Topic Subscribe
WATCH  3 pages [ <<    <    ( 1 )     2      3     NEXT    >> ]3060 viewsPOST REPLY
HeliProz . Boca Bearings . ExperienceRC
. .

Radio - Futaba FASST

 >

tail drift and gy401

mustang67ford

Key Veteran

Central Pennsylvania

I have a Gy401 gyro and it does an excellent job. Much better than the ball bearing gyro I had. Whenever I am hovering tail in, the tail boom slowly drifts to the right, nose to the left (counter clockwise looking at it from the top). Does this mean the gyro gain needs turned up (at 50% right now) or does it mean the tail needs a couple clicks of trim? Strange, because you would think it would have a harder time fighting the thrust. thanks

08-08-2010 Over year old.
tadawson

Elite Veteran

Lewisville, TX

Are you running in rate or heading hold? On a 401, you need to setup in rate mode first, and mechanically trim for no drift. *Then* try HH . . .

And how are you determining "50%"? A true 50% on the channel (center value) disables a 401 completely . . . 75% or 25% on the channel would give 50% gain in HH and rate respectively, if my memory is correct . . .

- Tim

Friends don't let friends become electrotarded . . . .

08-08-2010 Over year old.
cudaboy_71

Elite Veteran

sacramento, ca, u.s.

also, you can't use rudder trim on the 401.

by the book, you need to set it up mechanically in rate mode to hold with no trim; toggle between HH and rate mode 3 times and that locks in neutral for HH, and you're set.

if you're putting trim in the rudder in HH, it will initialize that as center each time you power cycle.

if it ain't broke, break it.

08-08-2010 Over year old.
HOMEPAGE  
Hamo

Veteran

Ireland

Whenever I am hovering tail in, the tail boom slowly drifts to the right, nose to the left
I think it's normal to have a slow drift. People will tell you that their gyro holds like a vice. Not true. A 401 only reacts to quick changes of direction, it does not detect small changes. Prove this to yourself by putting the helicopter on a table with the engine off and pushing the tail to one side slowly. You will see the tail servo does not respond to slow rotations. Give it a sudden move and the tail servo will move.
This is because the 401 and most similar gyros don't know the actual heading, in other words, a 401 doesn't know the helicopter is heading east or west or any other direction. It only responds to sudden changes of direction.
Hamo

08-08-2010 Over year old.
dkshema

rrMaster

Cedar Rapids, IA

This post ought to help get your 401 working correctly:

The pushrod should end up perpendicular to the servo arm when the servo is at neutral. You can achieve that by experimenting with how you install the arm (the splined shaft will allow many different mounting positions, probably only ONE that will be spot on, or very close. If you can only get very close, then use subtrim on rudder to get that 90 degrees geometry.

With the 90 degree geometry, you will get as much pushrod travel in one direction as you will with the opposite direction. If you don't have the 90 degree geometry, you will get a differential amount -- more one way than the other.

Initialize your gyro in Heading Hold mode. The red LED must be on solid after initialization to indicate HH mode. If it's blinking, you didn't start up in HH mode and the gyro will work poorly. Starting up in HH mode is an absolute must for the 401.

Switch from HH mode over to Rate mode. The servo will track the stick and return to center when you let go of the stick.

Set your Rudder Endpoints to 100%. They don't adjust what you think they do. Rudder Endpoint settings in a HH gyro only determine the maximum yaw ("piro" ) rate that the gyro will allow the heli to have.

The GYRO mounted TRAVEL LIMIT adjustment is what you use to tell the gyro how far it will allow the servo to travel, not the rudder endpoints.

Once you figure out how to put the servo arm on the servo to get the 90 degree geometry at neutral, set the TRAVEL LIMIT on the 401 to 100%. Set the DELAY to ZERO and leave it there. Set your rudder endpoints to 100% and leave them there.

Pick the distance out from the servo center for the ball-link that drives the TR such that with full rudder, your servo moves AT LEAST +/- 45 degrees from neutral without binding up the tail pitch slider at either end of its travel. You may end up having to fine-tune the TRAVEL LIMIT setting, but try to position the ball link such that you are as close as possible to 100% on the TRAVEL LIMIT adjustment, get +/- 45 degrees of servo travel, and no binding at the pitch slider.

With the servo at neutral and that 90-degree geometry, set up your tail rotor linkage PER THE HELICOPTER ASSEMBLY MANUAL INSTRUCTIONS. Again, fine-tune the TRAVEL LIMIT setting to make sure you don't bind at either end of travel on the pitch slider. Don't necessarily expect to get equal amounts of travel in each direction, some helis are just built that way.

