X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from [24.25.9.103] (HELO ms-smtp-04-eri0.southeast.rr.com) by logan.com (CommuniGate Pro SMTP 4.3c5) with ESMTP id 930112 for flyrotary@lancaironline.net; Mon, 02 May 2005 14:53:40 -0400 Received-SPF: pass receiver=logan.com; client-ip=24.25.9.103; envelope-from=eanderson@carolina.rr.com Received: from edward2 (cpe-024-074-189-178.carolina.res.rr.com [24.74.189.178]) by ms-smtp-04-eri0.southeast.rr.com (8.12.10/8.12.7) with SMTP id j42IqpL5012807 for ; Mon, 2 May 2005 14:52:52 -0400 (EDT) Message-ID: <001201c54f48$255e3de0$2402a8c0@edward2> From: "Ed Anderson" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] fuses vs circuit breakers - or something else Date: Mon, 2 May 2005 14:52:52 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_000F_01C54F26.9E1CDB50" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.2180 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 X-Virus-Scanned: Symantec AntiVirus Scan Engine This is a multi-part message in MIME format. ------=_NextPart_000_000F_01C54F26.9E1CDB50 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable MessageI agree, Al. Both will perform the function, therefore designing = so there is no single point of failure supercedes either choice. By the = way, Tracy's ECU can be powered through two different ways. The = original intended way and a sneak circuit way through the powering of = the injectors. I found this out when I wired a switch to the EC2 CPU = power terminal. When I turned off the switch the EC2 did not turn off = because the injectors still had voltage and there was a sneak circuit = that kept the EC2 with DC power. Tracy may have eliminated that sneak = circuit in later versions - but its there on mine. I used a common CB = for both ignition systems which is something I would do different had I = to do it over.=20 Ed ----- Original Message -----=20 From: Al Gietzen=20 To: Rotary motors in aircraft=20 Sent: Monday, May 02, 2005 2:28 PM Subject: [FlyRotary] fuses vs circuit breakers - or something else I think the key point in this discussion is not so much fuses vs = circuit breakers; but that we follow the philosophy of not having single = point failures in the flight critical systems. The rotary engine has = dual plugs/rotor, most induction systems have two injectors/rotor; = Tracy's ECU has dual units built in (although unfortunately, common = input power point); and most of us are using dual fuel pumps. Separate = and independent feeds to each of these can eliminate single point = failures.=20 The choice of fuse or breaker is as much opinion as it is technical = fact, and a winning argument for either in our airplanes isn't going to = happen. There are advantages and disadvantages to both. I have separate and independent power feeds to each set of coils, to = each set of injectors, to each pump, and to the ECU. I have a mix of = breakers and fuses. I happened to choose fuses (blade type) for the = injectors, coils, and pumps somewhat along the lines of Jim's argument - = I can protect those wires with 15 amp fuses. The ECU has one circuit = through a breaker, and one fused. These circuits are as simple and = direct as possible. Battery - to fuse - to disable switch - to = component. No intermediate contactors or connectors to fail. Of course = I also have two batteries. Fuses, of course, cost nothing, and can be changed out on a whim; so = there is no reason for them ever to be old and fatigued. CB's are a = thermal switch; a bit more complex, expensive and generally difficult to = change, so they are likely to get old. That will be the only point I = will make either way. You choose; CB or fuse. I think that choice is less important than = how you design and execute your circuit. FWIW, Al -----Original Message----- From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] = On Behalf Of Russell Duffy Sent: Monday, May 02, 2005 8:21 AM To: Rotary motors in aircraft Subject: [FlyRotary] Re: finally changed to fuses vs circuit breakers=20 You've been working field service long enough to know that fuses go bad, too. They de-solder; they break due to vibration; the ends corrode and lose connectivity. I've seen this happen on cheesy fuse holders. I have never seen, or = heard of it happening on an automotive fuse. Now, don't start telling = me stories of some crappy old car that had rats in the fuse holder, = because that ain't comparable. =20 I have items like fuel pumps separately fused, and to the wiring = rating, so they should never blow unless there's a good reason. Items = like the EC-2 are directly tied to power, via two attachment points. = This is how Tracy recommends it, because the controller will be it's own = fuse. =20 If I had the panel space, and believed CB's offered any significant = benefit, I wouldn't care about the cost and weight. =20 Gotta go pick up my new company van, and replace a switch in Mobile. Rusty (discussion for entertainment only) ------=_NextPart_000_000F_01C54F26.9E1CDB50 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Message
I agree, Al.  Both will perform = the function,=20 therefore designing so there is no single point of failure = supercedes=20 either choice.  By the way, Tracy's ECU can be powered through = two=20 different ways.  The original intended way and a sneak circuit way = through=20 the powering of the injectors.  I found this out when I wired = a =20 switch to the EC2 CPU power terminal.  When I turned off the switch = the EC2=20 did not turn off because the injectors still had voltage and there was a = sneak=20 circuit that kept the EC2 with DC power.  Tracy may  have = eliminated that sneak circuit in later versions - but its there on = mine.  I=20 used a common CB for both ignition systems which is something I would do = different had I to do it over.
 
