---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Sun 03/14/10: 9 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 05:54 AM - Re: Flap motor draw for Rv-7A (Lapsley R. and Sandra E. Caldwell) 2. 07:40 AM - Re: Knuckolls Z-12 Power Grid Questions (user9253) 3. 08:38 AM - Re: Re: Flap motor draw for Rv-7A (Robert L. Nuckolls, III) 4. 12:54 PM - Re: Knuckolls Z-12 Power Grid Questions (Valin & Allyson Thorn) 5. 03:35 PM - Re: Re: Knuckolls Z-12 Power Grid Questions (Robert L. Nuckolls, III) 6. 06:51 PM - Re: Re: Knuckolls Z-12 Power Grid Questions (Valin & Allyson Thorn) 7. 06:52 PM - Re: Re: Flap motor draw for Rv-7A (William Gill) 8. 07:40 PM - Re: Re: Knuckolls Z-12 Power Grid Questions (Carlos Trigo) 9. 07:53 PM - Re: Re: Flap motor draw for Rv-7A (Robert L. Nuckolls, III) ________________________________ Message 1 _____________________________________ Time: 05:54:57 AM PST US From: "Lapsley R. and Sandra E. Caldwell" Subject: AeroElectric-List: Re: Flap motor draw for Rv-7A > My measured current for my RV-& with the model 92345 motor was 2.0 > Amps when at the stop, ie stalled. I discount the theory that when > the lube is cold that the current could be higher since the motor has > an over ride clutch which slips at the end of travel and if the > mechanical load was higher in the middle of travel then at the stops > the clutch should slip. Of course the starting current could be > higher but I doubt if it would be briefly more than 4 amp.. I have > been using a 5 amp fuse without problems. > > Roger > Time: 09:21:37 AM PST US > From: Lincoln Keill > Subject: AeroElectric-List: Flap motor draw for Rv-7A > > Anyone know how many amps the flap motor draws on an RV-7A? -I don't see > it listed on the motor itself or on any of the documentation I've got and V > an's doesn't know offhand either. -I was going to use a 10A fuse and 14AW > G wire (total wire run of about 15 feet) which seems very conservative, but > I'd still like to know what the amperage draw is so I can calculate the to > tal "worst-case peak" amperage that my alternator& battery will need to pr > oduce. -Thanks. > Do not archive > Lincoln KeillRV-7A > > ________________________________ Message 2 _____________________________________ Time: 07:40:29 AM PST US Subject: AeroElectric-List: Re: Knuckolls Z-12 Power Grid Questions From: "user9253" Suggestions for Lancair Legacy IFR electrical schematic: Replace the battery current shunt with a voltmeter. The battery bus is on the wrong side of the firewall. It is not protected by a fuse. If the battery bus circuit starts smoking, there is no way to shut it off. The avionics master contactor coil needs a diode like the other contactors. A 30amp automotive relay can replace that contactor. Mount it on the engine side of the firewall so that it can isolate power in case of smoke in the cockpit. > "If we should find ourselves flying along and the battery goes dead but the alternators are still working." You are more likely to win the lottery. The wires feeding the Avionics bus are way too big. When you are flying in the soup and the avionics master contactor circuit fails, the glass panel will go dark. This could be a life threatening situation. Here is how to prevent that: Disconnect the diode from the battery bus and connect it to the avionics bus instead. Disconnect the avionics contactor supply wire from the System bus and connect it to the battery bus instead. Now there are two independent current paths to the avionics bus. The recommendation to shut off avionics while cranking the engine is based on an old wives tale. Ask Bob. If you still want to shut off the avionics bus while cranking, put a switch in series with the diode. But that introduces an unnecessary failure point. I hope this helps. Joe -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=290280#290280 ________________________________ Message 3 _____________________________________ Time: 08:38:16 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: Flap motor draw for Rv-7A At 07:13 AM 3/14/2010, you wrote: My measured current for my RV-& with the model 92345 motor was 2.0 Amps when at the stop, ie stalled. I discount the theory that when the lube is cold that the current could be higher since the motor has an over ride clutch which slips at the end of travel and if the mechanical load was higher in the middle of travel then at the stops the clutch should slip. Of course the starting current could be higher but I doubt if it would be briefly more than 4 amp.. I have been using a 5 amp fuse without problems. Thanks for taking the time to do some real measurements and share them with us. I'm having trouble visualizing the electrical and mechanical features of your flap extension system. Normally, a motor that is powered up but not turning will draw some value of current limited only by its internal resistance. This would be close to the data sheet stall current . . . on the order of 30A or more. In this case, we would expect the supply protection device to operate. This is another reason why the proper adjustment of limit switches is important. I