X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Sun, 29 May 2011 16:47:41 -0400 Message-ID: X-Original-Return-Path: Received: from raven.ravenwebhosting.com ([72.9.254.67] verified) by logan.com (CommuniGate Pro SMTP 5.4c3j) with ESMTPS id 4997547 for lml@lancaironline.net; Sun, 29 May 2011 09:04:31 -0400 Received-SPF: none receiver=logan.com; client-ip=72.9.254.67; envelope-from=paul@tbm700.com Received: from 111-57.202-68.tampabay.res.rr.com ([68.202.57.111]:64347 helo=[192.168.1.107]) by raven.ravenwebhosting.com with esmtpsa (TLSv1:AES128-SHA:128) (Exim 4.69) (envelope-from ) id 1QQfeo-0005Gt-Oy for lml@lancaironline.net; Sun, 29 May 2011 09:03:56 -0400 From: paul miller Mime-Version: 1.0 (Apple Message framework v1084) Content-Type: multipart/alternative; boundary=Apple-Mail-27--197970567 Subject: Re: [LML] Change the speed of the ROC servo for trim X-Original-Date: Sun, 29 May 2011 09:03:47 -0400 In-Reply-To: X-Original-To: "Lancair Mailing List" References: X-Original-Message-Id: <86A09241-20F7-4112-B8EC-92CE0887E922@tbm700.com> X-Mailer: Apple Mail (2.1084) X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - raven.ravenwebhosting.com X-AntiAbuse: Original Domain - lancaironline.net X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - tbm700.com X-Source: X-Source-Args: X-Source-Dir: --Apple-Mail-27--197970567 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=windows-1252 Jim, I had that issue. Lancair avionics put a 200k pot in series in the = original installation back in 2004. I have a 28v airplane driving the = 12v Ray Allen servo. You might have something different? I thought it = never worked because 98% of the pot travel results in the pitch trim = being fully off. But I found that there is a very small range where = there is speed control so that's where I'm at now (about 25% of the = original speed). It takes a few seconds to trim out pitch now--before = it was the "bump". The autopilot behaves much differently now without = huge bumps as it captures an altitude (Tru-Trak). If I get the chance later, I will probably swap out the 200k for a fixed = value and I'm guessing it should be something in the order of a few = ohms. It will be important for you to test any lower voltage setting = at altitude and have the ability to recover from a bad setting. If you = drive the trim at a lower voltage than rated it can work on the ground = but might not be sufficient to work in the flight levels leaving you = with no electric pitch trim. Best way to start is time the full up to = full down time trim speed and work from there. I went from 6 seconds to = about 25 seconds. Some day I'll add the pitot switch to further numb the trim speed at = cruise and wick it up a bit for approach. Ultimately, a PWM setup is = best and then there are no altitude concerns. Paul=20 Legacy=20 On 2011-05-29, at 8:32 AM, Jim Nordin wrote: > I know this has been discussed before and I=92ve given a cursory look = on the archives. But is there a simple way of adjusting / changing the = speed of the servo to slow it down some for pitch trim in a 4PT? The = pitch change is too fast at speed where just a small bump has too much = effect. > Jim --Apple-Mail-27--197970567 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=windows-1252 Jim, = I had that issue. Lancair avionics put a 200k pot in series in the = original installation back in 2004. I have a 28v airplane driving = the 12v Ray Allen servo. You might have something different? = I thought it never worked because 98% of the pot travel results in = the pitch trim being fully off. But I found that there is a very = small range where there is speed control so that's where I'm at now = (about 25% of the original speed). It takes a few seconds to trim = out pitch now--before it was the "bump". The autopilot behaves = much differently now without huge bumps as it captures an altitude = (Tru-Trak).

If I get the chance later, I will = probably swap out the 200k for a fixed value and I'm guessing it should = be something in the order of a few ohms. It will be important for = you to test any lower voltage setting at altitude and have the ability = to recover from a bad setting. If you drive the trim at a lower = voltage than rated it can work on the ground but might not be sufficient = to work in the flight levels leaving you with no electric pitch trim. = Best way to start is time the full up to full down time trim speed = and work from there. I went from 6 seconds to about 25 = seconds.

Some day I'll add the pitot switch to = further numb the trim speed at cruise and wick it up a bit for approach. = Ultimately, a PWM setup is best and then there are no altitude = concerns.

Paul

Legacy

On 2011-05-29, at 8:32 AM, Jim Nordin = wrote:

I know this has been discussed = before and I=92ve given a cursory look on the archives. But is there a = simple way of adjusting / changing the speed of the servo to slow it = down some for pitch trim in a 4PT? The pitch change is too fast at speed = where just a small bump has too much = effect.
Jim

= --Apple-Mail-27--197970567--