Dumb question about cyclic pitch

[Mart61]

So I know what cyclic pitch is. However I'm not quite sure how to control cyclic pitch from a transmitter.

Looking at my humble LP5DSM, a 5 channel transmitter, I have two sticks. The left stick controls throttle and rudder (yaw), the right stick controls elevator and aileron.

Now as I see it, the throttle controls the speed of each of the two motors in unison, whereas the rudder varies the speed differential between the two motors, thus inducing torque, causing the nose to turn in the opposite direction of the torque. As such the left stick has no affect on cyclic pitch.

Therefore, the right stick must be the cyclic stick as it is only by changing the cyclic pitch that one can cause the heli to move fore or aft, port or starboard.

Am I correct or way off the mark? And if I am correct, where does the cyclic input come from? Is it induced by the flybar on the top blades?

And why do the more complex helis require more than 4 channels to fly?

Told ya it was a dumb question...

[Mark_T]

The CX2 and the mCX are both fixed pitch so you don't have any collective pitch to alter

With a fixed pitch heli you are using the rotor speed to determine how high it goes, with a collective pitch heli you can vary the pitch as well as the rotor speed.

This is where one extra channel comes in along with setting pitch and throttle curves to determine what pitch and throttle setting you have for any given position of the left stick (mode 2).

I think you just got the collective pitch (up and down) stuff mixed up with the swash-plate movements (forward/backwards/left/right).

[mattydred]

is not a dumb question and you are about right.

cylic is the right stick on a mode2 transmitter which you have. we say throttle on left is mode 2 and throttle on right is mode1. there are other modes but these are the most commen. in my opinion mode2 is best.

the cyclic is elevator and aileron (right stick) and are servos connected to the swash plate to make the heli pitch up/down and roll left and right. you have a contra heli and that has 2 servos to the swash and a flybar.

most larger collective pitch helis have 3 servos to the swash and also have paddles on the flybar and are abit more complex.

if you have outgrown you contra heli the why not look at a new esky belt cp (£120 ebay) or a trex 450 v2 (£400ish)

matty

[waveydavey]

Not dumb at all. Your correct in thinking in mode 2 the right stick is indeed the cyclic. Aileron and elevator. I wouldn't have thought on your machine with contra blades you have too much cyclic to use. I am assuming that the machine is fixed pitch and the height is controlled by the speed of the blades. On a variable pitch heli the change in pitch of the blades is called the collective and it is this that contols the height along with the speed of the blades. The flybar assists in stability taking an amount of the control input away from the main blades by washing it out or mixing, not done on your heli.

The amount of channels are Aileron, elevator, pitch throttle and rudder. The throttle and pitch are normally mixed by the use of pitch and throttle curves in the tx but thats a whole different story.

Hope that helps

[Mart61]

I think you just got the collective pitch (up and down) stuff mixed up with the swash-plate movements (forward/backwards/left/right).

Yes I did in my fifth paragraph - now corrected.

Thanks for your input guys. So, if I understand correctly:

- the third servo to the swashplate is kinda like a "fine tune" that adjusts the collective pitch on the blades according to the throttle position
- no "physical" stick movement is required to this third servo
- rather it is controlled by the curves set up on the radio

This would, in effect, allow the rotors to generate an equal amount of lift from any of several throttle/pitch ratios.

Am I getting to understand now?

[brin]

Yes I did in my fifth paragraph - now corrected.

Thanks for your input guys. So, if I understand correctly:

- the third servo to the swashplate is kinda like a "fine tune" that adjusts the collective pitch on the blades according to the throttle position
- no "physical" stick movement is required to this third servo
- rather it is controlled by the curves set up on the radio

This would, in effect, allow the rotors to generate an equal amount of lift from any of several throttle/pitch ratios.

Am I getting to understand now?

hi mate found this thought you might like to read it

EVERY MANUFACTURER IS ADVERTIZIZING CCPM – WHY? BECAUSE IT WORKS SO WELL.


