electric backpack helicopter - possible ?

[Current-Pille]

Hi Guys, I had an idea flying around in my mind about an electric backpack helicopter and wondered if it is possible to make such a thing work.

The basic design would include two large counterrotating rotors each driven by a powerful outrunner motor. Of course gears maybe using drive belts would have to be used.
For each motor a Schulze Controller future-40.160H could be used, using 14s 5p Thunderpower 2100 Lipos.
The batterypack weighing only 7 kg (150 cells) can deliver 2 x 8000 W continuous output (also maximum of the controller at 160 A). That eaquals about 22 hp. I’m not quite sure how much thrust you can get from 16000 W if you are using very large rotors?

Assuming a total motor weigt of 3 kg plus structure and so on it might be possible to achieve a liftoff weight of about 40 pounds.
Unfortunately the operation time would certainly be very short – about 5 minutes. On the other hand it would be easy to add another identical battery to nearly double flight time.

If the power is not sufficient lighter Pilots could be used :rolleyes:

I have added a small pic for illustration...

[Tuner]

The only hard part is building the Rotor Blades.
Get somone to model some blades for you based off of your best estimated thrust and RPM. And it will be a snap to do the rest.
I think you might want to think a little more outside the box for you motor.

You might want to check out the human powered helicopter projects.

Only scary thing with this is it can kill you easily in a crash or ruff landing.

I cant wait for the day I can have one of these.

Scott

[HoverBovver]

Not electric but like this one?...
http://www.gen-corp.jp/GENH-4_en/figure/Hotnews2002/s_sunfun2002_4.jpg
http://www.gen-corp.jp/GENH-4_en/

[TMorita]

You will probably need about 40 hp, not 22 hp.

Both the Gen H-4 and the Hiller Rotorcycle used 40 hp engines.

Check out the Hiller Rotorcycle pictures in this thread:

http://www.rcgroups.com/forums/showthread.php?t=342433

Toshi

[Current-Pille]

On the homepage of the GEN H-4 there is some information about an earlier model with 3 engines (30 hp) an it says there was the disadvantage that it couldn't hover with 2 engines left. It seems as if you need something between 20 and 30 hp.
But the electric design might be constructed with a weight of only 20 kg in contrast to the 70 kg of the GEN H-4.

Another important difference is the rotor diameter (4m with the GEN H-4).
It's a fact that you get more thrust from a larger rotor.
One could well use a rotor diameter of maybe 6m to reduce the power required.
This is now some physics: If you want to achieve a certain thrust you can use a smaller or a larger rotor. The smaller rotor has to accelerate the airstream to a greater speed due to its smaller area to achieve the same thrust.
I have developed a small equation which only considers how much power you need to achieve a certain thrust given a certain speed that the off-flowing airstream has: F: thrust P: Power v: speed of the airstream

F = 2P / v (assumes 100 % efficiency which unfortunately is not the case )

You can see that the smaller the speed gets (same power assumed) the greater the thrust gets.
Since a greater mass flows through the larger rotor v can be slower.
This however requires less power than with the smaller rotor for the same thrust.

I have calculated an example:

thrust 1500 N (150 kg)

With a 4m rotor you theoretically need about 7800 W
but with the 6m rotor only 5200 W for this.
The airstream would only have about 7 m/s with the larger rotor.

I did not consider the efficiencies of the parts of the drivetrain:
motors 90 % ?
controller 99 % ?
gear 95 % ?
propeller 75 % ?

--> this would lead to about 8200 W

These reflections might be wrong and unfortunately don't tell how to actually design and build the required propellers but it kinda tells me something about the physical feasability of the project...

[treehog]

You might find that less HP with electric might match more HP from gas as thier are factors involved losses from vibration heat noise that electric dosnt always have

Biggest rotors turning slowly will supply the most lift for the least power but if rotor speed is tooooo slow impossible to control the outfit

Also problems are what solutions for motor failure cluch box autorotation etc


after afew scale model versions then
Make a full model and put in a dummyu same weight dimesions as a person and a few crashes later will enlighten you as to why flyig is a super risky activity if your funds have held out that long :eek:

for testing you can always use an umbilcal electric wire to power it for local hover

If you can affordthe orbital price of a few thousand LIPO it might work for five minutes cheaper with the umbilical or even cheaper is hire a crane instead

Ralf

[heloman4real]

Interested in a backpack helicopter? Gotta checkout this (new?) website. www.sporthelo.com

[mecevans]

why not use a big turboprop mabe using 3 or so

[Langenase]

Do you mean something like this?....
Take a look at
http://www.trekaero.com/index.html

[avianaut]

A friend told me recently that an electric powered MPG (Motorised Para Glider) is on the horizon. Apparently uses the same power system that is used on large scale model aircraft. Geared outrunner, and LiPo's. Still way short of helicopter power needs, but should be feasable. LiPo powered cars are in the works, so stay on it.

I agree with treehog though, a backpack heli will be very dangerous.

The Trekearo is defunct, I believe. And definitely not backpack-able!

Cheers.

[Troy]

A friend told me recently that an electric powered MPG (Motorised Para Glider) is on the horizon. Apparently uses the same power system that is used on large scale model aircraft. Geared outrunner, and LiPo's. Still way short of helicopter power needs, but should be feasable.
This is it:
http://www.marksparaglidingpages.com/videopop.php?videoid=150

[avianaut]

That looks like it! Thanks Troy. Current-Pille, go for it.

