V120D02S + 2801 PRO. Can you adjust Sub Trim?

[10inja]

can you use sub trim with the v120d02s and 2801 pro?

thanks

[jonbailie]

No, you shouldn't really use any subtrim with any flybarless helicopter, the fbl unit will take care of that.

What are you having a problem with? Setting up the helicopter? You should read up on finless bobs videos on how to set up the bird properly.

You need to bind to the transmitter, then put the throttle stick up half way. Make sure to unplug the motor from the esc, and turn off the flybarless system by flipping the little dip switch on the rx before doing setup. With your transmitter at mid stick, center your servos. Take off the servo horns and make them center. Next, adjust the servo to swash linkages so that the swashplate is level, and you have about the same amount of main shaft showing at the top and bottom of the swash (looking at it directly from the side). After that, adjust the swash to blade grip linkages so that you have zero pitch.

If you do all that and get it pretty close, you should be ok to fly. Turn the flybarless system back on, and plug the esc back in. Then, take her up and see how she flies.

Can you hover pretty well? It's a pretty stable bird, so it shouldn't be too hard. If the heli shakes or wobbles, you may need to turn down the flybarless gyro, but we can get in to that later.

[10inja]

thanks a lot for the email. you pretty much said it all

I read a bunch of posts and just couldn't figure out why you can't use subtrim, but I guess it's the flybarless.

ok, so I got to the part where you want to level the swash plate. I gotta figure out a way to do that. I tried to eye ball the whole thing and the heli can hover but as soon as I let go cyclic it takes to the left fast.

I will try to make something to level the swash plate and then the zero pitch and keep you posted.

thanks again.

[10inja]

actually that was with the pod to the adjust position, with it at wk position the heli is pretty stable, huge difference, I'm starting to see the light.
but I still want to level it a bit better as I don't think it's even close to 100%

[BHChieftain]

Deleted

[10inja]

so, I wanted to really have it 100%, I'm used to a TREX 500 and was wishing this would be controllable like the trex for inside the house, but no chance.

binded the heli to the transmitter at mid stick
set the heli on a table, leveled the heli using the level vial mounted on the tail boom.
put vials on the swash plate and adjusted the links from the servo to swash until swash was level on the vials.
put a pitch guage and adjusted the top links to get zero pitch.

it's all good now.

it's stable if all I'm doing is hovering, but once I move it, it's quick, it moves on it's own, it's not that easy to practice forward flight and things of that nature.

I'm not giving up, will keep practicing till I get better.

[hjns]

Did you try adjust expo or rate? Adding positive expo to the cyclic will give you a much nicer model to fly. Reducing the throttle curve will decrease headspeed, which may also help. However, don't go below 70%, or the tail won't hold anymore.

When leveling the swash, make sure that at midstick the servo arms are close to 90 degrees as well, as mentioned by the Jonbailie. Actually, you CAN use subtrim, but Walkera implemented it in a weird way, and as mentioned, with the 3-axis gyro, you don't really need it. I also assume that with "close to 100%" you mean "close to horizontal". That is really close enough for flying circuits in your living room.

Better spend more time in adjusting expo and flying than in leveling the swash. Can you hover your Trex nose in?

[10inja]

I never looked into expo, thanks for the tip. I will check that out tonight. you mean positive expo where the cyclic controls have less effect towards the center and more effects at the ends?

I did reduce the curve to 60% (so it's 0 to 60) but not sure if I like that too much. the tail holds if i'm just hovering or moving around a bit.

yes, I removed the servo arms and installed them as close to 90 as possible, they're pretty close, did that before leveling swash (thanks to jonbailie)

I am curious how walkera implemented the subtrim and why it doesn't work with 3 axis gyro.

yup, 100% as in swash plate horizontal and blades pitch gauge horizontal at zero degrees when the tail boom is horizontal ( not when the heli is on the table flat as the tail fin makes it tilted a bit).

hovering nose in with the TREX is a challenge for me ( I did that at higher altitude for a couple minutes a week ago), still learning that one, but hoving sideways is all good and moving around all good.

[hjns]

Hi 10inja,

The Trex500 is a huge huge machine compared to the 120 size. It is much more heavy, has a much larger rotor diameter, and is therefore much much much (you get the point) more stable.

