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Erik Olsen
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 Posted: Thu Oct 23, 2008 12:43 pm Post subject: Re: Big trains question about coupling |
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Wolf Kirchmeir wrote:
| Quote: | Quite true, but what I said doesn't I think conflict with this. 1 inch
of "free slack" is not worth mentioning, leastways not when you've
heard and observed 4"-6" of free slack in European freight trains
(plus as much or more in the buffers.) I should have been less
ambiguous, I suppose, but I thought my reference to what I saw and
heard in England way back when implied that the "free slack" on those
freight cars was enormous compared to what we know and love in our N.
American trains. 
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Loose-coupled British goods trains are quite a special thing. Please
don't think that is the norm for European freight trains.
In Denmark screw couplings have been in use on freight equipment since
the very beginning in 1847 except for a series of simple open goods
wagons (gondolas) that were taken over from the builders of the first
Danish line.
1 inch of free slack is indeed quite much. In European freight trains
with screw couplings there may be that much slack if the screw couplings
are not tightened properly, and it influences running remarkably. It
even increases derailment risk on rough track.
In Denmark the norm is that on freight trains screw coupling shall be
tightened enough that there is no free slack. On passenger trains screw
couplings shall be tightened enough that the side buffers are sligtly
compressed.
--
Venlig hilsen/Best regards
Erik Olsen
http://www.modelbaneteknik.dk/ |
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Roger T.
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| Posted: Thu Oct 23, 2008 2:14 pm Post subject: Re: Big trains question about coupling |
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| Quote: | Quite true, but what I said doesn't I think conflict with this. 1 inch
of "free slack" is not worth mentioning, leastways not when you've
heard and observed 4"-6" of free slack in European freight trains
(plus as much or more in the buffers.) I should have been less
ambiguous, I suppose, but I thought my reference to what I saw and
heard in England way back when implied that the "free slack" on those
freight cars was enormous compared to what we know and love in our N.
American trains. ;-)
Loose-coupled British goods trains are quite a special thing. Please don't
think that is the norm for European freight trains.
In Denmark screw couplings have been in use on freight equipment since the
very beginning in 1847 except for a series of simple open goods wagons
(gondolas) that were taken over from the builders of the first Danish
line.
1 inch of free slack is indeed quite much. In European freight trains with
screw couplings there may be that much slack if the screw couplings are
not tightened properly, and it influences running remarkably. It even
increases derailment risk on rough track.
|
I agree. Free slack action is a serious concern to North American
locomotive engineers. Freight cars will typically have at least 1 inch of
slack per coupler if not more, that's about 2" per car and on a 100 car
freight that's about 200 inches, or 16 feet or 4.9 metres of free slack and
that's not including run in and run out of cushion underframe slack. 16 ft
or 4.9 metres is nothing to sneer at when it comes to train handling. Not
sure if you live in North America Wolf nor how often you get over if you
don't but you need to read a bit more about our knuckle couplers. Even our
North American passenger trains have some free slack action whereas, I know,
European trains have none.
--
Cheers
Roger T.
See the GER at: -
http://www.islandnet.com/~rogertra/ |
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Roger T.
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| Posted: Thu Oct 23, 2008 2:38 pm Post subject: Re: Big trains question about coupling |
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| Quote: | I agree. Free slack action is a serious concern to North American
locomotive engineers. Freight cars will typically have at least 1 inch of
slack per coupler if not more, that's about 2" per car and on a 100 car
freight that's about 200 inches, or 16 feet or 4.9 metres of free slack
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Correction. I miss calculated.
If each car has 1" of free slack at each end, then a 100 car train has 199
coupled ends or 199 pairs of couplers coupled together which translates to
(1" per coupler x 2 couplers coupled together = 2" of slack per pair of
couplers) that's 199 x 2 = 398" or about 33' feet or about 10 metres.
Lots of free slack and that's not counting cushioned underframe slack.
--
Cheers
Roger T.
