X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from imr-da03.mx.aol.com ([205.188.105.145] verified) by logan.com (CommuniGate Pro SMTP 6.0.4) with ESMTP id 6173317 for lml@lancaironline.net; Sun, 31 Mar 2013 21:05:20 -0400 Received-SPF: pass receiver=logan.com; client-ip=205.188.105.145; envelope-from=Sky2high@aol.com Received: from mtaomg-ma03.r1000.mx.aol.com (mtaomg-ma03.r1000.mx.aol.com [172.29.41.10]) by imr-da03.mx.aol.com (Outbound Mail Relay) with ESMTP id 7AA421C0000B8 for ; Sun, 31 Mar 2013 21:04:45 -0400 (EDT) Received: from core-mta001c.r1000.mail.aol.com (core-mta001.r1000.mail.aol.com [172.29.234.129]) by mtaomg-ma03.r1000.mx.aol.com (OMAG/Core Interface) with ESMTP id 3EBDEE000081 for ; Sun, 31 Mar 2013 21:04:45 -0400 (EDT) From: Sky2high@aol.com Full-name: Sky2high Message-ID: <32242.d0f0fc6.3e8a372c@aol.com> Date: Sun, 31 Mar 2013 21:04:45 -0400 (EDT) Subject: Re: [LML] Re: Hydraulic gear pump failure - Relays To: lml@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="part1_32242.d0f0fc6.3e8a372c_boundary" X-Mailer: AOL 9.6 sub 168 X-Originating-IP: [67.175.156.123] x-aol-global-disposition: G DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mx.aol.com; s=20121107; t=1364778285; bh=GDAUI0+6WdRTmbUkmLE68dVvq2d/lqb1NzLJD8uQ8z8=; h=From:To:Subject:Message-ID:Date:MIME-Version:Content-Type; b=zLU7Z6M0Nh44W8SaXgKNROA4vBlJQb/iHOp1jwnEiJN2jUZ4jRwYHsrfOTwgZ/d// sTccusU0cjAm8qXueUZbB5QJHLn24ZOuac/b7ON5h8uyHiXbdw2k596tmfPVtY3j9r umkmtrHeS8PYSZH/cvI0PHkWmiMSsDmspBwKKaWc= X-AOL-SCOLL-SCORE: 0:2:375929504:93952408 X-AOL-SCOLL-URL_COUNT: 0 x-aol-sid: 3039ac1d290a5158dd2d15b6 --part1_32242.d0f0fc6.3e8a372c_boundary Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Content-Language: en Colyn, =20 For the 300 series only. A stuck pressure switch, hmmmm. In these=20 complex airplanes few will have a dedicated breaker for the pump relays an= d it=20 can be a problem when pulling any multi-use breaker. If one thinks about = it=20 long enough, a fuse for the relay power placed after the pump breaker will= =20 suffice with the added benefit that pulling the pump breaker removes all= =20 electricity from the entire hydro-electric mish-mash, thus resolving any= =20 power related problem. Then again, some have probably followed the Lancai= r=20 instructions to place the pump breaker on the baggage bulkhead - failing t= o=20 remember John Denver's reach behind experience. =20 =20 Blue skies, =20 Grayhawk =20 =20 In a message dated 3/31/2013 6:43:08 P.M. Central Daylight Time, =20 colyncase@earthlink.net writes: TYCO has a variety of models now. Some have ultra-low hold current and= =20 include the diode protection. Others omit the fancy stuff. They clearl= y =20 specify their maximum "break" current which is what you want a lot of it=20 you are trying to interrupt an errant high current circuit. e.g. in Bill= 's =20 example, if you had a stuck pressure switch, you could still shut down the = =20 power by pulling the breaker that powers the relay. =20 On Mar 28, 2013, at 2:12 PM, _Sky2high@aol.com_ (mailto:Sky2high@aol.com) = =20 wrote: Bill, et al, =20 Relays should have a diode reverse connected across the coil to stop the = =20 voltage surge generated by the field collapse when power is removed from t= he=20 coil. This will help protect the pressure switch contacts. =20 Grayhawk=20 =20 =20 In a message dated 3/28/2013 12:58:55 P.M. Central Daylight Time,=20 _super_chipmunk@roadrunner.com_ (mailto:super_chipmunk@roadrunner.com) wr= ites: =20 Would there be any drawback to using a higher- rated contactor? I found=20 the Lancair part to be a P.O.S.