[NSRCA-discussion] Twin elevator servo issue using Futaba 9 ZAP

Fri Aug 11 11:07:05 AKDT 2006

Hi Dave,

The MSA-10 can only adjust for centering and end points. In my case the
tracking between the elevator halves was much better when I used the
matchbox than when I used the Ailevators function in the 9zap WC2. I don't
know what the story is there and I don't think I made any errors in my
programming - it's a no brainer really as it is explained in the manual.

I am sure I could get the throws much closer if I used a multi point mix but
I simply ran out of time to set this up before my comp this weekend, however
you don't remove the lag between one channel and the other. The matchbox has
given me instant results which I can feel in my flying so I will stick with
it for the time being.

Regards,

Peter 

  _____  

From: nsrca-discussion-bounces at lists.nsrca.org
[mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of Dave Smith
Sent: Saturday, 12 August 2006 12:10 AM
To: NSRCA Mailing List
Subject: Re: [NSRCA-discussion] Twin elevator servo issue using Futaba 9 ZAP

Peter:   It was my understanding the MSA-10 only corrected for servo centres
and end point. From your description it seems to adjust travel anywhere in
the servo travel?

I have the same problem as you described,and would like to find I am wrong
in my assumption that the MSA-10 only adjusts end point and servo centering.

Thanks,,,,,,,,,Dave

----- Original Message ----- 

From: Peter <mailto:pentagon.systems at bigpond.com>  Pennisi 

To: 'NSRCA Mailing List' <mailto:nsrca-discussion at lists.nsrca.org>  

Sent: Friday, August 11, 2006 10:01 AM

Subject: Re: [NSRCA-discussion] Twin elevator servo issue using Futaba 9 ZAP

Hi all,

I appreciate all the feedback in relation to this topic.

I have had a closer look at my setup and have come to the following
conclusion.

1.	The mechanical setup of both elevators is close to identical but not
exact. This is certainly part of the problem. 
2.	Servos are not identical and therefore contribute to the problem 
3.	There is a slight delay between master and slave channels if using
the Ailevators function 

I went out and picked up one of the Futaba MSA-10 servo matchbox. This item
certainly removed a majority of my mismatch without touching too much else.
I had originally started to use a point mix and tried to fix it
electronically in the radio but it all became too difficult.

I went out this afternoon and flew the model with the matchbox and I could
certainly tell the difference. It was a big improvement over what I had
before; believe me I had spent a considerable amount of time trying to get
it right. The model tracked perfectly in very tight to medium sided loops
both upright and inverted. I also noticed a big improvement in the hourglass
maneuver as the model tracked more precisely.

Peter 

  _____  

From: nsrca-discussion-bounces at lists.nsrca.org
[mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of Bob Richards
Sent: Friday, 11 August 2006 8:31 PM
To: NSRCA Mailing List
Subject: Re: [NSRCA-discussion] Twin elevator servo issue using Futaba 9 ZAP

Brian,

I think there are two problems. 1) Movement commands from the radio arriving
at the servos at the same time (dynamic) and 2) Control surface throws
matching through the entire range (static).

What you are describing is a dynamic problem, ie: does the radio do all the
mixing and send the information to the servos *at the same time*.  In other
words, while the servos are moving, one is lagging behind the other since
the radio is processing one channel before the other. Also adding to the
dynamic problem are the speeds of the servos, they must be the same.

The other problem is what I was talking about, when the servos stop, are the
control surfaces tracking together. This depends on the linkage geometry as
well as the servos being linear.

A matchbox attempts to correct both problems. However, a matchbox only
matches 3 points in the entire travel range, and the problem described (as I
understood it) is that the throws don't match halfway between the neutral
and endpoints.  It would be nice if there were multiple points in the range
(5, or 7) that could be programmed in the matchbox. This feature could even
be used to program in expo, seperate from the transmitter.

Servos can have linearity problems due to the manufacturing tolerances of
the feedback potentiometers. I have seen pots (not from servos) that were
"adjusted" by milling away material around the perimeter of the conductive
material, but I wonder if anyone does this for the small servo pots used in
our systems.

IMHO, the processing speed is not as much of a problem for us, at least in
pattern, as we might think it is. It is much more important that the
surfaces end up at the same position, since that will affect the flight more
than the small difference in position *while the surfaces are moving*.

Bob R.

brian young <brian_w_young at yahoo.com> wrote:

I think this is a problem with the processing capability of the TX. You have
a progammed mix, it reads one channel then the next. I had a 9CAP where this
problem was very noticable. Now on my 9Z its not as noticable, it looks like
the slave servo is a little slow to catch up. Only real solution in my
opinion is a match box, y-cable or similar device.

I can sit back and pick which servo is the slaved just watching the
surfaces. 

Im understanding that your endpoints match when the surface are finished
moving, and the middle is matched as well. You should be able to stop at any
point in the travel and the pointers line up, when they stop moving. If this
is the case your linkage would be ok. 

I think the speed of the servos has passed the processing speed of the
radio.

Bob Richards <bob at toprudder.com> wrote:

That might be the cause, or it could simply be a difference in linearity
between the servos.

Bob R.

  _____  

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