great advantage.

Vince Homer
 

Sockmonkey

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How about a series system where the motor drives through an electric clutch to the prop. That way the motor can also be the alternator saving that weight. If you look at the power curve for most IC engines they flatten out at the top and if no more HP is demanded can run up an additional several hundred RPM. If you look at the power required to drive a prop that several hundred RPM can require considerable power that could be delivered by the electric motor. With a modest battery pack this extra HP could be available for take-off and climb out. Once cruise speed is established a small amount of IC engine HP is diverted to the electric motor, which is then operating as an alternator to recharge the battery pack. This all could be seamless with a FADEC like single throttle control and appropriate electronics.

Using an Excell prop design spread sheet I have let's look at a 48 x 54 prop spinning at 3500 rpm absorbing 75 HP. If we run the same prop to 4000 RPM it absorbs 112 HP. That's 37 HP more or 50% increase. That 37 HP could be provided by the electric motor. This is also a situation where an in-flight adjustable prop would be a great advantage.

Vince Homer
Makes sense to me. If you're using the electric for the power boost, I don't think you'd need the variable-pitch prop because you can get torque boost from the electric motor at both the high and low end. IIRC some automakers were trying to combing the starter motor, alternator, and flywheel into a single unit to save weight, but I dunno what happened with that.
 

231TC

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Aug 29, 2020
Messages
178
Electric-helicopter (converted Mosquito) with Emrax 228 motor (capable of 60 kW continuous) flies brilliantly.
Pilot says in comments below the vid : "This is the best and most fun machine I've ever flown"!
There are lots of other interesting comments and technical info below the vid.
Check out the pilot's channel also for more of his e-Heli vids.

That seems like a bad idea having separate motors for the tail rotor rather than driven off the main rotor.
 

EzyBuildWing

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Sep 23, 2009
Messages
321
Location
Sydney NSW Australia
Electric Mosquito Helicopter (e-Mosquito) has separate batteries for main and tail-motors, & separate-controllers for each tail-motor, plus redundancy of tail-motors as well. Very well thought out!
Pilot says best feature of his e-heli is the "silence"!
Pilot's Youtube channel below....he clearly answers all viewer's questions in the comments below his vids.
e-Mosquito could be great way to learn hovering.
Take a look.....Link below.
The Mazda Wankel rotary "range extender" should be vibration-free(well almost).

 
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