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G'day,
There is a major advantage of a permanently coupled train, aka solid drawbar, NIL coupler slack.
I have worked and ridden the Down Under Silver Streak, and the coupler slack is terrible.
So much so that you NEVER let the thing bunch up suddenly.
One bloke doing his road trials discovered this fact at Newbridge when he released the train brakes while stationary.
The coupler slack roll in was so severe that one passenger was hurled out of his top bunk and broke his leg.
Yes, tight-lock couplers can also achieve minimal coupler slack, but tight-lock type couplers are expensive.
And, the old buffer and screw-link system also minimizes coupler slack.
But, both tight-lock and screw link can still separate in transit.
Many moons ago, the NSWR screw-linked West Mail came apart a couple of times in transit, leaving us sitting still.
I have also seen a double decker V set interurban divided into two halves, the auto knuckle uncoupling.
Knuckle couplers have one disadvantage, if any height disparity exists and the train goes through a hole in the road, it can uncouple.
The knuckle jaws ride up and over each other.
A second major advantage of solid drawbar system being that electrical jumper couplings cannot be damaged due to accidental separation.
Yes, if a fault occurs with one car, then the entire train must be removed from service.
But, with adequate roll through maintenance, any serious problems should be prevented.
But, naturally nothing is perfect, and even a JR Shinkansen set recently suffered a bogie fracture.
This was thankfully detected in time to prevent a major derailment.
Zooming along at 350 kph may be fun, but hitting the ground at 350 kph wouldn't be so much fun.
A similar bogie fracture having occurred on a Japanese narrow gauge car which did derail.
As BW comments, if you convert your long distance train into an EMU or DMU style, then it also becomes more cost effective.
Plonking a large locomotive up front, and possibly also at the rear can increase operating costs.
PLUS, locomotives are generally much heavier than rolling stock, but possess generally quicker acting straight air brake.
So you had better bail off the straight air when you make a train brake application or have the train run into you.
Yes, EP or Epic ECP brake systems can overcome the old Westinghouse air brake inadequacies.
But, unless the locomotive is specifically designed to operate with such a brake fitted passenger train, it can be expensive to modify.
The Rocket here (XPT), which was based on the UK HST, suffers badly from coupler slack during braking and acceleration.
The individually coupled cars being the meat in the sandwich between the pair of locomotives.
However, ride a permanently coupled emu squirt, and the whole thing takes off and stops in unison.
NO bang crunch whallop due to coupler slack.
Yes, should a derailment occur with a permanently coupled train then the whole shebang can go bush.
But, this can actually be a more preferable result than individual cars uncoupling and spearing into each other.
This is the principle for FRA mandated petroleum tank cars.
They must have knuckle couplers that posses a bottom shelf.
This bottom shelf prevents the coupler jaw from riding up and disengaging.
Yes, the whole train then goes bush, but individual tankers don't uncouple and spear into each other causing a potential fire explosion.
Steve.
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