---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Mon 03/07/16: 10 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 12:24 AM - Re: Posting order (John Tipton) 2. 05:41 AM - Re: Wire Raceway (Art Zemon) 3. 05:45 AM - Re: Newbie Wiring Questions (Art Zemon) 4. 07:33 AM - Re: Newbie Wiring Questions (Robert L. Nuckolls, III) 5. 08:27 AM - Re: Newbie Wiring Questions (ashleysc@broadstripe.net) 6. 09:17 AM - Re: Newbie Wiring Questions (Robert L. Nuckolls, III) 7. 10:03 AM - Re: Newbie Wiring Questions (Robert L. Nuckolls, III) 8. 10:58 AM - Re: Newbie Wiring Questions (rayj) 9. 12:37 PM - Re: Newbie Wiring Questions (Robert L. Nuckolls, III) 10. 12:37 PM - Re: Newbie Wiring Questions (Robert L. Nuckolls, III) ________________________________ Message 1 _____________________________________ Time: 12:24:50 AM PST US Subject: Re: AeroElectric-List: Posting order From: John Tipton But do we need to see a diatribe by Steinbeck too !!! Sent from my iPad ----x--O--x---- > On 6 Mar 2016, at 10:53 pm, rayj wrote: > > > I think the choice of where to post depends on whether the exchange is viewed as a conversation or as building an archive. > > For a conversation, it's not necessary to review everything that has been said each time a reply is made. The latest addition to the conversation is immediately presented. Hence the preference for top posting. > > For later reading in an archive, bottom posting perhaps makes it more convenient to read. > > I subscribe to the list as email, so my comments refer to that format. > > do not archive > > Raymond Julian > Kettle River, MN > > The things we admire in men, kindness and generosity, openness, honesty, understanding and feeling are the concomitants of failure in our system. And those traits we detest, sharpness, greed, acquisitiveness, meanness, egotism and self-interest are the traits of success. And while men admire the quality of the first they love the produce of the second. -John Steinbeck, novelist, Nobel laureate (1902-1968) > >> On 03/06/2016 12:22 PM, H. Marvin Haught Jr wrote: >> >> Well.... I for one disagree with all of that and prefer top posting. But I feel no need to tilt windmills or to try to enforce my preferences in life on other folks! I agree with Jared. And I try to keep my obsessive compulsive urges to my private life and out of my interactions with other folks that may not suffer from the same compulsions! I am probably older that you are and long ago learned that life is more fun when I learned to "agree to disagree"! :) >> >> Sent from my iPad >> >>> On Mar 6, 2016, at 10:08 AM, Dj Merrill wrote: >>> >>> >>> FWIW, the Internet Etiquette RFC 1855 provides guidelines to crop the text you are replying to just the relevant part, with your reply below that text. >>> >>> "If you are sending a reply to a message or a posting be sure you >>> summarize the original at the top of the message, or include just >>> enough text of the original to give a context. This will make >>> sure readers understand when they start to read your response." >>> >>> https://www.ietf.org/rfc/rfc1855.txt >>> >>> >>> This post sums it up fairly well: >>> >>> https://www.redhat.com/archives/shrike-list/2003-August/msg00529.html >>> >>> >>> Top posting puts things out of order and makes comprehension very difficult IMHO, especially if someone is replying to a specific part of the previous message. >>> >>> Lots of opinions on this topic, even more so than which primer to use... ;-) >>> >>> -Dj, an old fart that has been on the "Internet" longer than it has been called that... :-) >>> >>> -- >>> Dj Merrill - N1JOV - EAA Chapter 87 >>> Sportsman 2+2 Builder #7118 N421DJ - http://deej.net/sportsman/ >>> Glastar Flyer N866RH - http://deej.net/glastar/ > > > > ________________________________ Message 2 _____________________________________ Time: 05:41:25 AM PST US Subject: AeroElectric-List: Re: Wire Raceway From: Art Zemon Charley, That looks like really good stuff. Thank you! You have my imagination bubbling about places to use each of those products. -- Art Z. On Sun, Mar 6, 2016 at 9:31 PM, Charlie England wrote: > For wire raceway, I found this stuff: > https://www.techflex.com/prod_ccp.asp > and > https://www.techflex.com/prod_f6w.asp > > As long as you leave a bit of extra length, the 1st can expand > substantially for future wire additions. > The 2nd allows wire to be added without being pulled through the