---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Tue 09/20/05: 4 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 09:51 AM - Re: RE load dump (Phil Birkelbach) 2. 04:15 PM - Re: Wire selection (Ken) 3. 11:33 PM - KT-76 connector (John Erickson) 4. 11:51 PM - Re: Wire selection (Jim Oke) ________________________________ Message 1 _____________________________________ Time: 09:51:22 AM PST US From: Phil Birkelbach Subject: Re: AeroElectric-List: RE load dump --> AeroElectric-List message posted by: Phil Birkelbach Come on Paul! Do you really think that you can use the phrase "Until my comments are accepted as fact.." and then not support those comments with any numbers that you can then say "...the ridicule of my test results clearly says it was a mistake..." No one is ridiculing your test results because no one has seen your test results. As far as I can remember you have never even shown us a diagram of your test setup. You say that you decline to publish in the detail that we want, but I don't want a lot of detail I'd probably be happy with a description of the test apparatus and a brief paragraph explaining the procedure and a graph or two. If this information exists and I've missed it please point out my error. We are all members of this list because we are building airplanes that need electrical systems in them. This list is not an academic one, although academics surely plays a major role. We would all like to build the most reliable systems that we can with the money that we have. To achieve this balance we need to be able to make decisions on what kind of risk we are willing to live with based on the mission of our airplane and where to spend our money to achieve that. To do that we need to be educated on the benefits and drawbacks of the different systems, and ideas. You and Eric seem to think that this list is a religious list where we all just do what Bob tells us to do. I must admit that the electrical system in my RV-7 is made up, almost entirely, of Bob's ideas. Most of which I completely disagreed with the first time I read them. I didn't do that because I decided that Bob was the electron god of aviation. I did that because through simple ideas, logic and PHYSICS I became convinced that it was the right solution for my mission and my pocketbook. I can't use any of the information that you seem to have to that end because I don't know where that information is. If you published a white paper on the "Load Dump Issue," and showed that some of Bob's ideas were flawed I bet you that he'd publish that white paper on his own website. If he doesn't then that hurts his own credibility. The fact that there is no such white paper leads me to believe that you yourself don't think that your data will stand up to public scrutiny. It may be way over my head, but once published in the public domain the credence of the numbers goes up because they are then under review. All we have now is "Cold Fusion." We are supposed to believe what you say because you told us you did the test. I am at a point with my airplane where I really need to know the answer to this issue. I have an operational problem with my ND IR 40A alternator that has Bob's CB OVM on it. I have the good old $15 contactor on the B lead. I also have an SD-8 backup alternator. What I didn't realize during the design of my system was that the SD-8 wouldn't put out enough voltage to allow me to check it at idle. So now I have to either stay on battery power until I get to the run up area, risk turning off the B-lead contactor when I get to the run up area or simply not check the SD-8 during pre-flight. I could run the engine up to 1500 RPM or so right in front of the hangar but that upsets the neighbors and since the oil hasn't had a chance to come up to temperature yet, it's not the best thing to do on the engine. If the "Load Dump" issue were quantified I could make an intelligent choice on whether to keep the system I have and shut the alternator down at run up, or to seriously think about changing to an externally regulated alternator. As far as I know all I have to help me with this decision is a bunch of arguing about the ethereal ghost of load dump that may or may not exist under different conditions. An oscilloscope trace and a schematic would make all the difference in the world. Phil On Sep 18, 2005, at 10:16, Paul Messinger wrote: > --> AeroElectric-List message posted by: "Paul Messinger" > > > I consider the entire subject (crow bar currents) closed. I feel no > need to > continue based on your statements as its simply not worth my time > to reply. > Until my comments are accepted as fact and we can get past that and > deal > with the real issues the ridicule of my test results clearly says > it was a > mistake to ever start this in the beginning. Further the snide > remarks from > others does not help clear the air. > > On the load dump test: > > Here is a quick review of the results > > 1. Eric and I gave up and I declined to publish in the detail you > seem to > need. Simply not worth the time that would be needed to reply to your > disbelief or need to duplicate tests that may require the exact > parts (as > part type is not enough) and this thread is proof of that. > > 2. The testing showed that there was NO problem with normal load > dump as > long as there was a battery connected to the system