---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Thu 12/18/14: 7 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 04:23 AM - Re: stacking ring terminals on terminal post (Jared Yates) 2. 07:46 AM - Re: stacking ring terminals on terminal post (Ken Ryan) 3. 12:43 PM - Re: stacking ring terminals on terminal post (Robert L. Nuckolls, III) 4. 04:01 PM - crowbar placement in system (Ken Ryan) 5. 04:31 PM - Re: crowbar placement in system (Jeff Luckey) 6. 04:41 PM - Re: crowbar placement in system (Ken Ryan) 7. 08:51 PM - Re: stacking ring terminals on terminal post (Jim Kale) ________________________________ Message 1 _____________________________________ Time: 04:23:52 AM PST US From: Jared Yates Subject: Re: AeroElectric-List: stacking ring terminals on terminal post Is this a case where a pair of wires could be crimped together in a single r ing terminal? > On Dec 18, 2014, at 01:17, Chuck Birdsall wrote: > > Currently being taught is no more than 4 terminals per post. If more conn ections are needed, then use two posts with a buss bar connecting the two of them - and no more than 3 terminals plus the buss bar per post. > > Reference is AC 43.13-1B Chapter 11 Sections 8 & 14. > > See also the section beginning at page 98 in this training manual: http:/ /www.keybridgeti.com/videotraining/manualdl/25827.PDF (which includes a disc ussion about washers). > > So, to answer the question directly - in my mind, the standard method woul d be to terminate all five wires with a ring terminal. Use two adjacent term inal posts on a terminal strip, bridge them with a buss bar and attach two t erminals to one post and three to the other. Alternatively you could make a short jumper wire with a terminal on each end, and use it to bridge two pos ts (you'll wind up with 4 terminals on one post and 3 on the other). *(Wires and/or buss bars sized appropriately for the current load.) > > Now I'm going to muddy the water a bit. 43.13-1B does say that more than 4 terminals can be placed on a post IF specifically authorized. In the Type- Certificated world that I live in, it's much easier to just wire it to the s tandard (4 or less per post) than it is to go get approval to do it differen tly - unless there is an "approved" source (such as an install manual for an STC'd item) telling me to do it differently. > > Chuck > > >> On 12/17/2014 8:02 PM, BobsV35B@aol.com wrote: >> Don't know what is being taught these days, but when I went through Aviat ion Electricians Mate school in 1947 we were told no more than three ring te rminals per post. No star washers were to be used because they interfered wi th good clean contact. >> >> Happy Skies, >> Old Bob >> Corporal USMC 646659 AEM >> >> In a message dated 12/17/2014 7:25:57 P.M. Central Standard Time, keninal aska@gmail.com writes: >> What's the accepted practice for stacking ring terminals on a terminal po st? Rotax 914 diagram shows 5 wires coming together at a capacitor. What's t he best way to make that connection? >> >> >> > > > ========================== ========= ========================== ========= ========================== ========= ========================== ========= > ________________________________ Message 2 _____________________________________ Time: 07:46:42 AM PST US From: Ken Ryan Subject: Re: AeroElectric-List: stacking ring terminals on terminal post Thanks for all the good answers. On Thu, Dec 18, 2014 at 3:25 AM, Jared Yates wrote: > > Is this a case where a pair of wires could be crimped together in a single > ring terminal? > > > On Dec 18, 2014, at 01:17, Chuck Birdsall wrote: > > Currently being taught is no more than 4 terminals per post. If more > connections are needed, then use two posts with a buss bar connecting the > two of them - and no more than 3 terminals plus the buss bar per post. > > Reference is AC 43.13-1B Chapter 11 Sections 8 & 14. > > See also the section beginning at page 98 in this training manual: > http://www.keybridgeti.com/videotraining/manualdl/25827.PDF (which > includes a discussion about washers). > > So, to answer the question directly - in my mind, the standard method > would be to terminate all five wires with a ring terminal. Use two adjacent > terminal posts on a terminal strip, bridge them with a buss bar and attach > two terminals to one post and three to the other. Alternatively you could > make a short jumper wire with a terminal on each end, and use it to bridge > two posts (you'll wind up with 4 terminals on one post and 3 on the other). > *(Wires and/or buss bars sized appropriately for the current load.) > > Now I'm going to muddy the water a bit. 43.13-1B does say that more than > 4 terminals can be placed on a post IF specifically authorized. In