X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Mon, 24 May 2010 19:31:46 -0400 Message-ID: X-Original-Return-Path: Received: from imr-da02.mx.aol.com ([205.188.105.144] verified) by logan.com (CommuniGate Pro SMTP 5.3.7) with ESMTP id 4324781 for lml@lancaironline.net; Mon, 24 May 2010 18:57:30 -0400 Received-SPF: pass receiver=logan.com; client-ip=205.188.105.144; envelope-from=Sky2high@aol.com Received: from imo-da02.mx.aol.com (imo-da02.mx.aol.com [205.188.169.200]) by imr-da02.mx.aol.com (8.14.1/8.14.1) with ESMTP id o4OMuoCE031880 for ; Mon, 24 May 2010 18:56:50 -0400 Received: from Sky2high@aol.com by imo-da02.mx.aol.com (mail_out_v42.9.) id q.e5c.126b43 (45329) for ; Mon, 24 May 2010 18:56:46 -0400 (EDT) Received: from magic-m25.mail.aol.com (magic-m25.mail.aol.com [172.20.22.198]) by cia-mc05.mx.aol.com (v129.4) with ESMTP id MAILCIAMC055-b1114bfb042e24c; Mon, 24 May 2010 18:56:46 -0400 From: Sky2high@aol.com X-Original-Message-ID: <71ed4.267c4568.392c5e2e@aol.com> X-Original-Date: Mon, 24 May 2010 18:56:46 EDT Subject: Re: [LML] Re: Legacy Trim Tab Servo Speed Control X-Original-To: lml@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="part1_71ed4.267c4568.392c5e2e_boundary" X-Mailer: AOL 9.5 sub 155 X-AOL-ORIG-IP: 67.175.242.202 X-AOL-IP: 172.20.22.198 X-Spam-Flag:NO X-AOL-SENDER: Sky2high@aol.com --part1_71ed4.267c4568.392c5e2e_boundary Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit _http://store.qkits.com/moreinfo.cfm/MX033_ (http://store.qkits.com/moreinfo.cfm/MX033) Here's half the solution for an experimenter - a PWM kit (12/24 VDC). Just replace the pot with resistors selected by flap position, an airspeed switch or other sophisticated sensor.. Grayhawk In a message dated 5/24/2010 4:55:48 P.M. Central Daylight Time, paul@tbm700.com writes: I concur with Chris about reducing voltage. The right way to do this would be with the full voltage and PWM (pulse width modulation) for the speed. That way full torque is available but speed will vary. In my past, I've done troubleshooting work on repairing the circuit boards on Cessna autopilots and that is exactly how they operate. More importantly, if anyone uses such a device at altitude, the full voltage will prevent motor stall from the air gap thinning out. Many of the older trim systems with dirty brushes and rotors fail at altitude but work perfectly fine on the ground for that reason. If someone builds it, I would add it or try it or buy it. Some additional comments on trim from the Cessna autopilot: 1) Trim is set to run faster up than down by about 20% for runaway and autopilot purposes 2) Airspeed controls the dual speed setting 3) on the C414A it took 32 seconds for full up to full down but that number has a lot to do with control if the trim starts to runaway. My Legacy is 10 seconds and that is too fast. If anyone wants the 28v circuit for such a system, I have the old manuals somewhere and the parts are simple discreet components with a 1000 Hz oscillator for PWM frequency. Great thread, hope something comes of it. Paul Miller L2K -- For archives and unsub http://mail.lancaironline.net:81/lists/lml/List.html --part1_71ed4.267c4568.392c5e2e_boundary Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable
 
Here's half the solution for an experimenter - a PWM kit (12/24= =20 VDC).  Just replace the pot with resistors selected by flap posi= tion,=20 an airspeed switch or other sophisticated sensor..
 
Grayhawk
 
In a message dated 5/24/2010 4:55:48 P.M. Central Daylight Time,=20 paul@tbm700.com writes:
I concur=20 with Chris about reducing voltage.  The right way to do this would= be=20 with the full voltage and PWM (pulse width modulation) for the speed.&nb= sp;=20 That way full torque is available but speed will vary.   In my= past,=20 I've done troubleshooting work on repairing the circuit boards on Cessna= =20 autopilots and that is exactly how they operate.  More importantly,= if=20 anyone uses such a device at altitude, the full voltage will prevent mot= or=20 stall from the air gap thinning out.   Many of the older trim= =20 systems with dirty brushes and rotors fail at altitude but work perfectl= y fine=20 on the ground for that reason.  If someone builds it, I would add= it or=20 try it or buy it.  Some additional comments on trim from the Cessna= =20 autopilot:
1) Trim is set to run faster up than down by about 20% for= =20 runaway and autopilot purposes
2) Airspeed controls the dual speed=20 setting
3) on the C414A it took 32 seconds for full up to full down= but=20 that number has a lot to do with control if the trim starts to runaway.&= nbsp;=20 My Legacy is 10 seconds and that is too fast.

If anyone wants the= 28v=20 circuit for such a system, I have the old manuals somewhere and the part= s are=20 simple discreet components with a 1000 Hz oscillator for PWM frequency.&= nbsp;=20  

Great thread, hope something comes of it.

Paul=20 Miller
L2K


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