- it was marked continuous duty but when pu= t=20 on a power supply it rapidly overheated and shorted to the case. =20 Instead I=E2=80=99m using an antique 50A Leach B-5B aircraft style that eas= ily =20 operated for hours. The pump supplied with my IV-P draws a maximum of 50A, = so=20 the Leach might be marginal but I think I=E2=80=99ll try it initially. =20 On Colin=E2=80=99s recommendation I also purchased a TYCO LEV100A5ANH , rat= ed 100A=20 that I could use instead, or elsewhere. The Leach draws 0.16A, the TYCO =20 draws 0.25A at 28V. The Lancair- supplied Suco pressure switch is rated for= =20 4A as best I can determine so either unit should be compatible. =20 I don=E2=80=99t know what other models might use but consider the contac= ts=20 inside the pressure switches. If they should get overloaded and weld close= d the=20 effect would be the same as welding the relay points. -Bill Wade =20 =20 =20 From: _Gary Casey_ (mailto:casey.gary@yahoo.com) =20 Sent: Thursday, March 28, 2013 9:36 AM To: _lml@lancaironline.net_ (mailto:lml@lancaironline.net) =20 Subject: [Norton AntiSpam][LML] Re: Hydraulic gear pump failure - Relays =20 =20 =20 Pardon me if I'm jumping into a discussion a little late (and a dollar =20 short), but there might be some confusion on how and why relays are designe= d =20 for intermittent duty. As an example, take a standard master relay. It i= s=20 rated for continuous duty and something like 80 amps. That means the coil= =20 won't overheat if left on forever and that the contacts also won't overhea= t=20 when passing 80 amps and that the contacts won't weld when interrupting 80= =20 amps. It is often the limitations when opening the circuit that=20 determines the rating. Current will try to keep flowing and if the contac= ts don't=20 separate rapidly and with enough force the inevitable arc could create=20 enough heat to weld the contacts and prevent opening. If it is desired to= =20 design a relay in the same package (for cost, size and weight reasons) tha= t can=20 be used intermittently to pass a much higher current the design parameters= =20 are different. More force is required to increase the rate at which the= =20 contacts are opened so a higher force spring is installed. Then more forc= e=20 is required to close the contacts, so fewer turns of heavier wire are used= =20 in the coil (that's right, FEWER turns, but that's another discussion). T= he=20 result is that the relay can now successfully switch maybe 300 amps, but= =20 the coil will overheat after a few minutes of operation. That's the=20 difference between a master and a starter relay. And I have never, ever h= eard of =20 using a relay as the "weak link" in the system. Gary ps: My Lancair list emails now come all messed up (see below). Why is=20 that? Am I doing something wrong? =20 The only caveat with that fix, Fred, is that intermittent relays are ther= =3D e for a purpose. They are supposed to be the weak link in a circuit where = =3D a continuous stuck relay could result in greater problems than a failure.=3D= 20 Does that protective function matter in this circuit?=3D0D Should be considered.=3D0D John=3D0D =3D --part1_32242.d0f0fc6.3e8a372c_boundary Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Content-Language: en
Colyn,
 
