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Old 08-19-2011, 04:57 PM   #1 (permalink)
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Default Inconsistent Piro Rate

Hi everyone,

I'm currently also using the big blue Vbar running 5.1V Pro on my Compass 6HV

But i'm currently experiencing inconsistent piro rate when doing prio globe or prio forward flight against wind.

How do i make it more consistent ??

My value for :
RC deadband - 5
Acceleration - 75
P Gain - 75
I Gain - 75
Yaw Rate - 130
Common Gain - 85

I used to get this inconsistent prio rate feeling on a GY401. But after changing to a GY611 the prio is very consistent.
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Old 08-19-2011, 05:00 PM   #2 (permalink)
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Make sure you have enough throw in the direction you piro.
For sample, a logo with quickUK tail (just perhaps 1-2 degree less throw than stock) suffers badly where as the stock setup works.
So every mm on the slider count.

That said, in piro globes, when you do stick stirring at same time, will be much better in the upcoming 5.2 version (coming soon)
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Old 08-19-2011, 05:35 PM   #3 (permalink)
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You can get more throw with the slider toward the tail case. Just remove or reduce the length of the inner spacer. I ground mine down some and may go a little further. Just be careful not to get too close or else the tail grip links will hit the slider control arm. You can even bevel the part of the arm that attaches to the slider where the grip links pass close to get yet more pitch.

I also removed the outer spacer completely.
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Old 08-20-2011, 03:08 AM   #4 (permalink)
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Do you guys mean more throw equal more consistent prio rate ??

Because i'm getting those whipping effect when doing prio globe/prio forward flight. Normally i'll only experience it when coming down of the prio globe. Or forward flight when there is wind.

No wind seems fine or not that bad
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Old 08-20-2011, 03:09 AM   #5 (permalink)
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Yes, exactly what i say, there is not enough throw to keep consistent piro rate in the wind.
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Old 08-22-2011, 07:18 AM   #6 (permalink)
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Today i tried removing the metal spacer and manage to run around 160 CCW throw and 130 on CW throw.

1st flight i'm still getting not very consistent prio rate when doing prio globes especially when coming down fast. I am still getting those whipping effect like it want and dont want to turn.

2nd flight i tried P gain 75, I gain 80. Not much different.

3rd flight i reset the value to 120CCW and 120CW of throw. I tried increasing the P gain to 80 and I gain remain at 75. It seems to be slightly better.

Do you think it could be the P gain causing this problem ?

I still dont really understand the P and I gain and how it will effect the prio consistency during fast forward flight or prio globe etc even after watching the video from MrMel.

Hmm... please advise
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Old 08-22-2011, 11:19 AM   #7 (permalink)
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If you're at 130 and 160 on the limits, you probably need a longer tail servo arm. I'm running into that situation myself and found an arm longer than the longest one I'm using. I'll find out how it goes this coming weekend.
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Old 08-22-2011, 12:04 PM   #8 (permalink)
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I am guessing your piro rate is in excess of the vbar's control limit? The vbar sensors are good for 500*/sec. Beyond that, you get what the physics will let you - uncontrolled.
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Old 08-22-2011, 01:32 PM   #9 (permalink)
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Quote:
Originally Posted by TheBum View Post
If you're at 130 and 160 on the limits, you probably need a longer tail servo arm. I'm running into that situation myself and found an arm longer than the longest one I'm using. I'll find out how it goes this coming weekend.
I'm running the futaba star horn (4 arm kind) using the most outer hole. I'm not sure about longer servo arm because any longer then the current one it look like it might hit the top boom clamp area or something ? plus the rod will be bend right ?

Ok keep us update on your longer tail servo arm =]
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Old 08-22-2011, 01:36 PM   #10 (permalink)
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Quote:
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I am guessing your piro rate is in excess of the vbar's control limit? The vbar sensors are good for 500*/sec. Beyond that, you get what the physics will let you - uncontrolled.
Hmm then how do i limit to 500*/sec ? is there anything can tell me how fast it's spinning ?
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Old 08-22-2011, 01:40 PM   #11 (permalink)
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You will be not at 500/sec with that big heli with 130 yawrate
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Old 08-22-2011, 02:12 PM   #12 (permalink)
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Dunno how the vbar manages this (the "letting rip" > 500*/sec bit). Also dunno which way he's spinning. If CCW, then there's no telling how fast he could go...
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Old 08-22-2011, 02:13 PM   #13 (permalink)
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It doesnt, but it's not relevant, even if wind is blowing 100mph, the relative rotation rate will not change, just need more throw to keep xxx degree/sec
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Old 08-22-2011, 02:36 PM   #14 (permalink)
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Quote:
Originally Posted by MrMel View Post
It doesnt
You positive? vbar will not allow - under any circumstances - tail to spin > 500*/sec? Interesting...