and NO OVP of your > design connected (see below). > > 3. We also investigated the case of NO battery as many want to have > that as > a backup mode of flight. As I have personally seen 3 aircraft > batteries fail > open in flight (two concord RG type and one Gill), I felt it was worth > including this in the testing. Your OVP module failed 100% of the > time (in > even small load dumps) but that was expected as it clearly was not > designed > to support that mode of operation (no battery). Adding a 25,000 MFD > capacitor reduced the alternator ripple voltage but did not control > the > small load sumps and your OVP continued to trip 100% of the time, > again not > unexpected as the trip time was far too short to allow even a cap > filtered > load dump to pass. Here transorbs worked well to clamp the peak > load dump > voltage spike. Adjusting the OPV trip voltage higher to allow for > transorb > clamping resolves the tripping issue with the OVP > > 3. The OVP module you offer as plans was built up on a 1" x 1.5" > pcb and two > made. Both had false trips 100% of the time when a large load was > switched > ON. This led to a simple design review of this OVP and we > discovered there > were two design errors that made the OVP sensitive to simple > changes in bus > voltage etc. One has been recently posted and the other is a > sensitivity to > contact bounce and the fast trip time. Besides the OVP design > issues the > contactor applying the load has contact bounce that was triggering > the OVP. > > There was no further effort on your OVP design (by us) as the > design concept > was very old and there are simple IC parts available that made a > simple > modern design with adjustable trip times off the shelf. Why try to fix > something that is decades behind the current technology?? as the > new design > had built-in production against false triggering it was a win win > solution. > Further there is the simple opening of the contactor coil and Zero > crowbar > current as the design does not use a crowbar. > > The solution we proposed was to be sure the OVP trip time was much > longer > than relay/contactor contact bounce (actually longer than a > expected load > dump event). Contact bounce on load removal also caused problems. I > did post > a reference from a major relay manufacturer that contact bounce on > contact > opening WITH a diode across the coil was very bad idea and not only > was > there contact bounce on opening there was the possibility of > contact welding > on opening. Use of transorbs clipped the load dump transient and > everything > worked right thru the transient even with no battery on line. > > 4. There was widespread (reported by Vans, and several builders who > directly > contacted me off list) false tripping by the OVP and resulting > alternator > failure where the alternator was internally regulated and the "B" lead > contactor was the common type that not only bounced on opening (due > largely > to the recommended diode) and also to the resulting load dump peak > voltage > that greatly exceeded the contactor maximum contact voltage rating. > Heavy > contact arcing was documented. This resulted in the recommended > Kilovac > contactor as its the only reasonable cost contactor with the proper > ratings > and there is no coil diode to cause problems on contact opening. > > 5. We then had a system design solution with a no false tripping > OVP and a > "B" lead contactor that did not damage the alternator. Eric is now > selling > the OVP design and has on occasion the Kilovac contactors that > allow safe > "B" lead opening. > > 6. I further investigated "rebuilt alternators" and found the term > misleading. Only parts that were failed were replaced. The term > should be > repaired not rebuilt. The popular ND 55 amp alternator has been > around for > more than 20 years and many have been rebuilt several times. Who > knows the > quality of the current regulator? Thus only brand NEW alternators > should be > used. > > 7. Replacing the fast trip and occasional false tripping OVP with a > modern > design eliminates false trips. Eliminating the Crow bar eliminated > the hi > current and its side affects (see below). If used, the proper "B" lead > contactor will prevent alternator damage often caused by the > improperly used > common contactor that is not designed or specified for this specific > application and further hindered with the incorrect application of > a diode > across the coil against major manufacturers worked wide. In fact > the common > diode across the coil is not recommended anywhere any time by relay > manufacturers. That its very common in use does not mean its a good > approach, It simply means that most engineers are lazy and copy > what has > been done in the past rather that research what is recommended so > the diode > persists even with its being the last and worst choice in a list of > options. > > IN conclusion the test results showed that much of the alternator > failures > were the direct result of the OVP design and associated contactor. > Its not > known if poor alternator regulators were a factor but even good > ones are > very likely to be damaged by the current design contactor used. Its > clear > that the contactor used has a very high potential of regulator > damage and > when coupled with a false trip prone (in some as yet defined > aircraft