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HelicopterFlybarless Rotor Head SystemsV-Bar › swash pitch problem, help.
02-18-2014 04:11 AM  3 years agoPost 1
S76 Mech

rrElite Veteran

Hatboro, Pa.

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Hey there. I have been flying my Goblin 500 / Mini-vbar combo since I built it back in the summer. I am running all new equiptment and its never been wrecked. Running Pro software in the controller. JR 3717HV servos at 7.4v.

The issue I'm having is the swash is pitching on me. I have always noticed this but now that its winter, I've decided to correct the issue. When I do pitch pumps from a hover, I notice that on Positive collective, the heli would pitch fwd. Conversely, on Negative collective, the heli would pitch aft.

Tonite, I decided to take a look at my setup so see if I found anything wrong. I have a swash leveler on the swashplate. In the TRIM menu, the swash is level at midstick. When I switch to Expert mode, I rechecked it at full positive and full negative pitch. The swashplate remains perfectly level, throughout the whole range.

Now, powerdown.
Unplug the mini-vbar from my laptop and re-initialize. While initializing the swash goes to midstick and is level. Then after initialazation the swash lowers to low stick and is pitching slightly aft. Without touching the cyclic stick, I move the collective to full positive. The swash is pitches forward. Lower the collective back down and the swash pitches slightly aft.

This is exactly what its doing in flight.

Any ideas??

Thanks

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02-18-2014 04:33 AM  3 years agoPost 2
Craigdieslemac

rrKey Veteran

Valdosta, Ga USA

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Sounds like you have more travel on your elevator servo than you do on the other two. Check your end points .. Subtrims.. Go through your transmitter setup again on the vbar software, make sure that is all correct.. And be sure to re-bind after all the changes have been made.
Jeff

Aut viam inveniam aut faciam

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02-18-2014 04:46 AM  3 years agoPost 3
S76 Mech

rrElite Veteran

Hatboro, Pa.

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First pic is full negative pitch (swash tilting aft).

Second pic if full positive pitch (swash tilting fwd).

I am checking the values in the DX7 now. I have no D/R's programmed in. I have 0 elevator subtrim. ATV's are 105%/103% on the elevator. In Tx menu in vbar I am 100/100 on ElE, AIR, Rudd, and Pitch. All midstick trims are 0.

Rebound. no change.

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02-18-2014 05:57 AM  3 years agoPost 4
chickens2252

rrApprentice

Okinawa

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from the manual

[13. Parameter Optimization
Different flight parameters, such as choice of main rotor blades, rpm,
Agility-Setting, style of flying require different reactions of the control
loop.
VBar 4.0 adapts to these flight parameters continuously.
Control loop optimization runs as a background task on VBar,
continuously optimizing the parameters on the cyclic axis.
The system needs a few flights to adapt to these parameters.
When you feel the flight behavior is just right, you can disable „optimize“
by unchecking the box to preserve the current state.]

1.First make sure you don't have any Throttle to cyclic mixing.
2. Then figure out if you have Optimize on or off. If you have it on and have had it on, then the software should have corrected this by now. If it was off, turn it on and go fly. Focus on pitch pumps. If it fixes itself turn optimize back off.

Tighten it tell it loosens then back it off a quarter

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02-18-2014 11:28 AM  3 years agoPost 5
Knucklehead

rrNovice

Bordentown, NJ USA

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Rick,

Does V-bar have a feed forward function? If it does, it will mix a little elevator-aileron to help compensate for torque to keep things level during relatively hard pitch commands. Kinda like collective to rudder precomp but with cyclic instead. My CGY 750 has this capability and it's pretty amazing the difference it makes and I don't fly at the level you do.

