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HomeRC & PowerAircraftHelicopterRadio - Servo - Gyro - Gov - Batt › Servos don't move at same rate...
04-11-2010 04:27 AM  8 years agoPost 1
3kidzheli

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columbia, ms usa

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If all my tx functions are set at neutrall and the swash servo bundle doesn't move at the same rate from top to botttom but end up at same point top and bottom what the heck is the deal??? I have the 6985 hitecs...

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04-11-2010 05:03 AM  8 years agoPost 2
dkshema

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Cedar Rapids, IA

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What transmitter/receiver do you have?

How much "different" is the movement of the one servo as compared to the other two?

If you were to swap the plug of the "slow" servo with one of the other two servos, is the same servo still "slow", or does the rate of movement remain with the same ball on the swash?

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Dave

* Making the World Better -- One Helicopter at a time! *

Team Heliproz

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04-11-2010 05:22 AM  8 years agoPost 3
3kidzheli

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columbia, ms usa

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I had a 9z and it was a movement that swaped from one side to the other through pitch range. Hard to exp perfect clear but the swash had a wable affect but always ended at full top and full bottom even. Now I have a fut 10faast and the effect is very very minimal but can notice it if I look hard. Just wonder what causes this... Haven't done any servo lead swaping on the rec, just been sucking it up and flying but it has done it on both helis.

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04-11-2010 05:43 AM  8 years agoPost 4
Wingman77

rrProfessor

Pulaski Tennessee

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are you sure it is a lagging or could it be that the linkage is not setup equally on the servos?

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04-11-2010 06:11 AM  8 years agoPost 5
dkshema

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Cedar Rapids, IA

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Swap servo leads to see what happens. This could simply be due to the processing in your radio and how it sends out the servo commands (channel order and timing).

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Dave

* Making the World Better -- One Helicopter at a time! *

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04-11-2010 06:49 AM  8 years agoPost 6
3kidzheli

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columbia, ms usa

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A linkage issue sounds relavent, this is a point I left out, the 9z was using two diff rx , one that came with tx and a lesser channel for the second. But if the swash is levell at center stick and all the functions are center that doesn't mean the servo arms are linear which would cause a floating action when the swash is cycled. BUT... how does this factor when I changed to a 10 faast and the problem went to minimum? I just got 3 new hyperion servos and the info says that some servos don't communicate the same with a diff tx brand due to fut has a cert center freq etc... could it be the servos? They don't tend to center with 9z but do with spectrum fut? I know I have made more of this than it is worth but just curious...

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04-11-2010 04:33 PM  8 years agoPost 7
dkshema

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Cedar Rapids, IA

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The "standard" neutral pulse width for servos is 1520 microseconds (1.52 milliseconds). [I guess I'm not quite sure when it happened, but there was a time where the neutral pulse was 1500 usec, but for now, the standard is 1520 usec].

The frame update rate for a standard servo is in the neighborhood of 50-60 Hz. About every 16 milliseconds, a new position update pulse is sent to the servos.

Some servos (mostly those designed for dedicated use with a gyro and tail rotor control) have adopted a neutral pulse width of 760 usec. Those servos cannot be used with your RX, since it doesn't support the narrow pulse width.

With the advent of digital servos, the position update rate has increased as well. Most digital servos will accept incoming pulses at a rate of at least 270 Hz, and upwards to 333 Hz. (That "DS" switch on many gyros -- notably the GY401 -- changes the pulse output rate from the low 50-60 Hz rate to the faster 270 Hz rate).

I would suspect that what you saw with the 9Z was an artifact of the method used in the TX to encode and ship out the pulse-width data. The three swashplate servos just don't get their position update at the same time, the pulses go out serially, and are staggered in time.

With newer generations of radios and the increased availability of CCPM-based heli designs, a conscious effort has been made at the programming and design levels to attempt to synchronize the movement of the three swash servos to eliminate that lag that you see.

That would explain the reason your 9Z sucks at CCPM, and your new 10 FASST system is better.

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04-11-2010 07:11 PM  8 years agoPost 8
helitom

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Pine Grove, Calif, USA

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What about one of the obvious things......bum servo?

The older I get, the fewer things seem worth waiting in line for.

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04-11-2010 08:48 PM  8 years agoPost 9
dkshema

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Cedar Rapids, IA

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Bum servo. Maybe, but not likely. That could easily be determined by playing musical plugs on the RX and seeing if the problem follows the servo or stays with the channel.

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04-12-2010 05:18 AM  8 years agoPost 10
3kidzheli

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columbia, ms usa

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Very good info. odd tho now that i recall the servos on my trex 450 didnt act this way. they were dig metal gear hitechs. anywho i will be swaping all my servos over to atlas hyperion in due time.

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04-12-2010 09:46 AM  8 years agoPost 11
hootowl

rrProfessor

Garnet Valley, Pa.

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Could be geometry. To exaggerate, think of one servo with a longer arm on it than the other by an inch. After setting end points so the travel is the same, the servo with the longer arm will get the swash to the top way before the servo with the shorter arm but they will both stop the swash at the same place.

If you use a farther ball distance on the slower servo, you mechanically "speed" it up. Naturally you will have to readjust the endpoints. The problem with longer arms is it reduces usable servo resolution because you are using less to it's travel.

Also Hitecs are programmable. If one truly is slower than the other there is a programmer that can change the speed. Maybe one was programmed a little different than the other.

Some radios, like my 12Z, have the ability to control servo speed for situations like this.

What heli is it. Do you have pictures?

Wolves don't lose sleep over the opinions of sheep

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04-12-2010 10:01 AM  8 years agoPost 12
3kidzheli

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columbia, ms usa

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I have a k3d and a crntury pred gasser. The perspective of a longer rod makes sense as well as changing the ebdpoint to equate the stopping points b oth posy and neg..... BUT~ I had all the programming at default settings zero and level. I left out a puzzle piece, the servos do not iondicate that "one" is slower than the rest but the indication that a warble effect is what I see. If at center stick and 0 deg pitch and endpnt at 100/100 how could the elevator kick up at top and pitch down at lower. The swash will dance slightly pitching differently through the transition on whole but end up level at top and bottom stick. I have jacked and played with programing and got it almost non existing, but as I stated already the faast tx almost cleared it up.

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04-12-2010 10:04 AM  8 years agoPost 13
3kidzheli

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columbia, ms usa

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I will also add I checked all rods and equal length, aswell as the servo horns position angles, this happens on both of my birds. same effect... ???

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04-12-2010 12:22 PM  8 years agoPost 14
hootowl

rrProfessor

Garnet Valley, Pa.

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You could try a different radio. If you know someone that has a more modern radio like a DX7 or a newer Futaba you could change the receiver and compare. The older Futaba radios did not do eCCPM very well. The symptoms you describe are exactly what the 9C does. I never had a 9Z.

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04-13-2010 02:23 AM  8 years agoPost 15
3kidzheli

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columbia, ms usa

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new tx??
my tx is a 10 faast fut its bran new.the issue is way less noticeable on it than the 9z.

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04-13-2010 02:25 AM  8 years agoPost 16
hootowl

rrProfessor

Garnet Valley, Pa.

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Sorry, the 10 should be spot on.

You have other issues. Either a slow servo or a bad setup.

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04-13-2010 02:28 AM  8 years agoPost 17
Raffy

rrElite Veteran

Chicago, Illinois

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If everything is centered, equal length rods, same servo speed then radio programming might not be setup correctly.

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04-13-2010 02:32 AM  8 years agoPost 18
3kidzheli

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columbia, ms usa

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That very well could be the truth. : )

There is no such thing as up, it's all out...

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