Quote:
Originally Posted by MrMel View Post
just need more throw to keep xxx degree/sec
Well, yes - if the vbar maintains control at < 500*/sec under all circumstances. And, of course, at 100mph into the wind, he will never get enough throw to get 500*/sec CW. CCW, on the other hand, should never whip - according to you. I wonder... - sookainian, which way 'round are you talking about?
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Old 08-22-2011, 02:37 PM   #15 (permalink)
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Your mixing up things.

a) you can get insane rates, but that require some special features, used in 3D moves with "blurr" piros.

b) Does not matter if you do CW or CCW, the RATE does not need to go over 500 degree, only the throw to maintain that rate, if you limit the throw, you will not get even 100 degree/sec so to speak, the more the wind is blowing the less degree/sec.
But if you set it up for 500 degree/Sec, and it has the throw and authority, it will hold this, regardless of wind.
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Old 08-22-2011, 02:51 PM   #16 (permalink)
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Quote:
Originally Posted by MrMel View Post
you can get insane rates, but that require some special features, used in 3D moves with "blurr" piros.
For my education, how does one do that?

Quote:
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But if you set it up for 500 degree/Sec, and it has the throw and authority, it will hold this, regardless of wind.
With the greatest respect, this simply cannot be true.

Assume a tail that can deliver exactly 500*/sec in zero wind, stationary hover, CW piro. It is maxed out at that point, throw- and thrust-wise. Now transition into FF, holding rudder at full stick (500*/sec). The tail spinning from 9 o'clock to 12 o'clock must now be slower than it spinning from 3 o'clock to 6 o'clock: the tail cannot achieve any more against the wind and slows to below 500*/sec (nothing the vbar can do), but with the wind the tail will try to accelerate past 500*/sec (which the vbar may reign back to the target of 500*/sec).
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Old 08-22-2011, 02:54 PM   #17 (permalink)
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>>For my education, how does one do that?

Havent tested it in a while so I cannot say for 5.1x, you need to check with Ulrich, I know Dahl used it last year.
But one way is to set zero gain.


Sorry, >>but with the wind the tail will try to accelerate past 500*/sec

Nope, relative rotation, regardless of wind the relative rotation rate is the same (i.e. Gyro can constantly hold 499 if throw is enough)

It's if it goes 499 -> higher = inconsistent piro rate.
You WANT it to keep the same,

The THROW will be different depending on wind to maintain 499
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Old 08-22-2011, 03:00 PM   #18 (permalink)
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Quote:
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Gyro can constantly hold 499 if throw is enough
Yes, of course. My point is that, between 9 o'clock and 12 o'clock in my example, there is not enough throw. Whereas the same max throw will generate more than 499 between 3 o'clock and 6 o'clock. Hence the whipping. It's normal. It happens with every tail, just a question of forward and/or wind speed.

Put another way, if the yaw rate demand from the Tx exceeds - in parts of the turn - the physically deliverable piro rate, then whipping must follow. Invariably. Unless, that is, the gyro cottons on to the fact that you are performing piros and lowers the yaw rate demand to the lowest rate observed in one 360* turn (such that the very fast "retreating tail" is slowed to the same rate that the "advancing tail" can achieve (at max throw)).
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Old 08-22-2011, 03:01 PM   #19 (permalink)
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Yep, but the 500/degree limit in the gyro has nothing to do with it.
ONLY the mechanical throw.
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Old 08-22-2011, 03:09 PM   #20 (permalink)
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Yes and no. In my extreme example - tail can deliver exactly 500*/sec and no more - it kind-of does: to achieve a consistent piro in FF, the pilot would need to lower his yaw rate demand to below 500*/sec, ie less than full rudder throw. In practice this may mean that he should lower his yaw rate slider to target a slower piro rate overall which in return can be maintained more consistently across the entire flight envelope.
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