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HelicopterMain Discussion › 120 or 140 CCPM
11-30-2007 12:16 AM  9 years agoPost 1
Rbush

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Hi,

Can somebody tell me the in's and out's of 120/140 CCPM.
Is one better than the other?
Why?

Thanks.

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11-30-2007 12:39 AM  9 years agoPost 2
GimbalFan (RIP)

rrProfessor

Big Coppitt Key, FL

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The more CCPM's your helis have the better. I run 875° on all my birds.

But seriously -- it's a fine distinction. Most important I believe is that you not run 140° unless your radio is intrinsically capable of it (like a Stylus). 140° does offer somewhat greater elevator axis leverage, with the possibility of a slight loss of some aileron axis leverage. 120° has the advantage the other way.

Other more knowledgeable guys will surely chime in.

op-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-t

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11-30-2007 01:55 AM  9 years agoPost 3
Rbush

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I have a JR 9XII (9303) and will be buying the Vibe 50 as soon as its here. I have the option to run 120 or 140 with this heli and TX combo.

This is why I ask. I'm not sure witch one would be better?

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11-30-2007 02:02 AM  9 years agoPost 4
fly4d

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The waters

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I would reccomend 120, just because thats most common used, but if i were you i would try both, it wouldn't hurt to see the difference for your self.

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11-30-2007 02:06 AM  9 years agoPost 5
GimbalFan (RIP)

rrProfessor

Big Coppitt Key, FL

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i would try both, it wouldn't hurt to see the difference for your self.
Considering the time necessary to change over the setup and reprogram the radio, any differences (which will be subtle anyway) will be quite hard to discern after the passage of so much time. Back to back flights on two different otherwise identical birds might not even reveal a difference.

There's probably still some subtle advantages mechanically which someone more knowledgeable will have to chime in on to clear up. It may even be that on one bird 140° has the advantage and on another brand/model 120° wins.

op-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-t

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11-30-2007 02:21 AM  9 years agoPost 6
Shawn Behrens

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stoopid question warning

If using 120ccpm and the swash afr values are not maxed out how could 140ccpm be any better?

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11-30-2007 02:30 AM  9 years agoPost 7
GimbalFan (RIP)

rrProfessor

Big Coppitt Key, FL

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If using 120ccpm and the swash afr values are not maxed out how could 140ccpm be any better?
Not sure.

120° allows the swash servo assembly to have slightly more aileron axis leverage than 140° because the two servos which actuate the aileron function are spread slightly further apart. 140° allows the swash servo assembly to have slightly more elevator axis leverage than 120° for the opposite reason.

I don't know any other way to explain the very subtle difference, and I don't know what types of flying each or either would provide an advantage for.

It's pretty clear though that with as subtle the difference is, only those flying at the highest skill level of the sport need be concerned with which they choose.

op-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-t

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11-30-2007 02:40 AM  9 years agoPost 8
fiveoboy01

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Waunakee, WI - USA

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Isn't interaction greatly reduced or eliminated with 140deg. without having to make a bunch of adjustments?

Mikado Logo 400, hopefully ready by spring.

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11-30-2007 02:43 AM  9 years agoPost 9
GimbalFan (RIP)

rrProfessor

Big Coppitt Key, FL

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With the right radio, any interaction in either setup can be programmed out. The amount of programming it takes shouldn't be an issue -- all that should matter is which swash setup works best for the bird or for how you fly it.

op-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-t

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11-30-2007 04:28 AM  9 years agoPost 10
oldboldpilot

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Southern California

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The purest set-up is mechanical - one servo for each axis. Zero interactions..

Why CCPM? Faster control action.. for the 3D guys.

The purest CCPM is 135 degrees. This "fixes" the unequal servo motions associated with 120 CCPM.

By this I mean you will see the minimum interactions between cyclic and collective - approaching mechanical.

Do you wonder why the Futaba 14MZ costs so much? Because (among other things) it has a built-in software function to dial out the 120 degree CCPM interactions..

Fly a 135 or 140 degree CCPM heli, and you don't need the 14MZ interaction feature.

Helis are Man's Defiance of the Laws of Nature - OCHC

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11-30-2007 06:37 AM  9 years agoPost 11
Portblock

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Van Nuys, CA

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Perhaps I missed it, but there is also the travel distance for the servos.

On 120 deg systems, look at the total travel for the servos in an elevator move, the aileron servos move less up and down than the elevator servo does.

So from one extreeme to the other, on elevator, say, full back to full forward, the elevator servo has to move roughly 35% more, and in doing so, will take longer time to travel than the other two servos.

What happens durring this is a slight change is in pitch for the moment the elevator servo gets to its position.

Ok, just my 2 cents.

The voices in my head can beat up the voices in your head.

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11-30-2007 09:51 AM  9 years agoPost 12
Rbush

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stoopid question warning

If using 120ccpm and the swash afr values are not maxed out how could 140ccpm be any better?
This is NOT a stupid question. JR have given us the option for 120 or 140 with both the Vibe 50 and 9XII. There for, if a big company offer this option, there must be a reason.

Thank you to everybody that has tried to help me, .

