Jump to content

Modelling GWR slip coach operation  

53 members have voted

  1. 1. How would you model slip operation?

    • Motorize the coach
      33
    • Use a free-wheeling coach
      6
    • Use some kind of hybrid approach
      9
    • Don't waste your time - do what the railways ultimately did and not slip coaches at speed
      5


Recommended Posts

The use of slip coaches was common on the GWR and the topic seems to come up occasionally - so hopefully my question is not redundant here. (I did do some searching.)

 

The RMweb archive pointed to this very helpful reference on GWR slip coaches. The provenance of this is link is interesting. I have the original "Railway Wonders of the World" article (Ca 1935/1936) which I inherited from my grandfather. Reading the original is what inspired this question.

 

Searches also pointed me to a thread illustrating some GWR slip coach timetables.

 

But my question is this:

 

What is the optimal way to model the operation of a GWR slip coach?

 

This is a bit of an armchair modelling exercise for me. I'm not quite ready to start it as a project, but nevertheless I'm interested to see if anyone has ideas they'd like to share.

 

There are two primary design problems that the model must solve

1. releasing the coupling

2. controlling the stop

 

Ideas I had varied from fully controlled 'motor' to relying solely on Newton's first and second laws of motion.

 

1. motorized coach

 

A DCC decoder could be used in a 'consist'/double heading mode and drive a motorized bogie on the coach. A function button could be programmed to disconnect the coupler and then throttle/brake controls could be used to drive the coach to a stop, though I'm not sure how a second throttle is assigned to the decoder in real-time.

 

Having a brake button programmed would be a very accurate way to simulate real operation.

 

2. free-wheeling coach

 

Some kind of uncoupler device could be mounted in the track at a suitable distance from the station and the coach would roll. A second track mounted stopping device (perhaps electromagnetic) would then stop the coach at the platform.

 

3. some kind of hybrid - like adding a flywheel to the coach

 

Other parameters

 

Making the automatically detachable coupler compatible with tension locks on the train portion might be a tricky challenge too. Perhaps a dedicated mating coupler would be needed on a preceding brake coach. I don't think Kadee style couplers aren't meant to disconnect at speed.

 

Lighting would be fun to include - particularly since the GWR had interesting lamp configurations for slipped sections. (From the 'Railway Wonders of the World' article):

At the rear end of the slip, the coach carries two lamps side by side, one red and the other white, encircled by red and white disks for day use. If two slips are run on the same train, the inner one carries this distinctive tail signal, but the outer one carries the lamps one above the other. When the "Cornish Riviera Express" carried three slips, a special tail-lamp arrangement had to be devised for the outermost one, and it was a triangle of three disk-encircled lamps, two red and one white.

I'd love to hear any ideas you might have, and thank you for reading this far. Edited by Ozexpatriate
  • Like 3
Link to post
Share on other sites
  • RMweb Gold

There are a number of decoupling options available now....... Kroik(?) springs to mind........ that can be controlled as a function by DCC or better still by RR&Co........one can initiate the uncoupling function at any specified measurement after entry into a block. One can also control the  original train speed in the block so in theory one could just rely on prototype practice........and reasonably lengthy platforms!

 

I do wish you hadnt raised this topic.......I am now seriously tempted to add it to the long list of potential operations on Granby!

 

Regards from a very damp Vancouver

  • Like 2
Link to post
Share on other sites

Many years ago I managed to make it work. I use standard tension locks with the hook that locks into the lip of the crossbar of the next coupling. The slip coach had the lip removed ( and the hook) so the main train coach hook just rested on the crossbar by friction. I made an uncoupling ramp operated by a pushrod that raised when required (based the idea on an old Hornby Dublo  3 rail uncoupler). Run the train at speed and the coach uncouples, pin point bearings allowing it to roll. There was some experiment to work out where to place the uncoupler, but it worked well. I did try to use just a piece of clear plastic (from a new shirt collar) betwen the rails but it sometimes uncoupled other stock. No need for DCC,  programming, solenoids etc - just a length of rod, a bell crank, piece of plasticard and a craftknife.

 

Used it all the time..... at first, but, as with other, 'gimmicks, it fell into disuse, and was not incorporated into the later layout after a house move.

 

 

Mike Wiltshire

  • Like 4
Link to post
Share on other sites

I would cheat.  Consider the Cornish Riviera which slipped for Westbury at Heywood Road Junction.  The main train used the avoiding line and the slip coach was rescued by a pilot loco, drawn into Westbury station and there attached to a Weymouth train.  On the model you would only see the pilot beetling off stage and returning shortly afterwards triumphantly hauling the slip coach. 