seem to recall that the RV flap actuator was a ball-screw with free-wheel clutches at each end of travel. If this is the case, then the current you measured wasn't a "stall" current in the conventional sense, but an motor unloaded value that is a by-product of the free-wheeling mechanisms. Drag of the free-wheeling clutches at ends of a ball screw are relatively insensitive to temperature variation as you've guessed. Were these measurements taken in flight - airloads on the flaps during extend cycle? Bob . . . ________________________________ Message 4 _____________________________________ Time: 12:54:21 PM PST US From: "Valin & Allyson Thorn" Subject: AeroElectric-List: Re: Knuckolls Z-12 Power Grid Questions Thanks Bob and Joe. I'm going to remove the ammeter for the battery and go with a tap for a voltmeter. I'll add a fuse for the line to the battery bus. Since the battery bus is going to power things like cabin lights, Hobbs meter, and clock it seems like it is best to put it on the back of the instrument panel near the switches, components it will power...? For future electronic ignition I thought I'd run a tap directly from the battery. Agree line to avionics bus was too big. On the avionics contactor relay, I thought the diode was for if it was switching inductive loads to prevent back EMF. Is a diode still recommended for an avionics bus with resistive loads? Do I misunderstand the diodes role here? I hadn't heard that Bob K. doesn't see a need to isolate the avionics from the main bus. I'd guess that with the power quality protection of modern avionics that the transient from the engine starter motor is not an issue these days. Still, with all that damn expensive electronics I'd rather not test it at each engine start. It's also nice to bring it all up and down with one switch. I agree that I can go with a lower capacity relay to handle the job. Thanks for pointing out that the avionics relay is a single point failure. What do you guys think about getting one fault tolerant by having two avionics bus relays/switches in parallel -- maybe one passing power from the Battery Bus and one from the System Bus? Are their some other single point failure modes that might need attention? This is very helpful, thanks. Valin Valin Thorn Lancair Legacy Project Houston, Texas USA ________________________________ Message 5 _____________________________________ Time: 03:35:38 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: Knuckolls Z-12 Power Grid Questions At 02:25 PM 3/14/2010, you wrote: >Thanks Bob and Joe. > >Im going to remove the ammeter for the battery >and go with a tap for a voltmeter. Ill add a >fuse for the line to the battery bus. Since the >battery bus is going to power things like cabin >lights, Hobbs meter, and clock it seems like it >is best to put it on the back of the instrument >panel near the switches, components it will power...? Then it's not a battery bus but an always hot bus without benefit of a battery contactor. The rule of thumb for always hot wires is 6" or less in length and/or fused not greater that 7A or breakered greater that 5A. This is why the battery busses are shown on short feeders and have small fuses EXCEPT where augmented by co-located relays. We've got lots of battery busses in TC aircraft and many do indeed have a goodly number of little bitty wires that fan out to other places in the airplane. > For future electronic ignition I thought Id > run a tap directly from the battery. Agree line to avionics bus was too big. Power it with its own fuse/breaker at the REAL battery bus. > >On the avionics contactor relay, I thought the >diode was for if it was switching inductive >loads to prevent back EMF. Is a diode still >recommended for an avionics bus with resistive >loads? Do I misunderstand the diodes role here? Diodes are check valves for electron flow in a host of applications which include trapping off inductive spikes from contactor coils and STEERING of power from some source to some load while preventing back-flow of power along the same path. A search of the website for "diode" yields a collection of discussions on various uses for diodes. > >I hadnt heard that Bob K. doesnt see a need to >isolate the avionics from the main bus. Id >guess that with the power quality protection of >modern avionics that the transient from the >engine starter motor is not an issue these >days. Still, with all that damn expensive >electronics Id rather not test it at each >engine start. Its also nice to bring it all up >and down with one switch. I agree that I can go >with a lower capacity relay to handle the job. Check out this article in particular: http://www.aeroelectric.com/articles/avmaster.pdf Go to the website at http://aeroelectric.com and do a search on avionics + master + switch for 15 hits on articles that discuss this topic. > >Thanks for pointing out that the avionics relay >is a single point failure. What do you guys >think about getting one fault tolerant by having >two avionics bus relays/switches in parallel - >maybe one passing power from the Battery Bus and >one from the System