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HelicopterRadio - Servo - Gyro - Gov - Batt › What am I doing wrong?
02-15-2011 02:14 AM  6 years agoPost 1
Toad95

rrNovice

Jacksonville, IL

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I cannot seem to get the tails set up correctly on my helis (I have several, with similar problems, one at a time though). I have a T-Rex 450, stock motor, stock esc with a GY-520 gyro and a DS3400g tail servo. I am not sure what the head speed is, although I know it is not to slow. The problem is a slight twitching every now and then (3-5 sec). I have the gain turned down to 55 om my JR10X. Much higher on the gain and the twitching is worse or I start to get a wag. The ball on the servo arm is set at 9mm and the is no binding (or support) in the linkage going to the tail. It is a micro heli pro tail. I would like to try to do a small ap project with it if I can get it calmed down. Also if you have any suggestions on how to make it less sensitive those would also be welcomed (I have 30% expo in the head, aile, elev, pitch). Please, if you have any suggestions, I am willing to try them.

Thanks, John

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02-15-2011 04:48 AM  6 years agoPost 2
dkshema

rrMaster

Cedar Rapids, IA

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Move the ball inward a couple of millimeters. 9 mm on a 450 is a bunch.

Try to get at least +/- 45 degrees of servo rotation from neutral in each direction without having the pitch slider bottom out at either end.

This will allow you to run higher gains, get better precision out of your servo, and will allow you to get more resolution out of the servo, as well.

If the ball is too far out from center, it only takes a small amount of servo movement to make a lot of tail movement occur. You also end up with low gain. Makes for a gyro and servo that perform poorly.

-----
Dave

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

Team Heliproz

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02-15-2011 11:02 AM  6 years agoPost 3
Richardmid1

rrProfessor

Leeds, England

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Sounds like static spikes or vibration, have the helis been crashed?

If so check the main shaft bearings and tail shaft bearings for notchiness (if thats a word?!). Check your pinion mesh isn't too tight and you could try spraying some light oil on the torque tube gears and main gears.

Also check your RX isn't too close to the motor or ESC.

9mm is fine especially on a high end JR servo like yours, im using 10.5mm with a 9257 on mine and its one of the best 450 tails ive had.

60% of the time, it works every time!

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02-15-2011 12:57 PM  6 years agoPost 4
dkshema

rrMaster

Cedar Rapids, IA

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Too much mechanical gain -- i.e. too long a servo arm -- forces you to use low gain, and it means only a very small movement at the servo translates to very large changes at the tail. That's just counter productive to putting an expensive, fast gyro and good gyro on your heli.

If you think you're having a great experience with a poor setup, try moving the ball inwards and upping the gain. You'll be surprised at how poorly what you thought was a great setup performed.

-----
Dave

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

Team Heliproz

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02-15-2011 01:22 PM  6 years agoPost 5
Richardmid1

rrProfessor

Leeds, England

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Too much mechanical gain -- i.e. too long a servo arm -- forces you to use low gain, and it means only a very small movement at the servo translates to very large changes at the tail
Totally agree but 9mm is not long for a 450 Pro and I bet he is getting what I believe to be the ideal 90 degrees of servo movement from limit to limit.

My setup of 10.5mm is not ideal but trust me it works and I bet (know) that it wouldn't improve my tails performance if I went to 9mm or less and upped the gain.

Different gyro but the same rule applies:

http://www.rcmodels.org/csm/
Servo Arm length

The faster the tail rotor can react, the better the potential reaction time of the tail rotor system. We are blessed with the fact that tail rotor servos have a rotary arm output. Whilst the actual operating speed of the servo is identical regardless of the length of the servo arm, we can change the effective reaction speed of the servo. The reason for this is that we can enhance the speed by fitting a longer servo arm and reducing the servo travel. Thus whilst the operating speed of the servo is identical, it does not have to travel so far to obtain full tail linkage travel on a longer servo arm.

Example:

I am using a tail rotor servo that operates at 0.10 of a second for 60 degrees of motion. I have then fitted a 10-mm servo arm to achieve 20-mm of linkage travel for 60 degrees of servo throw in each direction. By using the 10-mm arm quoted in this example, we have an actual servo response of 0.10 for the 60 degrees of motion required to obtain the correct amount of tail linkage travel. However, if I were to change to a 20-mm horn, the servo would only have to travel for 30 degrees to obtain the same 20-mm of linkage travel. So the servo is now moving half the distance and will in effect be twice as fast!

However, whilst a longer servo arm will increase the gyro reaction speed, the resolution (accuracy) of the servo will reduce and the gain sensitivity will increase as the servo arm length increases. So we have to adjust the length of the servo arm to match the overall tail rotor / gyro set-up.
Anyway, the OP has a tail twitch every 3-5 seconds, this will have very little to do with gain machanical or otherwise.

60% of the time, it works every time!

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02-15-2011 01:34 PM  6 years agoPost 6
Toad95

rrNovice

Jacksonville, IL

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Thanks for the input guys,

I will try both suggestions and post my results.

Thanks Again, John

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HelicopterRadio - Servo - Gyro - Gov - Batt › What am I doing wrong?
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