3 of 4 punts aansturing ?

fly4fun

fly4fun

hallo,

Is er een groot verschil in vliegeigenschappen, met een 3 punts of een 4 punts directe aansturing van de tuimelschijf?

in de zender kun je deze volledig programeren (mixen), zodat de beweging van de tuimelschijf nagenoeg het zelfde is!

De voordelen die ik zie zijn:

- Het scheelt een servo
- Minder kans op asynchrone lopen waardoor de servo's elkaar gaan tegenwerken, immers hebben ze bij een 3 punts alle vrijheid?
En (vooral bij digitale) deze te warm worden en mogelijk begeven.

nadelen:

- minder starre aansturing, (bijvoorbeeld bij 3D vliegen)
- ?
 
ik kan niet zeggen dat ik enige ervaring heb met 4-punts tuimelschijven,
maar je kan niet om het feit heen dat zelfs de duurdere 3D-heli's (mikado bijv) kiezen voor een 3 punts-tuimelschijf.
Misschien zeg ik nu iets doms, maar als je het mij vraagt moet dat dus wel een goed systeem zijn....
 
Minder mechaniek=snellere response door de traagheidswet.. ook is een 3punts swash makkelijker te besturen(eccpm) dan een mechanische mixer(dus 4 punts) omdat mechanisch heb je te maken met hefbomen welke de afstand een beetje fluctueren door draaiing van die hefboom(5 graden omhoog=5 cm omhoog bij het eindpunt van 85 naar 90 graden, maar die 5 graden is geen 5 cm van bv 50 naar 55 graden..)
 
Zelf heb ik een vario x-treme, met een 4 punts (directe) aansturing.
d.w.z. directe aansturing zonder mechanische mixer.
De servo's worden midels een vierpunts mixer op de zender aangestuurt

Ik ben nu bezig met een Bell 222, skyfox mechaniek van Vario.
Je kunt hier kiezen voor 3 of vier punts aansturing, of zelfs vierpunts met mechanische mixers, dit kan door midel van hevels waarbij de servo's in de romp worden geplaast.

Punt is nu, dat ik "drie" goede servo's van hetzelfde type heb liggen en aan het afwegen ben of een 4 punts aansturing de moeite waard is?

Ik kan me zo voorstellen dat het mixen van een 3 punts lastiger is, omdat de aansturing 120 gr is bij 3 punts, als op 90 gr bij 4 punts? immers kun je ze niet meer 2 aan 2 aansturen?

Maar wat zou het effect zijn op het vliegen?
 
Laatst bewerkt:
Effect op het vliegen. Null. ga je niet merken in ieder geval. als je kan kiezen tussen 3 of 4 punts aansturing zou ik gewoon gaan een 3 punts, daar je toch 3 goede servo's hebt liggen, en moderne zenders maakt het niks uit of je 3,4 of 10 punts aansturing hebt(bijvoorbeeld), mixen ze allemaal wel in en weg.
 
Artikel: 120 (140)gr of 90 gr aansturing

Na wat rondzoeken op internet vond ik het volgende artikel over dit onderwerp:

http://www.rchelicopterfun.com/ccpm.html


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 120 or 140 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.
The big disadvantage with mechanical mixing comes from all the linkages and levers; there is always a bit of slop or play in them. 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 also puts 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 complicated swashplate setup to avoid 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 with a good computerized programable radio and knowing the proper setup procedures.
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 all interact and 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 and for us average Joe fliers is totally undetectable.

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 interaction between all 3 CCPM servos 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 today's 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 off, 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°).
If you wanted to learn more about 120/140 CCPM swashplate setup , I have an e-book that goes through the entire process. Just click on that link or the image of the e-book if you are interested in it.
 
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