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

[Peter Pennisi]

Hi Jim,

Thanks again for your detailed responses. I really appreciate them.

My ATV settings are almost identical within 2-3 points of each other and the
geometry is fairly close as well.

I have spent the last 3 hours trying to get it as close as possible but I am
not happy with the setup especially at 1/2 elevator throw. The difference
between both elevator halves is quite noticeable which sort of explains the
aileron work load during all the looping segments of the P07 schedule which
are mostly performed at 1/2 elevator stick travel in my case.

I might try one of those match box thingy's which the IMAC guys use to gang
servos. This will certainly establish wether it is a Futaba associated
problem with delayed processing to slave channels. At least this way there
will be no master or slave as the device itself will do all the matching.
Therefore everything should be relative.


Regards,

Peter   

-----Original Message-----
From: Jim Woodward [mailto:jim.woodward at schroth.com] 
Sent: Friday, 11 August 2006 12:29 AM
To: 'Peter Pennisi'
Subject: RE: [NSRCA-discussion] Twin elevator servo issue using Futaba 9 ZAP
- off list

HI Peter,

I just went through this same ordeal in early July and spent hours trying
different ways to resolve it.  What I found was that the only way to get the
transition points to match (as good as possible) was to have the ATV equal
or within less than 5% percentage points of each other.  Use the subtrim to
get the servo arms 90 degrees to the pushrod.  Subtrim did not seem to
affect throw.  However, different end points definitely affected the
transition tracking. My control horns were 6/32 screws, so I adjusted the
clevis' to get the best final throw, then used the smallest ATV adjustment
possible to get the closest actual endpoints, while using long sticks
pointed at the end of the rudder.  This worked pretty good but was not
perfect.  Literally, I spend HOURS over several nights trying to get this
perfect.  

The other thing I noticed was that if there if your elevator 1/2s are not
perfectly flat (IE, there is some "airfoil" roundness still present on the
elevator), you have no way to guarantee that the flat sticks are starting
from the same position, really.  I then installed my "Budd" Laser meter on
each 1/2, and found that while the "sticks" seemed to indicate things were
OK, the laser meter indicated a different story.  So then I wondered, how
can I guarantee than I am installing either of them "perfect" to each side??
On ailerons it really doesn't matter, but for elevators it does....

I'm really not sold on the dual elevator servo setup. I used FUT 9650 servos
and channels 2 & 5 for the deal.  If I was not weight critical on the
electric plane, I would have installed a "Jomar" servo reversing Y
connector.  These offer "centering" on the servo that is getting reversed.
Also, one servo threw a little more than the other. I ran out of time to try
to "match" servos.  The whole thing was a mess and I haven't flown the plane
yet.  It is close but I tell ya, my "eye" was in the end about as good as
the measuring equipment I had on hand.  If you stand behind the plane and
see the way light hits the surface, you actually get pretty damn close.  My
friend Juan clips on one of those Gator cloths-pin angle deflection gauges
to each 1/2 and calls it a day.

Let me know what you come up with!

Thanks,
Jim




-----Original Message-----
From: nsrca-discussion-bounces at lists.nsrca.org
[mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of Peter Pennisi
Sent: Thursday, August 10, 2006 10:06 AM
To: 'NSRCA Mailing List'
Subject: [NSRCA-discussion] Twin elevator servo issue using Futaba 9 ZAP


 I am using a twin elevator setup (for the first time) in my current F3A
bird. I am having some servo tracking issues which I can't resolve. All end-
points and sub-trims have been adjusted perfectly however when I place some
long extension pins (6 inches) on my elevator halves directed back to the
centre of my rudder I notice one side leads while the other lags. At half
elevator stick the throws are different but the end points line up
perfectly. 

What are you guys doing to get this exact (if you can?)

I have one channel plugged into the elevator channel while the other is in
the gear channel. I am using the Ailevators function on the radio and
configured as suggested.


Thanks 

Peter


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