See the GER at: -
http://www.islandnet.com/~rogertra/ |
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Bernhard Agthe
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| Posted: Thu Oct 23, 2008 6:55 pm Post subject: Re: Big trains question about coupling |
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Hi,
David Nebenzahl wrote:
| Quote: | In a related vein, what about those buffers? Are there any inherent
advantages to either system: the Yurpeen with its separate buffers on
each side, or ours where the buffer is integral with the coupler and the
members connecting it to the centerbeam? Do European trains experience
the same issues with coupler slack that ours do? Inquiring minds want to
know ...
|
Did I say "it's always been done so"? Back in 1840 European trains
started out with side buffers and coupling chains (a short piece of
chains and a hook at each wagon!). Over time, they developed "three link
coupling" - basically three chain links, no more, no less. Still with
side buffers. Later on they found out, there is too much slack in three
link couplings, but by then the chains were often attached with a pole
from beside the wagons (no problem if you have loose chains). So they
developed a special link (the middle one in the chain) which needed to
be turned after coupling the train. This did reduce slack but did not
eliminate slack. The logical next step is the screw arrangement in use
today, couplers can be tightened enough to compress the buffers and to
allow for (almost) no slack. This works fine and has been in use for the
past fifty or hundred years. But then the guy has to go between the cars
to do the coupling - we talked about that...
Now, go back to about 1900 and take the ship to North America. They were
running longer and heavier trains than the Europeans (or wanted to) and
they were facing the same problem. What the Americans did, they changed
the system completely (not just improved it). They moved the buffer to
the middle (need only one, not two, save money and put the coupler
right into the new buffer (even less parts, even cheaper, save more
money). The design (which is still used, though in improved form) was
the most advanced one back then and serves today's railroads quite fine.
So you see, most of this has historical reasons ;-)
Now come the "modern Age" - European railroads found out that there is a
serious drawback with the hook-and-screw couplers: if you're running
passenger trains and want one part to stay on the main line and another
part to run the side line from a certain station on, that's highly
impractical (this concept has never been used much but is gaining
popularity now). So they adapted center buffer couplers as well, but -
being Europeans - they wanted the "BEST" design possible. The result is
the "Scharfenberg" type coupler, but they did NOT design a common
standard for it. There is actually only one company to produce the
design, the couplers are (comparatively) complicated and thus are
expensive. So they only get used in an insular fashion - the problem
with broken-down trains has been mentioned.
Now, just for the fun of it, take a look at Russia. Their couplers are
similar to the Janney couplers, but they use a different mechanical
design. I don't want to say it's better nor worse, just different. Check
it out on Wikipedia if you like. Basically the Russian type coupler was
discussed for europe-wide adaption, but they wanted it "gold-plated" and
with all extras for the cost of nothing. They did research a feasible
design with air and electrical connections, (they even made provisions
for reducing the possibility of derailments) but it was expensive. So,
as you'll guess, it never got adapted...
By the way, there will always be a little slack between the wagons, but
in today's railroad couplers it is reduced enough (if they get used
correctly). It's a relative question, an inch is not much in a
several-hundred-feet freight train, but it might be too much in an
high-speed passenger train...
Now, to get back on-topic with the model railroad theme... Consider the
coupling problem solved with knuckle couplers. They could even be
applied to models featuring side-buffer imitations, but you'll rather
find *huge* (and ugly) hook-couplers (HO) or Rapido-style (N). The
wagons will sport side-buffer imitations And the hook couplers
resemble hook-and-chain vaguely ;-)
Ciao... |
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Wolf Kirchmeir
Guest
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| Posted: Thu Oct 23, 2008 6:58 pm Post subject: Re: Big trains question about coupling |
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Roger T. wrote:
| Quote: | I agree. Free slack action is a serious concern to North American
locomotive engineers. Freight cars will typically have at least 1 inch of
slack per coupler if not more, that's about 2" per car and on a 100 car
freight that's about 200 inches, or 16 feet or 4.9 metres of free slack
Correction. I miss calculated.
