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i want to know how rc helicopters work

Old 08-17-2006, 04:23 AM
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socal swimmer
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Default i want to know how rc helicopters work

so basically i dont know how rc helicopters work. at all. i understand planes, like how they fly and how the surfaces cause the effects that they do, but not helis. like how does a heli put its nose down? how do they change the pitch of the blades? how do they get 2 sets of blades on the same shaft to rotate in opposite directions?

and by the way, i understand torque. that the second smaller blade on teh tail is to counteract it.

even if all i get is a link to a good sight, ill be more than happy. in fact i would love links to sights that explain it.
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Old 08-17-2006, 05:53 AM
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http://travel.howstuffworks.com/helicopter.htm
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Old 08-17-2006, 06:27 AM
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when there are two rotors on the same shaft, how do they get the second one to rotate in an opposite direction?

that was great, exactly what i needed!

and how many channels are generally needed to control a heli? that is, assuming you dont have bombs or other fancy stuff on there.
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Old 08-17-2006, 07:55 AM
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Counter rotating rotors would have 1 shaft inside the other, one spins 1 direction, the other spins opposite..
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Old 08-17-2006, 06:39 PM
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what about fixed pitch? does the whole plane (in the geometric sense) of rotation of the rotor shift a few degrees to one way?

Last edited by socal swimmer; 08-18-2006 at 05:16 AM.
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Old 08-26-2006, 05:37 AM
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Hi,

I thought the pitch was how much the blades dug into the air? I always thought that fixed-pitch choppers couldn't control the dig, but everything else was the same?

Correct me if I'm wrong, but I think that's how they work.

-- Zan
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Old 08-26-2006, 02:54 PM
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Originally Posted by socal swimmer View Post
so basically i dont know how rc helicopters work. at all. i understand planes, like how they fly and how the surfaces cause the effects that they do, but not helis. like how does a heli put its nose down? how do they change the pitch of the blades? how do they get 2 sets of blades on the same shaft to rotate in opposite directions?

and by the way, i understand torque. that the second smaller blade on teh tail is to counteract it.

even if all i get is a link to a good sight, ill be more than happy. in fact i would love links to sights that explain it.
hi heres an explanation of how helis work
A conventional RC helicopter generates lift by means of rapidly spinning large moving rotor blades. The blades are shaped as airfoils. The angle of attack on each blade is increased and decreased via linkages that are connected to a swashplate. The swashplate serves several functions using anywhere from 3 to 5 servos to control it. Essentially the top plane of the swashplate will determine the attitude of the rotor disks when the blades are spinning. To generate lift to raise the helicopter, collective is added. Collective will raise the swashplate along the main rotor shaft increasing the blades angle of attack until the heli eventually lifts from the ground. When in flight the throttle and collective are usually tied together to control the altitude. The collective and throttle are mixed together on most helicopters either by a mechanical linkage or a program mix on the transmitter and is controlled by the throttle stick.
The cyclic controls are what controls pitch (forward and backwards movement) and roll (side to side movement). Pitch is controlled by the elevator stick on the transmitter and roll is controlled by the aileron stick. Once the heli is in flight the servos will control the pitch of of the swashplate. When it tilts forward, the rotor disk (blades) tilt forward causing a forward motion of the heli. When the swashplate is tilted to the left or right it causes the heli to move in the corresponding direction. To slow the forward speed of the heli down or to flair for a landing, the swashplate tilts backwards .
The yaw of the heli is controlled by the tail rotor. The tail rotor is usually connected to the main motor via a shaft or belt. It's purpose is to counteract the torque from the main rotor blades keeping the nose of the heli pointing straight ahead. It is also used for pirouette maneuvers and for steering the heli in flight. The tail rotor is always spinning in the same direction and the thrust is varied or even reversed by a servo that adjusts the blade pitch. This is controlled by the rudder stick on the transmitter.
Most, if not all, RC helicopters use some sort of gyro to help the tail rotor over come the torque reaction from the main rotor blades. The gyro detects sudden movements in yaw and will tell the rudder servo to apply a blade pitch change in the opposite direction to keep the nose pointing in one direction. Some more advanced gyros contain a "Heading Hold" function. When activated the heading hold feature will keep the nose pointed at the last position inputted from the pilot. This feature makes it much easier to learn how to hover as it basically lets the pilot concentrate on Roll, Pitch and collective inputs. It is also heavily used when performing advanced aerobatics with a heli. hope that helps. clear skies and good flying
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Old 08-28-2006, 08:17 PM
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ok i understand all of that, but how do helis with fixed pitch rotors tilt forward, or backward, or side to side?
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Old 08-28-2006, 09:16 PM
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The "pitch" of a helicopter is the angle at which the blades are set. On a collective pitche chopper, when you increase the pitch, the angle of the blades change - they may cut into the air more, or less. This allows a powerful motor to do more work. It's sort of like changing gears on a bicycle, in a way.