 

Chris

  • Like 8
  • Friendly/supportive 1
Link to post
Share on other sites
  • RMweb Gold

Hello Oz

 

This operation would be great with DCC (which I don't have in 00, but did have some years ago on a US N layout, so I make the comment with some DCC experience).

 

On my analogue 00 layout, I bank freights up a gradient using the time-honoured cab control system. As the freights are very slow, there is no problem with flicking the handful of section switches as they proceed. The Brake Van and Banker have normal 'hook & bar' couplers - but with the hooks removed. When the summit is reached, the Banker simply drops off.

 

If a DCC-fitted Slip Coach had similar couplings, it could be independently driven to a stand in the station whilst the main train flies through. Or, could be brought to stand at a convenient point (perhaps a through road at a station), then combined as a consist with your Station Pilot and shunted accordingly.

 

Brian

  • Like 1
Link to post
Share on other sites

Many years ago the Newport Clubs Long Suffren layout had an operating slip coach, but that's about as much as I remember, so I can't help with how they did it.

 

Perhaps one of their members or ex members, not as in deceased as per Norwegian Blue's, is on here and can help.

 

SS

  • Like 1
Link to post
Share on other sites

I would definitely power the slip coach - they were 'driven' into the platform by the guard. I'd be inclined to either drive the coach the whole time, effectively banking the train, or consist it and break the consist at the appropriate time. It only needs to come on-scene at the back of the train, so it only needs to be 'attached' to the train for a short time (hency the option of driving the coach the whole time on a separate address to the train loco). If you want to actually uncouple, have no hook on the last coach and use a servo driven off a decoder function to lift the hook of the slip coach coupling (obviously this needs to be a straight pin rather than a tension lock hook so that it doesn't catch on the loop.

 

Adrian

Edited by Adrian Wintle
  • Like 2
Link to post
Share on other sites

Thank you to everybody for your ideas.

I'm not a DCC expert - though that was my first thought as a solution.

With a motored coach there seems to be two alternatives:

1. No coupling

I presume that a motored coach would have to have to be speed-matched to the locomotive with train combination if the slip coach were permanently driven by a second throttle with a second address.

2. With coupling

Setting aside the electromechanical details of the uncoupling ...

The way I understand it, when in consist/banking mode, are both decoders configured to respond to one throttle command? I presume it is possible to turn this off during operation to revert to separate throttles - in this case for the train and slip coach? (My guess is it has to be to model banking operations.) I'll have to do some DCC homework on banking.

Edited by Ozexpatriate
  • Like 1
Link to post
Share on other sites

Uncoupling

... to actually uncouple, have no hook on the last coach and use a servo driven off a decoder function to lift the hook of the slip coach coupling (obviously this needs to be a straight pin rather than a tension lock hook so that it doesn't catch on the loop.

... use standard tension locks with the hook that locks into the lip of the the hook) so the main train coach hook just rested on the crossbar by friction. I made an uncoupling ramp operated by a pushrod that raised when required.

I had brainstormed some variations on the theme of using a right-angled pin to hook into the tension-lock crossbar of the preceding coach, that could be levered off - either electrically via DCC, or mechanically by a device embedded in the track. It sounds like a reliable scheme can be implemented.

I also found this commerical US solution.

Edited by Ozexpatriate
Link to post
Share on other sites

Thank you to everybody for your ideas.

 

I'm not a DCC expert - though that was my first thought as a solution.

 

With a motored coach there seems to be two alternatives:

 

1. No coupling

 

I presume that a motored coach would have to have to be speed-matched to the locomotive with train combination if the slip coach were permanently driven by a second throttle with a second address.

 

2. With coupling

 

Setting aside the electromechanical details of the uncoupling ...

 

The way I understand it, when in consist/banking mode, do both decoders are configured to respond to one throttle command? I presume it is possible to turn this off during operation? (My guess is it has to be to model banking operations.) I'll have to do some DCC homework on banking.

 

If it were just the train coming on scene and dropping the slip coach, I'd be inclined to try driving the slip coach with a second throttle (on a different address) rather than trying to speed-match and consist it. With a coupling it would be easier to maintain the illusion as you wouldn't have to get the speeds exactly right (just have the slip coach a shade slower).

