Rudder sub trim Q

popadel · 03-05-2010, 02:35 AM

With every set up I have always had 0 trim on the rudder servo and a perfect hover in rate mode.
I am working on a 3G Trex 700 project that requires some modification and the only way to get full rudder movement left and right is to use a bit of sub trim. Its space limitation as i moved the BLS 251 into a confined space. Ruder servo horn is as close as i can get it and does not line up as i want it.

How bad is it to have 5-10 points sub trim in the tail servo? Will it affect my flight characteristics? This is a 5-6Kw heli with -+15 deg pitch and 710 blades so its destined for some serious acrobatics and accurate control.

Thanks
Adelin

crazyerick · 03-05-2010, 03:22 AM

Its a continious debate. I also followed your method but after listening to Finless and setting up 3 Align GP750's I have since done the subtrim route.

ACKopter · 03-05-2010, 07:24 AM

I always thought it was OK to use subtrim on the rudder, My personal experience with the Align GP750 gyro proved otherwise. I had constant drift in a hover and servo creep on the bench, once the subtrim was removed all problems went away.
FWIW this was on a stock Trex500ESP using all stock electronics and motor/ESC. Tail servo was the align ds520.

superjoe83 · 03-05-2010, 08:27 AM

as long as you rebind after getting everything set up AFAIK the gyro will use that as the new center point

ACKopter · 03-05-2010, 08:48 PM

Quote:

Originally Posted by superjoe83

as long as you rebind after getting everything set up AFAIK the gyro will use that as the new center point

Interesting, I really cant recall whether or not I did re-bind after my set-up. I used the subtrim as a result of being lazy and the bench creep forced me to set up my mechanical better so I'm better off in the long run anyway.

Pinecone · 03-06-2010, 06:35 AM

A lot depends on the gyro you are using.

Some are fine with subtrim. Some are not. Some require subtrim.

rcflier1 · 03-06-2010, 07:55 AM

you don't need to rebind, and subtrim is ok to use

TheBum · 03-06-2010, 08:04 AM

Quote:

Originally Posted by Pinecone

A lot depends on the gyro you are using.

Some are fine with subtrim. Some are not. Some require subtrim.

One example of one that is not fine with subtrim is the Spartan DS760 with 1.x firmware. A buddy had problems getting his gyro to initialize and we discovered he had enough subtrim added that the initialization inhibit was kicking in (a feature intended to cope with Spektrum receiver link delay times). The 2.x firmware doesn't have that problem because Spartan removed the feature and went with alternate methods.

ACKopter · 03-06-2010, 10:49 AM

The OP was refferring to the 3G and I belive it is the same as the 780 gyro in that system. crazyrick pointed out the finless vids and the GP750 which is the gyro I used and it did not work with any subtrim and I did not recall re-binding my set-up, in hindsight I thought that may have contributed to the problem. According to rcflier1 re-binding will not cure the issue either.
So then, regardless of what some believe and some dont,I guess if your having trouble with a drift then a good place to look would be subtrim provided you are absolutely sure it is not vibration related. Mine was creeping pretty bad during a static bench test so that very well ruled out any vibration induced causes.

03-05-2010, 02:35 AM	#1
popadel Registered Users Join Date: Jul 2009 Location: Johannesburg	Rudder sub trim Q With every set up I have always had 0 trim on the rudder servo and a perfect hover in rate mode. I am working on a 3G Trex 700 project that requires some modification and the only way to get full rudder movement left and right is to use a bit of sub trim. Its space limitation as i moved the BLS 251 into a confined space. Ruder servo horn is as close as i can get it and does not line up as i want it. How bad is it to have 5-10 points sub trim in the tail servo? Will it affect my flight characteristics? This is a 5-6Kw heli with -+15 deg pitch and 710 blades so its destined for some serious acrobatics and accurate control. Thanks Adelin __________________ TREX 700 YS 120, <>T-Rex 700E 3G, <>600 ESP 3G 4035-630, <>T-Rex 450 Pro 3G, 550E 3G Scorp 4035 560

03-05-2010, 07:24 AM	#3
ACKopter Registered Users My HF Map location Join Date: Jan 2009 Location: Branford, FL	I always thought it was OK to use subtrim on the rudder, My personal experience with the Align GP750 gyro proved otherwise. I had constant drift in a hover and servo creep on the bench, once the subtrim was removed all problems went away. FWIW this was on a stock Trex500ESP using all stock electronics and motor/ESC. Tail servo was the align ds520. __________________ I learned something new on 3/1/2010, Stupidity is expensive! To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.

03-05-2010, 08:27 AM	#4
superjoe83 Registered Users My HF Map location Join Date: May 2009 Location: Oregon City, Or	as long as you rebind after getting everything set up AFAIK the gyro will use that as the new center point __________________ T-Rex 450PRO V2, T-Rex 700E V2, T-Rex 500EFL Pro ICE100 Vertigo motor T-Rex 550 FBL BeastX, KDE/Neu, ICE100

03-06-2010, 06:35 AM	#6
Pinecone Registered Users Join Date: Sep 2006 Location: Maryland	A lot depends on the gyro you are using. Some are fine with subtrim. Some are not. Some require subtrim. __________________ Terry AMA#47402, IRCHA # 3395 Blade CP "Pro", Trex 450SE, PiccoZ, Quick of Japan EP8v2 EX, Hurricane 550, Hurricane 200, JR Vibe 50, Blade mCX, Bergen Intrepid Gasser, Pantera 50, Blade mSR, Novus CP

03-06-2010, 10:49 AM	#9
ACKopter Registered Users My HF Map location Join Date: Jan 2009 Location: Branford, FL	The OP was refferring to the 3G and I belive it is the same as the 780 gyro in that system. crazyrick pointed out the finless vids and the GP750 which is the gyro I used and it did not work with any subtrim and I did not recall re-binding my set-up, in hindsight I thought that may have contributed to the problem. According to rcflier1 re-binding will not cure the issue either. So then, regardless of what some believe and some dont,I guess if your having trouble with a drift then a good place to look would be subtrim provided you are absolutely sure it is not vibration related. Mine was creeping pretty bad during a static bench test so that very well ruled out any vibration induced causes. __________________ I learned something new on 3/1/2010, Stupidity is expensive! To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.

03-05-2010, 03:22 AM	#2
crazyerick Registered Users My HF Map location Join Date: Apr 2007 Location: Durban, South Africa	Its a continious debate. I also followed your method but after listening to Finless and setting up 3 Align GP750's I have since done the subtrim route.

03-06-2010, 07:55 AM	#7
rcflier1 Registered Users Join Date: Jun 2009 Location: long island ny	you don't need to rebind, and subtrim is ok to use

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