the > Type-Certificated world that I live in, it's much easier to just wire it to > the standard (4 or less per post) than it is to go get approval to do it > differently - unless there is an "approved" source (such as an install > manual for an STC'd item) telling me to do it differently. > > Chuck > > > On 12/17/2014 8:02 PM, BobsV35B@aol.com wrote: > > Don't know what is being taught these days, but when I went through > Aviation Electricians Mate school in 1947 we were told no more than three > ring terminals per post. No star washers were to be used because they > interfered with good clean contact. > > Happy Skies, > Old Bob > Corporal USMC 646659 AEM > > In a message dated 12/17/2014 7:25:57 P.M. Central Standard Time, > keninalaska@gmail.com writes: > > What's the accepted practice for stacking ring terminals on a terminal > post? Rotax 914 diagram shows 5 wires coming together at a capacitor. > What's the best way to make that connection? > > > * > > > * > > ________________________________ Message 3 _____________________________________ Time: 12:43:12 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: stacking ring terminals on terminal post At 09:44 2014-12-18, you wrote: >Thanks for all the good answers. > >On Thu, Dec 18, 2014 at 3:25 AM, Jared Yates ><email@jaredyates.com> wrote: >Is this a case where a pair of wires could be crimped together in a >single ring terminal? I've worked as a direct employee of 4 airframe companies and indirectly with a dozen others. I've observed no consistency in the rules-of-thumb adopted by the aviation community for configuring or limiting the mechanical architecture of terminal stacks on studs. When I've encountered company documents setting forth requirements, no explanation was offered to help anyone understand why that particular policy was put in force . . . the documents were so old that the authors were retired or dead. There was nobody to ask. Nonetheless, given that (1) they had been in place and enforced for decades and (2) no recorded problems having root cause with the practice, then the requirement must be golden. Obviously, every stud is good for one terminal and 20 terminals probably wouldn't fit . . . so someplace between 1 and 20, there must be an optimal number. In any case, the flower of wire-petals leaving the stud needs to fit without placing forceful interference between terminals. With the right terminals on small wires, one could imagine getting 8 wires to share the stud. I have seen a large cluster of wires stacked on a stud long enough to accommodate a spacer between two clusters. Worked good, lasted a long time but this wasn't on an airplane. One's personal quest for rational policy has to be founded in two sciences. (1) Compression forces for the purpose of obtaining gas-tight interfaces and (2) reverence for the inherent vulnerability of threaded fasteners to succumb to vibration . . . the bottom of every thread is a stress-riser. There is a huge window of opportunity between the requirements for compression loads that achieve gas-tightness and stress limits imposed by hanging mass on the end of a bending moment excited by local vibration. Bottom line is that as long as the stud is long enough to fully penetrate the nut and the wires are not all 2AWG, risks are very low. If the cluster fits and you've got 1-1/2 threads protruding from the nut, you're probably good to go. Bob . . . ________________________________ Message 4 _____________________________________ Time: 04:01:55 PM PST US From: Ken Ryan Subject: AeroElectric-List: crowbar placement in system I notice in the Z diagrams that the crowbar seems to be placed in the system downstream from the bus. Since we are trying to protect against over voltage from the alternator, it seems more sensible to place it between the alternator output and the battery. Is there a reason it's not done that way? (such as nuisance trips) ________________________________ Message 5 _____________________________________ Time: 04:31:34 PM PST US From: Jeff Luckey Subject: Re: AeroElectric-List: crowbar placement in system Remember that the Crowbar's mission is to blow the breaker that feeds the regulator thus shutting-down the alternator. Therefore it needs to be placed on the load side of the regulator breaker. -Jeff On Thursday, December 18, 2014 4:11 PM, Ken Ryan wrote: I notice in the Z diagrams that the crowbar seems to be placed in the system downstream from the bus. Since we are trying to protect against over voltage from the alternator, it seems more sensible to place it between the alternator output and the battery. Is there a reason it's not done that way? (such as nuisance trips) ________________________________ Message 6 _____________________________________ Time: 04:41:34 PM PST US From: Ken Ryan Subject: Re: AeroElectric-List: crowbar placement in system Oops! I knew that! Been staring at schematics too long. On Thu, Dec 18, 2014 at 3:28 PM, Jeff Luckey wrote: > > Remember that the Crowbar's mission is to blow the breaker that feeds the > regulator thus shutting-down the alternator. Therefore it needs to be > placed on the load side of the regulator breaker. > > -Jeff > > > On Thursday, December 18, 2014 4:11 PM, Ken Ryan > wrote: > > > I notice in the Z diagrams that the crowbar seems to be placed in the > system downstream from the bus. Since we are trying to protect against over > voltage from the alternator, it seems more sensible to place it between the > alternator output and the battery. Is there a reason it's not done that > way? (such as nuisance trips) > > > * > > > * > > ________________________________ Message 7 _____________________________________ Time: 08:51:29 PM PST US From: "Jim Kale" Subject: RE: AeroElectric-List: stacking ring terminals on terminal post These discussions on how many connectors on a single bolt caused me to recall an accident that a good friend was in. It was a large 46,000 lb. Army Boeing CH-47 Chinook helicopter. The helicopter had 8 fuel boost pumps distributed in 6 tanks to pump the fuel up to the engine driven pumps. The helicopter was lost when both of the turbine engines flamed out due to fuel starvation (not fuel exhaustion). All of the 8 boost pumps had the ground wires connected to one bolt. The bolt did OK, but due to vibration, the sheet metal it was anchored in failed and the bolt broke free of the airframe mount and thus the ground was lost to all of the fuel pumps. Boeing learned from that and soon had 4 ground bolts with the wires distributed between them, and a connector bus between all 4 bolts. It was a single point failure that had been overlooked by the design engineers. History has shown us a few lessons where rather simple design features were overlooked by very talented designers. Bottom line, there is more to this question than just how many terminals may be connected to one bolt. I have seen several references to single point failures in these discussions. Food for thought. Jim . . . . From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Robert L. Nuckolls, III Sent: Thursday, December 18, 2014 2:40 PM Subject: Re: AeroElectric-List: stacking ring terminals on terminal post At 09:44 2014-12-18, you wrote: Thanks for all the good answers. On Thu, Dec 18, 2014 at 3:25 AM, Jared Yates > wrote: Is this a case where a pair of wires could be crimped together in a single ring terminal? I've worked as a direct employee of 4 airframe companies and indirectly with a dozen others. I've observed no consistency in the rules-of-thumb adopted by the aviation community for configuring or limiting the mechanical architecture of terminal stacks on studs. When I've encountered company documents setting forth requirements, no explanation was offered to help anyone understand why that particular policy was put in force . . . the documents were so old that the authors were retired or dead. There was nobody to ask. Nonetheless, given that (1) they had been in place and enforced for decades and (2) no recorded problems having root cause with the practice, then the requirement must be golden. Obviously, every stud is good for one terminal and 20 terminals probably wouldn't fit . . . so someplace between 1 and 20, there must be an optimal number. In any case, the flower of wire-petals leaving the stud needs to fit without placing forceful interference between terminals. With the right terminals on small wires, one could imagine getting 8 wires to share the stud. I have seen a large cluster of wires stacked on a stud long enough to accommodate a spacer between two clusters. Worked good, lasted a long time but this wasn't on an airplane. One's personal quest for rational policy has to be founded in two sciences. (1) Compression forces for the purpose of obtaining gas-tight interfaces and (2) reverence for the inherent vulnerability of threaded fasteners to succumb to vibration . . . the bottom of every thread is a stress-riser. There is a huge window of opportunity between the requirements for compression loads that achieve gas-tightness and stress limits imposed by hanging mass on the end of a bending moment excited by local vibration. Bottom line is that as long as the stud is long enough to fully penetrate the nut and the wires are not all 2AWG, risks are very low. If the cluster fits and you've got 1-1/2 threads protruding from the nut, you're probably good to go. 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.