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HomeAircraftHelicopterBeginners Corner › Tail drift
02-10-2008 12:56 PM  10 years agoPost 1
gruffevans

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Isle of Man

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Hi,

I am looking for some advice about an annoying tail drift. I have a Mars 480 with a GY401 and Futaba S3154 on the tail powered from the BEC via a 5.1v step down. I have gone through the process of setting up the tail, adjusted the limit pot to prevent binding, checked the direction, set the gyro to digital output etc. I have set the mechanical links with the gyro in rate mode, and have no tail drift (although it needs one bump of right trim to hold the tail absolutely steady). When I go back to HH mode there is a very slow tail drift with the tail moving right (ie nose going left) such that I need to put a small dab of right rudder every 10 seconds or so to bring the nose back. The gyro sensitivity is set at 85% in the DX7 gyro sense menu (starts to wag at 90%). I don't think it is an interference issue as the problem is constant, and no other movement occurs except the slow drift of the nose left. I am beginning to wonder if it is a problem with the gyro

To be honest it is not the end of the world, but it is a bit of a PITA, and I thought a Heading Hold Gyro was meant to do away with these sort of things.

Any advice gratefully recieved!

Cheers,
Gruff

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02-10-2008 01:03 PM  10 years agoPost 2
stocky

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Taxachusetts

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With the gyro in HH after the gyro initializes, does the tail servo creep one way or the other? you may need sub trim to stop it.

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02-10-2008 05:17 PM  10 years agoPost 3
Gyronut

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Martinsville In.

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What heli do you have this on..??

Perhaps your HS is too low.

Rick

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02-10-2008 05:28 PM  10 years agoPost 4
Zaneman007

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Texas - USA

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Are you letting the gyro initialize in HH after setting up the rate mode?

If you add one step of trim, in rate mode then go to HH, it will drift.

After setting the heli in rate mode(adding the one step of trim). Re-initialize the gyro in HH. It will see the step trim as the new center position. Now when you flip back and forth it should hold in rate mode and HH.

Old Guys Rule!

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02-10-2008 08:52 PM  10 years agoPost 5
gruffevans

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Isle of Man

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Hi, thanks for the replies.

Stocky, no there is no obvious servo creep.

Gyronut, it is a Mars 480

Zaneman, yes Ihave let the gyro re-initialize in HH mode after setting the tail in rate mode.

If I shorten the mechanical link half a turn in rate mode the nose drifts right slowly needing 2 clicks of left trim to hold it. When I initialize in HH mode with this setup, the nose still drifts slowly left.

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02-10-2008 09:35 PM  10 years agoPost 6
fenderstrat

rrProfessor

Aston,Pa

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you cant have any trim or subtrim with a 401...you MUST get it mechanically perfect with 0 trim....the gyro sees this as rudder input and confuses the gyro

http://www.futabarc.com/team/team-tip-002.html

check step 16

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02-10-2008 09:59 PM  10 years agoPost 7
gruffevans

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Isle of Man

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Thanks for that Fenderstrat. I guess I will have to have another go at the mechanical link. So far, hovering in rate mode, the best I have been able to adjust it is with a very slow drift of the nose left. When I shorten the control link a further half turn, the nose starts to drift right. I don't seem to be able to get a mechanical set up that holds the tail completely still without just the smallest amount of trim in rate mode.

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02-10-2008 10:09 PM  10 years agoPost 8
Dood

rrProfessor

Wescanson

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one bump of right trim to hold the tail
DONT USE TRIM

  ▲
▲ ▲

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02-10-2008 10:20 PM  10 years agoPost 9
fenderstrat

rrProfessor

Aston,Pa

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It is time consuming but worth the effort...if you have a TINY ammount of drift in rate and I mean tiny....sometimes this is ok and it will hold in HH very well....although 0 drift is always best....if the links are at an inbetween spot....move the servo a small ammount...then try the links again to see if you can get it to a spot where you have no drift

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02-10-2008 10:46 PM  10 years agoPost 10
gruffevans

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Isle of Man

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Cheers,

I'll have a go moving the servo just slightly

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02-11-2008 02:19 AM  10 years agoPost 11
Zaneman007

rrElite Veteran

Texas - USA

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you cant have any trim or subtrim with a 401
That is not quite true. You can have trim in the 401. I will not see it as input, IF.... If you put trim into the gyro to get it to work in rate mode, then... REINITIALIZE the gyro in heading hold. The gyro will see the new position which includes the trim as center. Read the manual, and then try it yourself.

Don't get me wrong, I don't recommend using the trim in place of good mechanical set up. On the other hand one or two bumps on the trim.... I have done it. If you're doing three or more, yea pull out the wrench.

Old Guys Rule!

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02-11-2008 09:59 PM  10 years agoPost 12
T-BoneBrickman

rrNovice

Shepherdsville Kentucky United states

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Tail drift
The best way to set up a 401 is this.Set your trims on the radio back to center.The 401 will hold center right out of the box,although it might have some tail wag.Once center if you have a tail boom servo mount set the pitch of the tail blades at 8degees by adjusting the servo on the mount.If you pop your linkage of alot your putting unnesary wear on the links.You can do this by using a pitch gauge set at 8 degrees and run the tail blades up and down vertically and lign the edge of the gauge with the tail boom,and the tail blades will be in line with your center points of your gauge.Its a little tricky,but I found it a good place to start.Once you have it set to 8degrees you can arm the bird andwait til it locks. Then take it out of HH and hover notice wich way it drifts the loosin the servo mounts and slide the servo forwward or back slightly to change the pitch.You can leave one bolt loose on the servo mount so you can keep adjusting the pitch.Once you have it hovering straight you can put it back in HH.THus you will need no trim for center.If you still have drift you might have a bad GYRO it happens even if its new.And remember to adjust your gyro sensitivity to stop the wag.