tube, and > allows wire to exit at any point along the run without cutting open the > tube. > > Very flexible, can turn sharp corners, weighs next to nothing, very thin > 'wall', and good abrasion resistance. I used the split stuff to run down > the sides of my RV-7 from behind the instrument panel to the fuel > line/cable chase at the main spar. The unsplit stuff I've used to bundle > runs from subD connectors behind the panel. The 3/4" diameter version will > expand enough to go over a populated subD, if the shell is removed & the > wires bent 90 degrees. > > FWIW... > > Charlie > -- http://CheerfulCurmudgeon.com/ *"If I am not for myself, who is for me? And if I am only for myself, what am I? And if not now, when?" Hillel* ________________________________ Message 3 _____________________________________ Time: 05:45:53 AM PST US Subject: Re: AeroElectric-List: Newbie Wiring Questions From: Art Zemon On Sun, Mar 6, 2016 at 7:47 PM, Robert L. Nuckolls, III < nuckolls.bob@aeroelectric.com> wrote: > At 09:39 PM 3/2/2016, you wrote: > > Hello, > > I am starting to plan the wiring for my BD-4C. My immediate problem is > that I want to install the wires for things which will go in the rear of > the plane, and near the floor by the back seat, soon so that I can close up > the "tunnel" and (hopefully) not need to get in there again. > > > Why not run a conduit of pex or nylon tubing through the > covered tunnel environs? > Bob, Brilliant. Now why didn't I think of that? I ran a 3/8" piece of PVC to the tail "just in case I ever need it" but never thought of doing the same in the tunnel. There is a lot of value in hashing out even "obvious" questions with other people. Thank you. > > When I install such features, I always pull in one more > strand of wire than necessary and secure the pigtails > at each end. Then, when you need to add a wire later, > use your 'tag wire' to pull in the new wire PLUS > a new 'tag wire'. > I have used string for similar duties in my home, but fastening the new wire to the string has been worrisome. How do you do it with wire, butt splice? That seems like it would be more reliable and with smaller diameter than the tape that I have used at home. > > Running the bundle through a secured conduit eliminates > concerns for supporting the wires through the inaccessible > and invisible tunnel environs. > Good to know. That eliminates my only concern about using a conduit. > > The autopilot servos and the magnetometer have me wondering what to do. > Each needs power + 4 signal wires. The autopilot servos draw up to 1.7 A so > I think I use larger wire for the power than the signals. The magnetomer > only draws 0.12 A, though, so do I just get a cable with 5 or 6 conductor s > in it? Or should the power be a separate wire from a 4-conductor signal > cable? > > > As long as EVERY electron running one way through > a bundle is exactly paired with another electron > going the other way, there is no coupling of energy > from one wire to another. > I am building an aluminum airplane. I have not (yet) found guidelines for selecting from three scenarios: 1. Run a ground wire 2. Use a shielded wire 3. Use the fuselage as the ground Can you point me at something? > Finally, an off the wall question: How do you size a fuse for a circuit? > Do you just round up to the next highest integer or do you go bigger? I'm > thinking of the autopilot servos, average current of 0.9 A and max curren t > of 1.71 A. Should I use a 2 A fuse? 3 A? Put both on a single 5 A fuse? > Something else? > > > Does EACH servo get powered from its own bus-power-tap? > How many power feeders are depicted on the installation > instructions? > MGL's instructions are pretty sparse for their servos (at least compared to what they write for their AHRS and magentometer units, where they do specify a circuit breaker size): In order to accommodate the current required, 18 to 20 gauge wires should b e > used for the power wires (positive and negative supply). Thinner wires ca n > be > used for the signal wires. > If the servo is installed onto an bracket that is grounded (for example i n > an all > metal aircraft), ensure that the area created by the returning ground > (thick) power > cable is kept to a minimum =93 keep the distance between the wire a nd the > metal > construction to a minimum for the full length of the cable up to > termination into > the power bus. I'm inclined