For the 300 series only.  A stuck pressure switch, hmmmm.  I= n=20 these complex airplanes few will have a dedicated breaker for the pump rela= ys=20 and it can be a problem when pulling any multi-use breaker.  If one th= inks=20 about it long enough, a fuse for the relay power placed after the pump= =20 breaker will suffice with the added benefit that pulling the pump breaker= =20 removes all electricity from the entire hydro-electric mish-mash,=20 thus resolving any power related problem.  Then again, some have= =20 probably followed the Lancair instructions to place the pump breaker on the= =20 baggage bulkhead - failing to remember John Denver's reach behind=20 experience.  
 
Blue skies,
 
Grayhawk
 
In a message dated 3/31/2013 6:43:08 P.M. Central Daylight Time,=20 colyncase@earthlink.net writes:
= TYCO has=20 a variety of models now.   Some have ultra-low hold current and incl= ude=20 the diode protection.   Others omit the fancy stuff.   They cle= arly=20 specify their maximum "break" current which is what you want a lot of it = you=20 are trying to interrupt an errant high current circuit.   e.g. in Bi= ll's=20 example, if you had a stuck pressure switch, you could still shut down th= e=20 power by pulling the breaker that powers the relay.=20

On Mar 28, 2013, at 2:12 PM, Sky2high@aol.com wrote:
Bill, et al,
 
Relays should have a diode reverse connected across the coil to stop= the=20 voltage surge generated by the field collapse when power is removed = from=20 the coil.  This will help protect the pressure switch contacts.
 
Grayhawk
 
In a message dated 3/28/2013 12:58:55 P.M. Central Daylight Time, super_chipmunk@roadrunner.c= om=20 writes:
  Would there be any drawback to using a higher- rated contac= tor?=20 I found the Lancair part to be a P.O.S.- it was marked continuous duty = but=20 when put on a power supply it rapidly overheated and shorted to the=20 case.
 
Instead I=E2=80=99m using an antique 50A Leach B-5B aircraft style= that easily=20 operated for hours. The pump supplied with my IV-P draws a maximum of 5= 0A,=20 so the Leach might be marginal but I think I=E2=80=99ll try it initiall= y.
 
On Colin=E2=80=99s recommendation I also purchased a TYCO LEV100A5= ANH , rated=20 100A that I could use instead, or elsewhere. The Leach draws 0.16A, the= TYCO=20 draws 0.25A at 28V. The Lancair- supplied Suco pressure switch is rated= for=20 4A as best I can determine so either unit should be compatible.
 
  I don=E2=80=99t know what other models might use but consid= er the=20 contacts inside the pressure switches. If they should get overloaded an= d=20 weld closed the effect would be the same as welding the relay points.&n= bsp;=20 -Bill Wade
 
From: Gary=20 Casey
Sent: Thursday, March 28, 2013 9:36 AM
Subject: [Norton AntiSpam][LML] Re: Hydraulic gear pump fai= lure=20 - Relays
 
Pardon me if I'm jumping into a discussion a little late (and a do= llar=20 short), but there might be some confusion on how and why relays are des= igned=20 for intermittent duty.  As an example, take a standard master=20 relay.  It is rated for continuous duty and something like 80=20 amps.  That means the coil won't overheat if left on forever and t= hat=20 the contacts also won't overheat when passing 80 amps and that the cont= acts=20 won't weld when interrupting 80 amps.  It is often the limitations= when=20 opening the circuit that determines the rating.  Current will try = to=20 keep flowing and if the contacts don't separate rapidly and with enough= =20 force the inevitable arc could create enough heat to weld the contacts = and=20 prevent opening.  If it is desired to design a relay in the same= =20 package (for cost, size and weight reasons) that can be used intermitte= ntly=20 to pass a much higher current the design parameters are different. = ;=20 More force is required to increase the rate at which the contacts are o= pened=20 so a higher force spring is installed.  Then more force is require= d to=20 close the contacts, so fewer turns of heavier wire are used in the coil= =20 (that's right, FEWER turns, but that's another discussion).  The r= esult=20 is that the relay can now successfully switch maybe 300 amps, but the c= oil=20 will overheat after a few minutes of operation.  That's the differ= ence=20 between a master and a starter relay.  And I have never, ever hear= d of=20 using a relay as the "weak link" in the system.
Gary
ps:  My Lancair list emails now come all messed up (see=20 below).  Why is that?  Am I doing something wrong?
 
The=20 only caveat with that fix, Fred, is that intermittent relays are=20 ther=3Defor=20 a purpose.  They are supposed to be the weak link in a circuit whe= re=20 =3Dacontinuous=20 stuck relay could result in greater problems than a failure.=3D20Does=20 that protective function matter in this circuit?=3D0DShould=20 be  considered.=3D0DJohn=3D0D

=3D --part1_32242.d0f0fc6.3e8a372c_boundary--