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Old Nov 05, 2007, 03:31 PM
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Gyro behavior question.

I just installed the JR8900g gyro with servo combo in my raptor 30, and while hovering with no input to the rudder the tail would swing then stop. What can this be?

I'm using the Dx7 I would pretty much exclude interference

Also I noticed something weird, when I switched the power to on I noticed the tail servo (after it has initialized) would creep very slowly to the opposite side. This is during power up and the remote is on headlock mode. I switched the power to the receiver off than on again and it stopped. I'm a little nervous about that.
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Last edited by wrxsavvy; Nov 05, 2007 at 09:50 PM.
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Old Nov 06, 2007, 07:44 AM
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Quote:
Originally Posted by wrxsavvy
Also I noticed something weird, when I switched the power to on I noticed the tail servo (after it has initialized) would creep very slowly to the opposite side. This is during power up and the remote is on headlock mode. I switched the power to the receiver off than on again and it stopped. I'm a little nervous about that.
I would hazard a guess that they all do that in HH mode, but once the heli is flying it isn't an issue. At least my HH2000 gyro exhibits exactly the same behaviour. Also, if I spool up in HH mode then the tail wags around a fair bit until the tail rotor has enough authority to actually work. To minimise this I use rate mode to spool up and take of then flick into HH. EDIT:- I don't switch off and try again.

When you say the tail swings then stops - how far and how often and how much?

Tach.
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Old Nov 06, 2007, 07:51 AM
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Indeed, how far does it swing?

The other symptom is just the gyro's idea of stick center being off by a minute fraction. Don't worry about it, it's probably meaningless, although curing your other issue might make it go away.
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Old Nov 06, 2007, 08:34 AM
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Well, I don't know anything about that gyro, but on a Futaba 401, this is a symptom of the HH neutral point not being programmed correctly. On the 401, you can move the rudder stick back and forth 4 times fast, and let go. The tail blades (in HH mode) should snap to a center point of a few degrees of pitch. If they jump and then creep to full pitch, the neutral point needs to be re-programmed.

On the 401 you do this by resetting in rate mode, hover and use subtrim until stable hands off hover... land, and flip the rate/hh mode switch 4 times fast ending in HH mode (or simply unplug the receiver power in rate mode, and plug it back in with the transmitter in HH mode).

A lot of people skip this step but it's very important... it's where the gyro returns to when you let go of the stick. 90% of the time your heli will fly fine without doing this but occasionally the tail with either blow out or slide out 90 degrees while increasing throttle. I had all sorts of mystery tail blowouts until I did this. Now my preflight includes moving the rudder stick back and forth fast in HH mode to make sure the tail blades center correctly when I let go of the stick.

Not sure how to set this on your gyro, so this may not even apply.

-tom
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Old Nov 06, 2007, 02:16 PM
Ade
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the 770 is a tricky beast to get setup. one of our local guys has one and its been tough to get it to perform well.

what model is this on?

Ade
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Old Nov 06, 2007, 09:25 PM
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The tail wouls swing about 35-40 degres to the left. It did it a couple of times 10-15 seconds apart. The gyro Im using I belive sets up the neutral point when I turn on the reciever.
Hey Andrew I was able to fix the other issue. I noticed when I was looking at the screen of the dx7 that displays all the channels and there activity. I saw that the rudder activity would change a bit while switching flight modes. I adjusted the sub trims for each mode equally, and then adjusted the ball link to my rudder. (Iv'e seen multiple articles on this forum about that setup, It finally hit me) Now when I switch modes the tail slider dosn't creep.
Since I did the adjustments after the flight, im going to test the results this week.
If it still does it you think its still normal?
Ade the gyro is on a raptor 30.
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Old Nov 07, 2007, 07:48 AM
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You may have found it... the DX7 stores individual trim settings between modes. This drove me crazy when I first switched from futaba. Now I make sure to trim everything on sub trims... I don't even use the standard trims. I wish there was a way to disable the separate trim settings per mode because they are more trouble than they are worth (at least in my experience).
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Old Nov 07, 2007, 04:25 PM
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So far so good I took it up for 10 minutes and it was solid! I whipped the tail around quickly( Quickly doesnt paint the picture I never felt something so fast as this tail servo) It takes some getting use to because this servo is really quick.

Very noisy when activated, I read alot on forums with the same noise. I guess its normal? Anyone elso with the noise?
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Old Nov 07, 2007, 06:37 PM
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Separate trims per mode have no value on the tail, true... but on cyclic if your headspeed changes, they're really useful. I'm guessing that would be even more true on a flybarless multi-blade heli without a cyclic gyro.
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Old Nov 15, 2007, 08:04 AM
DSR
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Hi there
We had the creeping prob. Well I would say make sure all your trims are 0 on the rudder this is very important. Then switch the heli on but hold it very still. Now if it still creeps to a side use the sub trim to stop it from moving. It takes only a click or 2. Switch off and on just to make sure.

PS: This works on JR's G490T and the 770

Dawie
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Last edited by DSR; Nov 15, 2007 at 08:12 AM.
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Old Nov 15, 2007, 08:48 PM
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Quote:
Originally Posted by DSR
Hi there
We had the creeping prob. Well I would say make sure all your trims are 0 on the rudder this is very important. Then switch the heli on but hold it very still. Now if it still creeps to a side use the sub trim to stop it from moving. It takes only a click or 2. Switch off and on just to make sure.

PS: This works on JR's G490T and the 770

Dawie
Is your throttle 50% at mid stick or more?
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Old Nov 15, 2007, 11:34 PM
DSR
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I think it is just below 50% I think 46%.
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