to use a fuse for each servo, mostly because I don't have any reason to cheap out and save a fuse. We had some good discussion about that over the last few days, so I won't rehash it. > They probably speak to suggested wire > gages too. Unless your wire runs are especially LONG > (seldom in OBAM aircraft), then picking wires and > their respective protective devices is right out > of the book 5A/22AWG, 7A/20AWG, etc. etc. There's > no risk for having the wire oversized. There's nearly > zero risk for being a little 'undersized' wherein the > risk is for nuisance tripping of a fuse or breaker. > > 20AMPS will not burn a 22AWG wire suspended in free > air. See: > > http://tinyurl.com/6qr72fr > > So even if you found that some transient load on > the end of a 22AWG wire nuisance trips a 5A fuse, > then go up to 7A fuse but do not change the wire. > > 99* percent of wiring failures are open circuits. > Wire comes out of terminal, screw comes loose, > pin pushes back in a connector, etc. Most of > the remaining failures are HARD faults to ground > or within loads where the current will be many times > higher than the wire's installed protection. In > these instances you're interested in fast response > that does not overheat the wire. Compared to breakers > Fuses are VERY fast. Hence upsizing from 5 to > 7A fuse on a 22AWG wire is a yawn. > This is very good to know. I'm a "gotta know why" kind of guy. Understanding the rationale behind fuse selection makes it much easier for me to "size the fuse for the wire" instead of the load. Specifically, I had not thought it through far enough to realize that the current in a failure will be many times higher than the fuse's limit. That explains why using a smaller fuse doesn't offer any additional protection. > > How did you happen into the BD-4 project? That > was probably uncle Jim's finest contribution > to the OBAM aviation community . . . > Short version: I wanted a fast 4-place X-C airplane with modern avionics for my wife and me to travel in. I wanted to eliminate moving parts, in particular mechanical gyros and vacuum pumps. I didn't want to spend the money on a new factory-built plane or spend the money to completely upgrade my '68 Arrow. I am way more interested in function than beauty so the BD-4C was the natural choice. Long version: How I Chose to Build a Bede BD-4C (on my blog) Cheers, -- Art Z. -- http://CheerfulCurmudgeon.com/ *"If I am not for myself, who is for me? And if I am only for myself, what am I? And if not now, when?" Hillel* ________________________________ Message 4 _____________________________________ Time: 07:33:42 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Newbie Wiring Questions >For wire raceway, I found this stuff: >https://www.techflex.com/prod_ccp.asp >and >https://www.techflex.com/prod_f6w.asp > >As long as you leave a bit of extra length, the 1st can expand >substantially for future wire additions. >The 2nd allows wire to be added without being pulled through the >tube, and allows wire to exit at any point along the run without >cutting open the tube. > >Very flexible, can turn sharp corners, weighs next to nothing, very >thin 'wall', and good abrasion resistance. I used the split stuff to >run down the sides of my RV-7 from behind the instrument panel to >the fuel line/cable chase at the main spar. The unsplit stuff I've >used to bundle runs from subD connectors behind the panel. The 3/4" >diameter version will expand enough to go over a populated subD, if >the shell is removed & the wires bent 90 degrees. > >FWIW... > >Charlie Yeah, we had this stuff around at Hawker-Beech but I'm not sure I ever saw it used in the airplanes . . . I'll have to ask some guys who had more experience on the lines. We used it a lot for fabricating test harnesses, the techs called it 'snake skin'. I'm not sure one could pull new wires in with a tag line if the bundle was secured in an inaccessible space with adel clamps. The rigid diameter conduit approach preserves cross section under the clamps. But this makes for VERY flexible test harnesses. A string tied bundle can become quite stiff when individual strands of wire get bound tightly to each other under those constrictor knots. Bob . . . ________________________________ Message 5 _____________________________________ Time: 08:27:01 AM PST US From: ashleysc@broadstripe.net Subject: Re: AeroElectric-List: Newbie Wiring Questions Hi All; Recommend putting a nylon pull string into the tubing before burying it in the aircraft.