wiring > or operations) is the root cause. > > Use a modern non-crowbar OVP design and a contactor designed for the > application resolved most of the problem. Its not possible to > ignore the > likely hood of lesser quality regulators in rebuilt alternators so > only new > alternators should be used. > > With the demonstrated extremely high reliability of the ND brand of > internally regulated alternators is very questionable that there is > a need > for more that having the OVP simply remove the voltage to "I" lead > (the > field control lead) that shuts down the alternator. I have been > unable to > find any repair shop that has ever heard of an ND alternator having > uncontrolled runaway failure. No output or hi output that is still > controllable with the "I" lead. Prop bolts or crank shafts are more > likely > to fail and yes I have a report of a light twin having both engines > prop > bolts failing. > > Now for the hi current related problems. > > In an steel tube reinforced cockpit like the Glastar (or other > production > aircraft) its been proven that even the normal bus loads can > magnetize the > tube structure and cause compass errors of as high as 30 degrees. I > previously referenced a manufacturers mandatory service bulletin that > addressed this issue and also discussed with a owner of that type > aircraft > that had it happen to him. He is highly educated and a long time > IA. The > compass in question was a suspended well above the affected tubes > > This tells me that even 50 amp buss circuits need special wire > routing and > forget the 100+++ current transients from a crow bar. > > This alone says if you have a steel tubular cabin be careful and > forget a > crow bar approach. > > In any event this is my last word on either subject even if the > misquoting > etc continues. > > Paul > > > ----- Original Message ----- > From: "Robert L. Nuckolls, III" > To: > Subject: Re: AeroElectric-List: RE: Breaker Interrupt Rating > > >> --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" >> >> >> At 01:02 PM 9/17/2005 -0700, you wrote: >> >> >>> --> AeroElectric-List message posted by: "Paul Messinger" >>> >>> >>> Bob; >>> >>> I DID post (to this list) the exact specific technical parts etc. >>> details >>> of >>> my test and you seemed never recognize that fact. >>> >> >> Forgive me. I WAS watching for such information since I was the >> one who requested it. Can you give me an approximate date or repeat >> your post. I'll so search the archives if necessary. Give me one >> part number you cited. It will make the search so much faster. >> >> >>> That I used words and not >>> a schematic is not important in this case as a schematic is not >>> needed >>> with >>> such a simple circuit. I did use a different wiring diagram (of your >>> schematic) to duplicate what is in my aircraft however. >>> >> >> Then is it a fair presumption that as an skilled and articulate >> engineer that you've documented that portion of your system's >> wiring in a manner that can be scanned and shared? >> >> >> >>> But you cannot duplicate my results (as I under stand what you >>> mean by >>> duplicate) unless you use the exact same parts I used. The same >>> identical >>> part, not a part of the same brand and part number is required in >>> this >>> case >>> because of the very wide variation in the parts tolerances. >>> >> >> Absolutely! I've never done a test report without identifying >> or at least making full disclosure of parts used, techniques, >> measurements, etc. I'd be pleased for you to take the parts I >> used in >> >> http://www.aeroelectric.com/articles/Crowbar_OV_Protection/ >> DC_Power_System_Dynamics_C.pdf >> >> and show me how I mis-read or mis-interpreted data at the risk >> of making a bad deduction. You seem to accept the test results >> I posted but counter with "that's not what I got with MY test." >> Fine . . . tell us how you did it. >> >> >> >>> Only if a worst case analysis is properly done and the range of test >>> results >>> is determined can any test be duplicated by another using different >>> physical >>> parts of the same part number. The part to part variation in most >>> cases >>> and >>> clearly in this case is simply too large. >>> >> >> I'm mystified as to this part-to-part variation you cite. >> >> >>> Crow bar short circuit currents can vary from well under 100 amps >>> to over >>> 400 amps depending on the parts used and the wiring diagram used to >>> implement the same schematic. >>> >> >> I don't doubt it . . . but I'm still trying to visualize the >> 400A case. >> >> >>> Thus any test that results in a current from around 100 amps to >>> around 400 >>> amps is in fact a duplication of another's test results in this >>> case. >>> >>> Where there are small parts variations the duplicated test >>> results will be >>> much closer but NEVER identical. >>> >> >> You don't have to sell me on stacked up variability and test >> tolerances . . . I've been doing this since high school >> physics. >> >> >> >>> For example the following is true: >>> >>> #1 CB ratings vary widely in resistance and trip time, in fact, >>> close to >>> a >>> 10 -1 variation. between parts of the same brand and parts from >>> other >>> brands. Nothing strange about My CB having an internal resistance >>> 1/10 of >>> the one you used. CB internal resistance can and does vary from >>> approx >>> 0.003 >>> to over 0.030 ohms; a 10-1 variation >>> >> >> This I really need to see. What brand and part number exhibits >> such variability? The problem I'm having is that trip >> characteristics >> are an I(squared)*T event that depends on heat generated within >> the current sensing part of the breaker. ANY breaker that shows >> a 10:1 variability in resistance should be expected to show >> a similar variability in trip characteristics. There are no >> manufacturers I work with that would offer me such a product. >> >> Gee, a 5A breaker that can open anywhere between 2.5 and 25 amps! >> >> >> >>> #2 Battery internal resistance also varies again as much as 10-1 >>> depending >>> on the battery brand and ratings. My batteries have 1/5 to 1/10 the >>> internal >>> resistance of your battery. But then I do not use the Panasonic >>> brand or >>> similar types.I do use a very popular PS625 (dual at that) >>> battery with >>> much >>> higher specifications in most important parameters. Not that the >>> Panasonic >>> is bad but its not nearly the same in several (important to me) >>> electrical >>> specifications. >>> >> >> As I've repeated many times, I don't care if your battery >> is ZERO ohms. There's a rational, recommended installation >> technique for using my products where the MAJOR contributor >> of loop resistance is wiring, a minor contributor is circuit >> breaker heater resistance with so small an amount coming from >> the battery and fatwires that they can be ignored. Nonetheless, >> I'm intently interested in your .0035 to .0017 ohm battery. >> Do I recall that you're building a Subaru powered two-place? >> Batteries I can find with this level of performance start out >> at 60 pounds and go up from there. I presume you ARE planning >> on carrying passengers in this airplane . . . >> >> >> >>> #3 My wiring was an exact duplicate of what I have in my aircraft >>> and is a >>> fraction of what you had in your test. My wiring is less that 1/2 >>> the >>> internal resistance of your test wiring. >>> >> >> Very good. The systems I recommend and illustrate in the Z-figures >> are rooted in practices found in the vast majority of Certified >> and OBAM iron. Of course one should not toss away lots of >> performance in wire drops and soggy batteries . . . but then, >> wiring everything with 00 gage and installing batteries that >> would crank a Detroit Diesel in a N. Dakota winter has some >> seriously diminished returns on overall system design. If you >> have 1/2 the loop resistance illustrated in my experiments, you >> must have a rational for increased battery and wire sizes at the >> sacrifice of useful load. We'd be interested in understanding >> the design goals by which you arrived at this exceedingly low >> loss system. >> >> >>> I measures the battery internal resistance as well as the CB and >>> wiring >>> resistances before and after the testing series. >>> >>> The same CB was used in the simulated worst case test where the >>> current >>> was >>> 700 amps and there were at least 50 tests of the real circuit >>> where the >>> current was 400 amps. No degrading of any part including the SCR >>> in your >>> crow bar circuit which was over stressed several times its max >>> rating. >>> >> >> Then no doubt you can tell me what the battery part number was, >> what >> circuit >> breaker was used, what SCR was used, what diameters and lengths of >> wires were used . . . I'll pay you my consulting fee for the time >> it takes you to type that data into a posting here on the list. >> >> >> >>> This overstressing and lack of damage does not mean its a good >>> design idea >>> and more importantly does not mean that all CB's will survive >>> with no >>> damage. >>> >>> In this case the main short current drivers are the Battery, CB >>> and wiring >>> resistances. >>> >>> That alone suggests that 400 amps is easy to achieve as the circuit >>> resistance to get 400 amp vs. 130 amps only needs to decrease to >>> 1/3 or >>> so. >>> >>> Bottom line: I had 6 EXPERT, experienced, real electrical engineers >>> review >>> what I have done and ALL agreed with my test setup and suggested >>> 400 amps >>> was not the max current possible as I had not used the worst case >>> analysis >>> parts. >>> >> >> Then may we expect to see their names on the byline for a >> detailed report? As long you've opened the door to name dropping, >> I'll claim real signatures of dozens of folks representing systems >> designers, DERs, program managers, test pilots and test >> technicians who executed paperwork certifying this system on >> Mooney, Piper, Beech, Cessna and Cirrus aircraft. This is over >> and above thousands of OBAM aircraft customers who seem to be >> getting >> satisfactory performance from their purchases. >> >> For the moment, I have no greater assurances of the existence >> of your six "experts" than I do of the half dozen or so of >> my customers you claim were ALL having nuisance trip problems >> NONE of whom would call me for assistance and ALL of which >> declined >> an opportunity to exercise my well published 100% satisfaction >> or money back guarantee. >> >> >>> I had hoped this issue had gone away months ago as we will never >>> agree. I >>> only post here when I feel my comments are being misquoted to the >>> extreme. >>> Seems that will never end and frankly I am