Hi,

( Firstly )  - please excuse what might be a really stupid  question - but, since I'm new to all of this... I cant help thinking....

Isn't there some way ( even on a very small scale ) to use a combination of a small 2 stroke powered motor ( or a typical RC gas powered engine ) to spin a small generator and thus create power to assist in "trickle charging "  - or even powering a quad?

I understand there is a weight issue, but I'm thinking the right combination of ESC and motors ( electric ) and prop size could possibly provide enough grunt to lift the thing.

If this were possible, then using a real liquid fuel would ONLY make the drone progressively lighter  compared to the total weight at the start  as it consumes its supply of fuel - in the meantime,

While I'm at it - what about using DC to AC inverter technology some how to an advantage in power output?

 - Just asking.. lol!

[ there are no stupid questions -  the only time a question is stupid, is when you should have asked - but you didn't.]

Cheers!

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Hi rick.

I too have thought about doing something like what you mentioned above. i found this tiny engine on youtube that can possibly, with some mods, run a small generator that makes enough power to feed 3 motors, a kk2 board, 3-4 esc's, and the receiver. who knows, it might work?

http://youtu.be/ph2PMs2-7G4

Hi there 

Im new here Ive always been wanting to make a UAV with the intention of using Hydrogen cells I know they use them in RC cars and was going to experiment with the idea and thought this might be some thing you would like to look upon for alternative power.

Link below is to the site witch sells these little power plants i dont know to much about them as yet need to look into it.

http://arcolaenergy.com/store/product_info.php?cPath=&products_...

Hope this helps/Inspires some one

Jamie

Did you notice the UAV specifically designed cell on the site? http://arcolaenergy.com/store/product_info.php?cPath=37&product...

Not sure how much they are as it's all POA but if someone had some cash to throw down and find a solution (I don't have the cash but I do have the desire) then perhaps in a few years LiPo's will be a thing of the past and we'll all be brewing hydrogen from our tap water at home :P

Costs are high at the moment because it's not mainstream - My first Arduino wasn't mainstream when I purchased it and I paid $150 for a unit that is eclipsed by the $30 units today.  All it took was a lot of developers driving them to become more mainstream :)

I didnt notice but I have emailed them asking for a price have not heard back will email again as I really want one :) will find out price for you :)

Hybrid electric power sources have been discussed in some length before in this venue.  The bottom line is: not only are fossil fuel engines feasible for aviation on-board power generation (high energy vs. mass ratio), but they're IN USE today.  Adapting one on a small scale for an electric multicopter has yet to be done commercially, but the basic physics calculations are compelling.

http://diydrones.ning.com/forum/topics/confusion-over-engine-sizes-...

Just got a reply WTF!!!!!

'Hello Jamie,

Thank you for your email regarding AeroPAK.

I do not currently have detailed pricing for the various components of
AeroPAK.

However the base-price is around $20,000 (USD).

If you would like me to get in touch with head office to request a quote
or wish to further discuss your needs please don't hesitate to get in touch.'

Whats the crack with that? Think I will get a developer kit and experiment
http://arcolaenergy.com/store/index.php?cPath=29

The thread lives!

No way you could use that engine to fly a quad.  I would be surprised if it makes more than 1-200 Watts.

Interesting stuff.  Incredible to see those seemingly bright guys putting themselves in a virtual gladiator ring with that beast.  Nowhere to run if it goes wrong.

I'm also not sure how re-purposing a bunch of commercial RC Helicopter parts is a senior engineering project?

Anyway, I'd like to see the thing flying.  I've seen a number of these contraptions, but I have yet to see them do more than just hover.

Yep, seen them before.

On the first one... it's funny that I'm looking to replace the tail drive with a dedicated tail motor, to eliminate the complicated and unreliable tail drivetrain on my heli.  And here somebody is adding 4 of the systems to a quad which previously ran perfectly well with 4 motors. ;)

I'd also like to see video of these things actually *flying*.  The problem is, with variable pitch props, the "simple thruster" model that is being employed so well with Arducopter falls apart with a little airspeed.  All of a sudden, you need much more advanced control.

Now, it has to be said, my opposition to this idea of gasoline powered quads should hardly be considered "violent".  I'm just extremely skeptical.  Consider me the devil's advocate.  You are GOING to have to solve the problems I bring up.  You can do it in the initial design stages and save yourself some time and money, or ignore my points, and solve them after a few iterations.

I enjoyed reading Brad's proposed power system in the other post he just linked to.  I forgot about that.  There's a few things that might make his assumptions quite a bit worse than where he ended up with, showing a 3:1 power density benefit on the side of gasoline.

1) I think he did not include the weight of the motor-generator bracketry, nor the motor-frame bracketry.

2) Needs to include weight, and power loss due to cooling system.  I think you could probably expect to use at least a 1/2hp on a fan just to cool the motor.  It doesn't help that it's an airplane motor, with small cooling fins.  I realize that in a "clean sheet" design, you'd fix this.  But just something else to think about.

3) The energy density of gasoline being used, is that accounting for the reduced energy density of E10 fuels which are common?  Remember, the alcohol in them is pre-burnt, as they have oxygen in them already. ;)

4) I think the assumption of 10% conversion efficiency might be optimistic for engines of this scale.  There is a pretty simple law at work here, where the maximum theoretical efficiency of an engine scales with the volume of the combustion chamber.  We're not talking about a case where small hobby engines are cheaply made, I'm talking about a *something-eth* law of thermodynamics.  Smaller volumes have a higher combustion chamber surface to volume ratio, resulting in more energy going into the engine materials.  Then you also have incredibly poor carburetion efficiency and scavenging.

These are all the problems I see with this concept of having a gasoline engine driving a genset to make electricity for an electric propelled quad.

Not to say that these CANNOT be overcome with a maximum effort, clean sheet design.  I'm sure they can.  I just look at the economics of it.  You'd have to spend an aweful lot of money to develop a system to chase this theoretical 3-5X energy density improvement.  The resultant system would be pretty expensive.  And at the end of the day, you'd be competing with a battery that costs a couple hundred dollars.

Don't get me wrong, I completely understand that gasoline has a much higher energy density than LiPos, and this is the answer to long range flight.  I just think that using electricity as an intermediary power distribution system is a really tough road to go down.  Mechanical distribution is just that much simpler, and lighter weight.

The problem with mechanical distribution is that, at least using off-the-shelf hobby parts, it is extremely unreliable.  Both belts and shafts create a lot of vibration.  Belts are like flying Van de Graaf generators.  Shafts strip gears every time you touch a prop.  They're all unreliable.  I've been flying these things for a long time.  I've NEVER had an in-flight motor or ESC failure on a heli or quad.  I've had many tail drive systems failures.  And you want to put 4 of them on a quad?

Gotta cut this short, but I think that a gasoline powered  tandem rotor helicopter presents a pretty strong case of mechanical complexity vs. efficiency.

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