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Old 02-15-2012, 08:12 PM   #1
Jaso
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Default Tail servo frequency ?

Hi all .

I have a futaba 9256 on the tail of my E7 with the GT5 and nearly have it sorted to my taste only thing is the tail is still a bit off . I've played with it more this morning and it is better but on the way home I was wondering about the tail frequecy ?

I know when I set it up I could not for the life of me find a figure for rudder servo frequncy any where .

Does any body know where I can locate this figure for my servo ?
Will a higher frequency make the tail hold a little better ?

cheer.
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Old 02-15-2012, 08:44 PM   #2
guruduck
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I do not know frequency of S9256.

To my understanding, the tail servo frequency is the number of times per second the Gyro updates the tail servo for a new angular location. In theory, this frequency is higher the best provided it does not exceed servo rating. I yet have to test the performance difference of 200hz and 333hz

However, if you are just hovering and head speed remains steady and no cross wind is blowing, the tail servo output does not need to change much. That means, no matter 166hz or 200hz or 333hz, you still get the same heading hold result.

If your tail is not holding, then there must be other things affecting it. Keep looking.

Set 166hz for S9256 is a safe start.
then set to 200hz to see if servo overheat or jiggling or make loud noise.

My 0.02.
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Old 02-15-2012, 10:06 PM   #3
Jaso
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I have it set to 166hz as I figured as you have said that it would be a safe place to start .

I feel a bit scared to take it above this frequency with out knowing more about what is and isn't possible for the servo .

But as You said and my feelings tell me , there is more so an issue somewhere else causing the tail to not be 100 percent yet .

I have adjusted M+DMA pitch as suggested on another htread here and I think it was better after that but still not 100%.
I set it to +10 and that made it worse so I went -10 and that was better .
I'm looking at the GT5 configuration table in front on me and notice that the DMA pitch setting for a DS1015 and BLS 251 on a E720 are at -34 on the DMA pitch so maybe I should take that out some more and see if that helps ?
I'd say that the BLS 251 is probably closest to the s9256 for characteristics and also that figure of -34 is for the E720 being a 700 size heli so might be the go .

These are my tail figures for today after some tweaking -
Rudder -- P= 110
I = 100
DMA cyclic = -20
DMA pitch = -20

On further checking of manual on the DMA settings I just found that is suggests the DMA cyclic is normaly about 1/3 less than the DMA pitch !
Perhaps this is creating an additional issue also ?
By the suggested figures I probably should turn the DMA cyclis back to say -10 and try that or do that and even turn up the DMA pitch to -30 ?

Also has any one found an issue with continuing to just turn up the tail P figure ?
Most of the numbers I've seen people quote are around the 100 mark max .
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Old 02-15-2012, 10:13 PM   #4
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Also I forgot to mention , my tail is not holding 100% under load , not bogging of the head but just on anf off hard load it is a bit iffy .
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Old 02-16-2012, 02:32 AM   #5
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The S9256 was designed for the GY611 gyro and has a refresh rate of 560hz and centre pulse of 760us so use the same settings as the BLS251.

Have you tried 110mm blades or a higher head speed? The E7 is not the best on the tail at under 2200 head speed but the 110mm blades do help allot!
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Old 02-16-2012, 03:08 AM   #6
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Quote:
Originally Posted by Jaso View Post
I have it set to 166hz as I figured as you have said that it would be a safe place to start .

I feel a bit scared to take it above this frequency with out knowing more about what is and isn't possible for the servo .

But as You said and my feelings tell me , there is more so an issue somewhere else causing the tail to not be 100 percent yet .

I have adjusted M+DMA pitch as suggested on another htread here and I think it was better after that but still not 100%.
I set it to +10 and that made it worse so I went -10 and that was better .
I'm looking at the GT5 configuration table in front on me and notice that the DMA pitch setting for a DS1015 and BLS 251 on a E720 are at -34 on the DMA pitch so maybe I should take that out some more and see if that helps ?
I'd say that the BLS 251 is probably closest to the s9256 for characteristics and also that figure of -34 is for the E720 being a 700 size heli so might be the go .

These are my tail figures for today after some tweaking -
Rudder -- P= 110
I = 100
DMA cyclic = -20
DMA pitch = -20

On further checking of manual on the DMA settings I just found that is suggests the DMA cyclic is normaly about 1/3 less than the DMA pitch !
Perhaps this is creating an additional issue also ?
By the suggested figures I probably should turn the DMA cyclis back to say -10 and try that or do that and even turn up the DMA pitch to -30 ?

Also has any one found an issue with continuing to just turn up the tail P figure ?
Most of the numbers I've seen people quote are around the 100 mark max .
Dont care about numbers and other setups! Every model is specific. Tweak G-T5 until it will fly well. On my TDR i have DMA pitch 70 and DMA cyclic 5. Dont mess with DMA cyclic until you dont have correctly set DMA pitch.
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Old 02-16-2012, 03:55 AM   #7
Jaso
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Cool , thanks for the advice .

Back to it again shortly , I'll get this tail spot on if it's the last thing I do ! lol .
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Old 07-28-2012, 10:28 AM   #8
Graviteesuks
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I know this is an old thread but I can tell from many experiments with tail servo frequencies that the higher the frequency, the better the tail holds, especially in fast backwards flight like when you're doing a backwards inverted hurricane.

Also, as mentioned earlier in this thread, the slightly larger tail blades really help but only when you're flying at lower than normal headspeeds! When you raise the headspeed with the larger tail blades, you have to reduce the heading hold tail gain lower than youd like to keep it from oscillating, then it feels kinda mushy. I run my 700 class electric Raptor (E720) from 1300 to 1800 RPMs and at 1300 I found myself having to use 115mm tail blades but then it suffers some at 1800 because the tail gain is so low. My solution was to use different tail gains (one for each headspeed) but i gend to fly more at the lower headspeeds.
I also fly at 1600 so I use the Gyro Sens feature on my Tx to have three different tail gains that change when I change flight modes.

Bottom line is that higher gains, higher frequency, narrow pulse width all equal better stability in the tail. For a brief example, if you're running a 700 class heli at 2000 RPMs, using 105mm tail blades, the highest frequency possible along with a very fast servo and narrow pulse width you'll have a rock steady tail if there's no other problems with your bird.

Just my 2 cents worth but it cost me a LOT more than that to learn what I just wrote. :-D


If you haven't already figured it all out by now, I hope this helps! :-)

I use the Hacker 400kv Turnado which is 4500 watts and supposedly translates to about 6 hp if you buy that roughly 735 watts is equal to 1 hp in electric motors.?@"



Quote:
Originally Posted by guruduck View Post
I do not know frequency of S9256.

To my understanding, the tail servo frequency is the number of times per second the Gyro updates the tail servo for a new angular location. In theory, this frequency is higher the best provided it does not exceed servo rating. I yet have to test the performance difference of 200hz and 333hz

However, if you are just hovering and head speed remains steady and no cross wind is blowing, the tail servo output does not need to change much. That means, no matter 166hz or 200hz or 333hz, you still get the same heading hold result.

If your tail is not holding, then there must be other things affecting it. Keep looking.

Set 166hz for S9256 is a safe start.
then set to 200hz to see if servo overheat or jiggling or make loud noise.

My 0.02.
Guruduck
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Old 08-04-2012, 03:14 AM   #9
Jaso
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Thanks for posting. I never adjusted my tail servo frequency from 166 so i shall up it and give it a try for sure after reading your results.
I have a goblin 630 on it's way to me and should be here next week. I'm thinking it will be getting another GT5 in it after having a really good result from my current one in my E7.
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