=C2-The string can be pulled through with a vacuum cleaner. Tie on a loose fitting ball of foam or cloth=C2-at the leading end of the string to help pull the string through. Cheers!=C2-=C2- Stu. ----- Original Message ----- From: "Robert L. Nuckolls, III" Sent: Sunday, March 6, 2016 5:47:56 PM Subject: Re: AeroElectric-List: Newbie Wiring Questions At 09:39 PM 3/2/2016, you wrote: Hello, I am starting to plan the wiring for my BD-4C. My immediate problem is that I want to install the wires for things which will go in the rear of the pl ane, and near the floor by the back seat, soon so that I can close up the " tunnel" and (hopefully) not need to get in there again. =C2-=C2- Why not run a conduit of pex or nylon tubing through the =C2-=C2- covered tunnel environs? Then you can push/pull wires =C2-=C2- through at any later time at your convenience . . . after =C2-=C2- you've crafted wiring diagrams that comport with manufacturer' s =C2-=C2- instructions for each appliance. You can get a LOT =C2-=C2- of wires into a piece of 1/2 or 3/4" pex. =C2-=C2- Here's an exemplar 'bundle' of wires in a piece of =C2-=C2- 5/8" tubing . . . http://tinyurl.com/hez7eat =C2-=C2- When I install such features, I always pull in one more =C2-=C2- strand of wire than necessary and secure the pigtails =C2-=C2- at each end. Then, when you need to add a wire later, =C2-=C2- use your 'tag wire' to pull in the new wire PLUS =C2-=C2- a new 'tag wire'.=C2- I've got a 20 foot conduit that =C2-=C2- runs from my desk up the wall an out the roof to =C2-=C2- my antennas. The pipe already had 4 coax cables in =C2-=C2- it when I pulled a 5th into the bundle with no =C2-=C2- sweat. =C2-=C2- Running the bundle through a secured conduit eliminates =C2-=C2- concerns for supporting the wires through the inaccessible =C2-=C2- and invisible tunnel environs.
The autopilot servos and the magnetometer have me wondering what to do. Eac h needs power + 4 signal wires. The autopilot servos draw up to 1.7 A so I think I use larger wire for the power than the signals. The magnetomer only draws 0.12 A, though, so do I just get a cable with 5 or 6 conductors in i t? Or should the power be a separate wire from a 4-conductor signal cable?
=C2-=C2- As long as EVERY electron running one way through =C2-=C2- a bundle is exactly paired with another electron =C2-=C2- going the other way, there is no coupling of energy =C2-=C2- from one wire to another.
The rear seat intercomm has me wondering, too. It looks like 4-conductors w ill do, since there aren't any PTT switches. But shielded or not? I think n ot but would like some reassurance.
=C2- I'd use three conductor shielded where the shield is =C2- a fourth, ground conductor for one of the features at the =C2- far end.
Finally, an off the wall question: How do you size a fuse for a circuit? Do you just round up to the next highest integer or do you go bigger? I'm thi nking of the autopilot servos, average current of 0.9 A and max current of 1.71 A. Should I use a 2 A fuse? 3 A? Put both on a single 5 A fuse? Someth ing else?
=C2- Does EACH servo get powered from its own bus-power-tap? =C2- How many power feeders are depicted on the installation =C2- instructions? They probably speak to suggested wire =C2- gages too. Unless your wire runs are especially LONG =C2- (seldom in OBAM aircraft), then picking wires and =C2- their respective protective devices is right out =C2- of the book=C2- 5A/22AWG, 7A/20AWG, etc. etc. There's =C2- no risk for having the wire oversized. There's nearly =C2- zero risk for being a little 'undersized' wherein the =C2- risk is for nuisance tripping of a fuse or breaker. =C2- 20AMPS will not burn a 22AWG wire suspended in free =C2- air. See: http://tinyurl.com/6qr72fr =C2- So even if you found that some transient load on =C2- the end of a 22AWG wire nuisance trips a 5A fuse, =C2- then go up to 7A fuse but do not change the wire. =C2- 99* percent of wiring failures are open circuits. =C2- Wire comes out of terminal, screw comes loose, =C2- pin pushes back in a connector, etc. Most of =C2- the remaining failures are HARD faults to ground =C2- or within loads where the current will be many times =C2- higher than the wire's installed protection. In =C2- these instances you're interested in fast response =C2- that does not overheat the