The last slipcoach service

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Bigmet
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Re: The last slipcoach service

Postby Bigmet » Tue Oct 02, 2018 1:53 pm

GWR_fan wrote:.... Perhaps from an era when total elapsed time of the whole route was more important than actual slipcoach passenger inconvenience...

It was all about achieving end to end times by eliminating stops. The cause was lack of adequate locomotive power first and foremost: couldn't run expresses with sufficient passenger capacity over the whole route as they were too heavy, nor afford the time for stopping and accelerating back up to speed.

With DCC not only can you readily slip coaches, but you can do something which would have been very useful, and 'unslip' them as well. Koff. (We can dock spacecraft now, so why not couple extra vehicles onto a moving train? Technology moves on.)

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Bufferstop
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Location: Bottom end of N. Warks line

Re: The last slipcoach service

Postby Bufferstop » Tue Oct 02, 2018 2:13 pm

We recently went on a Pathfinder tour to Carlisle via the West Coast and back via The Settle Carlisle line. As far as Crewe we were pulled by a class 67, eleven coaches was its limit for the Lickey incline, so we were assisted by a class 66 which came on the rear as we left Bromsgrove. Just buffering up at around 20mph was enough of a shock even five coaches forward, I doubt any of the current auto couplers are up to the job of coupling any faster. When our Turbos joined the rear of a Paddington bound train at Oxford, the driver would bring it to a halt about six feet behind the waiting train, tell eveyone to sit down or hang on tight before a concerted shove into the back of it. If you weren't seated or holding on it was enough to knock you off your feet. Lord knows what happend on the one in front.
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Bigmet
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Re: The last slipcoach service

Postby Bigmet » Wed Oct 03, 2018 8:58 am

Indeed so. Current coupler tech on the railway is still at the 'mighty thud' stage of development.

But it doesn't inherently need to be so. Almost certainly a 'soft action' coupling would have to be automatically controlled, and the technology to do that is now fully available. If the need exists then funding an engineering team with the assignment would find a way.

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Bufferstop
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Re: The last slipcoach service

Postby Bufferstop » Wed Oct 03, 2018 9:47 am

Looking at the front of DMUs which have a cone and cup arrangement in the coupling, I'd guess that the maximum misalignment they can cope with is two to three inches, beyond that they would need human assistance. I've waved a shunter's pole in anger and I wasn't going to be beaten into ducking under the buffers by a b* Instanter that had decided to hang itself on its own hook. Bob Meanly at Tyseley bet me I couldn't get it off with the pole, what more encouragement did I need. I definitely wouldn't want to be doing it with the darned things on the move.
Growing old, can't avoid it. Growing up, forget it!
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Bigmet
Posts: 6242
Joined: Tue Aug 14, 2007 2:19 pm

Re: The last slipcoach service

Postby Bigmet » Wed Oct 03, 2018 10:35 am

Alignment is not a major problem to design for, particularly as automated servo mechanisms can take care of adjustment in a dynamic environment. It's the force required to 'make' and disengage the high integrity under load coupler lock that is a challenge to perform, if the requirement is that it do this with minimal external shock from the mechanism action.

But it can doubtless be done, just think of the interrupted screw breech as one 'make and break' mechanism pattern that has to deliver a high integrity seal every time it operates in a very challenging operating environment. If there is a necessity for a 'gentle action' coupler system, a good engineering team with enough money for the task will get there. (The proven of old engineering design maxim 'good, fast, cheap: pick any two' applies with full force here.)


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