saddened that it seems to >>> continue. >>> >> >> The List is a classroom. Folks will always be asking about these >> issues and as one of several teachers on the list, I have a duty >> to sort myth, old mechanic's tales, and bad science from >> fact as I understand it. If you want this discussion to end, then >> carry out your past threats never to post again. If you have >> facts to dispute, then be a teacher and publish counter balancing >> facts. Either is fine with me . . . but don't expect me not >> to continue to counter rumors, yours or anyone else's. I'm sure >> Greg Richter is fond of telling tales over a beer about how >> he crossed swords with that wild-eyed guy in Wichita and the >> telling probably gets better with each pitcher full. He too >> was amazingly reluctant to answering a single direct question. >> If you're ready to mark me off as hopeless, you're welcome to >> bow out . . . >> >> I've even offered $cash$ rewards for simple answers to >> specific questions. It would be worth it to me. My exorbitant >> consulting rate at the moment is $75/hour. If you could save >> me a hour of time digging around trying to figure out exactly >> how you arrive at some of your mystifying numbers, then >> I'd be money ahead to pay you cash for the data. I'd rather >> use the hour to add value to someone's airplane as opposed to >> sorting your jigsaw puzzle with many missing pieces. How about >> filling in your version of the pieces in the first figure on >> page 2 of the paper cited above and show us all how you >> generated a 400A crowbar event? >> >> >> >>> The basic issue of OVP crow bar short to open a CB is the real >>> discussion >>> where you believe its a good approach and I disagree is the >>> fundamental >>> issue and the short current is a distraction. >>> >> >> Hmmm . . . at least it's devolved to a 'distraction' . . . >> there have >> been times past when the crowbar event could be expected to cause >> all manner of bad day including in-flight reset of EFIS systems >> and engine stoppage. If you have a better approach, you're >> most welcome to join the rest of us in the free marketplace. >> >> >>> Please do not snip this email as it tends to put my comments out of >>> context >>> and change the meaning/intent of my comment. >>> >>> Better yet simply do not reply and we can both put this stupid >>> debate to >>> rest and get on with productive discussions. >>> >> >> If it's stupid, it's only because you're not debating. Any high >> school >> debate teacher would have tossed you out of this classroom >> years ago. >> My physics teacher would have tossed you out of his class too. >> I saw >> him do it to a kid that "dry labbed" an important assignment. >> This is >> not a classroom on debate, it's a classroom of simple ideas and >> physics >> as they relate to building the best airplanes to have ever flown. >> Show us your setup, show us your work and show us your data. >> >> Okay, how's this for a productive topic: >> >> How do you propose we offer a means by which an OBAM aircraft >> community a means for installing an internally regulated >> alternator >> such that its operation transparent to the paradigm under which >> generators and alternators have been operated on aircraft since >> day-one to wit: >> >> (1) Absolute pilot control over engine drive power source. >> >> (2) Failure and hazard free switching of the engine driven power >> source at any time and under any conditions. >> >> . . . of course, answers to the above will offer the OBAM >> aircraft >> builder a means by which any attractive OV protection philosophy >> can be added assuming he/she so desires. These are the questions I >> thought >> you were going to answer when you went off to do the tests over a >> year ago. Presumably you have the data necessary to make >> considered >> recommendations. We're all ears. >> >> Bob . . . >> >> >> >> > > ________________________________ Message 2 _____________________________________ Time: 04:15:48 PM PST US From: Ken Subject: Re: AeroElectric-List: Wire selection --> AeroElectric-List message posted by: Ken I don't think you want to run multiple wires to feed a single device. What protects you from fire if one of the wires shorts? This technique would be acceptable to lower the voltage drop in the wiring as long as the fuse was no larger than one of the wires can handle. It would not be acceptable to use a larger fuse and multiple wires to increase the current available to a device as then you don't have appropriate wire protection. That said - I mostly used awg 18 fused at 10 amps. I also used a good deal of awg 22 for signal wires and such as it is much easier to fabricate assemblies that use small connectors and much more flexible in bundles. But it is almost inescapable that you will need some larger wire for the alternator, batteries, and perhaps other things. I think you will find that the total cost of the wire is less than you may be imagining. Ken Ernest Christley wrote: >--> AeroElectric-List message posted by: Ernest Christley > >I'd like to keep my wire rack nice and simple. Instead of having >multiple spools of various wire sizes, I think it would be beneficial to >have just one spool of a multistranded cable. I don't see it weighing >significantly more. There's just not enough wire in the plane to make a >difference. The cable is more expensive, but the installation would be >simpler and safer. Simpler since, for instance, there would only be one >run of wire out to the wingtip lights. Safer since the wire by default >would have an extra jacket. Before anyone gets a chance to say it, I am >indeed accepting a less than optimum design in exchange for a lack of >the need to plan carefully. My response is that the offset from optimum >will not have measurable results in the final product, and the best laid >plans of mice and men... (so, it's 4:00 on Saturday. You've got a roll >of 22AWG left, but what you really need is 2ft of 20AWG. Aaargh!) > >So, with this goal in mind, what would be a good wire size that would >basically cover all the wiring needs, with the obvious exception of the >starter? 