Let me know,
Ed

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02-18-2014 11:43 AM  3 years agoPost 6
Ronald Thomas

rrMaster

Gainesville, Fl, USA

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When the VBAR is not in setup mode, the gyros are active so measuring any value at all (pitch, cyclic, etc) will be skewed.
If the swash is level in setup mode at the top middle and bottom, it is correct setup wise.
As to the hell tilting in flight, either you have a CG problem or maybe your elevator pre comp is a little high (main page, main rotor, expert parameters)

Team MikadoUSA 480XXTreme, 550SX, 600SX, 700XXTreme, 800XXTreme!!

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02-18-2014 12:28 PM  3 years agoPost 7
KevinB

rrKey Veteran

Saskatoon, Saskatchewan, Canada

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My vote would be your elevator precomp is too high as well. That's what is causing the swash tilt when not in setup mode on the bench too.
To set it correctly, from a level hover, do a full pitch climb out. If the heli pitches fwd, the precomp is too high. If the tail boom drops in the climb out, it's too low. Once upright is set, do inverted full negative punch-outs and recheck.

There is only one setting for the elevator precomp, so if you find you can't correct both the positive and negative punch-outs, it's likely your CG isn't quite right or your 0 collective position reference setting isn't actually 0 degrees on the main blades.

KevinB

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02-18-2014 04:00 PM  3 years agoPost 8
S76 Mech

rrElite Veteran

Hatboro, Pa.

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Thanks for the informative replies. I went back into the vbar main rotor menu and lowered the elevator precomp number from 8 (default) to 4. On the bench I could see the swash plate move from pitching forward to closer to level. I checked at low pitch as well and it was closer to level. So, I lowered the value even more from 4 to 0. I then rechecked level at both full pos/neg pitch. The swash remained perfectly level throughout the pitch range.

I'm gonna recheck in flight at lunchtime.

Is it okay to have the elevator precomp value at 0?

Also, I noticed within that same menu (main rotor expert) I noticed that there is a checkbook for (optimize control loop). If this is checked, does that mean I am IN optimization for the main rotor? I have never used the optimization features in vbar so I'm not sure. Same question applies to the tail rotor expert menu.

Again, thanks for the help on this.

Gaui Greatness X7, X5, NX4, X3

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02-18-2014 04:03 PM  3 years agoPost 9
Ronald Thomas

rrMaster

Gainesville, Fl, USA

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Zero is ok, the optimizers are on when the box is checked. If you use them, fly your normal routine till he heli feels "locked in" and then land and turn them off. Otherwise they will continue to adjust even when you are just cruising around and then it may feel different when the heli is flying "all out"….

Team MikadoUSA 480XXTreme, 550SX, 600SX, 700XXTreme, 800XXTreme!!

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02-18-2014 05:39 PM  3 years agoPost 10
S76 Mech

rrElite Veteran

Hatboro, Pa.

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Results...

Ok, here goes...

Since I built this heli back in the spring this problem has been there. Since I fly it rarely, I lived with the bobble and tilt of the swash. I said, Ahh... I'll get to it.

Well, I went out and got 2 flights on her just a few minutes ago. The first was simply awesome! Flat in a hover, pitch pumps, inverted, just perfect. Didn't take long for a quick beat-down to occur. The heli flew the best its ever flown. Totally locked-in. Fast, slow, didn't matter it was dead nuts on. Zero bobble on tic-tocs. When I landed, I walked back to my truck to get another pack and said... Holy Crap, that was the best flight on this heli to date!!!

In goes pack #2. Commence to beat-down #2. 2 minutes into the flight, I loose all power to the rotor. I auto into about a foot of snow and land on the skids. Run out into the field and retrieve the heli. Get it back to the truck and find out the problem.

Snapped the motor belt. Only casualty of the crash, broken landing gear. Thank you snow!!!

Anyways, thank you very much for the input on the elevator swash compensation. It was the fix! You fellas Rock!!!

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02-18-2014 11:26 PM  3 years agoPost 11
KevinB

rrKey Veteran

Saskatoon, Saskatchewan, Canada

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Glad to help. Sorry to hear about the crash though.

KevinB

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