Remembering to ALWAYS start the 401 up in HH mode, do so, then switch over to normal mode. Lift off to a hover and see which way (if any) the nose wants to yaw. Land, and ADJUST THE LINKAGE until you can hover and the nose doesn't want to turn left or right on its own.

Land, switch back to HH mode, go fly. If you find that the yaw ("piro" )rate is too slow for your liking, INCREASE the RUDDER ENDPOINT setting. This will speed up the yaw rate. If, on the other hand, the thing spins too fast, DECREASE the rudder endpoint settings.

Crank up the gain until the heli's tail oscillates in fast forward flight, then back off just a bit until the oscillation stops.

-----

You don't say what radio you have. The post below is written around the DX7 transmitter, but the principles apply to any radio. Read it, understand it, you'll be able to get your 401 working well.

http://rc.runryder.com/helicopter/p4285239/


-----

NEVER NEVER NEVER use the RUDDER TRIM tab on the TX when your heli is in HH mode. ALL flight modes MUST HAVE the SAME rudder trim setting. Changing the rudder neutral point by way of the RUDDER TRIM tab AFTER the GYRO has initialized will confuse the gyro (you moved where it thinks NEUTRAL should be) and it will work poorly, if at all.

-----
Dave

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

Team Heliproz

08-08-2010 Over year old.
nocontrol1

Senior Heliman

Melbourne, FL, USA

This post ought to help get your 401 working correctly:
He speaks the truth! Great post Dave, very informative for the 401.

Rob D.

08-08-2010 Over year old.
HOMEPAGE  
Hamo

Veteran

Ireland

Whenever I am hovering tail in, the tail boom slowly drifts to the right, nose to the left
Please define "slowly" as in how many seconds to turn 90 degrees.
Hamo

08-08-2010 Over year old.
mustang67ford

Key Veteran

Central Pennsylvania

My radio is a futaba 6xa/6xh. 0 is 0% and 100 is 100% so my transmitter is set to 50 for 50%. Since I got the heli set up, I only fly in HH mode, only flip the switch to normnal mode to fecenter the tail slider. As for the drift speed, I would say it would take maybe 1 minute +/- though I never left it drift that far to find out. Usually after about 5 to 6 seconds I need to make a correction.

You can use the trim tabs instead of mechanical adjustment. Use normal mode (not HH) and trim the heli. Land it, turn off the RX, program the trim and reset it, turn the heli on in HH mode. This is how you can trim it with the trim tab instead of mechanical. I am pretty familiar with the operation of the gyro, been doing a lot of reading and everything everybody has said is true other than only making mechanical adjustments, no pun intended.

All the posted info is very helpful but I still don't think my question got answered. If it did, I missed it and must apologize. Lets throw all the technical stuff away, such as gyro type and TX type, and make the question more generalized as follows: With a non specific gyro and a tail that drifts to a side, is this fixed by more gain or by trimming/mechanical adjustment? Thanks again for all the help, I just need a more generalized answer to be able to understand or maybe its not as simple of an answer as what I was expecting.

Thanks

08-09-2010 Over year old.
dkshema

rrMaster

Cedar Rapids, IA

Drifting. General question, general answer.

Poor gyro setup.

Poor mechanical setup.

Somewhere in your ship you have way too much vibration.

-----
Dave

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

Team Heliproz

08-09-2010 Over year old.
Hamo

Veteran

Ireland

As for the drift speed, I would say it would take maybe 1 minute
I think this is normal and too slow to be corrected by any RC gyro. Like I said before, put the heli on a table with the engine off, power up the Tx and then the Rx / gyro, wait till it initializes in HH mode, then do the test. Push the tail to one side slowly and you will see that the gyro will not detect the rotation. The tail servo will not move unless you give it a sudden push. Anyone who claims their gyro never drifts doesn't hover for any length of time so they don't see it.

Hamo

08-09-2010 Over year old.
LonR

Elite Veteran

Macomb,Mi

When setup like dkshema said,a GY401 will not drift at all.