Bus? Are their some other >single point failure modes that might need attention? Have you reviewed chapter 17 in the 'Connection concerning system reliability along with the notes that accompany the Z-figures? The philosophy and features for failure tolerance in each example is discussed. The e-bus was crafted to provide a failure-tolerant source for pieces of equipment particularly handy for extended flight in spite of single failures of hardware. There is risk for "cherry picking" features of any z-figure. Those things are all in there for a reason. May I suggest you 'back up' and consider your z-figure of choice (in this case Z-12) and explore how your design goals differ from what's illustrated. Bob . . . ________________________________ Message 6 _____________________________________ Time: 06:51:26 PM PST US From: "Valin & Allyson Thorn" Subject: RE: AeroElectric-List: Re: Knuckolls Z-12 Power Grid Questions Thanks Bob, I read your excellent Avionics Master Switch (AMS) article and re-read AeroElectric Connection's chapter 17. Since we've only recently progressed to the point in our Lancair Legacy project to where the electrical system design details have to be decided, I've only recently fully engaged in the subject. I was out of town on business when you came through Houston with your class so my wife attended without me (but I'm doing the electrical...?) So, I missed the previous debates, discussions on the AMS subject. I think you've convinced me that we don't need an AMS. I need to check on how you turn on a G900X integrated avionics system -- it may be the equivalent of an AMS anyway... I'll check Monday. With the addition of a 43 lb electric A/C system in our little Lancair Legacy, we're working to trim some weight out. We've saved 17 lbs with an MT prop vs. the Hartzell. If it were not for the weight concern I'd probably opt for the dual alternator/dual battery system (or if I were going dual electronic ignition). It seems that the Z-12 power grid is an excellent, reliable architecture for us. I'm not yet convinced that the Essential/Endurance Bus adds that much value. Though, if I found myself IFR with electrical problems (aka panic:)) the idea of flipping a couple switches to reconfigure would probably look like genius... It seems, though, that it might improve reliability more for Z-12 to have dual parallel battery contactors. What do you think about that? Thanks again, Valin BTW, I understand now what you mean by Battery Bus... It's by the battery :) I'm reworking that architecture. -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Robert L. Nuckolls, III Sent: Sunday, March 14, 2010 5:33 PM Subject: Re: AeroElectric-List: Re: Knuckolls Z-12 Power Grid Questions At 02:25 PM 3/14/2010, you wrote: >Thanks Bob and Joe. > >I'm going to remove the ammeter for the battery >and go with a tap for a voltmeter. I'll add a >fuse for the line to the battery bus. Since the >battery bus is going to power things like cabin >lights, Hobbs meter, and clock it seems like it >is best to put it on the back of the instrument >panel near the switches, components it will power...? Then it's not a battery bus but an always hot bus without benefit of a battery contactor. The rule of thumb for always hot wires is 6" or less in length and/or fused not greater that 7A or breakered greater that 5A. This is why the battery busses are shown on short feeders and have small fuses EXCEPT where augmented by co-located relays. We've got lots of battery busses in TC aircraft and many do indeed have a goodly number of little bitty wires that fan out to other places in the airplane. > For future electronic ignition I thought I'd > run a tap directly from the battery. Agree line to avionics bus was too big. Power it with its own fuse/breaker at the REAL battery bus. > >On the avionics contactor relay, I thought the >diode was for if it was switching inductive >loads to prevent back EMF. Is a diode still >recommended for an avionics bus with resistive >loads? Do I misunderstand the diodes role here? Diodes are check valves for electron flow in a host of applications which include trapping off inductive spikes from contactor coils and STEERING of power from some source to some load while preventing back-flow of power along the same path. A search of the website for "diode" yields a collection of discussions on various uses for diodes. > >I hadn't heard that Bob K. doesn't see a need to >isolate the avionics from the main bus. I'd >guess that with the power quality protection of >modern avionics that the transient from the >engine starter motor is not an issue these >days. Still, with all that damn expensive >electronics I'd rather not test it at each >engine start. It's also nice to bring it all up >and down with one switch. I agree that I can go >with a lower capacity relay to handle the job. Check out this article in particular: http://www.aeroelectric.com/articles/avmaster.pdf Go to the website at http://aeroelectric.com and do a search on avionics + master + switch for 15 hits on articles that discuss this topic. > >Thanks for pointing out that the