If each car has 1" of free slack at each end, then a 100 car train has 199
coupled ends or 199 pairs of couplers coupled together which translates to
(1" per coupler x 2 couplers coupled together = 2" of slack per pair of
couplers) that's 199 x 2 = 398" or about 33' feet or about 10 metres.
|
Ok, new figures accepted. But it's still not much compared to the length
of the train. A 100 car train will be 5,000 feet or more. Less than 1%
of train length.
| Quote: | Lots of free slack and that's not counting cushioned underframe slack.
|
So, what are the "issues with slack"? They vary, and not all of thme are
bad. As I understand it, free slack can be an advantage when starting a
train, as the load is incrementally increased as the slack runs out.
I've read that engineers will actually reverse the engine against the
train before moving forward. Is this common practice?
OTOH, on a line with many short grades, shorter than the train, slack
action (both kinds) can cause problems, which are minimised by running
shorter trains and running them slow. Eg, the Huron central (Sudbury -
Soo, runs through my town) runs trains around 40-50 cars averaging 50ft,
at about 15-20mph. They could run them up to 30-40mph, but the track is
very bad. ;-)
Sprung slack has more complicated effects. A certain amount is
necessary, to dampen horizontal shocks transmitted to the cars and
lading. Too much can be a problem, especially when helpers are used on
hilly lines on which long trains are run. Rough track can set up
oscillations. Not easy to analyse, even by people who study it or work
with it.
FWIW, the slack action in model trains is much more than on the
prototype. I just tested it on my layout, on a 7-car train, it's about 4
scale feet (HO)!
HTH
--
Wolf Kirchmeir |
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Roger T.
Guest
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| Posted: Thu Oct 23, 2008 10:31 pm Post subject: Re: Big trains question about coupling |
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"Wolf Kirchmeir"
| Quote: | Lots of free slack and that's not counting cushioned underframe slack.
So, what are the "issues with slack"? They vary, and not all of thme are
bad. As I understand it, free slack can be an advantage when starting a
train, as the load is incrementally increased as the slack runs out. I've
read that engineers will actually reverse the engine against the train
before moving forward. Is this common practice?
|
I was reading a technical article on line and it seems even my 2" of slack
was conservative. The article quotes up to six inches of slack per car or
50 feet 15.24 metres of free slack plus buffing and drawbar slack.
http://www.arema.org/eseries/scriptcontent/custom/e_arema/Practical_Guide/PGChapter6.pdf
Top of the last page in this technical paper provides the 6" and 50 feet
figures. It's difficult to find anything technical on the 'Net regarding
slack between cars.
When starting a 100 car freight with the locos in notch one, it is quite
possible for the front end of the train to be moving at between 10 to 15 mph
before the last car begins to move. In the days of cabooses, crewmen were
expected to be seated, facing forward, with their backs and heads firmly
against the back of their seat in anticipation of the violent snatch of the
slack running out. Crewmen were known to be suffer serious injury or even
death caused by slack action.
--
Cheers
Roger T.
See the GER at: -
http://www.islandnet.com/~rogertra/ |
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Bob May
Guest
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| Posted: Fri Oct 24, 2008 1:17 am Post subject: Re: Big trains question about coupling |
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Back in the steam engine days, the slack was pretty necessary to start a
long train. Remember that a steam engine can pull a train that it can't
easily start while a diesel can start a train that it can't get up to a
speed where it can run without running into heating problems in the electric
motors.
Back in the old days, the steam engines would start the head end of the
train and maintain a slow speed until the entire train was moving an
stretched out. At that time, the engineer would then start the acceleration
of the train.
Today, the engineers have to get the train up to a certain speed when at
full power or the electronics on the engine would shut down the power to the
electric motors as they would be overheating otherwise.
--
Bob May
rmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net
Roger T. <rogertra@highspeedplus.com> wrote in message
news:1ac9e3a14643951c575de2123d111ef9@grapevine.islandnet.com...
| Quote: |
"Wolf Kirchmeir"
Lots of free slack and that's not counting cushioned underframe slack.
So, what are the "issues with slack"? They vary, and not all of thme are
bad. As I understand it, free slack can be an advantage when starting a
train, as the load is incrementally increased as the slack runs out.
I've
read that engineers will actually reverse the engine against the train
before moving forward. Is this common practice?
