---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Sun 10/23/16: 7 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 05:51 AM - Re: Re: Coiled ignition systems (Robert L. Nuckolls, III) 2. 05:58 AM - Re: Hourmeter / oil pressure switch (Robert L. Nuckolls, III) 3. 07:23 AM - Re: Coiled ignition systems (user9253) 4. 08:39 AM - Coiled ignition systems () 5. 08:45 AM - Re: Hourmeter / oil pressure switch (Ken Ryan) 6. 08:52 AM - Re: Hourmeter / oil pressure switch (micreb) 7. 10:13 AM - Coil ignition (Chris) ________________________________ Message 1 _____________________________________ Time: 05:51:38 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: Coiled ignition systems At 02:37 PM 10/22/2016, you wrote: > >A 7 amp CB seems reasonable but a 7 amp fuse makes me a bit nervous. >I seem to recall that when I looked at ignition currents I noted >that they went up at high rpm, at high temperatures, and in some >rare cases when the engine was not turning. The Kettering-coil style ignition system draws the most with engine stopped and points closed. Current goes down after engine starts and slightly less at higher rpm. >I did not notice any automotive systems that lightly fused the >ignition circuits. No rational for doing it in cars . . . all fused feeders are relatively robust with respect to their loads. In the case of an always-hot battery feed, the AVIATION rational is 5A max breakered, 7A max fused. For a Kettering coil/points system, 7A fusing is very robust. > So while I've never measured over 5 amps on my soob units, my > personal recommendation is a minimum 10 amp fuse on ignition > circuits that feed multiple cylinders even if they are solid state. Those are CDI or other more modern techology and DO behave differently from the Kettering coil/points system. > It may be that the peak currents as seen on a scope caught my > attention or that I just like more headroom on critical fuses. I > think part of my thought process might have been that on my system > if one solid state coil driver shorted full on it would not > necessarily take out the system fuse. I don't have any idea what > the tolerance is on an ATC fuse. I have 700 hours on the original > 10 amp fuses that feed the 4 cylinder soob. I've had two cases of > one cylinder losing power due to a partial coil failure. Once > during initial ground testing and once at around 500 hours. These > are DIS coils that each feed two cylinders but in both cases only > one cylinder lost power. Understand . . . but that's a different breed of cat . . . Even so, even real beastly electronic CDI systems (Lightspeed comes to mind) only draw 2.5A at 28V into a constant-power switchmode power supply . . . so 5A at 14V for a 6 cylinder engine at red-line rpm. That's a LOT of watts. Waaayyyy more than necessary but I think Klaus's engines are expected to run on spark-power alone (just kidding). But consider a 10A feeder in an automobile: 7A continuous is a reasonable load factor for a 10A fuse. In a 14v system 7A is 100 watts. There's just no reason that the ignition system should use such power. Consider the ignition excitation system on a Rotax that a gets fly-by of a single magnet once every crankshaft revolution . . . compare that with the array of magnets, windings and cores on the same flywheel designed to 18A at 14 volts or 250 watts . . . a huge difference in energy budgets/requirements. But your point is well taken and the caveat here is to KNOW the requirements your particular system. When in doubt measure it. Bob . . . ________________________________ Message 2 _____________________________________ Time: 05:58:19 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Hourmeter / oil pressure switch At 09:06 PM 10/22/2016, you wrote: > >Hope someone might be able to help out here. >I have a three pin oil pressure switch that feeds my low oil >pressure light and turns on the Hobbs meter. >The reference I have is a wiring diagram from Aeroelectric somewhere >along the line but no figure or diagram number. >The only reference is on the part, D-86117. I can't seem to cross >it to anything useful to replace it. >Would someone have a good number to order a replacement? >Paul Here's an exemplar part http://tinyurl.com/zl7pxnt You can probably purchase a Standard Motor Products PS133 switch locally for the same or less money. There are probably dozens of similar parts offered by other companies . . . any 3-terminal device is suited to your task. Bob . . . ________________________________ Message 3 _____________________________________ Time: 07:23:49 AM PST US Subject: AeroElectric-List: Re: Coiled ignition systems From: "user9253" This discussion reminds me of the electric fire pump motor at work. I can not remember the size, but it was a big motor, 50 or 100 HP, 3 phase, 480 