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HelicopterMain Discussion › question about servo stutter
08-08-2009 10:46 PM  8 years agoPost 1
xxcysxx

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Baltimore, MD - USA

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i have a question. i'm setting up my raptor 90se with a new fasst receiver (r6008hs) yesterday and i notice something strange. i searched all day today through variuos forums and couldn't find a solution.

anyway, the problem is the pitch is kind of notchy or stutter when i move it up and down. like when i give it full collective and full negative collective. when i move it fast is not present, but when i move it moderately it more noticable. i can see the swashplate is kind of stuttering as its moving up and down the shaft. do you know what i'm talking about. i also remove the head and washout assembly to make sure and it does the same thing. the swashplate look like it is stuttering as its moving up and down the shaft. the pitch fork assembly move smoothly when i pop the linkage off and move it with my hand, so no binding there.

i tried changing to a different channel on the transmitter and using different gimbal sticks and it still does the same thing, like hooking the pitch servo to the elevator receiver channel and using the elevator stick. i tried swaping out the servo and it still does the same thing. however when i use a jr r790 pcm receiver with my 10x it move smoothly and no more stutter effect.

the transmitter is a 14mz with tm-14 fasst module, the receiver is r6008hs fasst receiver, the servo is a jr ds8717.

if you know anything please help me out.

thanks

Tam

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08-08-2009 11:23 PM  8 years agoPost 2
BrunoBL

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Pomerode, SC, Brazil -26.71, -49.17

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Remove the collective pitch arm link from the servo, move the link by hand. Do you feel anything binding? Should be really, really smooth. Also, do the opposite test: command the servo up/down with the Tx, with the link disconnected. Still the same stutter?

Don't exclude the possibility of the servo going bad. Once my 9254 tail servo started acting exactly like this. Full movement, it was OK. But slow & gradual, there was a funny noise. I was planning to replace it and was expecting the new one any day in the mail. Just one more flight with the old one and... it almost killed my heli. Froze up a few times, scared the h3ll out of me. Landed safely, grounded the heli until the new one arrived, which I should have done in the first place.


...Bruno.
Spectra G on Avgas 100LL, Jewel generator
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HelicopterMain Discussion › question about servo stutter
08-09-2009 01:47 AM  8 years ago •• Post 3 ••
NZ_Nitro

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New Zealand

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also
Grab the servo arm and move it while the power is on, or load it up with your fingers as you move it back and forth, could be stripped gears or missing teeth?

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08-10-2009 04:20 AM  8 years agoPost 4
xxcysxx

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Baltimore, MD - USA

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i spend some time yesterday figuring out the stutter.

the servos are fine. i have been flying them. no problem. i also swap them out to make sure it wasn't a culprit.

the pitch fork is also smooth without any binding or friction as well. i remove the head assembly from the swash up. leaving just the fork and swash plate in place. the fork move up and down with the swashplate smoothly when i move it by the link with my hand. no friction or binding.

anyway, what i did was i use another spare 6008hs receiver, its new by the way, and connect just the pitch servo to the spare receiver and power it with a separate 4.8volt receiver pack, just for the spare receiver to operate the pitch servo. the rest of the electronics onboard the heli remain unpowered. the stutter is still there even on the spare receiver. i change the receiver mode from normal to high speed and the stutter got "better". like it was smooth out a bit. but its still there. i can notice it. i switch back and forth from normal and high speed a few times to make sure, and indeed the stepping effect is lesser on high speed mode.

its like the servo resolution stepping effect. but noticeable when i move the collective stick moderately. not fast, not slow, just moderate speed. it can not be felt by hand or visually seen from the servo wheel alone. its very fine stutter. it's like the pitch fork of the raptor is amplifying this stutter effect.

anyway again, then i swap the spare 6008hs receiver for a 5114dps g3 pcm receiver and swap the transmitter tm-14 module to 72mhz. i use the same 4.8 volt battery. then magically the stutter effect is "gone". it is smooth just like my 10x with r790 pcm receiver. then out of curiosity, i swap the 5114dps receiver with a ar6100e receiver with the same 4.8volt battery pack and swap the 72mhz to dm-9 spektrum module. the stepping effect is worse than the 6008hs on normal mode.

so what's wrong with this picture.
is it the way fasst work? or is it the high speed and precition of the 8717 brings out the evil in high resoluton and low latency receivers?

Tam

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08-23-2009 01:34 AM  8 years agoPost 5
xxcysxx

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Baltimore, MD - USA

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i met another member at my club the other day who also own a 14mz tm-14 fasst and he flies a raptor 903D. which is similar to a raptor 90SE. he was using ace ds1015 digital servos. i ask him if i could check his transmitter and collective travel on his raptor, and it has the excact symtom as i experience on mine. i tried to explain it to him and showed him the the effect of this studder on his own heli and transmitter, and he still doesn't get what i'm talking about. WTF?

oh well.

i guess this must be normal for fasst system then. but i will tell you the 72mhz system is much smoother than the fasst system on the same transmitter.

i will stay tune and wait to meet another member at my club who own a jr 12x. i want to witness firsthand to see if it is smoother.

furthermore, i will try to make a video to demontrate this effect to see if anybody else can understand what i'm talking about.

Tam

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08-23-2009 09:48 AM  8 years agoPost 6
Jeff polisena

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westpalmbeachflorida usa

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I cant tell you the technical terms but the 14 mz is very sensitive . The space between points (I think frame rate pulse width) are real small where space between other tx points are further apart so servo is showing this . Now I said this people can correct with proper terminology but yes this seems normal . When you move stick fast servo acts normal ?

I stole it ,flew it and gave it back ;)

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08-23-2009 04:10 PM  8 years agoPost 7
hootowl

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Garnet Valley, Pa.

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He said in his first post when he moves it fast it is not present.

Wolves don't lose sleep over the opinions of sheep

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08-23-2009 04:33 PM  8 years agoPost 8
xxcysxx

rrKey Veteran

Baltimore, MD - USA

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I cant tell you the technical terms but the 14 mz is very sensitive . The space between points (I think frame rate pulse width) are real small where space between other tx points are further apart so servo is showing this .
well then how come when i attach the 72mhz module into the 14mz and use it with the r5114 pcm g3 receiver the studder goes away, and the studder came back when i attach the tm-14 module back to 14mz and use it with any fasst receiver. this studder effect is also on a club mate 14mz, too.

r5114 g3 pcm receiver is 2048 and r6008hs is also 2048. other difference is the transmitting frequency.

it cant be the pot, because the studder is not present when i use it with the 72mhz module.

Tam

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08-23-2009 06:49 PM  8 years agoPost 9
Jeff polisena

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westpalmbeachflorida usa

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You seem to already know more than me

I stole it ,flew it and gave it back ;)

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HelicopterMain Discussion › question about servo stutter
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