Newbie Question: What's CCPM and why a 120deg swashplate?

[darren_uk]

I'm quite new to model helis (although owned one since 1998, I have only dabbled so far).

This week I've come across CCPM and the 120 degree swashplates.

What are they for and why not the old 90 degree ones?

[rotorz]

Hi Dudes
CCPM by it's proper name Cyclic Collective Pitch Mixing offers a system of control to the swashplate that has been opened up by modern electronics in the transmitter we use.

With CCPM, pitch and cyclic mixing are handled by the transmitter while each of the three servos are linked directly to the swashplate eliminating the mechanical mixer and a whole lot of ball links and pushrods. This makes building and setting up a CCPM machine easier (in theory) since it uses fewer parts and needs fewer mechanical adjustments.
Because the servos are directly attached to the swashplate with short rigid links, CCPM offers a level of backlash-free precision that just can't be matched with other types of control systems. And because three servos work in unison to raise and lower the swashplate for pitch changes, three times the servo power is available in pitch while two times the servo power is available for cyclic inputs.

Continued Below

[rotorz]

CCPM
The swashplate is therefore more aggressively held in its position thanks to three servos working in unison rather than independently. 90 or 120 deg, mix depends on type of swashplate and geometry of the head supplied. Most modern heli's have options. My largest Heli uses 4 servo 90 degree mixing, modified from standard mechanical mixing and as this is an aged heli the differences were very notable in it's crispness of handling.

There are however disadvantages to ccpm because as always with these lose collections of flying nuts and bolts compromises.

The following link is an excellent site wich feature a broad range of swashplate controll layouts.

http://www.iroquois.free-online.co.uk/ccpm.htm

Happy Landings