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
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| Subject: | Re: 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 <cbirdsall6@cox.net> 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
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| Subject: | Re: stacking ring terminals on terminal post |
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?
>
>
> On Dec 18, 2014, at 01:17, Chuck Birdsall <cbirdsall6@cox.net> 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
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| Subject: | Re: 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
><<mailto:email@jaredyates.com>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
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| Subject: | 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
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| Subject: | Re: 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 <keninalaska@gmail.com> 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
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| Subject: | Re: 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 <jluckey@pacbell.net> 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 <keninalaska@gmail.com>
> 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
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| Subject: | 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 <email@jaredyates.com
<mailto: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 . . .
<http://www.buildersbooks.com>
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