If you have trouble nose-in with the Trex, you will have much more trouble nose-in with any smaller machine. This does not have to do anything with setup, it is just the nature of a much smaller machine.

As it is (probably) less costly to crash the D02 as compared to the Trex (just guessing here), you may want to practice nose-in with the D02. Once you have mastered that on the D02, you will be amazed how easy it is on the Trex.

For adding expo to the cyclic, go into the menu of the 2801 pro, and change the curves for elevator and aileron in such a way that a relatively large change in stick input around center will result in a small actual change in elevator / aileron. Further away from center the larger change in stick input will result in a large change in elevator / aileron. With the V120D02S, adding 40% expo to both curves is a nice start. If you still feel the heli is running away with you, add more expo. When you get used to the heli, reduce expo.

You can check the results easily without spooling up the heli, just move the cyclic around and look at the swashplate.

Adding positive expo will result in a heli that is slower to respond to your stick input around center. Although that may sound like a bad thing, in reality it will give you the time to correct any input without the heli running away from you, because the 3-axis gyro will keep the heli so stabilized that it may hover without your input for several seconds.

[jonbailie]

Subtrim is for helicopters that don't use an auto-stabilization system, like a 3-axis gyro. Keeping this feature in the radio makes it more compatible with more models.

In my normal mode, I've got +25% expo on my aileron and elevator channels. This makes it nice and smooth, and easy to hover. In my stunt modes, I've got -25% expo, which makes it very twitchy and agile. I wouldn't go to -25% right now, but the +25% should give you a nice, smooth flight pattern to start off with. If its still too mucho just add some more. Try to keep both the aileron and elevator channels at the same amount of expo, though. It's not super critical, but different settings can mess with your ability to control the bird.

[10inja]

thank jonbailie and hjns for all the help

will try the expos tonight and see how it goes, it's getting better with every flight and help from you.

[Heli-opolis]

I use sub-trim initially to set all the servo's at their mid point at mid-stick and then level the swash by first starting out making each of the servo-to-swash links the same length and then use a vernier caliper from the frame floor to each of the swash horns to fine tune it, since I don't have a swash leveler that fits.

Using a combination of aileron and elevator sub-trim, it is pretty easy to get all three servo's to be as close to their mid-points.

I wouldn't use sub-trim for flight time tuning though but then again, I dislike taking off the link sockets to make adjustments because they wear out and get loose over time but beyond using sub-trim to center the servo's, I find it gets confusing, fast.

[10inja]

Originally Posted by Heli-opolis

I use sub-trim initially to set all the servo's at their mid point at mid-stick and then level the swash by first starting out making each of the servo-to-swash links the same length and then use a vernier caliper from the frame floor to each of the swash horns to fine tune it, since I don't have a swash leveler that fits.

Using a combination of aileron and elevator sub-trim, it is pretty easy to get all three servo's to be as close to their mid-points.

I wouldn't use sub-trim for flight time tuning though but then again, I dislike taking off the link sockets to make adjustments because they wear out and get loose over time but beyond using sub-trim to center the servo's, I find it gets confusing, fast.

I tried that but subtrim doesn't move the servos on this heli with the e axis gyro

[10inja]

I tried expos, but I'm not sure if I like them, maybe I'm just not used to them, it's like I have less control now and it takes a beating on the stick to get out of hairy situations.
I'm still going to keep at it, it'll get better I'm sure

[BHChieftain]

Originally Posted by 10inja

I tried that but subtrim doesn't move the servos on this heli with the e axis gyro

http://www.helifreak.com/showthread....42#post3699342

See step 3-- you can use subtrim on Pitch channel (not the independent pitch servo), since the Pitch channel is really collective and there is no gyro control on that.

3) Reset the servo arms to be as close as possible to 90degrees at 50% throttle. Neat tip from the Helifreak video above is you can actually use Pitch subtrim to finetune (no gyro control on colletive pitch). There still is no ability to adjust each servo independently, but if both arms are slightly low, you can use pitch subtrim to better level them, or make one a little low and one a little high vs. one dead on and 1 way off.


You can also use Travel Adjust on Pitch Channel to remove binding (again, no gyro input on that channel), see same link.

Chief