Just 'cause the pitch it set doesn't mean that it wouldn't be able to move around. I believe you can still tilt the blades for steering. You'd also be able to control the tail on a fixed pitch heli, for steering. How do they tilt? Well, on my heli, there is a little box with small motors on it that pull or push the different sides of the blades, near the main shaft.

Have fun,

-- Zan
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Old 08-28-2006, 09:45 PM
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ok i thought about it a little more

the whole rotor would tilt. im not sure if the heli itself would, but the rotors would.

thanks for all the help. my question is answered and i believe that i understand helis now. yay! thank you!
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Old 01-10-2011, 10:05 PM
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I dont understand how the escs work the rotors? can anyone tell me please?

Heres what I have..

main rotor motor, seperate tail motor (honey bee cp3)

futaba tx and rx

what do i need to get these motors to work? and get the heli to fly?

Im guessing 2 esc's? then maybe mix with tx

Im stuck

mite just stick with my planes..lol ..if anyone can help id be very gratefull indeedy

cheers
Steve
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Old 01-10-2011, 10:07 PM
  #12  
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note.. it did have a 3 in 1 that fried.. linked to the original esky tx. which is broken too.

would like to get it all working with my futaba t7
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Old 01-10-2011, 11:29 PM
  #13  
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You are a bit confused on the meaning of fixed pitch. The pitch of the blades in a fixed pitch helicopter does not change insofar as to create more or less lift overall. IE if you measured one blade to be at an angle of say, 30* to the opposing blade, this will always remain so. However, the blades, while fixed to eachother, can still pivot on the shaft. This means swashplate imputs cause more lift on one side of the rotor disk, and less on the other. Thus allowing for cyclic control. The rotor disk itself, does not change its angle in relation to the helicopter.
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Old 01-12-2011, 03:29 AM
  #14  
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I'll simplify that a bit. both fixed pitch and collective utilize a swash plate for control of the main rotor system. on fixed pitch the lift is controlled by varying the motor speed, while a collective system maintains a specific motor rpm and moves the swash plate up/down to vary lift.

fixed pitch only needs 4 channels to operate while collective needs a minimum of 5 but most are 6 or 7. and the newer system incorporate a CPPM system that mixes cyclic and collective control through 3 servos.
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Old 01-13-2011, 01:21 AM
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Originally Posted by HOODY View Post
I dont understand how the escs work the rotors? can anyone tell me please?

Heres what I have..

main rotor motor, seperate tail motor (honey bee cp3)

futaba tx and rx

what do i need to get these motors to work? and get the heli to fly?

Im guessing 2 esc's? then maybe mix with tx

Im stuck

mite just stick with my planes..lol ..if anyone can help id be very gratefull indeedy

cheers
Steve

The honey bee CP3 comes with a built in X in 1 box that has built in mixes that will accommodate for the power split from the main to the rear tail motor. If you want to do this yourself because you wish to bypass the factory ESC or because you don't have a factory ESC. You need to enable a feature on your radio called "Revo mixing" or revolution mixing.

If this is not available you can often achieve the same thing with Custom Mix.

What you want to do is mix a % of the throttle channel to the rudder channel. Idealy what will happen is that for X power sent to the main motor kX (where k is some constant) power is sent to the tail motor.

Without a gyro your heli will still spin however in motor heli's getting the tail to stay put is a delicate balance between getting close enough with the motor tail mix and then letting the gyro correct the last tiny bit of impulse movement.

Now as for what this curve should look like or % values that might work unfortunately the manufacturer's have not released their stock values that are found in the X in 1 boxes so it's a mystery. Many people have managed to get motor tailed heli's to work with brushless motors so with mixing and a independent gyro this is possible. Keep in mind heading hold gyros work differently you do not want to add mix on a heading hold gyro unless it's the stock eflite / esky those may need some drift compensation.

