[NSRCA-discussion] Random tip on ATV and setup

[J N Hiller]

I have run into a similar problem when tweaking differential aileron
deflection. Equal endpoint adjustment percentages didn't yield equal
deflection increase or decrease. I assumed that different servos rotate a
slightly different number of degrees due to feedback pot accuracy. I never
checked them. I just use a deflection meter every time I make a change. I
never noticed a speed difference. Full deflection of 12 - 15 degrees happens
quite fast. As for elevators a single servo / cable setup eliminated all
deflection balancing problems.
I also set linkage as close as possible starting with 100% travel and
readjust the linkage if significant endpoint adjustments prove to be
desirable. I also like the odd number spline drive Futaba servos for
mechanical setup.
I found the intermediate setup to be lacking when I moved to advanced and
lacking again now that I am trying to fly masters and as a result my
airplanes have spent considerable time on the bench, and the wind is a
problem when trying to measure deflection at the field.
Jim Hiller


-----Original Message-----
From: nsrca-discussion-bounces at lists.nsrca.org
[mailto:nsrca-discussion-bounces at lists.nsrca.org]On Behalf Of
tocdon at netscape.net
Sent: Saturday, February 21, 2009 8:01 AM
To: nsrca-discussion at lists.nsrca.org
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 <mailto:tocdon at netscape.net>  <
tocdon at netscape.net <mailto:tocdon at netscape.net> > wrote:
From: tocdon at netscape.net <mailto:tocdon at netscape.net>  <
tocdon at netscape.net <mailto:tocdon at netscape.net> >
Subject: [NSRCA-discussion] Random tip on ATV and setup
To: nsrca-discussion at lists.nsrca.org
<mailto: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
<http://www.rcuniverse.com/buynow/keywordclick.cfm?bid_id=6405>  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
<http://www.rcuniverse.com/buynow/keywordclick.cfm?bid_id=3854>  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.

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