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Old Apr 23, 2012, 03:30 AM
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Question
fuel engine + micro alternator = possible Quadcopter?

I am sorry if this has already been discussed, I am new with little to no technical knowledge and haven't been able to determine if it's possible to build a quad with a small cc engine connected to an alternator that can power the electric motors. Can someone help me understand the math behind it? Or if it's even possible?

Thanks,
Vic
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Old Apr 23, 2012, 10:02 AM
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What you are wanting to do is have an electric motor that is recharged from a fueled engine. Your run time would still be limited by the tank size, why not just go fuel in the first place and save the weight.
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Old Apr 23, 2012, 10:55 AM
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Thank you for the quick response.
Are there any designs for fueled quadcopters?
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Old Apr 23, 2012, 11:09 AM
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I don't know of any engine driven quad copters.

I'd also suggest that at some point the power source indicates the sensible way to design a craft. Electric motors are dependable power sources and they are easily controlled for speed and power. They respond to the power input very quickly due to relatively low rotating mass.

Engines, on the other hand, are not reliable and do not produce the same power for the same throttle position with the same degree of predictability as electric motors from run to run. So to get around the varying power production with each run you need to run with one engine and connect it to the quad rotors with some form of drive system. Such a system would be heavy and complex compared to using 4 electric motors. But single rotor helicopters reduce the parts count and concentrate the engine and drive components into a smaller package. Which sort of makes engines far more suitable to single rotor systems than to quad rotor systems.

Which may explain why we don't see many quad rotor designs in any area other than modeling and why even in this field we only saw them show up in big numbers when lighter and more powerful brushless motors became widely available.
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Old Apr 23, 2012, 12:29 PM
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Thank you. Your responses are greatly appreciated. The goal I'd like to achieve is long flight time on a quad. Do you feel a solar panel has the ability to charge the battery quickly enough for contentious flight?
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Old Apr 23, 2012, 12:53 PM
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Why a quadcopter ?

A conventional winged platform for say aerial photography could give you longer flight times. It could even support solar panels easier as there is a nice wing surface to fit them to.

A large solar panel on a quadcopter could just act as a large drag plate and possibly restrict prop airflow.

Conventional winged models are quite capable of flying slowly, though perhaps not hover unless designed for that as specific requirement.

Perhaps if you specify your requirements, then clearer answer can be given.
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Old Apr 23, 2012, 01:45 PM
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Quote:
Originally Posted by VicTor D View Post
Thank you. Your responses are greatly appreciated. The goal I'd like to achieve is long flight time on a quad. Do you feel a solar panel has the ability to charge the battery quickly enough for contentious flight?
No a solar panel would not. Solar is a good idea but the technology is just not there. Most of the power from solar is lost in the conversion.

A 10 watt 17 volt solar panel measures 14 inches by 10 inches let alone that the 10 watts it generates is per hour. This would be more impractical then a gas motor.

If you are looking into extending a flight you could always try to figure a way to install a second lipo pack. You could possibly have it wired in to the esc and have a servo hit a switch to change the pack. I'm not sure how safe this would be as you would essentially be changing a battery pack mid flight, I personally wouldn't do this.
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Old Apr 24, 2012, 12:19 AM
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Rather than an alternator you would want a generator producing DC current into a small battery to buffer any variations in engine rpm and get consistent voltage to the receiver. Think of the old bicycle generators that ran off the side of the tyre, something like that connected straight to a 2 stroke engine.
If you add up the weights of the 2 stroke engine, fuel tank, the generator and the small battery, you will probably find it is a lot heavier than a normal lipo that would power a quadcopter.

Quadcopters are not very efficient flying machines. The most efficient flying machine is a slender winged glider, that's why solar powered planes are all this kind of plane, you have some chance of actually powering it.
Even if someone invented a solar panel that was 100% efficient it still would not produce enough power to extend the flying time of a quadcopter by more than a few seconds.
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Old Apr 25, 2012, 09:47 AM
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Back somewhere, sometime, this was done for single, conventional engine aircraft. Was way too heavy/complicated/expensive to go over very well. The term "Genesis", comes to mind, but mind, these days, is quite fuzzy.

