Air driven generator?

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pfarber

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Anyone ever think of or know of a production unit that would be air driven at say 50+ mph?

I see lots of military aircraft pods with electrical generators and was wondering it that was a possible emergency or even daily use thing on E/AB's?

Perhaps a unit with enough power to supply the alternator only or maybe a 20-30 amp unit for more gear?
 

bmcj

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Air driven generators are old school and used to be the de facto standard for many lightweight GA planes that sported an electrical system.
 

wsimpso1

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Wind generators are a poor way to get power if the engine is running. You make power at the engine, throw away a minimum of 12% of it to convert to moving airplane, turn the wind turbine with the moving airplane, lose a minimum of 12% of it to turn that shaft, then have to run a low speed alt or gen which is either heavy or low efficiency or both to make electricity. You standard belt or gear drive alternator only loses a couple percent getting power from the crankshaft and is light and high efficiency once it is spinning.

Then there are other issues like the fact you are on the battery until you get into flight, which may mean a lot of battery must be carried.

The two good uses for them is engine out emergency power and to power a gadget that is only used in flight that ship's power is inadequate for. There were some tactical pods that ran them, but in an era of stealth, they have one heck of a radar signature...

Bad idea for us. Stick one alternator on the traditional spot, another on the vacuum pump pad, be happy.

Billski
 
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Dana

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Wind generators have one advantage: they don't constitute an "engine driven electrical system", so the aircraft may be exempt from the transponder and ADS-B requirement in airspace where it's otherwise required.
 

Pops

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And you can use a solar panel on top of the instrument to help a little. 15 watt or so.
 

galapoola

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Interesting side note. The two fellows who hold the record for staying airborne 64 days in a Cessna 172 had a generator failure after a month of flight. They hooked up a wind generator on the strut. It was passed up from a moving car/truck and installed in flight. It did not produce enough energy to power the fuel transfer pumps, that had to be done by a hand operated pump.
 

Pops

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I have had 2 electrical failures in my life. One on an old straight tail C-172 with a generator. The other at 12K with center, I called center and informed them of the problem and will be turning everything off and saving the battery for the destination airport 150 miles away. They cleared me to land on runway of my choice when I get there. Wire broke at alternator.
 

Dan Thomas

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I built one for my A-65-powered Jodel. There's no place on an A-65 to take power off to drive anything without machining a special pulley to go between the prop and crank flange, and all I needed was an amp or so to keep the radio battery topped up. I used a small ball-bearing PM DC brush-type motor and welded up a tiny steel high-pitch prop for it, high pitch to limit RPM. Ran the output thru an LM317T chip with a couple of resistors to set the output voltage. Chip heat-sinked. It worked but generated enormous radio noise, no matter what I did to the circuitry. No amount of filtering or suppressing helped. I finally realized that that spinning steel prop was radiating the magnetic field along with all the brush spark noise. Took it off and used a larger battery and charged it occasionally.

A plastic prop might have been better, but anything with brushes and a commutator is going to produce some noise anyway. A brushless DC motor might be better adapted for this.
 

radfordc

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Aircraft Spruce has this one.... GENNIPOD GENERATION II | Aircraft Spruce

I made one for my Airbike ultralight. I used a Kubota garden tractor dynamo and mounted a large model airplane propeller on the shaft. The AC output from the dynamo went through a Key West Regulator/Rectifier and came out at about 15v DC and 4 amps as I recall.
 
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12notes

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You'd need at least 5 of them for 20-30 amps, but Aircraft Spruce does sell these:

I bought one for my project, but then found a small (21"x11", just under 1 lb) 100W flexible solar panel I can integrate into the wing. It should be more than enough to recharge the battery on my plane.
 
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Sockmonkey

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Might it be practical in a traditional plane to use an exhaust turbine from a supercharger to turn a generator? Wouldn't have to fiddle with belts so you it would be a fairly simple retrofit.
 

wsimpso1

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Might it be practical in a traditional plane to use an exhaust turbine from a supercharger to turn a generator? Wouldn't have to fiddle with belts so you it would be a fairly simple retrofit.
Turbocharger turbines turn on the order of 100,000 rpm, while most of our alternators need to stay below about 10,000 rpm... then the turbocharger shaft has bearings that are kept cool by routing engine oil over them and then back to the sump. So, with off the shelf turbines, you are going to need to run oil in and out and probably need a way to gear the turbine output down to drive an off the shelf alternator. Maybe a suitable sized turbine will run an alternator at reasonable speed, but that will be part of your challenge. You may need to program an Arduino and electric waste gate actuator to read alternator rpm and regulate the turbine. Then there is the entire issue of existing small turbines not being able to turn the alternator at all when engine power is not at least near cruise levels.

Billski
 
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radfordc

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Turbocharger turbines turn on the order of 100,000 rpm, while most of our alternators need to stay below about 10,000 rpm... then the turbocharger shaft has bearings that are kept cool by routing engine oil over them and then back to the sump. So, with off the shelf turbines, you are going to need to run oil in and out and probably need a way to gear the turbine output down to drive an off the shelf alternator. Maybe a suitable sized turbine will run an alternator at reasonable speed, but that will be part of your challenge. You may need to program an Arduino and electric waste gate actuator to read alternator rpm and regulate it.Then there is the entire issue of th turbine not being able to turn the alternator at all when down near idle.