Yup, almost every RC heli ad you see now a days talks about their helicopter having CCPM. Is it a gimmick, a new marketing buzz word like 3D (don’t get me started on that one)?
I am glad to say no – it is a huge benefit – it simplifies life for you, makes your servos happy, and makes your helicopter fly better.
Before I get ahead of myself, I better explain what CCPM stands for and what it does... the benefits will then become obvious. It is an acronym that stands for... Cyclic-Collective-Pitch-Mixing. This feature is only found on RC helicopters with collective pitch (as the name suggests), it doesn’t apply to fixed pitch helicopters.

I should mention that you will sometimes see CCPM referred to as electronic (eCCPM) or mechanical (mCCPM) mixing. While this is essentially correct I feel it adds too much confusion. Seeing that true CCPM is only produced electronically, that is how it will be referred to in this discussion.
MECHANICAL MIXING
Until CCPM came around, we only called our mixing method mechanical. A way to control pitch function and cyclic function by means of a complex series of linkages and levers. Most systems consisted of mixing the collective pitch servo movements with the left/right cyclic servo and the fore/aft cyclic servo movements to the swash plate.
This does make setup a bit more difficult and because of all the linkages and levers, there is always a bit of slop or play. This can be minimized on high end helis by using ball bearings on all these levers in stead of simple bushings, but of course that adds to cost and weight.
This method of pitch control does put a lot of strain on the pitch servo. It not only has to move the entire swash pate up and down to change the pitch angle of the main rotor blades, it has to overcome all the friction associated with all the linkages.
Mechanical mixing does have a few advantages, such as no swash plate variation issues and because the servos are usually mounted in a servo tray and not in the frame, they are exposed to less vibration.

These are minimal benefits seeing that todays servos are much tougher and there are ways to almost eliminate swash plate variations either mechanically or electronically.
ELECTRONIC MIXING
Cyclic-collective-pitch-mixing is only possible because of advances in computerized RC radio technology. The mixing functions are all done electronically within the RC radio and the servos move accordingly.
Now two, three, or sometimes four servos can be hooked directly to the swash plate with out any complex mixing linkages. This of course simplifies the helicopter, reduces the number of parts, weight, and cost. There is less slop in the system and this provides very precise control of your helicopter.

The problem of excessive strain on the pitch servo is also gone. Not just because the linkages are gone, but also because the work load is now spread over two or more servos.
There are basically three different CCPM "modes" available.

The most common uses three servos that are equally placed at 120° intervals around the swash plate. The problem with this is the left and right movement of the swash plate is a bit faster than the fore and aft movement. This will cause some slight variations in control as the servos catch up to one another to create the proper swash plate angle. I should point out that this variation gets worse at the extreme ends of swash plate travel; for learning or scale flying it is pretty much unnoticeable.

To cure this issue some manufactures now offer 140° CCPM. With the 140° set up the the geometry is evened out between the side servos and the front or back servo. This gives more consistent cyclic rates for all 3 servo inputs and reduces swash plate variations. As this is a new development, only a few RC radios are supporting 140° mixing. This method will undoubtedly become more popular because it works very well.

The third method is 90° CCPM in which two or sometime four servos are used and inputs are placed at 90° intervals around the swash plate (fore, aft, left, right). Again because of the consistent placement - swash plate variation is reduced. It makes sense on micro electrics in the two servo configuration saving the wight of a 3rd servo. On larger models however, it does put more strain on just two servos - a 3 servo set up is much better.

4 servo 90° mixing is hardly ever used even on the biggest of helis these days. The biggest problem with the 4 servo set up is the opposing servos 180° from each other, no matter how evenly matched and adjusted will end up playing tug of war. This not only puts excess strain on the servos, it eats into battery time.
OK, no system is perfect and CCPM does have a couple of draw backs. First has to do with that "variation" in swash plate movement I was talking about.
Even with the 90° or 140° CCPM set up, if your servos aren't matched (move at the exact same speed) you will run into variation issues. With todays equipment that is unlikely, but something to keep in mind and watch for as your servos age.

