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HomeAircraftHelicopterHelicopter Main Discussion › 90,120 140 swash
08-27-2018 07:57 PM  22 days agoPost 1
jmurray74

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Mebane NC USA

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What does that mean,just the position of the servos?Thanks
Jim

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08-27-2018 08:11 PM  22 days agoPost 2
fastrc1

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Planet Brooklyn, NY-USA

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It's how the swash plate Ball ends on the lower assembly are aligned. The servos don't necessarily have to be lined up with the balls directly as they can be actuated through off set arms, rods etcetera. 90 was the thing a while ago but now you usually see 120 in use with an occasional 135/140 thrown in there.

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08-27-2018 08:31 PM  22 days agoPost 3
ssmith512

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Indianapolis, IN USA

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Steve

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08-27-2018 09:01 PM  22 days agoPost 4
ticedoff8

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Morgan Hill, CA. USA

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For an eCCPM system, the 140* spacing provides a more true swash plate movement compared to the 120* spacing.

http://www.rcheliwiki.com/CCPM_layouts

The 90* layout is more geared towards the 1-servo collection with separate elevator and aileron (mCCPM) for cyclic.

I've only seen the 90* 4-servo layout used on 1 RC helicopter (Velos) and there are only 2 gyros that I know of that support that (Demon and Skookum)

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08-27-2018 09:23 PM  22 days agoPost 5
BeltFedBrowning

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Kansas City

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My Airstar Mongoose has a 4 servo layout

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08-27-2018 09:47 PM  22 days agoPost 6
ticedoff8

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My Airstar Mongoose has a 4 servo layout
Didn't they go out of business a long time ago?

If so, that would fall into the category of:
90 was the thing a while ago
https://airstarintl.com

Velos is still in business (for now) with their UAV heli
http://velosuav.com/
It is broadly based on the Velos 880

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08-27-2018 10:02 PM  22 days agoPost 7
ssmith512

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Indianapolis, IN USA

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ticedoff8
I've only seen the 90* 4-servo layout used on 1 RC helicopter (Velos) and there are only 2 gyros that I know of that support that (Demon and Skookum)
Many large scale heli's use 4-servo (I have 2) and Futaba CGY supports 4 servo as well.

Steve

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08-27-2018 10:26 PM  22 days agoPost 8
Rojoalfa

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Punta de Mata, Monagas-Venezuela

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/
/

It is a matter to phasing the rotor blades.

That is why you found several ways to drive the swashplate, because it is related to the number of blades.

In our two-blade rotor helicopter's world, it doesnt matter the phasing thing... And also the number of servos driving the swashplate.

But, the real thing begins when you decide to have three rotor blades and so on...

/

Saludos cordiales,

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08-28-2018 12:22 PM  21 days agoPost 9
ICUR1-2

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Ottawa, Ontario

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Phasing matters even on a 2 bladed Heli. Not ALL models have a fixed swash driver.

spending time, paying attention

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08-28-2018 12:36 PM  21 days agoPost 10
ICUR1-2

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Ottawa, Ontario

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Rojoalfa
That is why you found several ways to drive the swashplate, because it is related to the number of blades.
Has more to do with the model and the servo layout. The number of blades has no baring on this.

spending time, paying attention

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08-29-2018 11:07 PM  20 days agoPost 11
Rojoalfa

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Punta de Mata, Monagas-Venezuela

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/
/

I like the simplicity of thunder tiger raptor design, H1.

The direct drive of srimok kasama... Explosive!

120 degree swashplate from miniature aircraft...

Simple, the better.

/

Saludos cordiales,

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08-31-2018 03:38 PM  18 days agoPost 12
GMPheli

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W. Bridgewater, MA USA

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Here is a good explanation of the benefits of 140
https://rc.runryder.com/t374852p1/

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09-01-2018 07:04 PM  17 days agoPost 13
TMoore

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Cookeville, TN

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Curtis starting doing this on his models because 135/140 geometry was easier on the CCPM system. How you drive and move the swashplate has no bearing on what is going on above it so the phasing argument is a diversion from the real issue. A lot of radios back then had terrible latency issues and this was one way to get some of the lag out of the system.

The 4 servo system was originally designed for some Schluter, Heim machines and later Vario used it. I never liked it as it was a PIA to setup and making 4 servos work in concert was always difficult due to pushrod geometry and speed differences between the servos.