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02-11-2008 11:34 PM  10 years agoPost 13
BladeRex

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Temecula, Ca

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I can feel your pain gruffevans. I've been having the same problem w/ my Hurricane 550. I have 2 401 gyros and both hold rock steady on my Trex450 w/ a 9650 servo. On my Hurricane I've ran a 9252 (took 2 clicks of trim to hold in HH) and a 9254 (took 1 click of trim to hold) servos. I also have mine setup mechanically to hold straight in standard rate mode, I've tried running my servo arm from 12mm-16mm, seems to hold a bit better at 12mm but needs a bit more gain. More gain also seems to hold better but I get tail wag before it actually holds it straight. I've tried everything other than double gyro foam and shielding the gyro for motor noise. My LHS has the same setup as me but w/ a different motor and it holds fine so I'm thinking it might be motor noise so my next step is to try shielding the gyro. I'll let you know how it goes w/ that.

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02-12-2008 04:50 PM  10 years agoPost 14
gruffevans

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Isle of Man

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Thanks for the advice. Adjusting the tail pitch on the Mars 480 is done by lengthening/shortening the control rod as the gyro is fixed, although a little bit of movement at the gyro is possible. Still struggling to hold the tail in rate mode without any trim though. Its frustarting because I can make an adjustment that seems to hold the tail, but then the next time I go into rate mode the tail will start to drift again.

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02-12-2008 05:01 PM  10 years agoPost 15
kcass518

rrVeteran

Port Washington, NY - USA

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Hey,

I didn't read everything, but if you have a DX7 with the 401, check ALL your rudder trims. Presuming, I guess, that you're using Idle Up 1 or 2 when you're flying, if NORMAL, IDLE UP 1 and IDLE UP 2 Rudder Trims are not all centered, you will get drift when in Idle UP. I just found this out last week. I was having the same problem, and after SEARCHING, I found this tidbit. I checked my radio and guess what? I found my NORMAL trim was bumped to the left. Therefore, in NORMAL, when starting up, the gyro sensed the center and everything was fine. As soon as I clicked to Idle UP, it shifted the rudder trim and the gyro no longer held.

Hope this helps.

Ken

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02-12-2008 05:28 PM  10 years agoPost 16
BladeRex

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Temecula, Ca

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Hey,

I didn't read everything, but if you have a DX7 with the 401, check ALL your rudder trims. Presuming, I guess, that you're using Idle Up 1 or 2 when you're flying, if NORMAL, IDLE UP 1 and IDLE UP 2 Rudder Trims are not all centered, you will get drift when in Idle UP. I just found this out last week. I was having the same problem, and after SEARCHING, I found this tidbit. I checked my radio and guess what? I found my NORMAL trim was bumped to the left. Therefore, in NORMAL, when starting up, the gyro sensed the center and everything was fine. As soon as I clicked to Idle UP, it shifted the rudder trim and the gyro no longer held.

Hope this helps.

Ken
Do you hav e your Tx setup to switch gyro rate w/ the idle up switch and if so is you idle up gain set to standard rate? If so then the reason why you get drift when switching over is because you rudder is trimmed in properly. It is best to try and not have any trim if you can get it out mechanically (if you have a tail boom mounted servo then this is easy, if not you may need a bit of sub trim)but any trim in the Tx should only effect the 401 in standard rate mode not HH mode (assuming it was initialized in HH w/ the trim already present).

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02-12-2008 06:03 PM  10 years agoPost 17
kcass518

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Port Washington, NY - USA

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My Gyro is controlled by my GEAR switch and I always leave it in Heading Hold. I don't use SubTrim or Trim for the rudder, and all my trims are in the middle. I don't know if my explanation was clear enough, but before, my rudder trim was inadvertently to the left in NORMAL, but centered in Idle Up 1/2. When I turned on my Tx in Heading Hold, the gyro would initialize correctly in NORMAL. Then, when switching to Idle Up 1 or 2, the gyro would sense the change in trim (from Left to Centered) and it would interpret that as a change in rudder stick position, so it would not be locked into Heading Hold. That is what caused my drift. When I centered my NORMAL rudder trim and reinitialized the gyro, everything was fine.

BTW, it is not necessary to set up your servo position to eliminate the natural drift when in Rate Mode unless you plan on flying in Rate Mode. I leave mine in HH all the time, and I've set it up so that I get full throw right and left with the Limit set as high as possible. Yes, in rate mode it will drift, but who cares? I have full throw and it works fine. These are two theories on how to set up the 401, and I've tried both. I can't tell the difference when I'm in HH, so I prefer to use the full amount of travel that is available.

BladeRex, I don't know what's happening with your set up. My comments are strictly applicable to the DX7 when changing from NORMAL to Idle Up 1/2. My Futaba 9CHP held the same rudder trim setting in all modes, but the DX7 has the rudder adjustment separately for each mode.

Hope this helps.

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02-12-2008 07:00 PM  10 years agoPost 18
WHITEHOUSE HELI

rrApprentice

Michigan

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I am having the same problem. One possibility that you guys are leaving out. The gyro is bad. I have tried adjusting this problem from every angle. It may be that the gyro is just bad. Try sending the gyro back for a replacement.

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02-12-2008 08:45 PM  10 years agoPost 19
kcass518

rrVeteran

Port Washington, NY - USA

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Not to beat this to death, but now, I think BladeRex is saying the same thing I am - ie, if the trims are unified with each other in Normal and the Idle Ups, then you should have no drift after reinitializing your gyro.

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02-12-2008 09:15 PM  10 years agoPost 20
WHITEHOUSE HELI

rrApprentice

Michigan

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no luck
Its still not fixed.

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