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kenryan
Joined: 20 Oct 2009
Posts: 429
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 Posted: Wed Dec 17, 2014 5:24 pm Post subject: stacking ring terminals on terminal post |
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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?
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joemotis(at)gmail.com
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| Posted: Wed Dec 17, 2014 5:38 pm Post subject: stacking ring terminals on terminal post |
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With new star washers and noalox?
2/3
more than that??
uh uh..
One man's opinion
On Wed, Dec 17, 2014 at 5:21 PM, Ken Ryan <keninalaska(at)gmail.com (keninalaska(at)gmail.com)> wrote:[quote]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?
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BobsV35B(at)aol.com
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| Posted: Wed Dec 17, 2014 6:03 pm Post subject: stacking ring terminals on terminal post |
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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(at)gmail.com writes:
| Quote: | 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?
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cbirdsall6(at)cox.net
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| Posted: Wed Dec 17, 2014 10:20 pm Post subject: stacking ring terminals on terminal post |
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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(at)aol.com (BobsV35B(at)aol.com) wrote:
[quote] 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(at)gmail.com (keninalaska(at)gmail.com) writes:
| Quote: | 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?
|
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email(at)jaredyates.com
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| Posted: Thu Dec 18, 2014 4:23 am Post subject: stacking ring terminals on terminal post |
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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 <cbirdsall6(at)cox.net (cbirdsall6(at)cox.net)> wrote:
[quote] 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(at)aol.com (BobsV35B(at)aol.com) wrote:
| Quote: | 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(at)gmail.com (keninalaska(at)gmail.com) writes:
| Quote: | 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?
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[b]
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kenryan
Joined: 20 Oct 2009
Posts: 429
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| Posted: Thu Dec 18, 2014 7:46 am Post subject: stacking ring terminals on terminal post |
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Thanks for all the good answers.
On Thu, Dec 18, 2014 at 3:25 AM, Jared Yates <email(at)jaredyates.com (email(at)jaredyates.com)> wrote:[quote]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 <cbirdsall6(at)cox.net (cbirdsall6(at)cox.net)> wrote:
| Quote: | 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(at)aol.com (BobsV35B(at)aol.com) wrote:
| Quote: | 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(at)gmail.com (keninalaska(at)gmail.com) writes:
| Quote: | 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?
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3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
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3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
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3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
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[b]
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nuckolls.bob(at)aeroelect
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| Posted: Thu Dec 18, 2014 12:43 pm Post subject: stacking ring terminals on terminal post |
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At 09:44 2014-12-18, you wrote:
| Quote: | Thanks for all the good answers.
On Thu, Dec 18, 2014 at 3:25 AM, Jared Yates <email(at)jaredyates.com (email(at)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 . . . [quote][b]
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jimkale(at)roadrunner.com
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| Posted: Thu Dec 18, 2014 8:51 pm Post subject: stacking ring terminals on terminal post |
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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(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Robert L. Nuckolls, III
Sent: Thursday, December 18, 2014 2:40 PM
To: aeroelectric-list(at)matronics.com
Subject: Re: stacking ring terminals on terminal post
At 09:44 2014-12-18, you wrote:
| Quote: |
Thanks for all the good answers.
On Thu, Dec 18, 2014 at 3:25 AM, Jared Yates <email(at)jaredyates.com (email(at)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 . . . 01234567890123456789
[quote][b]
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nuckolls.bob(at)aeroelect
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| Posted: Sat Dec 20, 2014 6:11 am Post subject: stacking ring terminals on terminal post |
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At 22:49 2014-12-18, you wrote:
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 . . . .
This illustrates the value of the FMEA. Don't suppose
or calculate anything . . . assume the worst down
to the fundamentals . . . the simple ideas.
All those books full of rules-of-thumb are the
top-layer attempt to avoid unhappy circumstances
that can arise from an inability to look down into
the layers of potential failure.
I don't recall ever reading some words on bonding
and/or limits to terminals on studs suggesting,
"Oh, by the way, make sure that the thing you're
bolting to isn't going to break/burn off as a
consequence of stresses not addressed by this
rule."
The universe runs on physics. A huge puzzle
of patterns that under ideal conditions, fit
together with permanence and functionality.
Most cases of a puzzle piece jammed into a
less-than-best-fit is of little or no
consequence. But sometimes, a 'hit' on the
extreme end of the bell curve can cause the
assembled puzzle to fall apart . . . and
it's always a surprise.
The artful component of our science is to be
curious, cognizant and competent observers
of how the most rudimentary of puzzle pieces
have been assembled in the past . . . as
a study in both success and failure. It's
this knowledge of lessons-learned that offer
foundation for future successes and minimizing
risks in new adventures.
In this endeavor, you cannot have too many
observers nor is any intellectual exploration
without value. This is how the potential for
unhappy surprises are first resolved intellectually
sitting at our keyboards . . . thus minimizing
the risk of surprise at 5,000 feet . . . or
on short final to the rocks.
See: http://tinyurl.com/mwjbzt3
Bob . . .
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