View Full Version : Idea for a big chopper

11-03-2006, 05:33 AM
Hey all,

I am thinking about doing a helicopter project, and wanted some feedback.

The idea is to use a large helicopter, with a large payload bay, and be able to fly up to 5 lbs of payload. That is a lot, i know, but its an upper limit.

I would prefer electric power, with up to 45 minutes of flight (not sure if that is possible).

So does anyone think this could work? And any thoughts on parts to use?

11-03-2006, 12:37 PM
thats a hard order to fill on the electric side... have you e-mailed NASA?

I dont know of any easy answer for that one..

11-03-2006, 12:47 PM
It's very possible if your 5lb. payload happens to be batteries. You won't be able to do that if your carrying dead weight though.

11-03-2006, 03:53 PM
Maybe we should be asking what is in your 5 pound payload... perhaps the question isnt what heli you are looking for.. instead, what equipment you can use that is lighter.. Lightening your payload would open up the array of helis you can choose..

Are you carrying a camera? Video Camera? small dog? 2 of those 3 can be bought at extreemly lower weights than 5lbs.. then you have greater possibilities of aircraft...

11-03-2006, 04:35 PM
The payload is some communications gear and an autopilot. The batteries to power those are most of that weight, but average payload would be on the order of 2-3 pounds. A very small camera could be an option, but not required.

It sounds like electric is not viable, which is too bad really!!!

11-09-2006, 10:02 AM
you can certainly lift that much weight with an electric, but the 45min flight time is not possible unless (as noted by Motions) your payload is batteries. Unless you can adjust your payload or reduce the flight time it sounds like you need a gasser. Or just wait a few more years for the battery technology to catch up.

12-02-2006, 09:48 PM
does anyone know what the duration of load carrying full size helis is?

im thinking that not many heli platforms can do this at all.

turbine models would need a load of fuel, same for glow models (and they wont like 45 minutes operation).

perhaps consider a highly modified model with extreme blade length running off a gear train that allow more intertial flying capacity much like an auto gyro.....

12-02-2006, 09:49 PM
the best solution for this would be a blimp.

01-07-2007, 04:09 AM
Is there such a thing as a large RC blimp?!?

Brutal E
01-07-2007, 04:45 AM
Not that I know of most are small less than 6 feet long and only suited for indoor use. Payload would be minimal less than a few ounces, my guess. Might want to check into weather balloons on a teather. Or a rocket.

01-09-2007, 01:44 PM
No reason you cant r/c a larger blimp tho... :)

01-27-2007, 09:24 AM

(however. it is not common and there for Expencive)

I would look at RC aircraft that Plane. It is near the least resistance and there for can be most endurable per pound. Heli are a wast of Energy. But a Helo lot of Fun.

Side thought:
You could auto off a cliff which has an Upward wind. You could probably auto all day if you just need servo power and a Little to get up and Down once.

Endurance on a Heli is at a Proportionate speed. IE a heli hovering out of ground effect is wasting the most amount of Energy.

Why not a Tilt rotor Aero. Seen one here in AU. It would be usefull. but this is just Experimental and Compleatly Home built.

05-23-2007, 03:59 AM
Quote from octane-link

Hey all,

I am thinking about doing a helicopter project, and wanted some feedback.
The idea is to use a large helicopter, with a large payload bay, and be able to fly up to 5 lbs of payload. That is a lot, i know, but its an upper limit.
I would prefer electric power, with up to 45 minutes of flight (not sure if that is possible).
So does anyone think this could work? And any thoughts on parts to use?

What is the cutoff point for the size of an electric helicopter?
How would you go about calculating the blade size/gears/motor/battery combination for each evolution of helicopter as it grew in size?
Does this information exist somewhere?
Please post links if it does.

05-23-2007, 01:18 PM
Money would be the main factor for the cut off point in Electric Heli.

Enginuity. if you had to make one. you could use a Washing machine motor or a compressor motor. But that then leads us to the last Item of developement that is holding the size of electric craft down. the ESC.

speed controlers are the main factor. currently they are behind the size of Electric motors.

Even so. you could use two motors in a tanden contra rotating job. split this amongst the two speed controlers and you have plenty of power.

How would you go about calculating the blade size/gears/motor/battery combination for each evolution of helicopter as it grew in size?
evolution is the process of natural selection. what is the job of each size variant.