 

Yes, in consist mode, both decoders respond to the same commands (in advanced consist mode - currently the most common - it is usually a different address than the any of the components of the consist). In DCC terms, each element of the consist has an address, but if there is an address set in a specific configuration variable (CV19), the decoder will respond to commands for that address rather than its own address. This CV can typically be cleared during operation using Progamming on the Main (a.k.a. Operations Mode programming). How easy it is to do this will depend on the DCC system.

 

Adrian

  • Like 1
Link to post
Share on other sites

CV19 ... can typically be cleared during operation using Progamming on the Main (a.k.a. Operations Mode programming). How easy it is to do this will depend on the DCC system.

Thanks Adrian. I had looked up CV19, but I had no idea if it could be cleared while in motion, or if it required being on a static programming track.
Link to post
Share on other sites

Thanks Adrian. I had looked up CV19, but I had no idea if it could be cleared while in motion, or if it required being on a static programming track.

 

If you can go this way, dropping the slip coach out of the consist, the slip coach will then hav a 0 speed command, so judicious tuning of the deceleration might allow it to come to a rest in the station. I haven't actually tried breaking a consist in motion, though. Must experiment - I'm not even sure how PoM on my Lenz system works if the locos are in motion.

 

Adrian

Edited by Adrian Wintle
  • Like 1
Link to post
Share on other sites

My father in law who died recently had the pleasure of being slipped off the up Torbay Express at Reading. He said it was a wierd experience seeing the rest of the train going ahead without the slip coach. I would hardly describe it as being driven as the Gaurd could only slow the coach. It took an experienced Guard to get it right. I believe that cases where the station pilot had to resucue the coach were not unknown. If I were trying do to it on a model I would probably introduce a slight gradient down to the platform and a slight one up along the platform so the coach could roll nicely into place.

Don

Edited by Donw
  • Like 1
  • Agree 1
Link to post
Share on other sites

. I would hardly describe it as being driven as the Gaurd could only slow the coach. It took an experienced Guard to get it right. I believe that cases where the station pilot had to resucue the coach were not unknown. If I were trying do to it on a model I would probably introduce a slight gradient down to the platform and a slight one up along the platform so the coach could roll nicely into place.

Don

 

I used the term 'driven' as it took skill for the guard to manage the braking (and the limited brake cylinder volume) and stop the coach in the platform. It certainly wasn't a case of just unhook and then wind on the brake.

 

With gradients you risk roll-back, which certainly isn't prototypical. In DC I'd be inclined to add drag to the axles and experiment until the correct combination of train speed, detaching point, and drag was found.

 

Adrian

  • Like 1
Link to post
Share on other sites

Hello all,

 

Steve and myself were talking about slip coaches a few days back. One of the questions that we asked ourselves was at say Reading with through roads.

1], would the train run through the platform to slip the coach.

2}, run through on the through road and the station pilot pick up the slip coach from the through road.

3], the main train runs through on the through road, then the point is changed (along with the F.P.L and put back) and the slip coach runs into the platform.

 

Number 1, sounds OK but it will slow down the main train, but not as much as stopping.

Number 2, would seem the most logical, it may take a bit longer for the passengers, but it would still be quicker than getting the slow train.

Number 3, this one just sound all wrong. having to do at least three point moves ( F.P.L. out point thrown F.P.L. in) in front of a moving passenger train (the slip coach).

 

Can any one say for certain, what would have happened.

 

For the slip coach (we were talking about 7mm and DCC) power the coach and make the coupling work something like the real thing using one of the DCC functions. So it would be something like a clam shell for the hook.

 

OzzyO. 

Edited by ozzyo
  • Like 2
Link to post
Share on other sites

One of the questions that we asked ourselves was at say Reading with through roads.

1], would the train run through the platform to slip the coach.

2}, run through on the through road and the station pilot pick up the slip coach from the through road.

3], the main train runs through on the through road, then the point is changed (along with the F.P.L and put back) and the slip coach runs into the platform.

It's my understanding that 1, and 2, were used, though I had the impression that the coach was slipped before the train reached the station.

 

The portion for Weymouth was slipped on the main diversion past Westbury. See Chris' comment:

Consider the Cornish Riviera which slipped for Westbury at Heywood Road Junction.  The main train used the avoiding line and the slip coach was rescued by a pilot loco, drawn into Westbury station and there attached to a Weymouth train.  On the model you would only see the pilot beetling off stage and returning shortly afterwards triumphantly hauling the slip coach.