18AWG? 20AWG? Certain high current devices, like pitot heat, >could use multiple strands in a cable, or lower current technologies, >like Eric's thermal switch design. Stenair has 3 and 4 strand cables of >22AWG, which I think is a little small. Is there a good source for >larger aviation grade cables? > > > ________________________________ Message 3 _____________________________________ Time: 11:33:17 PM PST US Subject: AeroElectric-List: KT-76 connector From: "John Erickson" --> AeroElectric-List message posted by: "John Erickson" I've searched the archives and can't seem to find the answer anywhere. I need to replace the connector on the back of the rack for my KT-76 transponder. Anyone know what part number and manufacturer I could get one from to build a new harness? Thanks, John RV-10 #40208 Wings ________________________________ Message 4 _____________________________________ Time: 11:51:40 PM PST US From: Jim Oke Subject: Re: AeroElectric-List: Wire selection --> AeroElectric-List message posted by: Jim Oke Actually this wiring technique is used on some large aircraft such as the DHC-8-102 that I fly for work. Multiple runs are used in some of the main bus feeds possibly for redundancy and possibly to reduce weight. Theory is that for equal weight of wire, a number of small conductors will have more surface area and carry more current than than a single large conductor. Perhaps a design consideration in transport aircraft but hardly likely to be worthwhile in a light aircraft. Circuit protection is via a circuit breaker at each end of each wire in the group. The idea is that if a short occurs in the middle of a wire, the CB at one end will open normally but current will be fed into the other end of the wire via the others in the run and then open the CB at the other end isolating the wire. The remaining conductors will still be available to power the device or buss but at a reduced capacity. So more breakers are needed = higher parts count + more installation time & effort + ongoing maintenance. Perhaps worthwhile if you need 200 amps at a bus but not for a 5-10 amp landing light. Jim Oke Wpg., MB RV-6A Ken wrote: >--> AeroElectric-List message posted by: Ken > >I don't think you want to run multiple wires to feed a single device. >What protects you from fire if one of the wires shorts? > >This technique would be acceptable to lower the voltage drop in the >wiring as long as the fuse was no larger than one of the wires can >handle. It would not be acceptable to use a larger fuse and multiple >wires to increase the current available to a device as then you don't >have appropriate wire protection. > >That said - I mostly used awg 18 fused at 10 amps. I also used a good >deal of awg 22 for signal wires and such as it is much easier to >fabricate assemblies that use small connectors and much more flexible in >bundles. But it is almost inescapable that you will need some larger >wire for the alternator, batteries, and perhaps other things. I think >you will find that the total cost of the wire is less than you may be >imagining. > >Ken > >Ernest Christley wrote: > > > >>--> AeroElectric-List message posted by: Ernest Christley >> >>I'd like to keep my wire rack nice and simple. Instead of having >>multiple spools of various wire sizes, I think it would be beneficial to >>have just one spool of a multistranded cable. I don't see it weighing >>significantly more. There's just not enough wire in the plane to make a >>difference. The cable is more expensive, but the installation would be >>simpler and safer. Simpler since, for instance, there would only be one >>run of wire out to the wingtip lights. Safer since the wire by default >>would have an extra jacket. Before anyone gets a chance to say it, I am >>indeed accepting a less than optimum design in exchange for a lack of >>the need to plan carefully. My response is that the offset from optimum >>will not have measurable results in the final product, and the best laid >>plans of mice and men... (so, it's 4:00 on Saturday. You've got a roll >>of 22AWG left, but what you really need is 2ft of 20AWG. Aaargh!) >> >>So, with this goal in mind, what would be a good wire size that would >>basically cover all the wiring needs, with the obvious exception of the >>starter? 18AWG? 20AWG? Certain high current devices, like pitot heat, >>could use multiple strands in a cable, or lower current technologies, >>like Eric's thermal switch design. Stenair has 3 and 4 strand cables of >>22AWG, which I think is a little small. Is there a good source for >>larger aviation grade cables? >> >> >> >> >> > > > >