How to Make Homemade RC Helicopters
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Flying RC helicopter is really very exhilarating. Their versatility gives a RC pilot a complete access to the three-dimensional space in such a way that no other machines can! I have played RC helicopter for more than one year but still find that I have just learnt a few tricks that it can perform.
There are generally two micro-helicopters ( indoor ) in the RC market. I have already planned to buy one of them as they can fly inside the living room and even take off on ours hand. Unlike those operated by gas, these electric helicopters are very clean and give out no terrible noise at all. In one nightfall, I visited a web site, which is about how to make a hand made RC helicopter. I was totally impressed and started designing my own helicopter. Here is my helicopter:
The plan of the helicopter had finally been completed. It is not very well drew. The current plan available is only for the fixed pitch design. Please click the above photo for the plan.
The material that I use to make the main body of the helicopter would make you feel surprise. It is the circuit board ( after removing the copper layer ) that purchased from electronic shops. It is made of a kind of fiber which gives abnormal strength to it. (1)
Up to now, the basic structure of the helicopter is completed. The next step is to install the gear as well as the motor. You can take a look at the specification first. The gear I used is from Tamiya gear set that I bought long long time ago. I drill some hole on the gear in order to make it lighter and have a better look.. (3)
The skid set is made from balsa. They are very light and can be shaped easily. (6)
Swashplate is the most sophisticated part of a RC helicopter. It seems to be a simple unit of a factory one. However, it is a whole new thing of making one by yourself. Here is my design based on my own little knowledge about the swashplate. What you need includes:(7)
1 ball bearing ( 8*12)
1 plastic spacer (8*12)
rod end set ( for holding of the aluminum ball in the swashplate )
aluminum ball ( from ball linkage set 3*5.8 )
Make sure that the aluminum ball placed in the rod end can be moved freely. 2 holes were drilled on the plastic spacer in order to house two screws that used to hold the ball linkage.(8)
My instructions are too confusing? Here is my draft of the swashplate which might help you. I still find that my design is a little bit too complex. If you have a better design, please let me know!
For the rotor head, I choose the same material as the main body - the circuit board. First of all, I have to claim that the rotor head must be sturdy enough to withstand any vibration or it could be very dangerous.
The control system I used here is the Hiller system. In this simple control system, the cyclic controls are transmitted from the servos to the flybar only and the main blade cyclic pitch is controlled by the flybar tilt only.(12)
It is actually a 3mm collar which can be fit into the main shaft. A 1.6mm bar is inserted horizontally into the collar. The above unit makes the rotor head movable in one direction.(13)
As I mentioned before, the Hiller control system is used in my design. All the cyclic controls are transmitted to the flybar directly. (16)
The tail rotor consists of a motor, tail blades, tail shaft holding tube and a blade holder. The tail control is managed by changing the RPM of the tail motor. The drawback of this kind of control system is its sluggish response as the rotor pitch is fixed. However, it makes the whole design much more simpler and reduces a lot of weight.
In an ordinary R/C helicopter, the gyro work together with the tail servo. However, in this design, the gyro has to work together with the ESC (electronic speed controller). Will this work??? At the beginning, I try this with an ordinary gyro ( the large one for the gas helicopter). The result is really bad that the RPM of the tail rotor changes from time to time despite the helicopter is standing on the table. I buy a micro-gyro later which is specially designed for small electric helicopters and to my surprise this works great.(21)
The tail blade is made of balsa. They are covered with heat shrink tube in order to reduce the friction between the blade and the air.
The pitch and the weight of the two blades must be exactly the same. Tests must be performed to ensure that no vibration occur.(23)
Only two servos are used in my design. One is for the elevator and the other one is for aileron. In my design, the aileron servo is installed between the motor and the main shift holding tube. In this way, the tube has made use of the sturdy plastic case of the servo as one of its supporting medium.
The receiver I use is GWS R-4p 4 channel receiver. Originally, it is used with micro crystal. However, I can't find one which fit with my TX's band. So, I give my try to use the large one from my RX. It eventually works great and no problems have occurred up to now. As you can see in the above picture, it's really big when compared with the micro receiver. The receiver is only 3.8g ( extremely light weight ) which is very suitable for indoor helicopter.
#Although the receiver has only four channels, it can be modified to a five channel RX. (25)
Here you can see the speed controller that is used in my helicopter. It is placed at the bottom of the gyro (see the photo below). Woo!! Really small size with only 0.7g. It is a JMP-7 Esc that I bought from eheli. I really can't buy one from local hobby shops here in Hong Kong. Also, this tiny Esc works great with the gyro. I just simply connect the signal output of the gyro to the signal input of the Esc. (26)
This perfect micro-gyro is made by GWS. It is temporarily the lightest gyro that I can find in the world. Unlike the previous GWS gyro that I used in my gas helicopter, it is very stable and the center point is very accurate. If you plan to buy a micro gyro, it would certainly be a good choice for you! (27)
The motors in the above photo are 5v DC motor, micro DC 4.5-0.6, and micro DC 1.3-0.02 ( from left to right ) In my first attempt, the micro4.6-0.6 is used. The motor burns out quickly ( or I should say that the plastic component in the motor melts) as the power demand of the tail rotor is much larger than that I expected. At the moment, the 5v motor is being used in my helicopter which is still in very good condition.
The current tail motor is a 16g GWS motor which provide much more power. For more information, please go to the page "flybarless CP modification II" (28)
The first photo shown above is a Jeti 050 5A brushed electronic speed controller. It was used to control the speed 300 motor in my helicopter before. As the speed 300 motor is now replaced by a CD-Rom brushless motor, the Jeti 050 had been replaced by a Castle Creation Phoenix 10 brushless ESC. (29)
The following diagram shows how the components are connected to each other. The connections at the receiver is not in order. The GWS R-4p is originally a 4-channel Rx. It is modified in order to provide an extra channel for the pitch servo.
A computerized Tx is needed as the the tail control must be mixed with the throttle control. For a Piccolo micro helicopter, this task is performed by the Piccoboard. For my design, this is done by the function "Revo-Mixing" in the Tx.(30)
If any difficulties found please contact me firstname.lastname@example.org