View Full Version : RC Helicopter

04-30-2006, 03:42 PM
Hi Guys,

I was trying to make a RC helicopter but found that that what ever I do the rotor doesn't produce enough lift.

Has anyone tried this project.


04-30-2006, 04:07 PM
aerodynamic modelling requires a lot of expertise.. cant waste time on modelling.. so I bought an RC chopper off bazee and played with it ..


04-30-2006, 05:51 PM
me 2 :) ... bought one cant waste time on what im interested in .

04-30-2006, 09:57 PM
1. :lol: :lol: :lol: guys :!: :!:

2. What motor? What rotor?
3. Total weight of it all?

If none of above known, then replies 2,3;
else write, post pic;

05-02-2006, 10:09 AM

As Rao said it is really difficult to make helicopter as it requires lot of expertise in airodynamic field.

Motor I am using is from the CD rom drive but think it is heavy for the lift the rotor is producing.
Somehow I feel that the rotors I made are not in the airfoil shape and is producing the forces in opposite direction. But I don't have anyting to test my assumption. I tried using smoke to see how air is flowing but got a mixed observation.

I am gonna spend some more time on this. Will let u people know if I get some positive output.


05-02-2006, 11:14 AM
Hi kiran,
You need at least 5A in the CD motor and must be geared for abt 800- 1500 Rpm. Try 2 to 5 degree pitch of the rotor.
quite easy to make rotor blade, if you have patience.

It is the Rotor that develops Lift contrary to what people generally think.
Produce an aerofoil with Flat bottom, 25% chord and tilt about 5 degrees.
Chord is the thickest part. the leading edge (front) should be blunt and the Trailing edge should be sharp. The width should be 30% less at the edge.

05-02-2006, 11:54 AM
Hi Docel,

I have made the rotor blades using a light weight material used for making name plates. I tried to give the shape of airfoil as u mentioned but I am not sure about the accuracy.

Rotor dia : 12 cm. (2 baldes)
I have made the blades using a same strip, rather than making 2 different blades, and have drilled it in the middle to mount it over the motor. I am not using any gears.

The rotor motion is prducing a spin but isn't producing a lift. For this I extended the body using a scale. After using a scale the spin is reduced but there should have been some lift at least.

Is there any problem in the way rotor blade are made ? I have gone through Bernoulli theorem and thought that just by making the upper portion of wing thicker will generate the lift. I don't know where I am going wrong.

Anyhow I will try to make the blades using the measurements you have provided.

Can I get some more information on blades and motor to use for making a heli with body of size 3 match boxex (one over the other) and body length equal to 15 cms (a small plastic scale).


05-02-2006, 12:03 PM
Hey, thats too heavy :!:
The CD rom motor cant handle it. To be funny, the rotor should CUT your finger while it is turning :lol: That is when it will generate any useful lift.

A rubber band motor is the strongest you can make for flying, with the minimum weight.

Im in a hurry: will post a blade diag. in the afternoon.

05-02-2006, 12:11 PM
[quote="docel"]Hey, thats too heavy :!:
To be funny, the rotor should CUT your finger while it is turning :lol: That is when it will generate any useful lift.

It did not cut my finger. he he.

By the way what are the specification for motor and RPM required to generate such a lift. Say just to lift the motor and rotors. Is there some equation which equates weight with the rpm ?


05-02-2006, 11:28 PM
Hello Kiran,
Maybe you can checkout this link for help:
As far as I have seen, electric-helis use motors with rpm in excess of 20K to 25K and geared down appropriately.
If possible, try using ready-made prop blades available for electric rc planes. If you dream of bulding a 1 rotor (plus the tail rotor) heli, then best luck in your efforts, you are on your own. 4 rotor heli should not be a big problem though.
Mohit Bhoite

05-02-2006, 11:50 PM
cool link.. thanks mohit.. maybe I will try this out.

05-03-2006, 01:02 AM
Cool but quite exppensive :)

05-03-2006, 08:54 AM
Thanks for the link Mohit.

At present my Idea is not to make a well balanced RC craft, but to limit the flight to just an initial lift. This is just to identify various parameters and (Though if we search in google we will get that info) and their minimum values to lift the craft.

Will keep u people updated on this.


05-05-2006, 06:43 PM

Well I am an aeromodeller, although I am into Airplanes and not into Helis' but I can tell you, that for a heli to lift needs a lot of thrust, and so a cd rom motor cant do it! You can try a brushless motor. With Electric Heli Rotors! and if you keep your heli small and light may be you get the Initial lift!


05-06-2006, 06:56 PM
Hai evryone......