3 Servo 120 is something that a fast radio should have no issue with. Same for a fast FBL system. Fact is that the two servos operate at different rates during cyclic inputs than the single servo that is left and most FBL controllers/radios can handle this fine. Operationally it's hard to tell the difference between 120 and 135.

3 servo 135 systems take the balls and move them to a location that is a fixed distance/fore and aft centerline from the swash as opposed to an angular spacing as in a 120 system this movement results in a 135 degree spacing of the balls to maintain that relationship. The torque that can be applied to the swash is now much more constant as the servos are working at the same rate for a given input. A simple mix made this system work prior to the radio manufacturers comeing up with variables in their CCPM software to accommodate the system.

BTW, there is no such thing as eCCPM. There is only mechanical collective and CCPM. CCPM was invented by Futaba and Multiplex in Europe. Both radios could handle it while the Multiplex implementation was probably the best. Early radios using CCPM were abysmally slow in terms of latency.

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09-04-2018 03:25 AM  15 days agoPost 14
wjvail

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Meridian, Mississippi

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TMoore
BTW, there is no such thing as eCCPM. There is only mechanical collective and CCPM. CCPM was invented by Futaba and Multiplex in Europe.
Please explain. My understanding was that, in the beginning, each of 3 servos served one function. Mechanically they were linked to roll, pitch and lift the swash. That would be, Mechanical Cyclic Collective Pitch Mixing. If you wanted to lift the swash, i.e. add collective, one servo performed this function. If you wanted to tilt the swash side to side, i.e. roll the swash, again, one servo.

Eventually someone notice there are only 3 connections to the swash and 3 servos. We could electronically do what had previously been done with ball links, ball bearings and moving servos. We could do what had been done mechanically, electronically. The benefit would be that any request to move the swash would be the combined effort of all three servos. Mechanical Collective Cyclic Pitch Mixing would be replaced with Electronic Collective Cyclic Mixing.

"Well, Nothing bad can happen now."

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09-04-2018 03:27 AM  15 days agoPost 15
wjvail

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Meridian, Mississippi

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jmurray74
What does that mean,just the position of the servos?Thanks
Yup. Just the orientation of the balls around swash. There was a time before flybarless and super fast servos it mattered. It's less important today.

"Well, Nothing bad can happen now."

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09-04-2018 07:08 AM  14 days agoPost 16
TMoore

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Cookeville, TN

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wjvail
TMoore
BTW, there is no such thing as eCCPM. There is only mechanical collective and CCPM. CCPM was invented by Futaba and Multiplex in Europe.
Please explain. My understanding was that, in the beginning, each of 3 servos served one function. Mechanically they were linked to roll, pitch and lift the swash. That would be, Mechanical Cyclic Collective Pitch Mixing. If you wanted to lift the swash, i.e. add collective, one servo performed this function. If you wanted to tilt the swash side to side, i.e. roll the swash, again, one servo.

Eventually someone notice there are only 3 connections to the swash and 3 servos. We could electronically do what had previously been done with ball links, ball bearings and moving servos. We could do what had been done mechanically, electronically. The benefit would be that any request to move the swash would be the combined effort of all three servos. Mechanical Collective Cyclic Pitch Mixing would be replaced with Electronic Collective Cyclic Mixing.
Bill, do a search. Do you know how many times I've argued this point ad nauseum? Everything you need to know about this subject and my views on the subject are right here on RR.

I'll give you a clue though. There is no such thing as mCCPM either, you're opening paragraph was partially right but you made one huge error.

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09-04-2018 09:56 AM  14 days agoPost 17
wjvail

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Meridian, Mississippi

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TMoore
Bill, do a search. Do you know how many times I've argued this point ad nauseum? Everything you need to know about this subject and my views on the subject are right here on RR.

I'll give you a clue though. There is no such thing as mCCPM either, you're opening paragraph was partially right but you made one huge error.
I hear fatigue in your response and I can understand not wanting to re-post a topic that's been covered. Sorry if I opened an old wound.

A quick search shows that the discussion is one of the very oldest here on RunRyder. This thread is from October 2001. https://rc.runryder.com/t386p1/

I will confess I have likely been using the terms incorrectly. Still, they have become valuable terms to describe certain helicopter and radio features.

