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Old 07-21-2021, 12:35 PM   #1 (permalink)
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Default Pitch not matching on Positive / Negative

How can this be corrected?


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Old 07-21-2021, 12:41 PM   #2 (permalink)
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You need to set the endpoints in the advanced settings of the Ikon. At the same time you’ll level the swash at the top / bottom of travel.

There’s a description of the whole process here:

https://www.helifreak.com/#/topics/864535


Quote:
Originally Posted by ticedoff8 View Post
-Take the main blades and head off.
-Center the servo arm on all 3 swash servos so they are 90 deg (square) to the case of each servo.
Do that on "Wizard Menu: => "Swashplate Setup (Output)" (page 😎.
You need to start with these 3 servo arms "square" to their cases. Adjust the SRV-1, 2 & 3 using the + and - keys.
Be critical about this and use something with a square corner (like a metal ruler) to get this as close as you can mechanically. Don't eye-ball it.
Once the 3 servo are centered - NEVER ADJUST THEIR CENTERS IN THE iKON2 AGAIN.

Change to the "Advanced Menu" => "Common" = "Servos" screen.
Check the box "Check Mode"
Using a swash-leveling tool,
* Level the swash at 0-deg pitch. Center the collective stick and adjust the 3 swash-links to get the swash level. DO NOT adjust the servo centers to try to level the swash.

Level the swash at full up collective:
— Move the collective stick full up.
— Adjust the "Positive Throw" values for Servo 1, 2 and/or 3 until the swash is level at the top.

Level the swash at full down collective:
— Move the collective stick full down.
— Adjust the "Negative Throw" individually on Servo 1, 2 and/or 3 until the swash is level at the bottom.

Run the collective stick from full down to full up and watch the swash leveler tool and make sure its all good.

-Put the head / blades back on.
Adjust the main grip links to get 0-deg pitch (on both blades) when the collective stick is centered.

- Measure the +/- collective pitch.
If you have +14, but only want +12, go to "Advanced Menu" => "Common" => "CCPM" and take 1 or 2 points off the "Pitch Out Max"
If you have +12, but you want +14, then add 1 or 2 points.
This is like a logarithmic setting - small adjustments result in big changes

4 out of 5 times, the max positive pitch will not be the same as the max negative pitch.

Regardless, here is how you get equal pos / neg pitch.
Lets say you have +13 / -16.
Go back to "Advanced Menu" => "Common" => "Servos" and check the box "Check Mode".
Look at the "Negative Throw" values for all three swash servos.
After you centered the swash for the neg collective, they might all be something slightly different (eg: 690, 710, 675).
Now, subtract 5 points from ALL THREE servo's "Negative Throw" (685, 705, 670).
Check the neg collective. It might now be -15 deg.
Subtract 5 more from all 3 servos and check the neg collective.
Adjusting the "Negative Throw" endpoints of the servos will not change the center or pos pitch and the swash will stay level if you make the same value change on all three servos.

Now, after you've gone through the effort to get equal pos / neg collective values, you need to see how it flies.
From an upright hover, apply full pos collect and observe how fast the heli climbs straight up.
From an inverted hover, apply full neg collective and observe how fast the heli climbs straight up.
4 out of 5 times, it will climb fast from the upright hover than it will from the inverted hover when the head has equal pos / neg collective.
So, now you got to go back in and adjust the "Negative Throw" settings for the 3 servos so the inverted climb out looks the same as the upright climb out.
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Old 07-21-2021, 12:44 PM   #3 (permalink)
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Try going negative then positive and note the numbers.
Then go back to zero pitch.
Then go positive and negative and note the numbers.

You are probably just seeing the normal play in the whole system.
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Old 07-21-2021, 01:38 PM   #4 (permalink)
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Quote:
Originally Posted by MariaFan View Post
Try going negative then positive and note the numbers.
Then go back to zero pitch.
Then go positive and negative and note the numbers.

You are probably just seeing the normal play in the whole system.
Or even miss calibration of the digital gauge. Should probably check it before worrying too much about a 1/2 degree of slop.

Rick
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Old 07-21-2021, 01:59 PM   #5 (permalink)
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That is quite common as these models aren't built to NASA specs and have slop in multiple places. That tiny amount you show is irrelevant and IMO not worth bothering with.