wire. Compared to breakers =C2- Fuses are VERY fast. Hence upsizing from 5 to =C2- 7A fuse on a 22AWG wire is a yawn. =C2-=C2- But in any case, begin with the manufacturer's =C2-=C2- recommendations for the appliance being installed. =C2-=C2- They SHOULD know more about achieving efficiency =C2-=C2- and reliability for that device than anyone else. =C2-=C2- Further, when their product falls short of advertised =C2-=C2- performance, root cause will most likely be found =C2-=C2- In shortfalls of quality assurance in production =C2-=C2- or installation as opposed to design. =C2-=C2- Please don't take this as any kind of push-back =C2-=C2- for bringing those questions to the List but =C2-=C2- understand that some well considered answers require =C2-=C2- more knowledge than one might be expected to have =C2-=C2- in their hip pocket. The last two failure analysis =C2-=C2- programs I participated in started with a study of =C2-=C2- the prior art. I read the manuals, looked up patents, =C2-=C2- researched process recommendations for installing =C2-=C2- the parts. All those references were cited in my report =C2-=C2- bibliography and became part of a foundation =C2-=C2- for what turned into as simple, two paragraph conclusion/ =C2-=C2- recommendation. =C2-=C2- So like you wife admonished as you struggled =C2-=C2- with your kid's new bike on Xmas eve, "Gee =C2-=C2- dear . . . have you read the instructions?" =C2-=C2- Of course, if they were translated from Chinese =C2-=C2- by a second year language student . . . oh well . . . =C2-=C2- bring it to the List and we'll commiserate. =C2-=C2- How did you happen into the BD-4 project? That =C2-=C2- was probably uncle Jim's finest contribution =C2-=C2- to the OBAM aviation community . . . =C2-=C2-=C2-=C2-=C2-=C2- =C2- Bob . . . ________________________________ Message 6 _____________________________________ Time: 09:17:46 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Newbie Wiring Questions At 10:25 AM 3/7/2016, you wrote: >Hi All; >Recommend putting a nylon pull string into the tubing before burying >it in the aircraft. The string can be pulled through with a vacuum >cleaner. Tie on a loose fitting ball of foam or cloth at the leading >end of the string to help pull the string through. >Cheers! Stu. Yeah . . . a airhose blow gun works from the supply end too. I'll tie a piece of shop rag onto the end of the string then stuff about a foot of string in with the rag-wad, blow, stuff more string, repeat. Bob . . . ________________________________ Message 7 _____________________________________ Time: 10:03:33 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Newbie Wiring Questions > >I have used string for similar duties in my >home, but fastening the new wire to the string >has been worrisome. How do you do it with wire, >butt splice? That seems like it would be more >reliable and with smaller diameter than the tape that I have used at home. Kinda depends on how tight the bundle is in the tube . . . but my personal favorite is to do a soldered lap-splice to ALL of the strands being pulled. My tag wire is usually 20AWG. Overlap about 1/2" of tag wire strands with the new wires (+ new tag wire). Put a piece of heat shrink over it to 'smooth' the joint and then pull them in . . . >Good to know. That eliminates my only concern about using a conduit. Supporting wires hanging out in the breeze is intended to eliminate potential vibration/abrasion points and just control what otherwise might be a floppy bundle. WAaaayyyy back when, cotton over rubber insulated wire (Mil-W-76) wire was subject to imbrittlement when exposed to ozone, hydrocarbons, and just old age. Adequate support went to extending service life of the insulation. Tefzel doesn't suffer from this malady so 'floppy' bundles are more an issue of craftsmanship as long as the wires don't bang on a hard/sharp point. >I am building an aluminum airplane. I have not >(yet) found guidelines for selecting from three scenarios:=C2 > * Run a ground wire Except for the few examples of 'local grounds' illustrated in Figure Z-15, it is ALWAYS good practice to include ground returns in the same bundle that carries power and signals. Any appliance designer worth his soldering iron will do this and it should be obvious in the installation manuals. CAVEAT: when you DO see a local ground called out on a wiring diagram for some appliance having mixed signals/power wires