I am not an expert in this field. but, i have some experiance with wind turbine blades. I think the rotor have many similarities with a wind turbine in working.

By the way what are the specification for motor and RPM required to generate such a lift. Say just to lift the motor and rotors. Is there some equation which equates weight with the rpm ?


I tried to derive the equation of lift from basics , and i did it.The derivation is straight forward and simple.

Lift = CL.(rho/2).A.V2. for an aerofoil immerced in a flow of velocity V

where, CL is lift coeff, rho is air dencity,C is blade width.

In the blade V is changing from zero to (pi.D.N)/60.(From r=0 to r=R)

I integrate that with A =c.dr. and got...

Lift = (CL.rho.C.pi2.N2.R3)/5400 per blade....

It is pi square ,N square and R cubed :P .

But the problem is,

If radius =8 cm , width = 2 cm , lift coeff =1.2 and air dencity=1.17kg/m3

Then i get the motor rpm to be 6000 (!!!!!!!!!!!!!!)to generate a lift of 2N. ie 200gms, :oops:

Somebody pls tell me what is the problem ??????

And Kiran, dont get confused . I am sure u can make a rotor without these eqns. I think docel have a complete design. Better u make a rotor with that specifications.



05-06-2006, 09:48 PM
Hi Jabir,

Thanks for getting some numbers, otherwise planning for various components was becoming difficult for me.

After going through few sites on net I too found that the RPM should be around 2000-3000 for the main rotor blade. Anyhow I am trying to get some high speed motors (10000 rpm [Can I get from some where ?]).I will reduce the speed to appropriate level using gears.
(And as said earlier by sawan and Docel said CD rom motor is not going to work even for initial lift).

Few vendors near my house have agreed to make customized gears and rotor blades, so I am hoping that my model wll just up few mm atleast :)

Thanks & regards,

05-10-2006, 08:24 AM
Hi guys1
Sorry kiran: was off location frm 2nd may...getting fried at 45Deg. C @Chincholi/Shiroor.

Now, this Helicopter business is very tricky, not to mention expensive, difficult and very time consuming. I need to know a couple of things first.
1. This may be out-of-context with Robotics. Dont want the Admins irritated.
2. Are you REALLY SERIOUS :?: :?: Dont want to waste MY time on some impulsive/ temporary interests and end up talking to myself.. :lol:
3. Forget your 'local vendors' None of them can help :!:

:arrow: Promise me and the Forum that you will -
1. Be Serious
2. Complete what you started
3. Share what you do with everyone on this forum
4. Not abruptly elope with some other dame-of-interest... :wink:

Do you accept :?:

05-10-2006, 10:09 AM
Hi Docel,

Thanks for replying. Come down to bangalore as the temperature has gone down a bit with few spells of rain.

Docel, I am quite serious on this project. Rather than spending 5000/- on RC heli from ebay, I am spending couple of thousands on motors and gear boxes to get initial lift. I know this sounds crazy but I think it is acheivable.

I hope the above statement makes me eligible for the whatever points you mentioned in your earlier mail.

I agree that hobbiest (including me) usually take up with new ideas and new interests, but this heli, crafts, flight, interacting robo and AI are little above hobby list and no matter what happens I am going ahead with these.

Docel, I hope this one is not required .. 'Mein Gita pe haath rakh ke kasam khata hoon ....... ' :D just kidding.

Anyhow will keep you people updated on the progress...

Thanks Regards,

05-10-2006, 12:53 PM
Well, you sure did!!
Now I'll have to work over time.... :cry:

But ...This is my favourite subject. i dont have access to my notes and hard drive. But i'm preparing a small jig with what i can find here. Will post as soon as i get the CAM pics by evening.
Meanwhile, find a broken quartz clock or a CDROM drive and pull out all the gears. Keep them carefully. Find a new bamboo basket. Better still , go to BIT college. Opposite you'll find bamboo artisans. Get the thinnest and widest bamboo slice (.8 to 1mm X 25mm x 100mm). Eat some Ice cream and collect the sticks.
and wait... :)

05-11-2006, 10:15 AM
Hi Docel,

Can you give me a list of materials required for the RC Heli. I will collect all of them in a single shot. My Office closes by 6.00 so in the evening it is not possible, I will get these materials on coming saturday.


05-12-2006, 03:36 AM
Hello KIRAN,

Check this link...


I think it will help u...


05-12-2006, 09:29 AM
Nice Link.

Thanks Jabir..

05-12-2006, 02:33 PM
REally nice link :)

05-13-2006, 03:26 PM
Hi Docel,

I got the necessary material.
Termacol sheet, bamboo slices and old cd-rom drive.