I was reading a technical article on line and it seems even my 2" of slack
was conservative. The article quotes up to six inches of slack per car or
50 feet 15.24 metres of free slack plus buffing and drawbar slack.
http://www.arema.org/eseries/scriptcontent/custom/e_arema/Practical_Guide/PG |
Chapter6.pdf
| Quote: |
Top of the last page in this technical paper provides the 6" and 50 feet
figures. It's difficult to find anything technical on the 'Net regarding
slack between cars.
When starting a 100 car freight with the locos in notch one, it is quite
possible for the front end of the train to be moving at between 10 to 15
mph
before the last car begins to move. In the days of cabooses, crewmen were
expected to be seated, facing forward, with their backs and heads firmly
against the back of their seat in anticipation of the violent snatch of
the
slack running out. Crewmen were known to be suffer serious injury or
even
death caused by slack action.
--
Cheers
Roger T.
See the GER at: -
http://www.islandnet.com/~rogertra/
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Twibil
Guest
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| Posted: Fri Oct 24, 2008 1:45 am Post subject: Re: Big trains question about coupling |
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On Oct 23, 2:15 pm, <wkai...@mtholyoke.edu> wrote:
| Quote: | Anyone else remember the sound of a long train starting? The bang at the
head end as the slack was pulled out, then the bang bang bang as the slack
pulling moved down the train. That's something you don't hear any more..
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You also don't hear the occasional bang-bang-bang-bang-*CRASH*! as the
coupler broke a knuckle, or the draft gear failed catastrophically.
*AH*; the "good old days!"
~Pete |
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Erik Olsen
Guest
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| Posted: Fri Oct 24, 2008 2:06 am Post subject: Re: Big trains question about coupling |
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Bob May wrote:
| Quote: | Back in the steam engine days, the slack was pretty necessary to
start a long train. Remember that a steam engine can pull a train
that it can't easily start while a diesel can start a train that it
can't get up to a speed where it can run without running into heating
problems in the electric motors.
|
The reason for the difficult start was the use of friction bearings.
With roller bearings it is much easier to start a heavy train.
--
Venlig hilsen/Best regards
Erik Olsen
http://www.modelbaneteknik.dk/ |
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Guest
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| Posted: Fri Oct 24, 2008 2:15 am Post subject: Re: Big trains question about coupling |
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Wolf Kirchmeir <wolfkir@sympatico.ca> wrote:
| Quote: | So, what are the "issues with slack"? They vary, and not all of thme are
bad. As I understand it, free slack can be an advantage when starting a
train, as the load is incrementally increased as the slack runs out.
I've read that engineers will actually reverse the engine against the
train before moving forward. Is this common practice?
|
I think that was standard practice in the days of steam, when an engine
could pull a train it couldn't start. There was an advantage to back a
short distance, then start the train one car at a time.
Anyone else remember the sound of a long train starting? The bang at the
head end as the slack was pulled out, then the bang bang bang as the slack
pulling moved down the train. That's something you don't hear any more.
--
Bill Kaiser
wkaiser@mtholyoke.edu
There are three ways to do a job: good, cheap, and quick.
You can have any two.
A good, cheap job won't be quick.
A good, quick job won't be cheap.
A cheap, quick job won't be good. |
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Greg.Procter
Guest
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| Posted: Sun Oct 26, 2008 4:11 am Post subject: Re: Big trains question about coupling |
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On Tue, 21 Oct 2008 19:53:48 +1300, Roger T. <rogertra@highspeedplus.com>
wrote:
| Quote: | Watched "Von Ryan's Express" last night on TV, and was surprised when it
showed an Italian trainman coupling up cars: you could see the cars
being
pushed together, and when the buffers met, the guy ducked under one of
them, grabbed the coupling hook and connected it, then quickly ducked
back
out.
Anyone know if this was realistic? Seems incredibly dangerous to this
North Americano; but maybe that's just because of too many years of
indoctrination to such things as FRA regs and working rules ...
Everyday occurrence on practically every railway that used screw couplers
and buffers. Probably frowned upon but men did it anyway.
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It's still normal throughout Europe.
They screw couple against the sprung buffers so that the entire train
moves as one unit.
