RC India

Hi there,

I recently developed this hobbey of RC helis and wanted to build one. I am a software architect with no knowledge of electronics and mechanics :). However I started making one heli by taking parts from a remote car. I ripped apart the rc car and used its motors for making my own heli. while the model is ready now, I see a lot of vibration and heli just rotates on the ground without taking off. I have not yet fixed the tail rotor yet. The problem I think may be:
1. The main rotor blade is connected with the main motor with the help of one gear. The shaft is not wrapped with any tube and bearing might be causing the vibration.
2. Blades might be too heavy or may have wrong orientation, of center of gravity. I need help to understand what size and orientation of blades to be used. These are home made blades using a stiff fibre. What should be the angle of the blade and size?
3. What is the functionality of the tail rotor?

Since I am using all parts from a toy car, the ecs allows only clockwise and anticlockwise motion, without a proper acceleration control, I mean no speed control.

Can you please help me on this? I am attaching the pictures of my heli here..

Thanks,
Ashish

Gotta appreciate you for attempting to start your hobby with a DIY :thumbsup:

I suggest you first try to understand the basic technical mechanism of a helicopter, how it flies and such. Read about it.

To answer your questions,
1. It doesn't matter how many gears are used, even a single stage reduction, with just one gear should work fine as long as the power is transmitted as required. The shaft does require some sort of bearing for axial support in order to reduce vibrations, a torque tube of proper diameter should work fine too.

2.The basic parameters of the blades like size, weight and pitch (angle of blades, as you refer to it) are dependent on the amount of thrust required and the load capacity of the motor. There is no easy, straightforward method for you to determining these parameters. Trial & error is one usual way of going about it. The motor should be capable of spinning the blades fast enough to produce minimum hover thrust without heating much or burning up.

3. When the main motor spins the main rotor, torque is generated which tends to spin the heli in the opposite direction to that of the blades. The tail rotor is used to prevent this by counteracting the torque. It's also called an Anti-torque rotor. This is not all, Google about the function of tail rotors to know more.

Good luck  :thumbsup:

Yes your effort is really appreciable .
Totally agreed with Anjan . I think blades seems to be quite heavy . Plus They are totally Flat , you will need To give some angle . By flat I mean You need to work on AIRFOIL too. Airfoil or rotor blades , is the structure that makes flight possible. Its shape produces lift to fly. Helicopter blades have airfoil sections for different flying characteristics . You will need to choose the best airfoil for your heli flying type . I don't know much about that in deep but Wait for Senior members help.
On the tail rotor - Normally they are linked to main rotor via drive shafts and gears . Most helicopter have a ratio of 3:1 to 6:1 . That is, if main rotor turn one rotation , the tail rotor will turn 3 revolutions (for 3:1) or 6

Also what's your plan for Cyclic Controls ?

Does the tail rotor blades also scale down by the same ratio? My understanding suggests tail blade size would be critical too along with RPM.

Well that's a very good point . I think It's not the same way the ratio . Experts might have calculated through overall weight and power ratio of heli.

Yes, I realized it now ;D
I think it can do away with an ideal blade size and then change the tail rotor pitch for fine torque control. I'm not really sure, though.

Yeah Anjan that will save lots of time while tuning  :thumbsup:

On the first looks, 
That motor looks like the normal motor used on most toy remote cars, which use 3-4 AA size batteries. The current rating of these motors are very low of the order of few mili amps . This would give very little torque. But looking at the size of the heli its not sufficient even if you are able to get the blades corrected.

Hi friends,

Thank you for all your prompt responses. Its definitely going to help. The first thing I wanted to see was to see the model lifting from the air that would have given me lots of energy to study and move forward. My basic principle was to make a helicopter at a cheaper price out of old household items and present it to in nearby orphanage which will give them motivation for creativity.

However, with all the responses, I see that I am using a wrong motor to give it enough thrust to lift in the air. I have read that some motors are very powerful and meant for RC helis, but the limitation here with me is that I want to use the remote control and the ecs board that came with the toy which will save my lots of effort of buying and building ecs. But this board works on 3.6 volts Ni batteries which came along with the toy car.
If I use any other motor I will have to supply higher volts which will blow up the ecs board (sorry for my non-technical terms, as I am still learning these terms).