avionics relay >is a single point failure. What do you guys >think about getting one fault tolerant by having >two avionics bus relays/switches in parallel -- >maybe one passing power from the Battery Bus and >one from the System Bus? Are their some other >single point failure modes that might need attention? Have you reviewed chapter 17 in the 'Connection concerning system reliability along with the notes that accompany the Z-figures? The philosophy and features for failure tolerance in each example is discussed. The e-bus was crafted to provide a failure-tolerant source for pieces of equipment particularly handy for extended flight in spite of single failures of hardware. There is risk for "cherry picking" features of any z-figure. Those things are all in there for a reason. May I suggest you 'back up' and consider your z-figure of choice (in this case Z-12) and explore how your design goals differ from what's illustrated. Bob . . . ________________________________ Message 7 _____________________________________ Time: 06:52:10 PM PST US From: "William Gill" Subject: Re: AeroElectric-List: Re: Flap motor draw for Rv-7A You can surmise all you want about cold temps and related current draw, but there is a relationship. Don't think so, test at -5F and report. Otherwise, you're smply guessing. From: Lapsley R. and Sandra E. Caldwell To: aeroelectric-list@matronics.com Sent: Sunday, March 14, 2010 7:13 AM Subject: AeroElectric-List: Re: Flap motor draw for Rv-7A My measured current for my RV-& with the model 92345 motor was 2.0 Amps when at the stop, ie stalled. I discount the theory that when the lube is cold that the current could be higher since the motor has an over ride clutch which slips at the end of travel and if the mechanical load was higher in the middle of travel then at the stops the clutch should slip. Of course the starting current could be higher but I doubt if it would be briefly more than 4 amp.. I have been using a 5 amp fuse without problems. Roger Time: 09:21:37 AM PST US From: Lincoln Keill Subject: AeroElectric-List: Flap motor draw for Rv-7A Anyone know how many amps the flap motor draws on an RV-7A? -I don't see it listed on the motor itself or on any of the documentation I've got and V an's doesn't know offhand either. -I was going to use a 10A fuse and 14AW G wire (total wire run of about 15 feet) which seems very conservative, but I'd still like to know what the amperage draw is so I can calculate the to tal "worst-case peak" amperage that my alternator & battery will need to pr oduce. -Thanks. Do not archive Lincoln KeillRV-7A ________________________________ Message 8 _____________________________________ Time: 07:40:30 PM PST US From: "Carlos Trigo" Subject: RE: AeroElectric-List: Re: Knuckolls Z-12 Power Grid Questions Hi Valin I liked very much your wiring diagram, so when you finish re-doing it, please post it again. Thanks in advance Carlos > -----Original Message----- > From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list- > server@matronics.com] On Behalf Of Valin & Allyson Thorn > Sent: segunda-feira, 15 de Mar=E7o de 2010 1:48 > To: aeroelectric-list@matronics.com > Subject: RE: AeroElectric-List: Re: Knuckolls Z-12 Power Grid Questions > > > > Thanks Bob, > > With the addition of a 43 lb electric A/C system in our little Lancair > Legacy, we're working to trim some weight out. We've saved 17 lbs with an > MT prop vs. the Hartzell. If it were not for the weight concern I'd > probably opt for the dual alternator/dual battery system (or if I were going > dual electronic ignition). It seems that the Z-12 power grid is an > excellent, reliable architecture for us. I'm not yet convinced that the > Essential/Endurance Bus adds that much value. Though, if I found myself IFR > with electrical problems (aka panic:)) the idea of flipping a couple > switches to reconfigure would probably look like genius... It seems, > though, that it might improve reliability more for Z-12 to have dual > parallel battery contactors. > > What do you think about that? > > Thanks again, > > Valin > > BTW, I understand now what you mean by Battery Bus... It's by the battery > :) I'm reworking that architecture. > > ________________________________ Message 9 _____________________________________ Time: 07:53:33 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: Flap motor draw for Rv-7A At 08:51 PM 3/14/2010, you wrote: >You can surmise all you want about cold temps and related current >draw, but there is a relationship. Don't think so, test at -5F and >report. Otherwise, you're smply guessing. Gently my friend. He DID come forward with some observed current readings . . . and might be induced to go get some more. Yeah, temperatures can have a huge effect on currents because copper resistances go down and the grease (especially on worm gears) gets stiff. But let's not scare him off. He has hardware, test equipment, a demonstrated curiosity and a willingness to share! Bob . . . ------------------------------------------------------------------------------------- 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.