I certainly hear that almost every day. The park I take my dogs to is
above and parallel to a double siding where one or two freights pass
either very slowly or stop to allow the passenger train, or a third
freight, pass on the main line. If they misjudge the a bit, the
train(s) on the siding have to stop, and I get the stereo effect of
the compressing couplings boo boo boo boo boo boo boom. Some minutes
later, the opposite direction of stereo phasing greets me as the
freight re-starts.
Cheers
Joe
On May 26, 2009, at 20:29 , Bob Sullivan wrote:
There can be 6 inches of slack per car in a train. This can help you
start a train rolling as you stretch out the accordion one car at a
time. Remember the locomotives only weigh so much and the coefficient
of friction of steel wheels on steel rail is only .03 or so (even if
you're sanding the rail). Getting going can be tough. And being in
the 100th car back can give you a bad case of whiplash as the momentum
of 99 cars moving at 1/2 mile per hour accelerate you to 1/2 mile per
hour instantly!
But the slack can also play havoc with the train over the road.
Imagine a slight grade, followed by a dip, followed by another grade
and a 100 car train of loaded coal hoppers. The engines strain to
take you over the first grade and you stretch out all the slack on the
way up. But on the way down, you compress the slack out of the train
and then play 'crack the whip' on the way up, pulling the slack back
out. If you're lucky, you don't break a coupler and make 2 train
segments.
Regards, Bob S.
On Tue, May 26, 2009 at 8:08 PM, Adam Maas <[email protected]> wrote:
On Tue, May 26, 2009 at 8:03 PM, Joseph McAllister
<[email protected]> wrote:
On May 26, 2009, at 07:18 , Graydon wrote:
The fundamental limits on train size are engine traction and
drawbar
strength.
Remember that when starting the train, at some point the engine
to first
car drawbar has the entire mass of the train on it; this turns
out to be
more of an issue than engine traction. Past a certain size, you
get an
awful ping noise as a drawbar breaks, and then you have *two*
trains.
Isn't the drawbar heavily spring loaded, so as to allow the engine
to at
least get it's wheels turning a tiny bit before the weight of the
train is
slowly, but quickly, pressed upon it? I'm talking only a few
inches of
spring compression with a heavy load, but it does change the math
a bit.
Am unable to find any drawings or descriptions in cursory search,
so I may
be mistaken, confusing model railroad engines to line engines.
Anyone know
fer certain?
Joseph McAllister
Yes, and before starting a large train they push it together to take
up the slack, which allows the train to get teh front cars moving
before the rear cars, reducing the total force required as you only
have to overcome one cars coefficient of static friction at a time.
--
M. Adam Maas
http://www.mawz.ca
Explorations of the City Around Us.
Joseph McAllister
[email protected]
http://gallery.me.com/jomac
http://web.me.com/jomac/show.me/Blog/Blog.html
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