[NSRCA-discussion] Random tip on ATV and setup
James Oddino
joddino at socal.rr.com
Sat Feb 21 13:26:03 AKST 2009
Yes. I usually start with the ATVs around 120 (out of 140) and the
AFR at 100. A lot of throw and a short servo arm is good from a
torque standpoint. The only reason to set them low might be to reduce
the time to get to full throw as someone mentioned. I'd just look for
a faster servo to accomplish that.
Jim
On Feb 21, 2009, at 11:38 AM, John Konneker wrote:
> So Jim it's a good thing to set your ATV/AFR +100?
> JLK
>
> From: joddino at socal.rr.com
> To: nsrca-discussion at lists.nsrca.org
> Date: Sat, 21 Feb 2009 11:31:58 -0800
> Subject: Re: [NSRCA-discussion] Random tip on ATV and setup
>
> That is correct. I'll talk about Futaba but the same applies to
> other brands though the numbers and terminology may be different.
> The maximum resolution available is 2048 increments. This means
> that a receiver channel output pulse width can be at any of 2048
> values between 0.9 and 2.1 milliseconds. This translates to... the
> servo output arm can be at any of 2048 angular positions. In actual
> use we will have less resolution because to get to 0.9 or 2.1 you'd
> need to put the trim and subtrim hard over in opposite directions
> respectively. But you do want to maximize the pulse width range and
> you do this by keeping the ATV and AFR high (over 100). I try to
> keep the pulse width in the 1.0 to 2.0 millisecond range. I use a
> spline curve and don't use Dual rates. Then one must use the
> mechanical linkage to get the proper throw.
>
> And yes if you reduce ATV or AFR you will reduce the range of pulse
> width values but it would not be correct to call that clipping or
> compressing. I would call it lowering the dynamic range, but I
> better Google that to see what they say.
>
> Jim
>
>
> On Feb 21, 2009, at 9:40 AM, J N Hiller wrote:
>
> Jim, I was under the impression that reducing travel using duel
> rates reduced the resolution unnecessarily. I never did really
> understand if the pulses were clipped or compressed with rate
> changes. Help!
> Jim Hiller
>
> -----Original Message-----
> From: nsrca-discussion-bounces at lists.nsrca.org [mailto:nsrca-discussion-bounces at lists.nsrca.org
> ]On Behalf Of James Oddino
> Sent: Saturday, February 21, 2009 9:18 AM
> To: General pattern discussion
> Subject: Re: [NSRCA-discussion] Random tip on ATV and setup
>
> Hi Don,
>
> You lost me with this one and I must confess I didn't study the
> previous posts. I did question your basic premise that using
> Subtrim was a bad thing. I agree it is bad if it is being used to
> make up for a bad linkage setup but it is okay to use it as long as
> the servos are going through identical angles and the servo speeds
> are the same. ( The servo speed, measured in degrees per second, is
> not a function of the transmitted signal.)
>
> The way to approach twin elevator servos, is to match the servos
> prior to installing them in the airplane by installing the control
> horns as close as possible to their neutral positions with the
> stick, trims, and subtrims at zero and then touch up the neutrals
> with the subtrims. You need a large protractor and pointer on the
> servo to do this. Then set the end points to the same maximum
> throws, to more than you would ever want. Then touch up the neutral
> with the subtrim again and the endpoints again until they track
> exactly. Then never touch the Subtrims and ATV again.
>
> Use the AFR or Dual rates to set your desired throws in the plane
> and do any neutral trimming with the normal trim. These functions
> affect both channels equally if you are set up right. Never use ATV
> or independent channel subtrims or end point adjustments to set the
> throw in the airplane.
>
> Hope this helps. I know it will force you to make perfect linkage
> setups if you want the elevators to track.
>
> Regards, Jim O
>
>
>
>
>
>
> On Feb 21, 2009, at 8:00 AM, tocdon at netscape.net wrote:
>
>
> 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.
>
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