The next possible draw back with Cyclic-Collective-Pitch-Mixing is that with all the servos responsible to correctly position the swash plate, if one servo failed, you would loose complete control of your helicopter.

With the mechanical system if one servo fails, you will still have partial control. I really don't buy this argument at all. First, servo failure is much more likely with one servo doing all the work instead of spreading the work load over two, three, or four. Second, even with a mechanical system if a servo fails, it is still almost impossible to control and save the heli.
I think you can appreciate the benefits of Cyclic-Collective-Pitch-Mixing are much greater than the "possible" draw backs. CCPM simply works and works well. It is something you should definitely insist on.
Almost all mid to high end helicopters (that have collective pitch) come standard with Cyclic-Collective-Pitch-Mixing these days. There are also CCPM upgrade kits available to convert a mechanical system into an electronic system.
Keep all this in mind when you are getting your Helicopter or Radio. Don’t get a helicopter that has Cyclic-Collective-Pitch-Mixing if your RC radio doesn’t support it. Also make sure your radio will support the CCPM system you have (90°, 120°, or 140°).

[Deweydaddy]

So I know what cyclic pitch is. However I'm not quite sure how to control cyclic pitch from a transmitter.

Looking at my humble LP5DSM, a 5 channel transmitter, I have two sticks. The left stick controls throttle and rudder (yaw), the right stick controls elevator and aileron.

Now as I see it, the throttle controls the speed of each of the two motors in unison, whereas the rudder varies the speed differential between the two motors, thus inducing torque, causing the nose to turn in the opposite direction of the torque. As such the left stick has no affect on cyclic pitch.

Therefore, the right stick must be the cyclic stick as it is only by changing the cyclic pitch that one can cause the heli to move fore or aft, port or starboard.

Am I correct or way off the mark? And if I am correct, where does the cyclic input come from? Is it induced by the flybar on the top blades?

And why do the more complex helis require more than 4 channels to fly?

Told ya it was a dumb question...

If there is one thing I can say about this forum it would be that the members truly enjoy helping others. Every question answered no matter what. Dewey

[Deweydaddy]

hi mate found this thought you might like to read it

EVERY MANUFACTURER IS ADVERTIZIZING CCPM – WHY? BECAUSE IT WORKS SO WELL.


Yup, almost every RC heli ad you see now a days talks about their helicopter having CCPM. Is it a gimmick, a new marketing buzz word like 3D (don’t get me started on that one)?
I am glad to say no – it is a huge benefit – it simplifies life for you, makes your servos happy, and makes your helicopter fly better.
Before I get ahead of myself, I better explain what CCPM stands for and what it does... the benefits will then become obvious. It is an acronym that stands for... Cyclic-Collective-Pitch-Mixing. This feature is only found on RC helicopters with collective pitch (as the name suggests), it doesn’t apply to fixed pitch helicopters.

I should mention that you will sometimes see CCPM referred to as electronic (eCCPM) or mechanical (mCCPM) mixing. While this is essentially correct I feel it adds too much confusion. Seeing that true CCPM is only produced electronically, that is how it will be referred to in this discussion.
MECHANICAL MIXING
Until CCPM came around, we only called our mixing method mechanical. A way to control pitch function and cyclic function by means of a complex series of linkages and levers. Most systems consisted of mixing the collective pitch servo movements with the left/right cyclic servo and the fore/aft cyclic servo movements to the swash plate.
This does make setup a bit more difficult and because of all the linkages and levers, there is always a bit of slop or play. This can be minimized on high end helis by using ball bearings on all these levers in stead of simple bushings, but of course that adds to cost and weight.
This method of pitch control does put a lot of strain on the pitch servo. It not only has to move the entire swash pate up and down to change the pitch angle of the main rotor blades, it has to overcome all the friction associated with all the linkages.
Mechanical mixing does have a few advantages, such as no swash plate variation issues and because the servos are usually mounted in a servo tray and not in the frame, they are exposed to less vibration.