600LE,OS55,OS PowerBoost pipe,Align 610's,Spartan

08-09-2010 Over year old.
HOMEPAGE  
Hamo

Veteran

Ireland

When setup like dkshema said,a GY401 will not drift at all.
I bet you it will. Try it yourself. Try the test I suggested and you will see the 401 will not respond to slow drift, only quick movenents

Hamo

08-09-2010 Over year old.
CX1

Key Veteran

Canada

Hamo turn up the gain and it will

drift is usualy caused by not letting the gyro initialize properly on startup on a well set-up gyro.
Vibration can also be a cause,
never use trim of any kind

use rate mode to center your tail slider and servo arm and thats about it unless you plan on using rate mode

do what bob says

http://www.helifreak.com/showthread.php?t=23209

08-09-2010 Over year old.
HOMEPAGE  
MinAirUSA

rrAdvertiser

Billings, MT USA

You can use the trim tabs instead of mechanical adjustment. Use normal mode (not HH) and trim the heli. Land it, turn off the RX, program the trim and reset it, turn the heli on in HH mode. This is how you can trim it with the trim tab instead of mechanical. I am pretty familiar with the operation of the gyro, been doing a lot of reading and everything everybody has said is true other than only making mechanical adjustments, no pun intended.
This is not correct. You must trim mechanically in NON HH mode first. Your sub trim, and trim tab should be 0. Why not give it a try?

Miniature Aircraft USA

08-09-2010 Over year old.
BarracudaHockey

rrMaster

Jacksonville FL

Turn up the gain a little bit and look for fuel foaming or fin blur because it sounds to me like you have a high freq vibration causing precession.

Andy
AMA 77227
http://www.jaxrc.com

08-09-2010 Over year old.
Hamo

Veteran

Ireland

Hamo turn up the gain and it will
My gain is set up as high as possible without tail oscillation.
At this setting there is a very slow drift and what I am saying is that the 401 can not correct a very small drift because it doesn't know the heading. It only responds to sudden changes. I do tic-tocs, inverted flight, flips, rolls etc and the 401 holds the tail good. The drift is only noticeable if I hover for a length of time without touching the rudder.
Hamo

08-09-2010 Over year old.
BarracudaHockey

rrMaster

Jacksonville FL

Sorry but thats just not correct, well you're right in that it doesn't know a compass heading, but it can keep a helicopter tail drift free.

Whats happening, I'd bet money, is precession from vibration

Andy
AMA 77227
http://www.jaxrc.com

08-09-2010 Over year old.
LonR

Elite Veteran

Macomb,Mi

Hamo
Hamo turn up the gain and it will
My gain is set up as high as possible without tail oscillation.
At this setting there is a very slow drift and what I am saying is that the 401 can not correct a very small drift
You should go through everything because that gyro will not drift when setup right.Ive had 5 GY 401's and never had a problem with drift,not even in rate mode.Im so picky about setting my tail up that i'll take the ball off the heli/link and put it in the wrong way just so I can get that half turn then screw it back in.Sometimes I have to do that when changing a tail link or ball because i'll get a tiny bit of drift to the left/right no matter which way I turn the link because it only needs a half turn.

600LE,OS55,OS PowerBoost pipe,Align 610's,Spartan

08-09-2010 Over year old.
HOMEPAGE  
Hamo

Veteran

Ireland

Whats happening, I'd bet money, is precession from vibration
I did a test on the bench under ideal conditions in that there was no wind effect , no vibration, no other external factor involved.
Powered up the transmitter, then the helicopter (in HH), engine off, and a few seconds later the 401 red light was solid and the tail pitch was where it should be. (I set this correctly in rate mode and the tail is stable in rate mode if there's no wind). Now if I push the tail slowly in one direction the gyro does not respond, ie, no servo movement. This is simulating a small drift due to a light breeze and is proof that the 401 can not correct a small drift. I continued slowly till the helicopter was rotated 90 degrees and the tail pitch didn't change. Will you please go out and hover for 60 seconds without touching the rudder and tell me the tail still points in exactly the same direction.
Hamo

08-09-2010 Over year old.
dkshema

rrMaster

Cedar Rapids, IA

Is setting the heli on a table and very slowly pushing the tail a real-world test? Would you REALLY ever be able to see THOSE conditions in a running, hovering heli?

-----
Dave

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

Team Heliproz

08-09-2010 Over year old.
WATCH  3 pages [ <<    <    ( 1 )     2      3     NEXT    >> ]3060 viewsPOST REPLY
JR AMERICAS . HeliDirect . Heli-Max
. .

Radio - Futaba FASST

 >

tail drift and gy401

 Print TOPIC Advertisers 

Topic Subscribe

Saturday, August 2 - 9:33 am - Copyright © 2000-2014 RunRyder • EMAILEnable Cookies