[NSRCA-discussion] Random tip on ATV and setup

Sat Feb 21 07:19:38 AKST 2009

I recently started flying a T-Rex 450 and wanted to avoid using sub trim for leveling the swashplate

at all costs and to have the arms as close to level as possible.  

Someone told me that JR servo arms come in a couple different series with the splines

offset slightly relative to the arms.  I have a BUNCH of them from my heli days in the '80s as well as from

the JR servos I have bought recently.  I couldn't find the markings the person told me to look for but I did

find thru trial and error there are differences in some servo arms.  Worth looking for if you are trying to get the

linkage geometry as close as possible without subtrim.

JLK

To: nsrca-discussion at lists.nsrca.org
Date: Sat, 21 Feb 2009 11:00:43 -0500
From: tocdon at netscape.net
Subject: Re: [NSRCA-discussion] Random tip on ATV and setup

Bob,

Good article.  If the right elevator ATV is set up at lets say 120 percent (down elevator) then the other side is set at like 90 percent (up elevator)- what would the speed be to go down more than the speed to go up.   This is with respect to the left elevator, assuming its set at 100 percent up and down.  Since its less steps, and same step speed (1.17us per step) times 1024 equals 1.2 milliseconds times 60 degrees if throw is like .024 seconds, but with a servo speed of .2 seconds per 60 degrees times 2 (120 degrees throw total up and down) puts it at about 2 percent difference (of .4 seconds).  Maybe I should have gotten up early and gone with Chris to the WRAM...

Bottom line his program setup was straight out of the mad kitchen chef show.   When I asked him why he originally did not take the time to set it up mechanically, I just got kind of a blank stare-  like if the radio CAN do that, then what's the problem.   When we set everything to normal, zero sub trim, and mechanically adjusted the servos and control arms- everything worked fine.  Now this is an extreme example but I got to thinking that if you minimize these electronic setup things it will help with precision.   I try to use little or no subtrim, but do use ATV in the amounts up to 5  or 7 percent to get the end point throws just right. 

Cheers,
Don

-----Original Message-----
From: Bob Richards <bob at toprudder.com>
To: General pattern discussion <nsrca-discussion at lists.nsrca.org>
Sent: Thu, 19 Feb 2009 8:55 pm
Subject: Re: [NSRCA-discussion] Random tip on ATV and setup

Don,

If I am understanding this correctly, the servos are actually moving the same speed (degrees/second). However, because of the mechanical setup differences, the two servos were having to travel different amounts to get the two elevator halves to move the same amount. Regardless, you are correct that a problem in the linkage geometry should never be corrected using radio settings.

The step size of the 1024 Futaba radio is fixed, at 1.17us. I discovered this when I wrote about the Futaba radios in the Kfactor back in Jan '95.

http://www.toprudder.com/hobbies/fut7uap.pdf

Bob R.

--- On Thu, 2/19/09, tocdon at netscape.net <tocdon at netscape.net> wrote:

From: tocdon at netscape.net <tocdon at netscape.net>
Subject: [NSRCA-discussion] Random tip on ATV and setup
To: nsrca-discussion at lists.nsrca.org
Date: Thursday, February 19, 2009, 10:32 PM

Sub trim is a function that moves the servo to get the control surface centered. This in conjunction with end point adjustments can have an adverse effect on servo speeds. You are basically stretching the number of steps for the same amount of travel, among the servos. I was at the FARM club helping out a giant scale newbe last fall and he was flying a third scale H9 Extra 330 with Futaba 8 channel and Hitec servos. One of his servos literally trailed the other one by about 20 or so degrees when moving the elevators up and down in a rapid fashion. He said a servo was bad. Actually, backing up a bit- when he was flying he asked my help to trim his plane and handed me the transmitter . When I tried some waterfalls, it peeled off really bad. When I landed, that is when I saw the elevators moving at different speeds. Upon inspection I found he used the electronic sub trim to get the servos aligned and massive atv end point to get the ends the same throw. He also had the ATVs set at nealy 150 percent. I think he was like, off one complete servo arm tooth and used the sub trim to get the servo back to center. After about 2 hours getting everything mechanically adjusted, the plane flew so much better. It went from something nearly crashing to a competitive IMAC and 3D setup. Any case, I had an identical experience when helping a flyer in Vanceboro, NC last year (after the pattern contest completed). Exact same issue on his (scal e) plane. He thought the Rx was bad until I showed him what the deal was. After mechanically adjusting to get it close, all was well. 

A Good Credit Score is 700 or Above. See yours in just 2 easy steps! _______________________________________________
NSRCA-discussion mailing list
NSRCA-discussion at lists.nsrca.org
http://lists.nsrca.org/mailman/listinfo/nsrca-discussion
_______________________________________________
NSRCA-discussion mailing list
NSRCA-discussion at lists.nsrca.org
http://lists.nsrca.org/mailman/listinfo/nsrca-discussion

A Good Credit Score is 700 or Above. See yours in just 2 easy steps! 
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.nsrca.org/pipermail/nsrca-discussion/attachments/20090221/a6873a6f/attachment.html>