running elsewhere, it's NEVER wrong to extend your ground up to the panel with all the other wires. > * Use a shielded wire Only when called out by the system designer. Shielding breaks only one coupling mode for noises that is seldom encountered in modern aircraft appliances. If the instruction manual doesn't call out shielded wire, adding it is unnecessary. I've seen is used many times where it probably doesn't make any difference . . . probably by some guy whose solder station includes zinc-chloride flux. Shielding never hurts but it is very seldom necessary or beneficial. I use shielded trio as 4-conductor wires in audio systems only because it's convenient and the wire is commonly available . . . usefulness of the 4th conductor's qualities as a shield is problematic. > * Use the fuselage as the ground . . . only on those devices called out on Z-15 >I'm inclined to use a fuse for each servo, >mostly because I don't have any reason to cheap >out and save a fuse. We had some good discussion >about that over the last few days, so I won't rehash it. Can the installation manual for this system be downloaded? what's the FEMA for this system look like? Can the system still be useful with one actuator being un-powered? Keep in mind that 99.999% of ALL circuit protection installed in DC vehicular power systems will go the lifetime of the vehicle having NEVER been called upon to operate. This is why I blanch at the idea of using breakers vs. fuses. They use up a lot of dollars, install time, panel space, weight, etc while adding nothing to system safety when compared to the simple out of sight, out of reach fuse. See: http://tinyurl.com/hbhlv93 http://tinyurl.com/ht8wtl5 http://tinyurl.com/j3lfdbr >This is very good to know. I'm a "gotta know >why" kind of guy. Understanding the rationale >behind fuse selection makes it much easier for >me to "size the fuse for the wire" instead of >the load. Specifically, I had not thought it >through far enough to realize that the current >in a failure will be many times higher than the >fuse's limit. That explains why using a smaller >fuse doesn't offer any additional protection. Good for you. Most of the hangar lore about breakers and wires seems to impart images of smoke and fire pouring out from under the panel along with admonitions: "Tho shalt not oversize thy breakers less wires melt and open the gates to hell-in-the-air." In fact, insulation quality is the wire's limiting factor for current rating working hand in hand with controlling voltage drop. I've only experienced burned wires one time (improperly installed p-leads and disconnected crankcase ground). I've experienced and/or conducted analysis on dozens of bad smells and smoke that came from INSIDE a device and would probably never operate the breaker. Looking through the accident reports for TC aircraft, it's exceedingly7 difficult to find instances of bad days in the cockpit due to electrical faults. Many electrical emergencies in OBAM aircraft have roots in poor craftsmanship, piloting skills and/or system architecture. See: http://tinyurl.com/ky7szec Fuse and wire sizing is pretty straight-forward and way down on the list of reliability/safety concerns. Just keep in mind that for every condition that will open a fuse on some appliance useful for comfortable termination of flight, there are dozens to hundreds of conditions more likely to bring the system down without blowing the fuse. If loss of any single appliance drives your pucker=pressure up, then having a Plan-B for continued comfortable flight without that appliance. >=C2 > >=C2 =C2 How did you happen into the BD-4 project? That >=C2 =C2 was probably uncle Jim's finest contribution >=C2 =C2 to the OBAM aviation community . . . > > >Short version: I wanted a fast 4-place X-C >airplane with modern avionics for my wife and me >to travel in. I wanted to eliminate moving >parts, in particular mechanical gyros and vacuum >pumps. I didn't want to spend the money on a new >factory-built plane or spend the money to >completely upgrade my '68 Arrow. I am way more >interested in function than beauty so the BD-4C was the natural choice. > >Long version:=C2 >How >I Chose to Build a Bede BD-4C (on my blog) I'll read it . . . thanks for the heads-up . . . Bob . . . ________________________________ Message 8 _____________________________________ Time: 10:58:12 AM PST US Subject: Re: AeroElectric-List: Newbie Wiring Questions From: rayj I don't know if it's applicable to aircraft wire types, but I have found wire lube makes pulling wire in a full conduit and/or long runs significantly easier. Raymond Julian Kettle River, MN The things we admire in men, kindness and generosity, openness, honesty, understanding and feeling are the concomitants of failure in our system. And those traits we detest, sharpness, greed, acquisitiveness, meanness, egotism and self-interest are the traits of success. And while men admire the quality of the first they love the produce of the second. -John Steinbeck, novelist, Nobel laureate (1902-1968) On 03/07/2016 12:01 PM, Robert L. Nuckolls, III wrote: >> >> I have used string for similar duties in my home, but fastening the >> new wire to the string has been worrisome. How do you do it with wire, >> butt splice? That seems like it would be more reliable and with >> smaller diameter than the tape that I have used at home. > > Kinda depends on how tight the bundle is in > the tube . . . but my personal favorite is to > do a soldered lap-splice to ALL of the strands > being pulled. My tag wire is usually 20AWG. > Overlap about 1/2" of tag wire strands with the > new wires (+ new tag wire). Put a piece of heat > shrink over it to 'smooth' the joint and then > pull them in . . . > > >> Good to know. That eliminates my only concern about using a conduit. > > Supporting wires hanging out in the breeze is > intended to eliminate potential vibration/abrasion > points and just control what otherwise might be > a floppy bundle. WAaaayyyy back when, cotton over > rubber insulated wire (Mil-W-76) wire was subject > to imbrittlement when exposed to ozone, hydrocarbons, > and just old age. Adequate support went to extending > service life of the insulation. Tefzel doesn't suffer > from this malady so 'floppy' bundles are more an > issue of craftsmanship as long as the wires don't > bang on a hard/sharp point. > > >> I am building an aluminum airplane. I have not (yet) found guidelines >> for selecting from three scenarios: >> >> 1. Run a ground wire > > Except for the few examples of 'local grounds' illustrated > in Figure Z-15, it is ALWAYS good practice to include > ground returns in the same bundle that carries power > and signals. Any appliance designer worth his soldering > iron will do this and it should be obvious in the > installation manuals. CAVEAT: when you DO see a local > ground called out on a wiring diagram for some appliance > having mixed signals/power wires running elsewhere, it's > NEVER wrong to extend your ground up to the panel with > all the other wires. >> >> 1. Use a shielded wire > > Only when called out by the system designer. Shielding > breaks only one coupling mode for noises that is seldom > encountered in modern aircraft appliances. If the instruction > manual doesn't call out shielded wire, adding it is unnecessary. > I've seen is used many times where it probably doesn't make > any difference . . . probably by some guy whose solder > station includes zinc-chloride flux. Shielding > never hurts but it is very seldom necessary or beneficial. > > I use shielded trio as 4-conductor wires in audio > systems only because it's convenient and the wire > is commonly available . . . usefulness of the 4th > conductor's qualities as a shield is problematic. > >> 1. Use the fuselage as the ground > > . . . only on those devices called out on Z-15 > > >> I'm inclined to use a fuse for each servo, mostly because I don't have >> any reason to cheap out and save a fuse. We had some good discussion >> about that over the last few days, so I won't rehash it. > > Can the installation manual for this system be > downloaded? what's the FEMA for this system look > like? Can the system still be useful with one > actuator being un-powered? > > Keep in mind that 99.999% of ALL circuit protection > installed in DC vehicular power systems will go > the lifetime of the vehicle having NEVER been > called upon to operate. This is why I blanch at > the idea of using breakers vs. fuses. They use up > a lot of dollars, install time, panel space, weight, > etc while adding nothing to system safety when > compared to the simple out of sight, out of reach fuse. > > See: > > http://tinyurl.com/hbhlv93 > > http://tinyurl.com/ht8wtl5 > > http://tinyurl.com/j3lfdbr > > >> This is very good to know. I'm a "gotta know why" kind of