05-15-2006, 08:58 PM
Hi Docel,

was waiting for your reply. Just wanted to see how are the airofoil blades that you had made and had promised to post the pic of the same.

Thanks & regards,

05-31-2006, 05:25 PM
Hi kiran.

Any improvements ????

Please share with us....



06-01-2006, 03:24 PM
Hi Jabir,

Thanks fr enquiring.

Ya little.. I was co-ordinating with southafrican company for miniature motors. I have recv the catalogue fr that. I found another shop in chikpet, bangalore who are making similar motors. Next week I am going to concentrate on heli body ( for supporting motors )..

By next week I should get some results.

No response from Docel, I think he is busy now a days.

Will keep u people updated..


06-12-2006, 10:45 AM
Hi Guys,

I have started my work on Heli. As of now I have made the body of the heli and fixed the motor. The rotor blades are yet to be made.

I am facing difficulty in geared assembly.
I managed to assemble the gear but found that it get jammed on the run.
I may need to use bearings to keep the gear motion smooth.

Facing difficulty in getting RF modules.
I don't know much in this, but can someoen guide from where I can get these. ( Toy car is one option ).

Thanks & regards

06-16-2006, 06:20 PM
Hi kiran,

I have some questions........

What is the specs and rpm of the motor?
What is the total weight with the batteries?
What is the transmission ratio?
And, what is the problem with the gear train?

As I already said I have no experience with this thing. So I made a detailed "research" for the last two days for designing a rotor. My conclusions are attached. Sorry for the poor quality of pics. Don’t get confused with the math. This is only pure theory. I don’t know what will happen in practice. :oops: :oops:

U can use either a bended sheet type blade (eg: blades of a ceiling fan) or an airfoil cross-section(like wings of an aircraft) blade. The later will be heavy and difficult to fabricate. But, unfortunately I don’t know more about the selection of the cross section. I suggest airfoil cross section.

Try to make a blade with radius and width an in my design and try different setting angles, I am sure u can make one.




06-17-2006, 02:52 PM
Hi Jabir,

Thanks for getting the mathematical formula. I will write it down.. I too have also searched net for the mathematical formula. I have it in the office. So will post it next week.

Thanks again for the formula.

Motor specs : 5000 rpm/Volt [No load rpm]
Gear ratio : not yet planned but around 10:1
Weight ~ 250-300 gms.


06-18-2006, 07:51 AM
Hello Kiran/ Jabir!!
Good work on the derivations jabir. While most of it looks ok you must remember these:

1. The SIZE of the system vastly affects the drawn formulae, basically due to unknown tolerances and measurement erors.
The size for Kiran's heli is between 8" to 10" dia. I have decided this as anything bigger is not advisable of a begginer.

2. Since the size is decided, materials are limited to Very Light, Strong, Flexible and rigid (?) :; the entire blade system should be within 10gms. After adding Tip weight for Gyro action, it should be abot 20 gms max.

3. This will necessitate a Power of 20 to 30 watts.
The Power is a funny factor as it increases with the overall weight of th e system.
Consider the blade @20gms. The 'dynamic' weight of the blade while rotating increases due to centrifugal force. This force will offset or reduce the gravitational weight component ( force distribution). When lift is generated by the blade, it means that the blades have to support the system weight plus the centrifugal force due to rotation. You can calculate the tangential force of the blade.
The heli 'hangs " by the blades.
Now , the total weight will be the Rotors, Hub, Shaft, Body, Motor, Gears and Battery. Any small change will affect the system. In a heli, all this must be balanced perfectly Symmetrically. Any offset will set the entire system into beat-frequency vibrations which are totally unpredictable and dangerous. A 10gm blade travelling at 3000RPM and suddenly released has some great penetrative powers, believe me!
Hence Kirans search for a wireless remote!!!

4. All the above rules out metal. The measurements in mm leads to micron tolerances for any accuracy. Hence, designing the rotor using formulae is not possible for miniatures, unless supported by accurate Laboratory measurements. eg; a tip weight difference of 1% between blades will tear the rotors and or the heli to pieces in no time. 1% of 20gms / 2 blades is.......?? You will need a jewellers Scale to measure this!!
And the flying pieces can damage you quite a bit too.
Remember: a rotating body is a force multiplier and builds up tremendous amounts of potential energy.
( incomplete...maybe after breakfast)
Kiran is coming home to-day for discussion. Wish you were here too jabir!

06-19-2006, 05:48 AM
HEREs an excellent link:

06-20-2006, 01:44 AM
Off topic, maybe. but check these links!