Cheers.

[pmackenzie]

I’m not quite sure how much thrust you can get from 16000 W if you are using very large rotors?


Using 11,600 watts with a smaller blade, we got approx 110 pounds of thrust.
Measured with the highly scientific method shown below.
For a much larger blade I suspect you would need a higher drive ratio, either 2 stage or planetary.
Pat MacKenzie

[avianaut]

Langenase (and Trek Aerospace), my apologies! Not defunct at all. My error, sorry.

Cheers.

[Troy]

Using 11,600 watts with a smaller blade, we got approx 110 pounds of thrust.
110lbs of thrust is pretty impressive. I would imagine with the right blade design, gear ratio, and a light enough frame, you could achieve vertical hover capabilities with this power system.

[Tuner]

Im sure the batteries alone are near at 50lbs????

[ronmeister]

110lbs of thrust is pretty impressive. I would imagine with the right blade design, gear ratio, and a light enough frame, you could achieve vertical hover capabilities with this power system.
True, I'm guessing you will need 20,000 watts for vertical capabilities, especially depending on the weight of the "flyer"/"pilot."

[Troy]

Im sure the batteries alone are near at 50lbs????
Pat can answer that exactly, but I believe the whole system weighs around 50-60lbs. Otherwise, the poor pilot would have difficulty walking around with it strapped to his back.

If you keep the system light, you would need a heck of a lot less power than a Trek-Aero style set up. Not to mention twin, counter rotating blades is inherently more stable than side-by-side ducted fans. Ever flown the E-flight Blade CX? It's very tame and easy to fly. You suffer in forward flight with that stability but it's better to make it there in one piece.. ;)

[pmackenzie]

Pack weight is 30.5 pounds.
The pack is much larger than required for our power.
It could easily be 1/2 the weight and still put out 200 amps without even breathing hard.
We were after duration.
Each cell is rated at 150 amps, so the 14S8P pack could in theory put out 1200 amps at about 46 volts - 55,200 watts :eek:
(Our wiring is not capable of supporting that much current)
More details on the pack here:
http://www.rcgroups.com/forums/showthread.php?t=523329
Pat MacKenzie

[mecevans]

how much thrust is really needed to fly?i was thinking of building one of these and how much are the chutes?

[meatbomber]

wow at this price
OVIWUN models are currently available for $14,995. Each unit arrives in its own shipping and storage container, which includes one OVIWUN aircraft, a radio transmitter and receiver, battery charger, open source software, and a basic instruction manual.

Don't expect them to flood the VTOL modell market just yet :P

[Amp User]

If you dont require the need to climb fast verticaly, it would seem most people would be happy with a slow moderate climb that feels safe and stable. I would think a setup to control a preset altitude so the operator can fly low and not worry about winds would be a nice safty feature. I think that outrunner with some gearing could produce enough tork to swing a 12foot blade.

[Langenase]

Nice meat-chopping machine uh?

[michaellabib]

Dear all,

Believe it or not the ML-001 will be available in the markets in very limited numbers by the beginning of 2009 and it will come ready to fly no assembly required just unfold it wait until the proper RPM achieved and your are ready for takeoff. I know the majority if not all find this hard to believe but it is true. An eclectically powered compact and self contained prototype will be in the sky very soon. It will not use any if those old ideas i.e. counter rotating blades, tip jet or even ducted fans the simplicity of the design will astonish you and the safety you get is second to none even by comparing it to a modern helicopter. The reason I posted this is that I found you guys interested in this concept which really delighted me. For further information drop me an email michaellabib@gmail.com

[treehog]

Dear all,

Believe it or not the ML-001 will be available in the markets in very limited numbers by the beginning of 2009 and it will come ready to fly no assembly required just unfold it wait until the proper RPM achieved and your are ready for takeoff. I know the majority if not all find this hard to believe but it is true. An eclectically powered compact and self contained prototype will be in the sky very soon. It will not use any if those old ideas i.e. counter rotating blades, tip jet or even ducted fans the simplicity of the design will astonish you and the safety you get is second to none even by comparing it to a modern helicopter. The reason I posted this is that I found you guys interested in this concept which really delighted me. For further information drop me an email michaellabib@gmail.com


Let me guess it tethered to a long electric cable


Really a vidio and pitures and some basic evidence better than a magic carpet wind up anti gravity mumbo jumbo from a new sign up member and the firs5 post says he has the machine
Email not a chance


Ralf

[inventing_man]

An electric "roto seat" could work , but the cost of lipo batts is still way too expensive , :mad:

[TMorita]

Dear all,

Believe it or not the ML-001 will be available in the markets in very limited numbers by the beginning of 2009 and it will come ready to fly no assembly required just unfold it wait until the proper RPM achieved and your are ready for takeoff. I know the majority if not all find this hard to believe but it is true. An eclectically powered compact and self contained prototype will be in the sky very soon. It will not use any if those old ideas i.e. counter rotating blades, tip jet or even ducted fans the simplicity of the design will astonish you and the safety you get is second to none even by comparing it to a modern helicopter. The reason I posted this is that I found you guys interested in this concept which really delighted me. For further information drop me an email michaellabib@gmail.com

Well, I have some rare Canadian cat trees for sale.

Contact me for more info.

Toshi

[AgoMago]

Not electric but simple. :D
http://www.youtube.com/watch?v=f09_yvcASLM

ago