Anyway. If it's OK, I'll save reading up on the subject for a rainy day. As I mentioned in another post, with the advent of super high speed cyclic/collective servos and capable FBL controllers, the subject is more valuable as a historical interest than practical knowledge.

"Well, Nothing bad can happen now."

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09-04-2018 02:53 PM  14 days agoPost 18
TMoore

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Cookeville, TN

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wjvail
TMoore
Bill, do a search. Do you know how many times I've argued this point ad nauseum? Everything you need to know about this subject and my views on the subject are right here on RR.

I'll give you a clue though. There is no such thing as mCCPM either, you're opening paragraph was partially right but you made one huge error.
I hear fatigue in your response and I can understand not wanting to re-post a topic that's been covered. Sorry if I opened an old wound.

A quick search shows that the discussion is one of the very oldest here on RunRyder. This thread is from October 2001. https://rc.runryder.com/t386p1/

I will confess I have likely been using the terms incorrectly. Still, they have become valuable terms to describe certain helicopter and radio features.

Anyway. If it's OK, I'll save reading up on the subject for a rainy day. As I mentioned in another post, with the advent of super high speed cyclic/collective servos and capable FBL controllers, the subject is more valuable as a historical interest than practical knowledge.
Just one question for you; in a mechanical collective system name me one function that is getting mixed. Here you said: "Please explain. My understanding was that, in the beginning, each of 3 servos served one function. Mechanically they were linked to roll, pitch and lift the swash. That would be, Mechanical Cyclic Collective Pitch Mixing. If you wanted to lift the swash, i.e. add collective, one servo performed this function. If you wanted to tilt the swash side to side, i.e. roll the swash, again, one servo." In that system which function is getting mixed?

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09-04-2018 05:24 PM  14 days agoPost 19
wjvail

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Meridian, Mississippi

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TMoore
Just one question for you; in a mechanical collective system name me one function that is getting mixed. Here you said: "Please explain. My understanding was that, in the beginning, each of 3 servos served one function. Mechanically they were linked to roll, pitch and lift the swash. That would be, Mechanical Cyclic Collective Pitch Mixing. If you wanted to lift the swash, i.e. add collective, one servo performed this function. If you wanted to tilt the swash side to side, i.e. roll the swash, again, one servo." In that system which function is getting mixed?
I haven't done any further reading since my last post but I think I understand the point you are making and I don't disagree.

Some discussion:
My first radio was a Kraft Bicentennial 76 series 5 channel. It didn't do a lot but one new fancy feature was V-Tail mixing. It was a small switch that enable V-Tail*. Up until that point there was only mechanical mixing. Until the advent of this electronic mixing you had to have a mechanical device that achieved the desired results.

http://www.fatlion.com/sailplanes/vtail.html

As it applies to model helicopters... The outer ring of most of our swashes has three control balls. We also have to achieve three control functions - pitch, roll(cyclic), and collective. Very conveniently we have three servos to achieve these goals. 3 servos, 3 input points, 3 functions. It would seem pretty simple to hook one servo to each of the input points and call it job done. Obviously that isn't going to work. We need some mechanism to mix these three servos to input the proper control to the swash. We need a mechanical mixer (to achieve the desired Cyclic/Collective control). We need a Mechanical Cyclic Collective Pitch Mixer.

Time passed and someone noticed that we could do something similar to my Kraft V-Tail mixing from the early '70s. We could in fact run one servo directly to each of the swash input points and electronically achieve the desired movement of the swash. In effect we could electronically mix the three servos to achieve cyclic and collective control.

I think I see the point you are making. I don't disagree. Many of my fixed wing models have programmed mixes to achieve some desired performance. For instance, when I put the flaps down it get the slave response of down elevator. In this case you have a master and slave input mix. Most of our helicopters don't have mixing like this. There is no master slave mix. There is only pitch, roll and collective. In this sense Cyclic Collective Pitch Mixing seems like a misnomer as these functions are not mixed. Have I got that about right?

________________________
* As a side note, it was very easy to bump this switch either before flight or airborne and have one mother of an out of control airplane.

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09-04-2018 05:37 PM  14 days agoPost 20
BeltFedBrowning

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Kansas City

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My JR gasser had something similar. I considered it MCCPM

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