guy. >> Understanding the rationale behind fuse selection makes it much easier >> for me to "size the fuse for the wire" instead of the load. >> Specifically, I had not thought it through far enough to realize that >> the current in a failure will be many times higher than the fuse's >> limit. That explains why using a smaller fuse doesn't offer any >> additional protection. > > Good for you. Most of the hangar lore about > breakers and wires seems to impart images of > smoke and fire pouring out from under the panel > along with admonitions: "Tho shalt not oversize > thy breakers less wires melt and open the gates > to hell-in-the-air." > > In fact, insulation quality is the wire's limiting > factor for current rating working hand in hand > with controlling voltage drop. I've only experienced > burned wires one time (improperly installed p-leads > and disconnected crankcase ground). I've experienced > and/or conducted analysis on dozens of bad smells and > smoke that came from INSIDE a device and would probably > never operate the breaker. > > Looking through the accident reports for TC aircraft, > it's exceedingly7 difficult to find instances of > bad days in the cockpit due to electrical faults. > Many electrical emergencies in OBAM aircraft have > roots in poor craftsmanship, piloting skills and/or > system architecture. > > See: > > http://tinyurl.com/ky7szec > > Fuse and wire sizing is pretty straight-forward > and way down on the list of reliability/safety > concerns. Just keep in mind that for every > condition that will open a fuse on some appliance > useful for comfortable termination of flight, > there are dozens to hundreds of conditions more > likely to bring the system down without blowing > the fuse. > > If loss of any single appliance drives your > pucker=pressure up, then having a Plan-B for > continued comfortable flight without that > appliance. > > >> >> >> >> How did you happen into the BD-4 project? That >> was probably uncle Jim's finest contribution >> to the OBAM aviation community . . . >> >> >> Short version: I wanted a fast 4-place X-C airplane with modern >> avionics for my wife and me to travel in. I wanted to eliminate moving >> parts, in particular mechanical gyros and vacuum pumps. I didn't want >> to spend the money on a new factory-built plane or spend the money to >> completely upgrade my '68 Arrow. I am way more interested in function >> than beauty so the BD-4C was the natural choice. >> >> Long version: How I Chose to Build a Bede BD-4C >> >> (on my blog) > > I'll read it . . . thanks for the heads-up . . . > > > Bob . . . > ________________________________ Message 9 _____________________________________ Time: 12:37:12 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Newbie Wiring Questions At 12:55 PM 3/7/2016, you wrote: > >I don't know if it's applicable to aircraft wire types, but I have >found wire lube makes pulling wire in a full conduit and/or long >runs significantly easier. TC aircraft are generally designed up from a clean piece of paper and don't benefit from inclusion of conduits. From the TC perspective, it's a weight penalty that project management would really argue against. I have seen conduits that run through wet-wing tanks and occasionally along the rear spar for wing wires. Those conduits were never really 'tight' on the wires. Pex is so slick inside that you would need to have it REALLY full of wire before there was risk to successful addition of a few new wires. Bob . . . ________________________________ Message 10 ____________________________________ Time: 12:37:12 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Newbie Wiring Questions At 12:55 PM 3/7/2016, you wrote: > >I don't know if it's applicable to aircraft wire types, but I have >found wire lube makes pulling wire in a full conduit and/or long >runs significantly easier. TC aircraft are generally designed up from a clean piece of paper and don't benefit from inclusion of conduits. From the TC perspective, it's a weight penalty that project management would really argue against. I have seen conduits that run through wet-wing tanks and occasionally along the rear spar for wing wires. Those conduits were never really 'tight' on the wires. Pex is so slick inside that you would need to have it REALLY full of wire before there was risk to successful addition of a few new wires. 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