Is there a reason you can not go Petrol ? (Sorry for the sin word :silly: ) but untill the unit size you want becomes availble. you could use a bit gas.

PS. 5 pounds is nothing. 45 min is Woh!... now 5pounds is something.

calculating the blade size/gears/motor/battery combination
if it was me. i would start with Load size and work from there. endurance is the next factor. then work on the rest.

05-23-2007, 06:49 PM
Yes money is a key factor !

I was wondering if there was an exponential curve to the
possibility of building a larger and larger electric copter.
We know the current limitations of full scale turbine petrol copter
so we have a reference point on that end but is there a point
(notwithstanding the current electronic limitations) where
the weight of electrical gear will not allow a copter to get any
larger. (Probably not until there is a 10kw speed control and
a battery the size of a van ! )
I`m sure an engineering type fellow would be able to answer this
question based on power density of electric versus petrol just as
we experience now within the range of model helis.
There is the glider that has the solar cells on the wings, wonder if
the same thing could be done with a copter? The blades could be wide chord with solar cells and then place solar cells as the frame/canopy/tail boom, etc.

05-23-2007, 11:36 PM
sorry Double posted. This post can be deleated.

05-23-2007, 11:47 PM
OK, Just a concept heli here, working with your suggestions on solar cells.
Current tech on solar sells can allow for slight bending of the cell. without damage to the cell. one could use the structural spars in the blade/wings them self as the conducting conduit. small capacitors in the wing would allow for the moments of less power to keep a steady power. but.

the weight would still be a tad high on the blades and the centrifugal forces MAY? be so great now that the hub has to be re enforced. (Not sure the power gain would be more than the now increased power drag ?) (Some one told me there was a solar cell that was near 200% more efficient than the current market tech of solar cells, I heard this from an unreliable source :{ , I know not of it or its weight)

If solar cells were so powerful. then it would seam to me that an ultimate wing with immense surface area could be developed (Not sure about spinning it though) and a Powered glider with multiple wings would work on a non hindered Scale. IE the larger and more wings you add the more efficient it would become.

OK sorry there. back to the Heli.

use liPo and Brushless. the power curve. I suppose I to would be interest in a definitive answer. IE will the be a Positive effect with the increase in size or negative effect on endurance.

lets say you have a 15kg aircraft. what would be the power required to hover that from its Prop.
now lets say we have a 15 Kg heli. would the power be less or more to hover it.
less of cause. (But the aircraft would use less power in a cruse)

what is the current/ultimate limitation to Turbine heli (Real)

Tip speeds
blade construction
Operating costs / useful ness.

Look at the 22 osprey.

The curve you talk about is dependant on so many things. but yes as you increase size you will need to increase strength (Thus weight) and Power thus weight and so it could seem to go around and around .

I am not an engineer. (As if you couldn't have guessed that) but I can see your point.

Set up a min comp. Have the Weight as a variable and time (OF flight) and speed of craft as a fixed element in a design concept.

Fix to max speed required 30kts (Designer would love this)
Duration of flight (Min 30 min)
1/ 5kg
2/ 10kg
3/ 20kg
4/ 30kg
5/ 60kg

I suppose another requirement would be Elevation required (Operational ceiling)

You got my head thinking. I even played with a model in G3 to look at blade chords and speeds. If you had this Sim I would send you an av.


Brutal E
05-24-2007, 12:37 AM
Actually there is a company that has the tech to print solar cells. They are flexible like paper and could be used to cover everything from wings to sidewalks.

05-24-2007, 03:00 AM
So where could this begin...

Taking todays technology, and before we introduce the solar cell idea,
which blade, motor, gear, battery speed control, etc would hover the
longest, (therefore ,the thought being, the most efficient overall)
Once we have established this base then we might find that too small a copter won`t carry enough battery, too large a copter is too heavy/draggy for example.
Do we know which combination today would stay in the air the longest?
Once we had that then we could incorporate these features into a solar cell copter and hopefully by all methods available we would be able to expose enough solar cell area on a sunny day to fly on limited power.
It would be something to be able to fly whenever it was sunny, no fuel, no chargers, etc.
Is there an FAI class for electric heli endurance? Or as it might seem since it does not have the impact of 3D it probably never developed.

05-24-2007, 04:04 AM



Im guessing around 130w per KG.

Now find a motor.

AXI (http://www.modelmotors.cz/index.php?page=60&kategorie=5330D) or ?? PS Outrunners have the torque low down.Now over to Vario or ?? to find some mechanics.

how many Lipo's would you need ??

