---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Mon 03/15/10: 8 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 04:53 AM - : Re: Flap motor draw for Rv-7A (Fred Stucklen) 2. 07:13 AM - In search of the elegant solution (was: Z-12 considerations) (Robert L. Nuckolls, III) 3. 09:06 AM - Re: Flap motor draw for Rv-7A (Lapsley R. and Sandra E. Caldwell) 4. 11:31 AM - Re: Running Big Battery Wire Through Firewall (Robert L. Nuckolls, III) 5. 11:49 AM - Lamar solid state contactors (Robert L. Nuckolls, III) 6. 02:21 PM - Re: : Re: Flap motor draw for Rv-7A (thomas sargent) 7. 04:29 PM - Re: Knuckolls Z-12 Power Grid Questions (user9253) 8. 07:15 PM - Continued: Preferred Method for Redundant Power Sources to Single Input (jon@finleyweb.net) ________________________________ Message 1 _____________________________________ Time: 04:53:31 AM PST US From: "Fred Stucklen" Subject: AeroElectric-List: : Re: Flap motor draw for Rv-7A Interesting. I've tried 5 AMP fuses on three different RV's to date, and all blew the fuses while Trying to deploy the flaps during the first flight. Installing a 10 Amp fuse always solved the problem. Frederic Stucklen RV-6A N925RV 2008 Hrs (Sold) RV-6A N926RV 875 Hrs (Sold) RV-7A N924RV 335 Hrs Flying Time: 08:38:16 AM PST US From: "Robert L. Nuckolls, III" Subject: 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 2 _____________________________________ Time: 07:13:50 AM PST US From: "Robert L. Nuckolls, III" Subject: AeroElectric-List: In search of the elegant solution (was: Z-12 considerations) At 08:47 PM 3/14/2010, you wrote: > > >Thanks Bob, > >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. Yes, I recall meeting your wife and commiserating over your absence! >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 agree. >I'm not yet convinced that the Essential/Endurance Bus adds that much value. Where does it DEVALUE? If you subscribe to the notion that modern avionics have outlived the myths that promulgated the AMS, then the task remaining is to craft a failure tolerant system. The E-bus goes to that point. Further, it provides the means by which electrical loads during an alternator-out configuration can be predicted in advance. This is critical to an easily implemented and well considered plan-B. >Though, if I found myself IFR with electrical problems (aka panic:)) Why panic? That's the whole point of the plan-B exercise. We KNOW that things are going to break. If one has plans for every contingency, then where's the driver for 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? If that's what you want to do, by all means. But you'd probably be flying one of a few dozen aircraft in the history of aviation that was so equipped. There are tens of thousands of airplanes that have successfully launched and recovered into IMC with less reliable equipment, heavier electrical loads and wired like a 1965 C-172. Accidents having root cause in electrical system failure are already exceedingly rare . . . and many if not most of those could have been mitigated if not avoided by understanding (well considered plan-B) and good preventative maintenance (batteries, belts, attach brackets, etc) on the part of the owner. Z-12 or any other z-figure offers a recipe for success that has been filtered through years of discussion and actual practice on thousands of airplanes. Rather than stirring in new ingredients, it would seem a better plan to deduce ways in which the architecture fall short of mitigating demonstrable risks. Then there's the matter of WHERE to put things and HOW to wire them all up. Risks to your future in-flight comfort will be driven more by the processes by which you carry out the plan than the ingredients that go into the plan. This idea is supported by the numerous dark-n-stormy night stories we've studied here on the list. We've also been privy to information from the gleaned from the wreckage of several airplanes. NONE of those events were forced by the failure of single pieces of of properly installed hardware. Bob . . . ________________________________ Message 3 _____________________________________ Time: 09:06:24 AM PST US From: "Lapsley R. and Sandra E. Caldwell" Subject: AeroElectric-List: Re: Flap motor draw for Rv-7A I guess I did not make myself clear. I believe the clutch in the RV-7 is a friction clutch. In other words the motor never stalls, but the clutch slips. Thus max steady state current draw is set by the breakaway torque not any air loads. Of course the current draw varies with temp, but I will still claim the peak current will be the starting current. That too varies with temp. I would futher claim that the peak starting current will occur if the flap is at the stop, and you attempt to restart the flaps in that same direction, thus starting the flap motor at max torque. However this would be a transient and mat not blow the fuse. It does not blow my 5 amp fuse, admittedly at benign temps. Since I do not have a environmental chamber at home I will be unable to meet your request to measure at -5 deg. Roger 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 ________________________________ Message 4 _____________________________________ Time: 11:31:13 AM PST US From: "Robert L. Nuckolls, III" Subject: RE: AeroElectric-List: Running Big Battery Wire Through Firewall At 08:37 AM 3/10/2010, you wrote: > >David, > >I can tell you there is more than one way to skin a cat, but if you look >at one of the gazillion Piper Cherokees out there, the cable runs from >under the back seat along the left panel through the generally dry >rotted grand-daddy grommet to the contactor mounted on the firewall. >Size does matter but for 2 or 4 GA that won't make a difference. Good >enough for Piper... I don't think I've yet seen a commercial-off-the-shelf firewall feedthru where the insulating material would have stood off Jack Thermin's "puff the magic dragon" test. Electrically and mechanically, these critters function as advertised. The price is low and they seem adequately robust. However, if one subscribes to the notion of protecting firewall integrity with processes like . . . http://www.aeroelectric.com/articles/Firewall_Penetration/firewall.html then devices like . . . Emacs! and . . . Emacs! Are incompatible with the design goal cited in the article. So if your design goals include attention to details of fire-wall integrity, then perhaps single fat-wires are best brought through grommets with fire-shields and application of fire-putty per Tony B's writings. Bob . . . ________________________________ Message 5 _____________________________________ Time: 11:49:37 AM PST US From: "Robert L. Nuckolls, III" Subject: AeroElectric-List: Lamar solid state contactors I've been in communication with folks at Lamar and was updated on their plans and current offerings for solid state contactors. I'm going to be receiving an engineering data package on the product line. They'll be sending me some samples to play with as soon as I get a few more boxes unpacked in M.L. I've been both competitor and collaborator with these folks (and their corporate ancestors) for many years. In my experience they're both capable and forthright in their dealings with the aircraft industry. If anyone on the List is waiting for ME to accomplish anything specific in terms of evaluating the Smartswitch, you may be wasting your time. After my conversation this morning I judge that there is very low risk for integrating the Lamar devices offered by Aircraft Spruce into your project. Bob . . . ________________________________ Message 6 _____________________________________ Time: 02:21:41 PM PST US Subject: Re: AeroElectric-List: : Re: Flap motor draw for Rv-7A From: thomas sargent Fred: I have a 5 amp fuse on mine too. I haven't flown yet, so all the operation of the flaps has been in the hangar, but I have not yet blown a fuse. Do these things really use a clutch? I thought it was a screw that just runs off the end of the threaded portion of the shaft at either end and the n re-engages when you reverse it. I don't know where I got that notion. I could easily be wrong. I'm just point out that min/max flap extension may not be high current events. On Mon, Mar 15, 2010 at 4:29 AM, Fred Stucklen wrote: > Interesting I=99ve tried 5 AMP fuses on three different RV=99s to date, and > all blew the fuses while > > Trying to deploy the flaps during the first flight. Installing a 10 Amp > fuse always solved the problem > > > *Frederic Stucklen* > -- Tom Sargent ________________________________ Message 7 _____________________________________ Time: 04:29:03 PM PST US Subject: AeroElectric-List: Re: Knuckolls Z-12 Power Grid Questions From: "user9253" > "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?" A relay has two (or more) circuits. The coil is one circuit and the relay contacts are in another circuit. The two circuits can be completely isolated from each other. The purpose of a diode connected across a relay (or contactor) coil is to protect the controlling switch from high voltage spark generated by the relay coil when it is shut off by the switch. That high voltage has nothing to do with the load on the relay contacts, whether that load is inductive or resistive. In fact, a relay coil will produce a high voltage when it is shut off, even if nothing at all is connected to the relay contacts. The bigger the coil, the bigger the spark. A relay coil will not make as big of a spark as a contactor coil. Connecting a diode across a relay coil will prolong the life of the switch that controls it. The diode arrow should point towards positive. > "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?" Yes, that will work. What you are proposing is similar to the E-Bus. And it is similar to what I proposed in my previous post, although I might not have explained it clearly. Even if you do use two relays, the diode must still be used to prevent high current from flowing from the avionics bus (AKA E-Bus) to the system bus. > "I'm not yet convinced that the Essential/Endurance Bus adds that much value." The important feature of an E-Bus is that is has two independent current paths. It would be easy to turn your avionics bus into an E-Bus by adding the alternate feed path from the battery bus and a diode to prevent back-feeding the system bus. > "It seems, though, that it might improve reliability more for Z-12 to have dual parallel battery contactors." Yes, that will work, but will cost more and weigh more than using a relay and diode along with an E-Bus that will accomplish the same thing. It can be satisfying to design one's own electrical system. However, there could be failure modes that you might not be aware of. The big advantage of using one of Bob's drawings is that they have been proven over time and scrutinized by many eyes. Any bugs have been worked out. Your schematic looks great in colors. After a couple of minor changes, it will be similar to Z-11. -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=290394#290394 Attachments: http://forums.matronics.com//files/e_bus_106.jpg ________________________________ Message 8 _____________________________________ Time: 07:15:45 PM PST US Subject: AeroElectric-List: Continued: Preferred Method for Redundant Power Sources to Single Input From: jon@finleyweb.net =0AHi Bob,=0A =0ARegarding this archive thread: [http://forums.matronics.c om/viewtopic.php?p=272463#272463] http://forums.matronics.com/viewtopic.p hp?p=272463#272463=0A =0AI am interested to know the answer to the final question. It was also the first question that came into my head after readi ng your response. I'm not sure whether or not the answer matters but suspec t that knowing the answer will answer that question!! ;-) =0A =0AGordon Smith wrote:=0A"In this case when the two always-on sources differ by a vol t or two, for whatever reason, Do the sources provide power proportionally to their voltage or will it be a 100% feed from the highest voltage source? " =0A =0AThanks!=0A =0AJon Finley=0AN314JF - Q2 - Subaru EJ-22=0A[http://ww w.finleyweb.net/Q2Subaru.aspx] http://www.finleyweb.net/Q2Subaru.aspx ------------------------------------------------------------------------------------- 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.