If somehow I get to lift this object with the same motor I shall get some motivation to go ahead. I have worked on the new blades today, I will try to take some time out tomorrow and fix it with the main shaft. I have also worked on a tube to give support to the main shaft to reduce the vibration.

I will keep you all updated.

Here is some help from my side... I Was Also a failure in making a diy heli few years back.. Almost Completed the project with more perfection still i was not able to lift that up..
I stopped working on it due to time restrictions..
Now What you want to consider is make it light yet strong...
Using mseal in landing gear will make it heavy and weak too..
Use some time to make a plan.. Do it carefully and you will succedd..
Attaching some picture of a diy heli progress... Certainly not mine..  :giggle:

more

Thanks arun.sreelakam, can you please let me know the motor that you used.

It looks like a coreless micro DC motor.

first_flyer, I don't mean to discourage you, but your attempt to build a heli, especially a micro heli, from toy car parts sounds like a blind shot not worth spending time over if you are seriously looking to build something that can fly. It would be naive of me to say it's impossible, you can always tweak with the same if you're trying to explore the possibilities, you just might get it flying, you never know. :o
Attempting to build any micro scale flying machine requires weight and power considerations at very critical tolerances, a few less milligrams and a few extra milliwatts can make considerable differences. All this calls for choosing parts and materials that are as light as possible and at the same time, powerful enough to make flight happen.
The best thing I think you can do at this stage is, get one of those cheap micro helis and try to understand at first hand, what goes where, why it's there and what it does. Also, you may try and reverse engineer it too.
I guess, you can grab one of those for 700/- at Big Bazaar, maybe cheaper at 400-500/- in the National Market area or source a used one on this forum.

If you want, I can get you a broken one for free, structurally okay, electronics fried, battery and IR remote are missing. You can use it to understand the mechanism and maybe salvage some parts from it. PM me if you need it.

Good luck. :thumbsup:

 

Hi Anjanbabu,

Thanks for your message. It is really not discouraging, but I think thats the right direction to go. By the way I have improved on the body now the whole body weight is only 90 gms. and I have also improved on the blades. Look at this video and let me know if there is any hope with this model without changing the motors. Its sure jumping and trying to lift itself. May be when I shot the video the battery was not fully charged and there wasnt enough power, as well as there is still no tail rotor to stop it moving anti-clockwise.



http://youtu.be/z6Pyc40Otvc
 (http://youtu.be/z6Pyc40Otvc)







 

Hello Everybody i am begineer and searched the post for making a first heli (Diy) . So i found this thread actually i just have a micro heli
so i want to buy a rc plane and want to make my first big rc heli in budget . :help: .
No problem For plane But i need help making my first Rc heli So please help me out for the parts as i am a first timer want to do in a good budget.
I have problems in parts so what do we need in making one rc heli :-
1.body
2.motors,blades,rotors,wires.
3. Transmitter and reciever
I know this much only so please help me out with rest of the parts .
 Little confused ???

I don't suggest to DIY a Heli (U will understand why hehe). Better get a kit and put decent electronics in it .
Even if you Make a heli , it will be very hard to make it fly in a perfect manner .

Thanks for the advice i will see what can i do i have to search good combo . So lets see what happens .but thanks for the advice.

First_flyer which battery are you using ?

I am using NI-cd 3.6 volts battery

First_Flyer, I agree to what Anjan has to say, building a DIY for heli needs quite a bit of calculations and controling/tweaking the different parts that are used. Its definitly possible, but as you said, unless you taste that first flight, the motivation is generally not there to carry forward.

I started with a Heli roughly 1.5yrs back, the real motivation came only once i was able to take off my model and the fear to crash a 15k model was enough for me to get on to SIM and take on the challenge.

So my advice would be to keep this model at this stage, take up a SIM and buy a micro FP (or a CP if you really want to hit the road with fire in your belly) and become comfortable with flight and its basic principals. You will crash your heli, the repairs will make you understand a lot of insights of how the models are setup properly and over the course of times once you have enough information, you may re-visit this little project.

Just my 2 cents.