You see my point. Colect what is available. add the weights together and find the Power requirement from there.

No curve as you mentioned. PS> without needing to carry any usefull payload. you probably could make a Vtol that flew in flight and charged in flight for a burst at landing with solar cells. but. :blah: $$$$$$.00

05-24-2007, 03:58 PM
Buy a gasser heli and go with a second tank. With low head speeds and large blades, many gasoline helicopters can stay aloft for 30-40 minutes without modification (on the same size of tank as a glow-powered .90-sized model). The added payload of 5lbs would reduce that, of course, thus the extra tank. Add a battery charger to the heli...it can provide more than enough power to keep its own batteries charged via a small brushless motor used as an alternator.

Your all-up cost is going to be between $2K and $3K for that kind of setup, I think.

05-24-2007, 04:37 PM
I'm ready for a bigger heli. I just want to ask anyone's advise which way to go - electric or one that uses gas.
I live in Chicago,windy city, and my problem is flying the heli outside. Since I bought my cx2 more than a month ago I've only flown it twice outside,pretty sad, although i really enjoyed flying it outside, so now i just want to go not for a real big one but one that can just handle the wind.
I'm not really a hobbyist:{ so an easy set up is what i would like and durable too that can take the crash.

thanks in advance...

05-24-2007, 09:12 PM
Bad news mkle66, helicopters dont take crashes like a CX.

What you want to do to is prevent crashes. (Keeps you more happy). you can give yourself a head start by geting a simulator. I like Realflight. Others will tell you get a free one or a cheep one or a good one. But any one will help you to a point where you are comfortable with all orientations of a heli, enough to prevent a few crashes.

Good choice with going slightly large for stability. the heavier the heli, the more stable it will be in the wind (Generaly).

Look around and make a choice based on parts and avalability. (Pick a Well known Manufacturer, this way you can almost guarentee parts to be available for a longer time)

And lastly. Practice,practice,Practice.

05-24-2007, 09:51 PM
Electric and glow are (roughly) comparable in performance and price up to .50-sized (600-sized, in electric helicopter terminology). Once you get up to .90-sized (700-sized), both get much more expensive. That's when gasoline engines become economically feasible, though more expensive than glow in the short term.

However, at $3 a gallon instead of $25+ for 30% nitro fuel, they pay for themselves quickly...

Anyway, whatever floats your boat. The T-Rex 600 comes in both an electric and nitro variety. Electric definitely has a lot going for it, and if you buy the recommended system from Align you will be pleased with the T-Rex 600E. Nitro also has a lot going for it, and you will be pleased with the 600N.

I stepped up from a CX to a T-Rex 450 (the 600's older, smaller brother). It's a fine heli, a little twitchy though. If I had it to do all over again, I'd have gotten something bigger (.30-.50 sized) rather than go with the 450 first.

The Hirobo Lepton is a nice 500-sized (.30-sized) electric helicopter. And, of course, the Thunder Tiger Raptor .30 is the most ubiquitous nitro-powered trainer helicopter in existence.

My suggestion? Go for one of the Thunder Tiger Raptor 50, Thunder Tiger Raptor e620, Align T-Rex 600N, or Align T-Rex 600E. These are a little bit larger than a .30-size, have substantially more lift and auto better, and have prices within reason (around $1000 for a decent setup). The electrics will cost you a bit more on the front side in the cost of battery packs, while the nitro-powered helis will cost you a bit more on the back side in fuel costs.

A gallon of nitro fuel costs $18. You get about 11 flights per gallon on a .50, with a flight time of 12-14 minutes. This is a cost of approximately $1.63 per flight, or approximately 14 cents per minute of flight.

Batteries for the T-Rex 600E cost about $250 apiece. You get one flight per pack and have to recharge, but the packs should last at least 200 cycles. So the cost of a battery is, at the most (barring a battery-destroying crash!) $1.25/flight, with flight times of about 6-7 minutes for a cost of about 20 cents per minute of flight.

Ultimately, economics won't make the decision for you. It boils down to what you want to fly, whether you mind wiping down your heli, whether you mind the risk of your battery investment being lost in a crash, whether you want a lower cost per flight or a lower cost per minute, whether you mind a starter, whether you mind the safety risks of LiPos, whether you are willing to risk buying cheap packs from China or if you insist on domestic products, etc.

Lots of things to weigh, good luck!