The advantage is that there is far less shock damage to goods being
carried.
The disadvantage is that the loco must be powerful enough to start the
train all at once, but as European trains are short and run fast this is
not a problem.
Greg.P. |
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Greg.Procter
Guest
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| Posted: Sun Oct 26, 2008 4:17 am Post subject: Re: Big trains question about coupling |
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On Thu, 23 Oct 2008 07:01:03 +1300, David Nebenzahl
<nobody@but.us.chickens> wrote:
| Quote: | On 10/21/2008 6:14 AM Bernhard Agthe spake thus:
David Nebenzahl wrote:
Watched "Von Ryan's Express" last night on TV, and was surprised when
it
showed an Italian trainman coupling up cars: you could see the cars
being pushed together, and when the buffers met, the guy ducked under
one of them, grabbed the coupling hook and connected it, then quickly
ducked back out.
Anyone know if this was realistic? Seems incredibly dangerous to this
North Americano; but maybe that's just because of too many years of
indoctrination to such things as FRA regs and working rules ...
Actually in the "Old World" there are no "Janney Couplers" - only the
buffer-and-hook-and-screw type (Russia has a central buffer coupler, but
that's incompatible to everything else).
So what you did see was actually the harmless variant - I did
personally
observe the trainmen walking in there (between the buffers) just a few
seconds before the trains actually met. While this might be against
regulation, ducking under the buffers (especially when he comes from
atop a platform) is acrobatic...
First of all, thanks to all who answered my question.
Now to bring up a related issue: I hate to say this, but those Yurpeen
cars and locos, with their prominent buffers, just look plain funny to
me. The buffers sticking out always give them, in my mind, a sort of
Thomas the Tank Engine look.
Now, before you type out an angry reply to this, understand that I do
realize that this is totally due to my North American railroad
prejudices, and my familiarity to knuckle couplers, which I'm sure also
look funny to a lot of folks outside of N.A.
In a related vein, what about those buffers? Are there any inherent
advantages to either system: the Yurpeen with its separate buffers on
each side, or ours where the buffer is integral with the coupler and the
members connecting it to the centerbeam? Do European trains experience
the same issues with coupler slack that ours do? Inquiring minds want to
know ...
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The advantage of the side buffers is the elimination of slack, and the
resulting damage to goods.
The planned Euro centre coupler was to be the ultimate in fine tolerances
so that the inherant slack would be negligable, but of course that level
of manufacturing tolerance costs!!!
Regards,
Greg.P. |
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Greg.Procter
Guest
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| Posted: Sun Oct 26, 2008 4:19 am Post subject: Re: Big trains question about coupling |
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On Thu, 23 Oct 2008 10:51:48 +1300, Roger T. <rogertra@highspeedplus.com>
wrote:
| Quote: | The only difference between Europe and North America is that Europeans,
even
within the same country, mush the operational detriment, have not
standardised on one coupler system.
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Huhh???? They standardised in 1849!
| Quote: |
This can and does result in a passenger m.u. failing on the mainline yet
the
following train cannot come up behind it and give it a push because their
coupler systems and completely incompatible. They in effect, have to
call a
"tow truck" , in the UK known as "Thunderbirds" I gather after the
1960s/70s
TV show of the same name, to come and rescue the stalled unit. Result?
Delays of hours rather than minutes if both 'trains' were equipped with a
standard coupler.
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Britain's railways aren't a part of "Europe" as such.
| Quote: |
--
Cheers
Roger T.
See the GER at: -
http://www.islandnet.com/~rogertra/
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Greg.Procter
Guest
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| Posted: Sun Oct 26, 2008 4:25 am Post subject: Re: Big trains question about coupling |
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On Thu, 23 Oct 2008 12:54:56 +1300, Wolf Kirchmeir <wolfkir@sympatico.ca>
wrote:
| Quote: | Erik Olsen wrote:
David Nebenzahl wrote:
In a related vein, what about those buffers? Are there any inherent
advantages to either system: the Yurpeen with its separate buffers on
each side, or ours where the buffer is integral with the coupler and
the members connecting it to the centerbeam? Do European trains
experience the same issues with coupler slack that ours do? Inquiring
minds want to know ...