06-20-2006, 08:36 PM

06-29-2006, 01:53 AM
Kiran, Your pics are posted :


Some good work done there! Too bad you broke a blade :cry:

06-29-2006, 11:58 AM
Thanks Doc,

I will buy few more bamboo strips.. Will make another set of rotor-blades by weekend.
BTW where can I get good thermacol, one with smaller granules thats used for packing toys and electronic items like TV/Computer etc.

06-29-2006, 06:19 PM
Thanks Doc,
where can I get good thermacol, one with smaller granules thats used for packing toys and electronic items like TV/Computer etc.

...Inside the same boxes and packs... :D

06-29-2006, 06:56 PM
Hello kiran....

I just saw the pics. U are doing great yaar!!!!! :lol: :lol: :lol: :lol:
Also congrajulations!!!!!!!!!!!! YOU GOT THE PERFECT GUIDE!!!!!!!!!!!

Did u got the necessary lift ? And what is that coating over the bamboo strips?
Is it a NACA airfoil ? Dimensions and weight ?.
Also what is the motor power?
Sorry for the errors in my design. I diid it myself man. So i am not sure it is error free. :oops: So if u have a good design got from the net please post it if u have time


06-30-2006, 04:56 AM
http://img403.imageshack.us/img403/6140/sinitialeffort3sa.th.jpg (http://img403.imageshack.us/my.php?image=sinitialeffort3sa.jpg)http://img20.imageshack.us/img20/4465/bladeperspective4yl.th.jpg (http://img20.imageshack.us/my.php?image=bladeperspective4yl.jpg)http://img403.imageshack.us/img403/1425/initialeffort28mf.th.jpg (http://img403.imageshack.us/my.php?image=initialeffort28mf.jpg)


Photos and Efforts of KIRAN PARASA

06-30-2006, 02:20 PM
Thanks Docel,

Jabir, The blades I have made are for trial. I was trying to get a hang of it. I am gonna make a new set... Will tell u then..

haven't yet tried to put the blades on the motor. For that I need to work on gear system, Thats next stage. Right Doc ?

BTW motor specs are :
Johnson Electric Turbo 400 Motor
-Rpm(Kv): Approx 1200 Rpm/V
-Max Current: 6 - 9A
-Max Eff: 95%
-Recommended Rotor Blade: 5 X 4 Prop ( & above, depending on your plane design and requirements )
-Total Length: 38mm (Motor only)
-Motor Body Diameter: 26mm
-Shaft Diameter: 2mm
-Shaft Length: 6mm
-Recommended Input Voltage: 6 - 12 Volt


06-30-2006, 08:24 PM
Hai docel/kiran...

Thanks for the motor info. :D

I got a software for heli calculations. It is Interesting and also confusing!!!!!!!!!! :roll: :roll:


Kiran, if u are using a NACA airfoil, use this software to estimate the cross-section....Try 2412 or 2414...


BTW what is the cost of the motor?


07-17-2006, 05:44 PM
Hi Docel/Jabir,

Just to update everyone on the progress on the heli rotors..

Following are some pictures ...

Bamboo strips carved to get rotor shape :-)
<img>http://img145.imageshack.us/my.php?image=image123fr0.jpg </img>

Top view

Perspective .

Parasa Kiran

07-17-2006, 08:03 PM
Hi ,
I have updated the new files here as well as on http://ph.groups.yahoo.com/group/bangalorerobotics/photos/browse/94e1

Kiran's Rotors Act 2

http://img145.imageshack.us/img145/9495/image123fr0.th.jpg (http://img145.imageshack.us/my.php?image=image123fr0.jpg)

http://img115.imageshack.us/img115/6626/image124kp3.th.jpg (http://img115.imageshack.us/my.php?image=image124kp3.jpg)

http://img106.imageshack.us/img106/1306/image127lk8.th.jpg (http://img106.imageshack.us/my.php?image=image127lk8.jpg)

http://img145.imageshack.us/img145/602/image128ws5.th.jpg (http://img145.imageshack.us/my.php?image=image128ws5.jpg)[/u]

08-02-2006, 11:14 PM
Hai kiran.

Great work , man.
Did u tested it ? Please, I cant wait any more!!


08-03-2006, 01:13 AM
Hi jabir!
Why not attempt it too.....The more the merrier!!

08-03-2006, 09:54 AM
Thanks Jabir.
Doc’s guidance and tricks helped me in getting the rotors in proper shape.

I think still lot of work is pending, right Doc ?

08-25-2007, 03:42 AM
Mr. jabir

I am very much interested to see the images plz fix the broken links..

know my present work status and help...