Ed
----- Original Message -----
From:=20 Al = Gietzen=20
Sent: Monday, May 02, 2005 2:28 = PM
Subject: [FlyRotary] fuses vs = circuit=20 breakers - or something else

 

I think = the key=20 point in this discussion is not so much fuses vs circuit breakers; but = that we=20 follow the philosophy of not having single point failures in the = flight=20 critical systems.  The rotary engine has dual plugs/rotor, most = induction=20 systems have two injectors/rotor; Tracy=92s ECU = has dual=20 units built in (although unfortunately, common input power point); and = most of=20 us are using dual fuel pumps.  Separate and independent feeds to = each of=20 these can eliminate single point failures.

 

The = choice of fuse=20 or breaker is as much opinion as it is technical fact, and a winning = argument=20 for either in our airplanes isn=92t going to happen.  There are = advantages=20 and disadvantages to both.

 

I have = separate and=20 independent power feeds to each set of coils, to each set of = injectors, to=20 each pump, and to the ECU.  I have a mix of breakers and fuses. I = happened to choose fuses (blade type) for the injectors, coils, and = pumps=20 somewhat along the lines of Jim=92s argument =96 I can protect those = wires with 15=20 amp fuses.  The ECU has one circuit through a breaker, and one=20 fused.  These circuits are as simple and direct as possible.=20 Battery - to = fuse - to=20 disable switch =96 to component.  No intermediate contactors or = connectors=20 to fail.  Of course I also have two batteries.

 

Fuses, of = course,=20 cost nothing, and can be changed out on a whim; so there is no reason = for them=20 ever to be old and fatigued. CB=92s are a thermal switch; a bit more = complex,=20 expensive and generally difficult to change, so they are likely to get = old.  That will be the only point I will make either=20 way.

 

You = choose; CB or=20 fuse.  I think that choice is less important than how you design = and=20 execute your circuit.

 

FWIW,

 

Al

 

 

 

 

-----Original=20 Message-----
From: = Rotary=20 motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Russell = Duffy
Sent: Monday, = May 02,=20 2005 8:21=20 AM
To: Rotary motors in = aircraft
Subject: [FlyRotary] Re: = finally changed=20 to fuses vs circuit breakers

 

You've been working field service long = enough to=20 know
that fuses go bad, too.  They de-solder; they break due=20 to
vibration; the ends corrode and lose = connectivity.

I've seen=20 this happen on cheesy fuse holders.  I have never seen, or = heard of=20 it happening on an automotive fuse.  Now, don't start = telling me=20 stories of some crappy old car that had rats in the fuse holder, = because that=20 ain't comparable.  

 

I have=20 items like fuel pumps separately fused, and to the wiring rating, so = they=20 should never blow unless there's a good reason.  Items like the = EC-2=20 are directly tied to power, via two attachment points.  This = is how=20 Tracy recommends it, because the controller will be it's own=20 fuse.  

 

If I had=20 the panel space, and believed CB's offered any significant benefit, I = wouldn't=20 care about the cost and weight.  

 

Gotta go=20 pick up my new company van, and replace a switch in=20 Mobile.

 

Rusty=20 (discussion for entertainment only)

 

 

 

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