Lastly there are many X in 1 to ESC signal convertors that will take the motor pulses designed for a brushed motor and output an ESC signal these are useful if you want to quickly get up an running in an brushless tail. So there you have it.

Motor'ed heli's in general aren't easy to adapt you can't simply just stick on any old ESC and expect it to work. The tail is usually brushed and you need convertors if you wish to go brushless.
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Old 01-13-2011, 01:30 AM
  #16  
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Originally Posted by jmann71 View Post
I'll simplify that a bit. both fixed pitch and collective utilize a swash plate for control of the main rotor system. on fixed pitch the lift is controlled by varying the motor speed, while a collective system maintains a specific motor rpm and moves the swash plate up/down to vary lift.
This is true but most heli's we fly don't have the luxury of nice governors so the RPM does in fact move around during the pitch range. The theory is sound however collective pitch heli's get their lift by changing the angle of attack in the blades and the fix pitch helis gain more lift by spinning the rotors faster.

fixed pitch only needs 4 channels to operate while collective needs a minimum of 5 but most are 6 or 7. and the newer system incorporate a CPPM system that mixes cyclic and collective control through 3 servos.
For those that are wondering the first 4 channels are:
(the numbers are manufacturer dependent)

(Almost all heli's are CCPM so a combination of servos are used for each movement the channels in this case represent "axis of freedom")

1: Pitch -- This controls the nose up nose down movement
2: Roll -- Controls the left and right tilt of the heli
3: Throttle -- Controls the amount of power the main motor delivers
4: Yaw / Rudder -- Controls tail rotation about the Z axis
5: Collective -- Controls the angle of the blades.

In general Channel 6: Gyro Gain: controls the gain of the tail stabaliziation

Channel 7: Retracts / accessories
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Old 01-14-2011, 09:14 PM
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Originally Posted by jmann71 View Post
I'll simplify that a bit. both fixed pitch and collective utilize a swash plate for control of the main rotor system. on fixed pitch the lift is controlled by varying the motor speed, while a collective system maintains a specific motor rpm and moves the swash plate up/down to vary lift.

fixed pitch only needs 4 channels to operate while collective needs a minimum of 5 but most are 6 or 7. and the newer system incorporate a CPPM system that mixes cyclic and collective control through 3 servos.
I proper get that now, just sat reading this going oooooooh I seeeeee!

I thought fixed pitch was to make the heli only go forward/backwards and spin using tail rotor.

which i know sounds quite boring.. but thats all i want it to do..lol (Im a plane flyer at heart) I got given this by my dad who crashed it. Just thought Id try n get it to fly again. seems a waste to chuck it away.
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Old 01-14-2011, 09:19 PM
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Thanks Vortex for taking time to write back, im so new to helis and information like youve just explained to me makes me feel like ive just jumped another few hurdles in understanding how these helis fly. i did think at first i could just go down my extensive spares (for my plane) draw and pick out a few bits and could get the honeybee up again.
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Old 01-14-2011, 09:21 PM
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seems very very very hard to fly, took me a few months to learn to fly my easystar properley.. Im guessing helis would take years....
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Old 01-18-2011, 01:06 AM
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General minimum time to first hover hover (30-60 sec) averages around 2 weeks of "on the ground" training (Heli spin up never leaving the ground).

Your first sustained hover should be around 1 month depending on how serious you are. It'll feel great but it's not as controlled as you would like. And then at around 3 months you'll finally have a tight nailed in hover where you can compensate for slight winds.

Then the fun begins as you learn all different orientations. Some pilots prefer to learn some basic forward flight before fully committing to learning nose in. As much as I agree that learning nose in is more important I also fully understand how boring just hovering is so to spice things up I can condone a bit of forward flight before fully dailing in your nose in.

Sims are far more importantly initially than later on. Where as later on you may learn the basics of a new move in the sim but complete them in real life. At some point later on (years) you will discover sims train bad habits like get used to not moving around while you fly or rotating your body with the heli because your too used to sitting in place. At this point you should reduce sim time and focus more on real flight time.

I'm not a 3D pilot yet but I have all my upright orientations down and I can do most upright flight without a hitch flying backwards is still a bit of a challenge.

Total time in the hobby so far is 3 years.

Total time to hover for me was around what I outlined I was only able to solidly hover by 3 months and in tail in only. Total time to all orientations was a full year +.

Total time to being able to do proper forward flights was around 2.5 years.

Part of the problem with heli's is there is no crash you can walk away from. I have not experienced such a crash.
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