One great advantage with side buffers and screw couplings is that
slack can be completely removed by tightening the screw coupling. This
is normally used on European passenger trains and makes the ride much
smoother than I imagine is possible with the Janney-type couplers with
a lot of slack in them.
They don't have any slack worth mentioning, actually. There buffers are
in fact integral with the knuckle coupler (they are part of the coupler
box.) Thus, there is little slack even in a freight train. The "issues
with slack" mentioned by Dave are nothing compared to the bang-bang-bang
that I used to hear when a British freight train slowed down or started
up on the line a 1/2 block from where I used to live in England.
HTH
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Britain used non-screw (3 link chain) couplers on it's goods rolling stock
from 1800 to the 1960s.
That it lasted so long was due to private owner (coal) wagons being
standardised in 1923. (rough handling was hardly a problem with coal)
Screw couplers on other goods stock was gradually introduced in the 19th
and 20th century.
Greg.P. |
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Greg.Procter
Guest
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| Posted: Sun Oct 26, 2008 4:32 am Post subject: Re: Big trains question about coupling |
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On Thu, 23 Oct 2008 15:34:56 +1300, Wolf Kirchmeir <wolfkir@sympatico.ca>
wrote:
| Quote: | Roger T. wrote:
"Wolf Kirchmeir"
They don't have any slack worth mentioning, actually. There buffers
are in
fact integral with the knuckle coupler (they are part of the coupler
box.)
Thus, there is little slack even in a freight train.
Not true Wolf.
See:- http://www.ataassociates.com/RailArt.htm#Slack
"On mechanically sound cars, mechanical free motion or free slack
between
adjoining couplers can be one inch. Couplers are attached to draft gears
that absorb the shock or impact. Draft gear slack is called spring
slack.
Spring slack on a conventional box car is about five inches. Many
intermodal
(piggyback) cars have shock control devises or sliding centre sills
that can
have fifteen inches of slack in each end.
Quite true, but what I said doesn't I think conflict with this. 1 inch
of "free slack" is not worth mentioning,
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Of course it is, especially when the norm is wagons coupled under tension.
(ie nil)
| Quote: | leastways not when you've heard and observed 4"-6" of free slack in
European freight trains (plus as much or more in the buffers.)
|
Where on earth did you witness that?
(Britain of course not counting as anywhere on Earth, and certainly not
Europe ;-)
| Quote: | I should have been less ambiguous, I suppose, but I thought my reference
to what I saw and heard in England way back when implied that the "free
slack" on those freight cars was enormous compared to what we know and
love in our N. American trains. ;-)
"Draft gear slack" is necessary - it's actually the buffing action,
provided by the traditional side-buffers on European cars, and by
integral buffers in all center couplers used today (some mine- and
industrial tramway-cars excepted.) Cushion frames are designed to
_increase_ that buffing action. By contrast, "free slack" is a necessary
evil in knuckle couplers, it's the play within and between couplers that
enables the knuckles to slide past each other and lock.
|
That "free slack" is the problem. It leads to quite different modes of
operation between Europe and the USa.
| Quote: |
AFAIK, there should be no free slack with screw couplings, but when I
observed switching in Austria a couple years ago, there was definitely
more than an inch of free slack. The buffers parted 20cm or more when
the loco started up the cut of cars. The coupler links were simply
lifted into place (ie, "three link couplings" in effect), to save time I
guess.
|
You probably witnessed a shunting move in a station area.
| Quote: |
A 100 car train of conventional cars in good mechanical condition will
have
50 feet of slack.
That's about 8ft of free slack, and up to 42ft of draft gear slack. But
the train will be 5400 ft long (a 50ft car has a coupled length of about
54ft), so this slack amounts to less than 1% of total train length. Not
much, really. The free slack 9the bad kind ) is less than 1/4% - very
good, I'd say. Hence my "no slack worth mentioning." ;-)
Intermodal trains and trains with cars in poor mechanical
condition can have much more slack."
It's the free slack that's the problem, since it causes unsprung shocks,
which are bad, esp. for the couplers.
HTH
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