Billski
So simple....what could possibly go wrong?
 

103

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Aircraft Spruce has this one.... GENNIPOD GENERATION II | Aircraft Spruce

I made one for my Airbike ultralight. I used a Kubota garden tractor dynamo and mounted a large model airplane propeller on the shaft. The AC output from the dynamo went through a Key West Regulator/Rectifier and came out at about 15v DC and 4 amps as I recall.
The Gennipod was developed by Jim Hardy if the Gen 2 GenniPod prop is flipped it can support speeds over 120 otherwise it is optimal for 60-90 I think. Can you advise what speed generated 4A?

MAtt
 

pfarber

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Wind generators are a poor way to get power if the engine is running. You make power at the engine, throw away a minimum of 12% of it to convert to moving airplane, turn the wind turbine with the moving airplane, lose a minimum of 12% of it to turn that shaft, then have to run a low speed alt or gen which is either heavy or low efficiency or both to make electricity. You standard belt or gear drive alternator only loses a couple percent getting power from the crankshaft and is light and high efficiency once it is spinning.

Then there are other issues like the fact you are on the battery until you get into flight, which may mean a lot of battery must be carried.

The two good uses for them is engine out emergency power and to power a gadget that is only used in flight that ship's power is inadequate for. There were some tactical pods that ran them, but in an era of stealth, they have one heck of a radar signature...

Bad idea for us. Stick one alternator on the traditional spot, another on the vacuum pump pad, be happy.

Billski
I forgot to add 'auto engine' and I guess I should have BOLD/CAPITALIZED/flashing neon colored the 'emergency' part.

While a second Lithium battery might be a better bet, we're talking emergency situations. It doesn't need to be perfect, it just needs to do what it needs to do. Say 6-10A for a fuel pump, an amp or two for the ECU, a couple for the coils, say 30-40A for an engine and radio on an emergency bus. Car motors need a lot of gadgets to run... I've accepted any/all performance hits for the simple ability to actually afford to be able to fly.

That 'minipod' was 2lbs for 4A.

Duralast Gold New Alternator 14130N 40A, 11lbs with pulley. Not a huge penalty. You could shave off some weight. Getting it to spin 2000rpm to get enough out of it... that's might be an issue.

Batteries age, and need to be maintained/charged. A second alt. would just sit there until you needed it.
 
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Sockmonkey

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Turbocharger turbines turn on the order of 100,000 rpm, while most of our alternators need to stay below about 10,000 rpm... then the turbocharger shaft has bearings that are kept cool by routing engine oil over them and then back to the sump. So, with off the shelf turbines, you are going to need to run oil in and out and probably need a way to gear the turbine output down to drive an off the shelf alternator. Maybe a suitable sized turbine will run an alternator at reasonable speed, but that will be part of your challenge. You may need to program an Arduino and electric waste gate actuator to read alternator rpm and regulate it.Then there is the entire issue of the turbine not being able to turn the alternator at all when down near idle.

Billski
As I understand it, with a basic turbo there is a trade-off between high and low end performance, so in this case you use one that sacrifices the high end for the low end.
One other thing that can be done is to have a spring-actuated bypass vent that can route some of the exhaust past the turbo straight into the exhaust pipe to prevent it overspeeding and make it run cooler.
 

Dana

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The Gennipod was developed by Jim Hardy if the Gen 2 GenniPod prop is flipped it can support speeds over 120 otherwise it is optimal for 60-90 I think. Can you advise what speed generated 4A?
I looked through the Genipod manual on the ACS website, looks a bit, dare I say, amateurish, and thin on specs. A couple of statements in the manual make me think the seller (or at least whoever wrote the manual) doesn't really understand the way the system works.
 

wsimpso1

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As I understand it, with a basic turbo there is a trade-off between high and low end performance, so in this case you use one that sacrifices the high end for the low end.
One other thing that can be done is to have a spring-actuated bypass vent that can route some of the exhaust past the turbo straight into the exhaust pipe to prevent it overspeeding and make it run cooler.
I suspect that finding such a COTS turbine is unlikely. Even big marine diesels, the ones that make tens or thousands of horsepower, have turbochargers that run as fast or faster than we can expect our COTS alternator to survive. So it most likely means a gear box of some sort or some combination of custom turbine/alternators.

A spring bypass would regulate turbine speed based upon a delta P. Nice and simple, but since overspeed is what must be prevented, you will have to operate the system VERY conservatively to always prevent overspeed - two out of four quadrants of operation that must be compromised. Might still be OK, but a lot of work has to be done to get to this point...

A solid state alternator speed sensor (it only needs to pick off the alternator ripple frequency to get a speed signal) can feed info to an Arduino or other programmable controller, which then operates a COTS electric wastegate actuator, and now you can control device speed, which is what you want. The same device can also ramp down rpm when the battery is "full" or ramp it up when charge state is down. As long as you have the Arduino, why not also use it to give you a reading on battery nominal operating time available right now. Add one thermocouple and you can also give state of engine oil (time to recommended change). Many other useful operating issues can be added...

All of this is predicated on having a turbine and alternator that can run in the right speed range with the range of exhaust gas volume you have from your engine. Have fun.

Billski
 
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