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HomeRC & Power✈️Aircraft🚁HelicopterRadio - Servo - Gyro - Gov - Batt › Futaba 401 Gyro Set Up Question
06-05-2011 10:58 AM  9 years ago
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notam

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Biloela, Queensland, Australia

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Futaba 401 Gyro Set Up Question
When I initialize my 401 gyro on the bench I noticed that the servo arm drifts and I had to use 15 steps to the right on sub-trim to keep the arm centered. Is this gyro suppose to have a little drift in HH mode on start up? Why does it drift on the bench, is there something wrong?. Cheers.
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06-05-2011 02:43 PM  9 years ago
pH7

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Sterling Heights, MI - USA

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This is perfectly normal. In HH the gyro tries to maintain the exact same heading. In flight, with no rudder input, it is always making extremely minor corrections that cause the tail to maintain its heading. On the bench, there still will be a first minor correction, but since the heli does not respond, the gyro gives more of the same correction, the heli still does not respond (since it is sitting still on the bench), so the gyro gives even more of the same input. Pretty soon the tail pitch has gone completely to one extreme and that darn heli still hasn't responded. This is just the HH gyro trying its best to do its job. It doesn't understand that your aren't actually in the air.

You should just set the sub-trim to zero and leave it there.
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06-05-2011 11:24 PM  9 years ago
RCHSF

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NC

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Setup your heli in Rate mode First. Set your end points to below 50, Both so you know it's in rate mode. (if useing end points on say, your gear ch) If useing a 7 ch radio, and 7 ch rx, use the gyro sensing menu, and set your bottom setting to around 40, and flip your switch on the top left backwards, Not your F-Mode Switch, the Gear ch, that you select to combine in your tx with gyro sens, this will put your gyro in Rate Mode. Then it will go to dead center and stay put. Then set your sevo arm straight up, in the middle. And then when your done. Put your gyro back into HH Mode.
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06-06-2011 07:17 PM  9 years ago
pH7

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Sterling Heights, MI - USA

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Set your end points to below 50, Both so you know it's in rate mode.
You really don't want to do that. When the 401 is powered on, it MUST be in Heading Hold mode. After it initializes correctly, flip the switch to rate mode and then do the rate mode setup. If it is in rate mode on power up, you can't even depend on the gyro at all.
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06-08-2011 05:16 AM  9 years ago
dkshema

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Cedar Rapids, IA

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PH7 is correct. RCFlyer's advice will lead to you nothing but grief and a gyro that would make a better boat anchor than anything else.

The 401 REQUIRES that it be in Heading Hold mode when power is applied. If you have properly initialized the 401, the red LED will come ON and STAY ON after it goes through its power up sequence.

If it comes up blinking, you've not initialized it properly and it won't work very well and may drift everywhere. You will have to restart the gyro and make sure your TX is set to select HH mode when power is applied.

Second thing is to NEVER NEVER NEVER NEVER use any form of trim (rudder trim, sub-trim) AFTER the 401 has gone through its initialization sequence. To do so will confuse it, as you will have moved the neutral position it learned from your RX at power-up.

If you have this hooked to a Spektrum or JR 2.4 GHz system, make sure that when you bind the RX that you have the transmitter set to select heading hold mode in the gyro.

All rudder trim settings must be IDENTICAL in all flight modes, again, if the neutral position changes after the gyro is initialized, the gyro will be confused and will not operate well.

Make sure that your gyro is located away from your speed control if this is an electric heli. Stray electromagnetic fields from the ESC can screw up the gyro.

Beyond the basics, the remainder of your setup dictates how well this gyro will perform.

If your setup requires that you run a very high gain, you may encounter the symptoms you are experiencing. This would be an indication that you have the ball link placed too closely to the center of the servo.

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Set the DELAY to zero.

Set the rudder endpoints to 100%

Make sure any Revolution Mix and/or Acceleration Mix in your transmitter is disabled or set to ZERO.

If you are using a digital servo, set the DS switch ON.

Set the TRAVEL LIMIT to 100%.

At neutral rudder servo, adjust the TR pitch control rod to center the pitch slider on the TR shaft.

To figure out where to put the ball link on the servo arm, place the ball at a distance from center that will allow you to get AT LEAST +/- 45 degrees of servo travel from neutral when you move the rudder stick side to side without binding the tail pitch slider at either extreme. Mount the ball at that point. Fine tune the TRAVEL ADJUST pot so that you don't bottom out the pitch slider at either end of rudder travel. The goal is to achieve AT LEAST +/- 45 degrees of servo travel, have the TRAVEL LIMIT close to 100%, and not mechanically limit servo travel at either end.

This should allow you to run a reasonable amount of gain, use the servo at its best resolution, and have very good control of the tail, good control of the yaw (piro) rates, and a gyro that holds and works very well.

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Start the gyro in HH mode, switch to rate mode. Lift off to a hover, and adjust the TR linkage for a hover with no yaw tendency. Re-tune the TRAVEL LIMIT to make sure you don't bottom out the pitch slider.

Go back to HH mode and fly.

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To speed up the yaw (piro) rate, increase the value of the rudder endpoint settings. To slow down the yaw rate, decrease the rudder endpoint settings.

Adjust the left and right rudder endpoints to try to achieve left and right piro rates as evenly as possible. With the 401, you most likely will not be able to achieve equal left and right piro rates, however. They will be close, but not right on.

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To find the best overall gain setting, fly in fast forward flight, and adjust the gain up until the tail begins to oscillate. Back off the gain just to the point where the oscillation ceases.

Enjoy.

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If you're using a DX7 transmitter, this should tell you all you'll ever need to know about using your transmitter. If you're using a different radio, most everything still applies...

https://rc.runryder.com/p4285239/
-----
Dave

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

Team Heliproz
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