X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Sat, 30 Mar 2013 10:15:17 -0400 Message-ID: X-Original-Return-Path: Received: from cdptpa-omtalb.mail.rr.com ([75.180.132.120] verified) by logan.com (CommuniGate Pro SMTP 6.0.4) with ESMTP id 6170978 for lml@lancaironline.net; Fri, 29 Mar 2013 11:36:13 -0400 Received-SPF: pass receiver=logan.com; client-ip=75.180.132.120; envelope-from=super_chipmunk@roadrunner.com X-Original-Return-Path: X-Authority-Analysis: v=2.0 cv=XL2yuHdE c=1 sm=0 a=+kuJ7Sa7hUpxs7xJxzDFzQ==:17 a=AeF9CLZUGkAA:10 a=f0c_NzsTPb4A:10 a=zTVDa7HKqxcA:10 a=doupyKFmAAAA:8 a=1MIwLPKACiwA:10 a=3oc9M9_CAAAA:8 a=Ia-xEzejAAAA:8 a=VOv2MHRxtipaiv0KvuwA:9 a=QEXdDO2ut3YA:10 a=U8Ie8EnqySEA:10 a=EzXvWhQp4_cA:10 a=0vUscowIxtUA:10 a=aB0cBlJQRZhJFGH_:21 a=IrJq22y9lYdFtDYM:21 a=CjxXgO3LAAAA:8 a=GtyHIT7iLzqIq77eTiMA:9 a=_W_S_7VecoQA:10 a=rC2wZJ5BpNYA:10 a=TnZn3fQNFdCrtibN:21 a=+kuJ7Sa7hUpxs7xJxzDFzQ==:117 X-Cloudmark-Score: 0 X-Authenticated-User: X-Originating-IP: 76.179.81.18 Received: from [76.179.81.18] ([76.179.81.18:49393] helo=WilliamHP) by cdptpa-oedge04.mail.rr.com (envelope-from ) (ecelerity 2.2.3.46 r()) with ESMTP id CF/54-25887-AC4B5515; Fri, 29 Mar 2013 15:35:39 +0000 X-Original-Message-ID: From: "Bill Wade" X-Original-To: "Lancair Mailing List" References: In-Reply-To: Subject: Re: [LML] Re: Hydraulic gear pump failure - Relays X-Original-Date: Fri, 29 Mar 2013 11:35:34 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_007F_01CE2C71.86FB8440" X-Priority: 3 X-MSMail-Priority: Normal Importance: Normal X-Mailer: Microsoft Windows Live Mail 15.4.3555.308 X-MimeOLE: Produced By Microsoft MimeOLE V15.4.3555.308 This is a multi-part message in MIME format. ------=_NextPart_000_007F_01CE2C71.86FB8440 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Thanks Scott- That=E2=80=99s a good point that I had forgotten = about. Another method is to use Metal Oxide Varistors- something Bob = Nuckolls (AeroElectric Connection) used to recommend. They absorb spikes = and are bidirectional so there=E2=80=99s no worry about polarity. I used Panasonic ERZV20D180=E2=80=99s on the 14V Navion relays when I = got a 337 for a dual battery system. That was okayed by an aircraft = designer/ DAR so I have some confidence in the choice. There has been no = problem with the system during six years of use. I just ordered ERZV20D390=E2=80=99s for the 28V Lancair relays- = they=E2=80=99re comparable in performance to the others but higher = operating voltage. Panasonic is apparently discontinuing the series so = if anyone is interested they might want to buy soon. Others are = available but I didn=E2=80=99t find such high capacity in a quick = search. Mouser Electronics has them at reasonable prices. =E2=80=93Bill = Wade From: Sky2high@aol.com=20 Sent: Thursday, March 28, 2013 2:12 PM To: lml@lancaironline.net=20 Subject: [LML] Re: Hydraulic gear pump failure - Relays Bill, et al, Relays should have a diode reverse connected across the coil to stop the = voltage surge generated by the field collapse when power is removed from = the coil. This will help protect the pressure switch contacts. Grayhawk=20 In a message dated 3/28/2013 12:58:55 P.M. Central Daylight Time, = super_chipmunk@roadrunner.com writes: Would there be any drawback to using a higher- rated contactor? I = found the Lancair part to be a P.O.S.- it was marked continuous duty but = when put on a power supply it rapidly overheated and shorted to the = case. Instead I=E2=80=99m using an antique 50A Leach B-5B aircraft style = that easily operated for hours. The pump supplied with my IV-P draws a = maximum of 50A, so the Leach might be marginal but I think I=E2=80=99ll = try it initially. On Colin=E2=80=99s recommendation I also purchased a TYCO LEV100A5ANH = , rated 100A that I could use instead, or elsewhere. The Leach draws = 0.16A, the TYCO draws 0.25A at 28V. The Lancair- supplied Suco pressure = switch is rated for 4A as best I can determine so either unit should be = compatible. I don=E2=80=99t know what other models might use but consider the = contacts inside the pressure switches. If they should get overloaded and = weld closed the effect would be the same as welding the relay points. = -Bill Wade From: Gary Casey=20 Sent: Thursday, March 28, 2013 9:36 AM To: lml@lancaironline.net=20 Subject: [Norton AntiSpam][LML] Re: Hydraulic gear pump failure - = Relays Pardon me if I'm jumping into a discussion a little late (and a dollar = short), but there might be some confusion on how and why relays are = designed for intermittent duty. As an example, take a standard master = relay. It is rated for continuous duty and something like 80 amps. = That means the coil won't overheat if left on forever and that the = contacts also won't overheat when passing 80 amps and that the contacts = won't weld when interrupting 80 amps. It is often the limitations when = opening the circuit that determines the rating. Current will try to = keep flowing and if the contacts don't separate rapidly and with enough = force the inevitable arc could create enough heat to weld the contacts = and prevent opening. If it is desired to design a relay in the same = package (for cost, size and weight reasons) that can be used = intermittently to pass a much higher current the design parameters are = different. More force is required to increase the rate at which the = contacts are opened so a higher force spring is installed. Then more = force is required to close the contacts, so fewer turns of heavier wire = are used in the coil (that's right, FEWER turns, but that's another = discussion). The result is that the relay can now successfully switch = maybe 300 amps, but the coil will overheat after a few minutes of = operation. That's the difference between a master and a starter relay. = And I have never, ever heard of 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 that? Am I doing something wrong? 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.=3D20 Does that protective function matter in this circuit?=3D0D Should be considered.=3D0D John=3D0D ------=_NextPart_000_007F_01CE2C71.86FB8440 Content-Type: text/html; charset="utf-8" Content-Transfer-Encoding: quoted-printable
Thanks Scott-
           &n= bsp;         =20 That=E2=80=99s a good point that I had forgotten about. Another method = is to use Metal=20 Oxide Varistors- something Bob Nuckolls (AeroElectric Connection) used = to=20 recommend. They absorb spikes and are bidirectional so there=E2=80=99s = no worry about=20 polarity.
 