These are minimal benefits seeing that todays servos are much tougher and there are ways to almost eliminate swash plate variations either mechanically or electronically.
ELECTRONIC MIXING
Cyclic-collective-pitch-mixing is only possible because of advances in computerized RC radio technology. The mixing functions are all done electronically within the RC radio and the servos move accordingly.
Now two, three, or sometimes four servos can be hooked directly to the swash plate with out any complex mixing linkages. This of course simplifies the helicopter, reduces the number of parts, weight, and cost. There is less slop in the system and this provides very precise control of your helicopter.

The problem of excessive strain on the pitch servo is also gone. Not just because the linkages are gone, but also because the work load is now spread over two or more servos.
There are basically three different CCPM "modes" available.

The most common uses three servos that are equally placed at 120° intervals around the swash plate. The problem with this is the left and right movement of the swash plate is a bit faster than the fore and aft movement. This will cause some slight variations in control as the servos catch up to one another to create the proper swash plate angle. I should point out that this variation gets worse at the extreme ends of swash plate travel; for learning or scale flying it is pretty much unnoticeable.

To cure this issue some manufactures now offer 140° CCPM. With the 140° set up the the geometry is evened out between the side servos and the front or back servo. This gives more consistent cyclic rates for all 3 servo inputs and reduces swash plate variations. As this is a new development, only a few RC radios are supporting 140° mixing. This method will undoubtedly become more popular because it works very well.

The third method is 90° CCPM in which two or sometime four servos are used and inputs are placed at 90° intervals around the swash plate (fore, aft, left, right). Again because of the consistent placement - swash plate variation is reduced. It makes sense on micro electrics in the two servo configuration saving the wight of a 3rd servo. On larger models however, it does put more strain on just two servos - a 3 servo set up is much better.

4 servo 90° mixing is hardly ever used even on the biggest of helis these days. The biggest problem with the 4 servo set up is the opposing servos 180° from each other, no matter how evenly matched and adjusted will end up playing tug of war. This not only puts excess strain on the servos, it eats into battery time.
OK, no system is perfect and CCPM does have a couple of draw backs. First has to do with that "variation" in swash plate movement I was talking about.
Even with the 90° or 140° CCPM set up, if your servos aren't matched (move at the exact same speed) you will run into variation issues. With todays equipment that is unlikely, but something to keep in mind and watch for as your servos age.

The next possible draw back with Cyclic-Collective-Pitch-Mixing is that with all the servos responsible to correctly position the swash plate, if one servo failed, you would loose complete control of your helicopter.

With the mechanical system if one servo fails, you will still have partial control. I really don't buy this argument at all. First, servo failure is much more likely with one servo doing all the work instead of spreading the work load over two, three, or four. Second, even with a mechanical system if a servo fails, it is still almost impossible to control and save the heli.
I think you can appreciate the benefits of Cyclic-Collective-Pitch-Mixing are much greater than the "possible" draw backs. CCPM simply works and works well. It is something you should definitely insist on.
Almost all mid to high end helicopters (that have collective pitch) come standard with Cyclic-Collective-Pitch-Mixing these days. There are also CCPM upgrade kits available to convert a mechanical system into an electronic system.
Keep all this in mind when you are getting your Helicopter or Radio. Don’t get a helicopter that has Cyclic-Collective-Pitch-Mixing if your RC radio doesn’t support it. Also make sure your radio will support the CCPM system you have (90°, 120°, or 140°).

Nice read. Thanks Dewey

[Mart61]

Thanks everyone for the inout and thanks to Dewey for the great read - I now know what CCPM is!

[Deweydaddy]

Thanks everyone for the inout and thanks to Dewey for the great read - I now know what CCPM is!

That most excellent read came from Brin. Your welcome anyway. Dewey