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david.nelson(at)pobox.com Guest
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Posted: Tue Jun 17, 2008 10:18 am Post subject: Slow make/break contacts |
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Hi Bob,
While I was looking for the S700 series specs on Carling's www site, I
came around a line of switches (F Series, in particular) with "slow
make/break" contacts. This struck me as odd. Under what circumstances
would one want to spread the contacts slowly?
Thank you,
/\/elson
~~ Lately my memory seems to be like a steel trap .... without any spring. ~~
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nuckolls.bob(at)cox.net Guest
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Posted: Tue Jun 17, 2008 3:47 pm Post subject: Slow make/break contacts |
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At 01:15 PM 6/17/2008 -0500, you wrote:
Quote: |
<david.nelson(at)pobox.com>
Hi Bob,
While I was looking for the S700 series specs on Carling's www site, I
came around a line of switches (F Series, in particular) with "slow
make/break" contacts. This struck me as odd. Under what circumstances
would one want to spread the contacts slowly?
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It's not that you WANT to, it's an artifact of an inexpensive
switch. You can buy switches with very fast contact spreading
velocities and fast/forceful closing characteristics but these
will use a mechanism that is much more complicated than:
http://aeroelectric.com/Pictures/Switches/Carling_Cutaway.jpg
While the el-cheeso switch does have an spring loaded, over-center
action, it's still classed as a slow make-break device because
you can "tease" it open and "sneak up" on a closure by holding
the handle and preventing it from exploiting the over-center
behavior.
In a fast make/break device, you can't tease it. Once past the
point of no return, the switch snaps to the new position with
gusto.
Bob . . .
----------------------------------------)
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
----------------------------------------
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david.nelson(at)pobox.com Guest
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Posted: Wed Jun 18, 2008 5:06 am Post subject: Slow make/break contacts |
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Very well, then. Boy, those marketing folks can sell anything! Thank you,
Bob.
Take care,
/\/elson
do not archive
~~ Lately my memory seems to be like a steel trap .... without any spring. ~~
On Tue, 17 Jun 2008, Robert L. Nuckolls, III wrote:
Quote: |
<nuckolls.bob(at)cox.net>
At 01:15 PM 6/17/2008 -0500, you wrote:
>
> <david.nelson(at)pobox.com>
>
>
> Hi Bob,
>
> While I was looking for the S700 series specs on Carling's www site, I came
> around a line of switches (F Series, in particular) with "slow make/break"
> contacts. This struck me as odd. Under what circumstances would one want
> to spread the contacts slowly?
It's not that you WANT to, it's an artifact of an inexpensive
switch. You can buy switches with very fast contact spreading
velocities and fast/forceful closing characteristics but these
will use a mechanism that is much more complicated than:
http://aeroelectric.com/Pictures/Switches/Carling_Cutaway.jpg
While the el-cheeso switch does have an spring loaded, over-center
action, it's still classed as a slow make-break device because
you can "tease" it open and "sneak up" on a closure by holding
the handle and preventing it from exploiting the over-center
behavior.
In a fast make/break device, you can't tease it. Once past the
point of no return, the switch snaps to the new position with
gusto.
Bob . . .
----------------------------------------)
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
----------------------------------------
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Eric M. Jones
![](images/avatars/12254050275185097a1ec18.jpg)
Joined: 10 Jan 2006 Posts: 565 Location: Massachusetts
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Posted: Thu Jun 19, 2008 9:52 am Post subject: Re: Slow make/break contacts |
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I'm going out on a limb here, because all this stuff is older than the Internet....but I vaguely recall that there is a perfectly good reason for these Series-F switches--
Cogging and trim applications where you want minimum ON time, and you want to tease a motor to move a crane or even aircraft elevator trim.
I don't think this is anyone's ripoff marketing idea at all.
"A witty saying proves nothing."
--Voltaire
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_________________ Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net |
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nuckolls.bob(at)cox.net Guest
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Posted: Thu Jun 19, 2008 6:51 pm Post subject: Slow make/break contacts |
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At 08:03 AM 6/18/2008 -0500, you wrote:
Quote: |
<david.nelson(at)pobox.com>
Very well, then. Boy, those marketing folks can sell anything! Thank you, Bob.
Take care,
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Not sure it's a marketing issue so much . . . just a factual statement
of performance. Probably 99.99+ percent of all switches operated by
the fingers are slow make/break devices. This included those things
on the walls of your houses. It's a rare instance that potential
stresses on a switch warrant the added cost of crafting a fast
operating switch.
I was in M.L. last week and needed to rip a long hunk of
2 x 10. Dug out "Old Shagnasty". A 10" table saw
grandpa bought before I was born . . . I remember seeing it
on the job sites when I was 6 or 7. That was the first time I'd
seen both ends of a Bowden cable. Grandpa or one of the
sons had rigged this choke cable to a fat switch built into
the base of the Big Kahuna motor sitting a platform beneath the
saw such that pushing and pulling on knob at the operator
end would toggle the switch down below. Pretty cool gizmo
even in the eyes of a first grader.
When I pulled on that knob, it moved with considerable
resistance at first. Thought it was just stiff for not
having been used for 10+ years. But as I pulled the switch
handle past the point-of-no-return, it literally jumped
in my fingers and raced to complete the stroke faster than
I could pull it. The saw came to life and I made a
satisfyingly expeditious cut through that match stick
with a REAL saw.
Later when sucking up the sawdust with a sweeper, I took
a close look at the switch and recalled having disassembled
one just like it many moons ago. This was a Cutler-Hammer
product with 10-32 screw terminals on the back. I recalled
that not only was it a very robust spring loaded, non-teasing,
over-center mechanism, the contacts were little KNIFE switches
http://aeroelectric.com/Pictures/Switches/knife_switch_1.jpg
This kind of switch doesn't arc badly on closure because
you're not slamming masses together and hoping that they'll
quit bouncing eventually . . . This incorporation of the
knife switch also arcs less on opening because the design
was double-make, double-break . . . you had two sets of
contacts WIPING in series for twice the spreading velocity
augmented by the benefits of a non-teasing transfer mechanism.
That explains in part why that switch has performed for
decades from before I was born and is still working
today. If you really want that level of performance
for your airplane (or any other application) they're
still made. But the suckers are about 2 x 2 x 2"
behind the panel and wire with really big terminals.
Guarantee they'll last the lifetime of your airplane
but probably not a good return on investment. They
probably make smaller versions.
I just found a nice switch training manual from one of
the pillars of the switching industry. I've posted it
at:
http://www.aeroelectric.com/Reference_Docs/Switches/CH_Switch_Training_Manual.pdf
I think that 10" saw sits on it's original base and
getting wobbly. The rubber power cord jacket is craking
too. Zach and I are planning to build a new base on
retractable casters and replace the power cord with stuff that
isn't cracked. If all goes well, that saw will cut wood for
5 generations of workers in the Nuckolls family woodshop
. . . with what I believe is the original switch.
Bob . . .
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