Today's Message Index:
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1. 03:53 AM - Screw Terminals (racerjerry)
2. 06:42 AM - Re: Screw Terminals (user9253)
3. 09:05 AM - Re: Re: Screw Terminals (Eric Page)
4. 09:05 AM - Re: Screw Terminals (Robert L. Nuckolls, III)
5. 11:54 AM - Re: Check My Work (David Lloyd)
6. 11:59 AM - Re: Check My Work (David Lloyd)
Message 1
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Screw type terminations scare the hell out of me - except when they are done correctly.
I have seen way too many products & screw type terminal strips installed
in OBAM aircraft that were designed for static operation that do not have
any type of locking mechanism to counter normal vibration. Most quality switches
come with terminal screws that have a captive lock-washer as well as a plain
thin washer under it so as to provide a locking mechanism for the screw head,
but not scar the device being attached.
I am very partial to aircraft quality internal star lock-washers. They are inexpensive,
corrosion resistant and do not side load the screw/stud as common split
lock-washers are prone to do. They are also thinner than a split washer.
If I am installing against a ring terminal; unless it's captive, I normally omit
the plain washer and let the stars bite into everything for a solid, secure
and vibration resistant connection. The internal star lock-washers should be
replaced each time they are removed, but at least check that ears are not completely
flattened out. $2 worth will last you a lifetime.
Current prices from Aircraft Spruce:
MS35333-37 (#6) $0.02
MS35333-38 (#8) $0.02
AN960-6L (#6) $0.02 or $1.60 /100
AN960-8L (#8) $0.02 or $1.60 /100
--------
Jerry King
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=455423#455423
Message 2
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Subject: | Re: Screw Terminals |
It turns out that the split ring lock washers that we have been using for years
are not actually lock washers at all. In fact, their spring characteristic can
actually cause fasteners to loosen sooner. I have not seen split ring lock
wasters used on newer cars. Internal star lock washers are good. Even better
are wedge-lock washers. They are used in pairs with the wedges facing each
other. When a bolt or nut starts to loosen, the wedges move apart slightly.
That causes the fastener to stretch, which makes it difficult for the fastener
to loosen anymore. It requires much more force to loosen than to tighten fasteners
installed with wedge-lock washers. Matco brakes and Sensenich props use
wedge-lock washers without any other locking devices or safety wire.
Youtube movie about wedge-lock washers:
https://www.youtube.com/watch?v=IKwWu2w1gGk
I am not recommending wedge-lock washers for small screws. But I am recommending
that split ring lock washers NOT be used anyplace on an aircraft, or for any
application with the intent of preventing a fastener from loosening.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=455430#455430
Message 3
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Subject: | Re: Screw Terminals |
Very interesting product. It appears to work well, but I wonder if the radial
impression marks that they create can serve as stress risers in softer materials
like aluminum. Also, it looks like it wouldn't take very much over-torque
to gall an aluminum surface or scrape off the cladding.
Perhaps this is why aviation still predominantly uses castle nuts on flat washers.
Not advocating against Nord-Lock, just thinking out loud...
Eric
> On Apr 25, 2016, at 6:41 AM, user9253 <fransew@gmail.com> wrote:
> [...] Even better are wedge-lock washers. They are used in pairs with the wedges
facing each other. When a bolt or nut starts to loosen, the wedges move
apart slightly. That causes the fastener to stretch, which makes it difficult
for the fastener to loosen anymore. It requires much more force to loosen than
to tighten fasteners installed with wedge-lock washers. Matco brakes and Sensenich
props use wedge-lock washers without any other locking devices or safety
wire.
> Youtube movie about wedge-lock washers:
> https://www.youtube.com/watch?v=IKwWu2w1gGk
Message 4
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Subject: | Re: Screw Terminals |
At 05:52 AM 4/25/2016, you wrote:
>
>Screw type terminations scare the hell out of me - except when they
>are done correctly. I have seen way too many products & screw
>type terminal strips installed in OBAM aircraft that were designed
>for static operation that do not have any type of locking mechanism
>to counter normal vibration. Most quality switches come with
>terminal screws that have a captive lock-washer as well as a plain
>thin washer under it so as to provide a locking mechanism for the
>screw head, but not scar the device being attached.