As stated, you can adjust it out within the FBL unit software if you must, or the other option is to adjust all three swash links mechanically to shift zero pitch swash position a bit to even it out, but dont be surprised if your perfect values are screwed up again a bit after a few flights
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Old 07-21-2021, 02:36 PM   #6 (permalink)
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That is close enough. These pitch gauges are not that accurate, and any slop in the heli makes it even worse. Don't get so wrapped up in the number. Go fly the heli and do a climbout, full collective, both upright and inverted. Do it with little wind outside to make it a bit easier, but watch the climb rates/acceleration. Adjust the pitch from there to get it even.

That is really the whole purpose of setting pitch, is so it feels even both upright and inverted.
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Old 07-21-2021, 02:51 PM   #7 (permalink)
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JimJW: Thank you. That worked well. Now getting 12.0+ 12.1-

Ill take that!


Side note, I kind of figured it would not make much of a difference, however my OCD is now happier
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Old 07-21-2021, 03:19 PM   #8 (permalink)
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As others said, use the pitch gauge to make sure you've a reasonable range to start with, but then test climbouts in the air.

If you want equal climb rates both positive and negative you really need to adjust by feel. After I've tuned the model in the air I almost always end up with different pitch amounts positive and negative, and have no idea what my final pitch range is. All that matters is that the model flies how I like, and is as close to even positive and negative as I can get it when flying.

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Old 07-21-2021, 06:35 PM   #9 (permalink)
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I NEVER have leveled at the top and bottom ranges and have never seen any ill-effects in the near 30-odd systems I've built. It's a big waste of time. I equate it to those guys that work so hard to get a perfectly vertical main shaft before starting - pointless.
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Old 07-21-2021, 07:09 PM   #10 (permalink)
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Quote:
Originally Posted by jrman83 View Post
I NEVER have leveled at the top and bottom ranges and have never seen any ill-effects in the near 30-odd systems I've built. It's a big waste of time. I equate it to those guys that work so hard to get a perfectly vertical main shaft before starting - pointless.

I only leveled at mid stick. Top and bottom seemed a bit much.
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Old 07-21-2021, 07:24 PM   #11 (permalink)
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I’ve never gone through the entire process either. Just level the swash at center. I have Heli’s that are off by 1-2 degrees and they still fly.

There are other options as well, including adjusting the collective endpoints (not recommended). But the ‘best’ way is to adjust the endpoints to even out the travel, at least for Ikon. (And as others have recommended, to adjust the links, but it’s a bit more difficult to get right)
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Old 07-21-2021, 08:08 PM   #12 (permalink)
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The few degrees of pitch difference are due to how the links slant out from the swash to the blade grip arms. It's just the geometry of the head. A few helicopters don't have this effect notably the Compass Chronos and the Trex 760X, the Chronos because all of the links are perfectly vertical at center collective with no slant (they shortened the servo arms and increased the diameter of the upper swash ring to compensate for the reduced blade grip arm lenght) and the 760X because they have slanted the blade grip arms down by 20 degrees so that the angle between the links and the arms is a 90 degree corner.


Out of the two the Chronos's solution is more elegant. The only reason slanted head links because the norm is because FBL heads were originally addons for machines designed for a flybar and they needed longer arms to work with the swashplate and servo geometry. For some reason this became standard FBL design even though as seen in the Chronos there is a better way of designing an FBL head.
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Old 07-21-2021, 09:38 PM   #13 (permalink)
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+12.0 to - 11.4 seems a bit much. IIRC, when that happens to me I set one with the FBL limits and the other with the pitch channel limit..

Works great for me.

Hope this helps some.
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Old 07-25-2021, 12:35 PM   #14 (permalink)
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Try offsetting the servo arm. If the collective is uneven, cyclic will be uneven as well.
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Old 07-25-2021, 03:50 PM   #15 (permalink)
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Quote:
Originally Posted by Family Guy View Post
Try offsetting the servo arm. If the collective is uneven, cyclic will be uneven as well.

See my previous post, except for the Chronos or Trex 760X collective will always be uneven, and yes cyclic is too. I wouldn't worry about it because even if the positive and negative collective is perfectly even cyclic is still uneven due to the sine geometry of the servo arm rotation interacting with each other. You just can't get "perfect" geometry with three servos and ECCPM. If you want perfect head geometry you're going to have to go back to mechanical mixing. ECCPM was a tradeoff for mechanical simplicity in exchange for worse head geometry.
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Old 07-28-2021, 06:58 PM   #16 (permalink)
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If everything is not perfectly 90 degrres, you will have uneven points. Just trim out in the radio & ride the wave man
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