dkshema
rrMaster
Location: Cedar Rapids, IA
My Posts This: Topic Forum | Barracuda's pretty close.
The numbers in the SWASH MIX menu do nothing more than control HOW MUCH TOTAL MOVEMENT you will get for AILERON CYCLIC, ELEVATOR CYCLIC, and COLLECTIVE PITCH.
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If you were flying a standard mix, non-CCPM helicopter, if you needed more or less aileron or elevator CYCLIC movement of the swashplate, you would adjust the ENDPOINTS/ATV for the AILERON or ELEVATOR channel. If you needed more or less collective PITCH, you'd adjust the ATV/Endpoints for the collective pitch channel. If you needed to REVERSE the servo movement for one or all three of these channels, you would do the reversing in the REVERSE menu of your TX, for the channel that needed to be switched.
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But, since you have a heli whose swashplate is setup for 120 degree CCPM control, it requires that three servos work in unison to move the swashplate correctly. The individual control adjustments take on new meaning, as you have to deal with the electronic mixing that is occurring in the radio.
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The electronic mixing requires a few things to work differently in your transmitter. First, the channel reversing function in your TX ONLY affects one of the three servos, not the action of all three. The channel reversing feature in your TX ONLY allows you to get the three servos moving correctly, with respect to each other, and has nothing to do with them moving correctly with respect to the function they are controlling.
For instance, for aileron control, two servos need to move in opposite directions, one up, one down. The third servo does nothing. But if your servo reversing switches are in the wrong position, those two servos may both move up, or both move down. Fix THAT using the reverse function for ONE of the TWO servos.
Elevator requires that two servos move up (or down) in unison, while the third moves opposite (generally the elevator servo). IF all three move UP (or down), you reverse the elevator channel.
Collective requires that all three move up, or down in unison. Generally, if you get the elevator and aileron channels moving correctly with respect to each other, the collective takes care of itself.
BUT -- you may find that although the servos move correctly with respect to each other, they may move opposite of the direction required for the FUNCTION.
This is where the SWASH MIX/SWASH AFR menu comes into play. By simply changing the SIGN of the aileron, elevator, and/or pitch function, you reverse that function instead of messing with the channel reversing stuff.
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The ATV/Endpoints no longer adjust the travel of the FUNCTION, they only adjust the travel of an individual servo. So, if you find your swashplate level at mid collective/zero degrees, but that it tilts as it goes full up or full down, you use the individual endpoint/ATV settings to correct the movement of the individual servo that is moving too far, or not enough. You don't affect the other two servos in this manner.
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The SWASH MIX/SWASH AFR menu is also where you control how much total collective travel you get (full stop to stop) with the SIZE of the pitch number, and how much aileron and elevator CYCLIC pitch you get by adjusting the SIZE of the AILE and ELEV numbers in the swash mix menu.
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Finally, the numbers in the swash mix menu do NOTHING to center the swashplate in its travel range for that zero degree setting.
This is accomplished by making sure your servo arms are where they are supposed to be AT NEUTRAL (generally horizontal, parallel to the ground unless your pushrods have some weird geometry). When you have all three SERVO ARMS properly positioned at NEUTRAL (mid-stick on both sticks), you adjust the pushrods controlling the swashplate to get the swash not only level, but in the center of its overall travel range.
When you have accomplished THAT, you then adjust the pitch links up on the head generally to get all mixing arms level, and ZERO degrees pitch in BOTH blades.
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Barracuda mentions the idea of setting your pitch curve to a big FLAT LINE at 50%. I picked this idea up from Ron Lund's Heliproz South website. If you have a 5-point pitch curve radio, set points 2, 3, and 4 at 50%, and point 1 at 0, point 5 at 100.
In doing so, as long as the collective stick is anywhere between points 2 and 4, the servos will be centered (neutral) and you can make your pushrods to level the swash, and center it in its overall travel range. You can set the rest of the pushrods to level the various mixing arms, and to set ZERO degrees pitch in both blades.
Finally, you can go to points 0 and/or 100 to set the overall pitch travel using the PITCH number in the SWASH MIX/AFR menu.
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To figure out what the AILE and ELEV numbers "should" be, use your pitch gauge to figure out what your cyclic pitch is.
If you turn the head so that the flybar is perpendicular to the sides of the heli (main blades -- one in front, the other over and parallel to the tail boom), set your collective stick to the ZERO degree setting, you can measure CYCLIC PITCH values for the AILERON function.
Put the pitch gauge on the MR blade sticking out front, about mid-way on the blade. MOVE THE AILERON stick side to side. Go full LEFT (or right) and measure the amount of pitch from ZERO degrees that the blade moves. Adjust the AILERON number in the SWASH MIX/AFR menu to get +/- 6 or 7 degrees of aileron cyclic.
Turn the head 90 degrees, keeping the collective at the ZERO degrees pitch setting. The flybar is now over and parallel to the tail boom, and sticking out in front, the MR blades are perpendicular to the sides of the heli.
This time, move the ELEVATOR stick to its full extreme, measuring the amount of pitch the MR blades get as you do. This time, set the ELEV number in the SWASH MIX/AFR menu to get that same +/- 6 or 7 degrees of cyclic.
If you've made it this far:
1. Your servos move correctly with respect to each other, even if you swapped the plugs at the RX for the Aileron and Pitch servos.
2. The servos move correctly with respect to the stick movements.
3. Your swash stays level from full negative pitch to full positive pitch.
4. You have adjusted your linkages to get the swash level and centered at mid stick.
5. You have zero degrees pitch in both blades at mid stick.
6. You have set the full positive and negative pitch values and know how to adjust the COLLECTIVE number in the SWASH MIX/AFR menu to increase or decrease overall travel.
7. You have set the maximum cyclic values for aileron and elevator and know how to set these using the AILE and ELEV numbers in the SWASH MIX/AFR menu.
8. You understand what the ATV/Endpoint settings do for a CCPM head and can use this to keep the swash level throughout its travel range.
9. You understand what the channel reverse settings do for a CCPM head. Next time you build a CCPM heli, you will be able to get things moving correctly in a matter of minutes.
10. You understand how to reverse the pitch, aileron, and elevator movement by changing the SIGN of the value associated with the function (AILE, ELEV, PITCH). The next time you set up a CCPM heli, you will be able to get the three functions following the stick correctly in a matter of minutes.
Go to the individual pitch curve settings and using your pitch gauge, set your normal and idle up pitch curves.
If you've gotten your gyro and tail properly set up, you're ready to go hover, track the blades, and fine-tune your pitch and throttle curves.
Go fly.
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* Making the World a Better Place -- One Helicopter at a time! *
Dave |