  I used Panasonic ERZV20D180=E2=80=99s on the 14V Navion = relays when I got a=20 337 for a dual battery system. That was okayed by an aircraft designer/ = DAR so I=20 have some confidence in the choice. There has been no problem with the = system=20 during six years of use.
 
I just ordered ERZV20D390=E2=80=99s for the 28V Lancair relays- = they=E2=80=99re comparable=20 in performance to the others but higher operating voltage. Panasonic is=20 apparently discontinuing the series so if anyone is interested they = might want=20 to buy soon. Others are available but I didn=E2=80=99t find such high = capacity in a=20 quick search. Mouser Electronics has them at reasonable prices. = =E2=80=93Bill Wade
 
Sent: Thursday, March 28, 2013 2:12 PM
Subject: [LML] Re: Hydraulic gear pump failure -=20 Relays
 
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 = the=20 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,=20 super_chipmunk@roadrunner.com writes:
  Would there be any drawback to using a higher- rated = contactor? I=20 found the Lancair part to be a P.O.S.- it was marked continuous duty = but when=20 put on a power supply it rapidly overheated and shorted to the = 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 = 50A, so=20 the Leach might be marginal but I think I=E2=80=99ll try it = initially.
 
On Colin=E2=80=99s recommendation I also purchased a TYCO = LEV100A5ANH , 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 4A=20 as best I can determine so either unit should be compatible.
 
  I don=E2=80=99t know what other models might use but = consider the contacts=20 inside the pressure switches. If they should get overloaded and weld = closed=20 the effect would be the same as welding the relay points.  -Bill=20 Wade
 
From: Gary=20 Casey
Sent: Thursday, March 28, 2013 9:36 AM
Subject: [Norton AntiSpam][LML] Re: Hydraulic gear pump = failure -=20 Relays
 
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 = designed=20 for intermittent duty.  As an example, take a standard master=20 relay.  It is rated for continuous duty and something like 80 = amps. =20 That means the coil won't overheat if left on forever and that the = contacts=20 also won't overheat when passing 80 amps and that the contacts won't = weld when=20 interrupting 80 amps.  It is often the limitations when opening = the=20 circuit that determines the rating.  Current will try to keep = flowing and=20 if the contacts don't separate rapidly and with enough force the = inevitable=20 arc could create enough heat to weld the contacts and prevent = opening. =20 If it is desired to design a relay in the same package (for cost, size = and=20 weight reasons) that can be used intermittently to pass a much higher = current=20 the design parameters are different.  More force is required to = increase=20 the rate at which the contacts are opened so a higher force spring is=20 installed.  Then more force is required to close the contacts, so = fewer=20 turns of heavier wire are used in the coil (that's right, FEWER turns, = but=20 that's another discussion).  The result is that the relay can now = successfully switch maybe 300 amps, but the coil will overheat after a = few=20 minutes of operation.  That's the difference between a master and = a=20 starter relay.  And I have never, ever heard of using a relay as = the=20 "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 = where=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
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