Les
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Old Apr 28, 2012, 09:42 AM
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Actually a brushless electric motor as an alternator with a rectifier and voltage regulator would be the way to go.

BUT, you are burning fuel in a fairly inefficient engine, to generate electricity (Losses) to be rectified and regulated (losses), and then run electric motors (losses).

Yes you could do this, but you are better off using a larger battery pack.

Which is the same answer you got over on HeliFreak.
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Old Jan 14, 2015, 03:59 AM
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Quote:
Originally Posted by VicTor D View Post
I am sorry if this has already been discussed, I am new with little to no technical knowledge and haven't been able to determine if it's possible to build a quad with a small cc engine connected to an alternator that can power the electric motors. Can someone help me understand the math behind it? Or if it's even possible?

Thanks,
Vic
i had come across the same project too and im half way building it,firstly let me tell u im using a nitro engine which is not so powerfull but i faced a lot of problems im converting the ac source from the generator to dc it adds weight d rectifier d power distribution boards plus u need precise power calculations and power regulations to make sure nothing get fried on ur quad i some how came to a solution to this problem by extending the antennas so that d power make dissipate der using a power source like this depends on d efficiency of ur engine if u use a moderate rpm den ul get a moderate power u can't think of using a transformer to jump d voltage either or u can hav arduino look after all dis so its very essential to have a adru pilot to look after evrtyin onboard trust me a lot of thing happen dat u dont expect!!! so conniving to this good luck in building and once again be precise in ur power output u have anytin else jus ask
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Old Jan 14, 2015, 04:32 AM
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Isn't the main reason that quadcopters are electric powered, is because an IC engine vibrates too much for camera work.
The same reason is probably why most, (all ?) model aerial photography fixed wing planes are electric powered.
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Old Jan 14, 2015, 04:36 PM
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Good luck with your project Arron. But really I still have to ask why you are bothering to do it this way unless you simply want to address the challenge of making it work. With modern batteries being so good it's just a lot easier to pack more batteries up in the copter instead of lifting the weight of the engine, alternator or generator and the fuel.

In the end you need X amount of watts worth of energy to lift and fly the quad copter. If the engine does not generate enough power for the output of the generating system to provide at least that many watts then the onboard filter batteries will run down and the copter will have to land before it runs out of fuel. As you say you can't modify it. The engine and generating system either makes enough power or it doesn't.
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Old Jun 30, 2015, 07:49 AM
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Quote:
Originally Posted by aaron de souza View Post
i had come across the same project too and im half way building it,firstly let me tell u im using a nitro engine which is not so powerfull but i faced a lot of problems im converting the ac source from the generator to dc it adds weight d rectifier d power distribution boards plus u need precise power calculations and power regulations to make sure nothing get fried on ur quad i some how came to a solution to this problem by extending the antennas so that d power make dissipate der using a power source like this depends on d efficiency of ur engine if u use a moderate rpm den ul get a moderate power u can't think of using a transformer to jump d voltage either or u can hav arduino look after all dis so its very essential to have a adru pilot to look after evrtyin onboard trust me a lot of thing happen dat u dont expect!!! so conniving to this good luck in building and once again be precise in ur power output u have anytin else jus ask
Are you still working on this project?
Quote:
Isn't the main reason that quadcopters are electric powered, is because an IC engine vibrates too much for camera work.
The same reason is probably why most, (all ?) model aerial photography fixed wing planes are electric powered.
That's true about AP planes, but for quadcopters there appear to be no gas powered ones because the power to weight ratio is not good in small models with gas, and also now you've got four gas motors to deal with (reliability issues), plus I have to imagine they can't spin up as quickly (as necessary to control flight, moving each motor independently). You can run a single gas motor and clutches for all the other four but that's also very difficult (some people on youtube are trying this if you look up gas powered quadcopter).

As a practical mater gas is a bad idea for a quadcopter for sure. However, it's interesting
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Old Jun 30, 2015, 11:46 AM
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Ist post.
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