CCPM setup

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Good CCPM setup is important to avoid CCPM interaction between the various controls.

The procedure outlined below is a variation of the one described by Finless Bob's CCPM setup 101.

This procedure applies specifically to 120 degree CCPM, as used in the T-Rex 450 and other similar helicopters.

If you've accidentally broken your transmitter settings then our Quick and dirty CCPM setup for Trex, Blade 400 3D, Belt CP, King, etc may be sufficient.

Contents

Groundwork

Before installing the servos in your helicopter, verify which channels of the receiver correspond to which servos on the model.

Select a blank model on the transmitter, and select the appropriate CCPM layouts.

Connect servos to channels 1, 2, 3 and 6 of the receiver. Power can be supplied from a NiCd flight pack, or from a lipo via an ESC / BEC plugged into any remaining channel, but with no electric motor connected!

Move the collective pitch control: all the servos should move. If they don't, you probably have not enabled CCPM mixing, or may have throttle hold enabled.

Move the cyclic pitch control forwards and backwards: three servos should move. The remaining servo is connected to your throttle channel (probably channel 1 or 3, depending on the manufacturer).

Move the cyclic control left to right: two servos should move. These servos should be connected to the links on the left and right of the swashplate. The remaining one of the three servos should be connected to the front or back of the swashplate, depending on the helicopter design.

Mechanical setup

Install the servos in your helicopter, and either connect them roughly to the swashplate, or assure yourself that you understand how the servos movement affects the position of the swashplate.

Temporarily connect the servos back to the receiver as determined previously, and switch on the radio. As the swashplate movement is likely uncoordinated at the moment, ensure that none of the servos are binding; if they are, disconnect power immediately, and adjust the linkages so that they don't bind.

Gently move the collective up and down. Use servo reversing to ensure that the servos move the swashplate up and down together, rather than tilting it.

Gently move the cyclic forwards and backwards. If the swashplate tilts in the opposite direction of the commanded input, go into the CCPM parameters menu of your transmitter (also called, among other things, swash mix), and change the sign of the 'elevator' value; that is, if it is positive, make it negative, and vice versa.

Gently move the cyclic left and right. If the swashplate tilts in the opposite direction of the commanded input, go into the CCPM setup menu, and change the sign of the 'aileron' value.

Your swashplate should now follow the control inputs you make, if rather approximately.

Return to the CCPM setup menu, and set the value to 0%; this essentially disables the collective control. If the cyclic is then allowed to centre, we can begin to configure the swashplate to its neutral zero degrees pitch position.

Ensure that the servo arms and linkage rods are configured as given in the helicopter manual. Typically, any place a servo arm or bell crank connects to a push rod, the linkages need to be at 90 degrees. For all the swashplate servos, adjust the position of the servo arm on the servo output shaft, and adjust the linkage lengths to achieve this.

Firstly we shall set up the head linkage lengths approximately, and then return to fine tune the swashplate position.

Head setup

0-deg-head-setup-1.jpg
Zero degrees head setup

Head setup revolves around setting up the correct zero pitch position. At zero degrees pitch, we want the washout arms to be level and flat, and the Bell-Hiller mixer arms to be flat, too.

Place the swashplate and the head on the mast, so that the initial settings can be made.

The swashplate height at zero degrees pitch is determined firstly by the length of the linkages from the flybar control arms to the washout, and secondly by the length of the linkages to the swashplate from the servos. The main constraints we have to work with is ensuring that the washout block does not slide off the washout guides at minimum pitch, or bind against the rotor yoke at maximum pitch, and that the flybar control arm is correctly centered. Typically the values given in the manual are good, but if none are given, then the appropriate length can be found by adjusting the flybar to washout links until the washout arms are level in the middle of the washout's available travel.

Connect the final links to the swashplate, adjusting the length of the final pushrods so that the swashplate is as close to perpendicular to the mast as possible, and the washout arms remain level. Special tools are available to check the level of the swashplate.

Remove the head, but leave the swashplate on the mast. Using the swashplate leveling tool, first ensure that the swashplate is as level as possible by adjusting the length of the final pushrods. If you think you have disturbed the height of the swashplate, refit the head and confirm the washout arms remain level. When the swashplate is as level as possible mechanically, use the subtrim function of your radio to set the swashplate level exactly.

Refit the head. Ensure that the flybar control arm is still at zero degrees, and adjust the flybar to washout linkages in opposite directions to achieve this if it is not so.

Connect the remaining linkages in the head. Adjust the length of the swashplate to Bell-Hiller mixer arms to ensure that the mixers are horizontal (or the linkage rods are at 90 degrees, depending on the mixer design). The length of all these links should be identical, so once one is set up, the others can be set up using calipers.

Finally, adjust the length of the Bell hiller mixer to blade grip linkage to ensure the blade is at zero degrees pitch. This length can also be carried to other similar links using calipers.

Return to the CCPM setup menu on your transmitter, and adjust the pitch value until you achieve a suitable collective pitch range, say +10 degrees at full collective, -10 degrees at minimum collective. If the range appears asymmetrical, then one or more of the linkages is probably not quite at right angles or aligned properly. Depending on how fussy you are, this may not be a problem.

On some helicopters some of these linkages are not adjustable. In that case, other linkages will need to be changed to correct any errors they introduce.

CCPM interaction setup

Remove the head and return the swashplate leveler to the mast. Move the collective to approximately 75% (about hover pitch), and use the radio's servo travel adjust function to level the swashplate at this setting, using the minimum adjustment possible. When level, increase to full collective and verify that the swashplate remains level; if not adjust the servo travel to give similar error at both positions. Repeat this exercise the other side of zero pitch, at 25% and 0% collective.

External links

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