True . . .
All mil-qualified switches will come with internal
tooth lock washers and I've never encountered a
condition precipitated by a loose screw.
Switch and breaker panels are never assembled in
a production airframe. They are put together on
sub-assemblies in good lighting, air conditioned
spaces by people standing upright or sitting
on a chair.
The sub assembly, with a medusa of pendant cables
and wires is assembled to the airframe with a few
screws and 'plugged in' with perhaps a few fat
wires dropping onto studs.
Most breakers and switches with threaded fasteners
have steel screws into brass 'nuts'. Recommended
torque values for fastening are in the 8 in-lb
range . . . and this number is generally 60%
of ultimate. Assembly benches at Beech used
torque limiting screwdrivers to do final tightening
of threaded fasteners. You can often pick up
adjustable, torque limiting screwdrivers off
eBay.
Few OBAM/SE-TC aircraft are assembled like leggos
. . . and none will be easy/convenient/comfortable to
troubleshoot. Further, the assembler is comparatively
Wwaaaayyy down on the learning curve for achieving
consistent tightening torque.
At the same time, we have an opportunity to do
FMEA studies which guarantee that NO single
disconnection for loose screw or any other
reason causes a bad day in the cockpit. Many
variations in desirable switch styles/features
will drive the decision toward threaded fasteners
which are not evil, only different. It's like
the difference between crimped and soldered.
Both are entirely satisfactory when applied
with confidence . . . it's just another skill
to learn.
Bob . . .
Message 5
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Subject: | Re: Check My Work |
At first glance, that pic shows a poor solder joint.
The wire is captured correctly but, the joint to the terminal is poor. The
solder should pool out in a graceful way and appear very attached. Someti
mes best to lightly sand the terminal metal first so solder can attach to b
ase metal.
D
---------------------------------------------------------------------------
-----
----- Original Message -----
From: Art Zemon
To: aeroelectric-list@matronics.com
Sent: Sunday, April 24, 2016 12:53 PM
Subject: AeroElectric-List: Check My Work
I found some old dogbone connectors in the basement and have been doing s
ome practicing. Googling didn't turn up any examples of a well soldered joi
nt so please give me some feedback. (I did find a YouTube video of someone
teaching soldering... he had a roll of electrical tape!) The wire is 20 AWG
in this sample:
Is that how it should look?
BTW, it is a pure delight to use the WES51. I have never bought anything
better than a $25 soldering pencil for myself. I wish I could have afforded
something like this back when I was in junior high and in high school and
was building lots o' stuff.
Thanks,
-- 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
---
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Message 6
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Subject: | Re: Check My Work |
Oops. . . I probably spoke out of turn.
I did not see the 2nd image where the wire passes thru and is soldered on b
oth sides. That joint maybe Ok. . The only flaw is that I cannot see the
smooth fan-out of the solder edges. It looks like the solder is fighting
against some sort of plating on the terminal. On a joint like that, I woul
d probably try to flow some solder on the terminal first. Just enough to ge
t a wet look but, not enough to block the wire hole. If that flows normall
y, then attach the wire and flow additional material to bind it all in one
unit.
----- Original Message -----
From: Art Zemon
To: aeroelectric-list@matronics.com
Sent: Sunday, April 24, 2016 12:53 PM
Subject: AeroElectric-List: Check My Work
I found some old dogbone connectors in the basement and have been doing s
ome practicing. Googling didn't turn up any examples of a well soldered joi
nt so please give me some feedback. (I did find a YouTube video of someone
teaching soldering... he had a roll of electrical tape!) The wire is 20 AWG
in this sample:
Is that how it should look?
BTW, it is a pure delight to use the WES51. I have never bought anything
better than a $25 soldering pencil for myself. I wish I could have afforded
something like this back when I was in junior high and in high school and
was building lots o' stuff.
Thanks,
-- 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
---
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