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11-30-2007 09:55 AM  9 years agoPost 13
GimbalFan (RIP)

rrProfessor

Big Coppitt Key, FL

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I believe he was referring to whether or not HIS question would be thought of as stupid, not yours.

After further thought, I believe the linkage scheme between the servos and the swash on that Vibe50 are what will best determine which swash type you choose, since you apparently have a radio that will allow you to slow down the shorter-traveling aileron servos to match the elevator servo appropriately in either swash type.

I'd choose whatever swash actuation scheme permits the straightest linkage connections and most uniform linkage & servo horn movements. Use servos that're powerful enough and at least leverage won't be an issue.

op-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-t

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11-30-2007 10:06 AM  9 years agoPost 14
Rbush

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I can see that point of view now Gimblefan.

I apologise to you sbmon if I have read your post wrongly.

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11-30-2007 10:18 AM  9 years agoPost 15
synodontis

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United Kingdom

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The purest CCPM is 135 degrees. This "fixes" the unequal servo motions associated with 120 CCPM.

By this I mean you will see the minimum interactions between cyclic and collective - approaching mechanical.

Do you wonder why the Futaba 14MZ costs so much? Because (among other things) it has a built-in software function to dial out the 120 degree CCPM interactions..

Fly a 135 or 140 degree CCPM heli, and you don't need the 14MZ interaction feature.
A 14MZ cannot dial out 120 degree CCPM interaction, all it can do is to make them minimal as not to be "noticeable". Also 135 and 140 will STILL have interaction. A 14MZ makes it less so because we have 2048 resolution, whereas something like a 10X only has 1024 resolution. I haven't done the geometrical calculations of CCPM but I'm certain it will contain geometrical resolution issues that will prevent it ever from being as good as mechanical, it's just that to all intents and purposes having higher resolution servos and better software will minimise these interactions as to make them not "noticeable".

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11-30-2007 10:35 AM  9 years agoPost 16
Rbush

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OK, putting my original question in a different way. Whitch has less interaction if using a 'standard' TX (9XII), 120 or 140?

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11-30-2007 11:12 AM  9 years agoPost 17
ChristianM

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Oslo, Norway

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140 deg CCPM system has less interaction than 120 deg system, period.
The reason is that on a 140 deg CCPM system all the servos travel the same distance during an elevator input as oldboldpilot mentioned. On a 120 deg system two of the servos travel a shorter distance for an elevator input thus the servos arrive at the commanded position at different times causing interaction. The 14MZ can reduce this effect by slowing down the servo commands sent to the RX for the servos traveling the shorter distance. This however is only an approximations since the actual servo speed depends on the load. Fast and strong servos reduces the effect of this interaction but it is there non the less.

Edit: On a 120 deg CCPM system, during a fast collective pitch change there will also be an elevator input for the same reason.

If your heli can be setup with 140 deg and your radio supports it then use it as it will be one less interaction and unless you have the 12 or 14MZ or the CSM CycLock then there is nothing you can do to get rid of it. This is why Curtis invented the 140 deg CCPM in the first place.

There is also a system called the 135 deg CCPM system which is a special case of the 140 CCPM where the CCPM ratio for the elevator command is the same as the ailron command. This means that the servos will move the same distance for X degree elevator command as for the same X degree ailron command. This will eliminate interaction during for example piro flips.

Christian

Burn fuel, be happy

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11-30-2007 11:55 AM  9 years agoPost 18
synodontis

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United Kingdom

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CSM CycLock does not get rid of the 120 interaction issue. All you are doing is off loading the issue to a black box on the heli, you set the transmitter to normal mechanical mixing and the CSM CycLock processes the command to CCPM for the servos. The advantage with this is if done right, and I don't quite know yet, the CSM CycLock can use a higher resolution on the servos to get over the 1024 steps and make a better CCPM implementation than if it were to come from the transmitter. Also it would be faster since it needs to send less information. If you do a collective up/down that's just one servo change, for a CCPM that would be 3 servo changes.

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11-30-2007 02:46 PM  9 years agoPost 19
kingair

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Utah - USA

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From rchelimag
140° Versus 120° CCPM
There are a small number of helis out there that are offered in a 140° CCPM version. The huge advantage a 140° system has over a 120° is that the geometry is more evened out between the two side servos and the front servo. This gives a more equal cyclic rate all the way around, where on a 120° setup the left/right cyclic is slightly faster than the fore/aft. The drawback is that there are still only a handful of radios with 140° mixing available (though a radio with a 120° program can be made to work with a 140° setup with some simple mixing). Also, only a handful of kits with 140° CCPM are currently available.

There is a very fine line between "hobby" and "mental illness."

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11-30-2007 02:55 PM  9 years agoPost 20
colsy

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Cambridge, UK

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ChristianM, explained it to perfection.

Also worth noting anyone with (1) spare mix can run
140 degree swashes with a 120 degree limited radio.

It's only (a) mix of pitch to elevator. worked out at +23% on my VIBE90 with DX7.

Col.

Only Quote From Experience.

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HelicopterMain Discussion › 120 or 140 CCPM
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