volts. There was no circuit protection, just a disconnect switch. The reasoning is that it is more important to save the factory from fire than to protect the fire pump motor or wiring. If anyone is interested, you can read about fire pump requirements: http://ecmweb.com/code-basics/power-pump Some aircraft builders might apply the same reasoning to their engine ignition system by using an oversize fuse. They would rather have the wires and coils burn up than take a chance on a fuse blowing and the engine quitting. Of course smoking components should be on the engine side of the firewall. I am not recommending a fuse size that would actually allow wires to smoke, just saying that a fuse could be one or two sizes bigger for a critical application. -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=461537#461537 ________________________________ Message 4 _____________________________________ Time: 08:39:04 AM PST US From: Subject: AeroElectric-List: Coiled ignition systems This discussion reminds me of the electric fire pump motor at work. I can not remember the size, but it was a big motor, 50 or 100 HP, 3 phase, 480 v olts. There was no circuit protection, just a disconnect switch. The reas oning is that it is more important to save the factory from fire than to pr otect the fire pump motor or wiring. If anyone is interested, you can read about fire pump requirements: http://ecmweb.com/code-basics/power-pump Some aircraft builders might apply the same reasoning to their engine ignit ion system by using an oversize fuse. They would rather have the wires and coils burn up than take a chance on a fuse blowing and the engine quitting . Of course smoking components should be on the engine side of the firewal l. I am not recommending a fuse size that would actually allow wires to smok e, just saying that a fuse could be one or two sizes bigger for a critical application. I would (ass u me) that the manufacturer=99s specs on installation o f an electronic ignition would spec wires to handle the maximum current dra w of the unit under all operating conditions. If one were to fuse it to th ese specs, then there should be no wire burning, and the fuse will not blow unless there is a failure causing more than the maximum current flow. Thi s might mean that if you have a =9Ccurrent hungry=9D device, th e fuse could possibly be a bit larger than the 7 amp max normally specified on production aircraft. If you have a problem with using a larger fuse, e ven though it is protecting your wiring, then I would suggest that the alte rnative is to purchase and install an ignition system with a current draw t hat is within your comfort zone. Roger ________________________________ Message 5 _____________________________________ Time: 08:45:57 AM PST US From: Ken Ryan Subject: Re: AeroElectric-List: Hourmeter / oil pressure switch Here's another possibility: Carter A68301 On Sun, Oct 23, 2016 at 4:57 AM, Robert L. Nuckolls, III < nuckolls.bob@aeroelectric.com> wrote: > At 09:06 PM 10/22/2016, you wrote: > > > Hope someone might be able to help out here. > I have a three pin oil pressure switch that feeds my low oil pressure > light and turns on the Hobbs meter. > The reference I have is a wiring diagram from Aeroelectric somewhere along > the line but no figure or diagram number. > The only reference is on the part, D-86117. I can't seem to cross it to > anything useful to replace it. > Would someone have a good number to order a replacement? > Paul > > > Here's an exemplar part > > http://tinyurl.com/zl7pxnt > > You can probably purchase a Standard Motor > Products PS133 switch locally for the same > or less money. There are probably dozens > of similar parts offered by other companies > . . . any 3-terminal device is suited to > your task. > > > Bob . . . > ________________________________ Message 6 _____________________________________ Time: 08:52:57 AM PST US Subject: AeroElectric-List: Re: Hourmeter / oil pressure switch From: "micreb" THANKS again Bob. One of the few part numbers I didn't record...... Live & Learn... Paul -------- I'd rather be flying than building but there's an end to the means here (I hope). Read this topic online here: http://forums.matronics.com/viewtopic.php?p=461545#461545 ________________________________ Message 7 _____________________________________ Time: 10:13:48 AM PST US From: "Chris" Subject: AeroElectric-List: Coil ignition Thanks everyone for your input. I will wire it up as suggested. Chris ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message aeroelectric-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/AeroElectric-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/aeroelectric-list Browse Digests http://www.matronics.com/digest/aeroelectric-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.