 
Link to post
Share on other sites

 

 

The portion for Weymouth was slipped on the main diversion past Westbury. See Chris' comment: 

 

It was slipped prior to Heywood Road just before the Westbury cut off began, and brought to a stand at the junction. There was a spur provided on the route into Westbury, where the pilot  (often one of the 54XX) would be waiting to haul the slip into the station. The coach was not slipped on the cut off route. If it had been, it would be a nightmare to retrieve and route back into the station.

 

In the late 1930's the Weymouth slip was sometimes released in the station. Even before the outbreak of war, the Westbury cut off was being used as a store for ammunition.

 

Mike Wiltshire

  • Like 2
Link to post
Share on other sites
  • RMweb Gold

Hello all,

 

Steve and myself were talking about slip coaches a few days back. One of the questions that we asked ourselves was at say Reading with through roads.

1], would the train run through the platform to slip the coach.

2}, run through on the through road and the station pilot pick up the slip coach from the through road.

3], the main train runs through on the through road, then the point is changed (along with the F.P.L and put back) and the slip coach runs into the platform.

 

Number 1, sounds OK but it will slow down the main train, but not as much as stopping.

Number 2, would seem the most logical, it may take a bit longer for the passengers, but it would still be quicker than getting the slow train.

Number 3, this one just sound all wrong. having to do at least three point moves ( F.P.L. out point thrown F.P.L. in) in front of a moving passenger train (the slip coach).

 

Can any one say for certain, what would have happened.

 

For the slip coach (we were talking about 7mm and DCC) power the coach and make the coupling work something like the real thing using one of the DCC functions. So it would be something like a clam shell for the hook.

 

OzzyO. 

At Reading trains usually slipped in the Up Main Platform Line (No.5 Platform as it then was, currently No.8) and I recall seeing somewhere a long time back a picture of a slip taking place in that line.

 

You suggestion Number 3 was very, very much against the Rules and all the principles of safe working and would have been not far off physically possible in any case.  I suspect the idea of slipping in the platform was to avoid blocking/locking up the junction at West Main.

  • Like 3
Link to post
Share on other sites

At Reading trains usually slipped in the Up Main Platform Line (No.5 Platform as it then was, currently No. 8) and I recall seeing somewhere a long time back a picture of a slip taking place in that line.

 

Photographed many times by Maurice Early. Detailed shots published in several of his books of before, during and after the slip operation

 

Great Railway Photographers - Maurice Early (page 24/25 and A history of Slipping and slip coaches (Pages 46-52).

 

I am not sure if this is unique or not, but the massive up bracket signal from the Basingstoke/Berks & Hants line at Reading had a lower bracket containing two 'slip' distants (one for platform, other centre through line) to advise the guard if it was clear to slip or not. If the signals were at caution, the guard new NOT to operate the slip as the train would be stopping, This was to prevent detachment and then running into the back of the train if a hard brake application of the main train became necessary.

 

Again signal photographed by Maurice Early but sadly not included in either of above publications.

 

Mike Wiltshire

  • Like 2
Link to post
Share on other sites

From what my FiL could remember ( bearing in mind it was pre 1939) the actual slipping was a short distance in front of the platform the gaurd applied the brake to reduce the speed which resulted in the train pulling away the coach then coasted into the platform wirh further brake applications to control the speed. 

Don

  • Like 4
Link to post
Share on other sites

At Reading trains usually slipped in the Up Main Platform Line (No.5 Platform as it then was, currently No. 8) and I recall seeing somewhere a long time back a picture of a slip taking place in that line.

 

You suggestion Number 3 was very, very much against the Rules and all the principles of safe working and would have been not far off physically possible in any case.  I suspect the idea of slipping in the platform was to avoid blocking/locking up the junction at West Main.

 

Thanks for that Mike, No. 3 was a non starter in my mind but was included for completeness. Reading Mikes reply about the slipping distants it sound like option 1 or 2 could take place at Reading. As Reading is a busy place I can understand why they would try and slip into the platform.

 

OzzyO. 

  • Like 1
Link to post
Share on other sites
  • RMweb Gold

Thanks for that Mike, No. 3 was a non starter in my mind but was included for completeness. Reading Mikes reply about the slipping distants it sound like option 1 or 2 could take place at Reading. As Reading is a busy place I can understand why they would try and slip into the platform.

 

OzzyO. 

Reading was 'standard' in so far as the meaning of Slip Distants was concerned although they were not a widespread fitment (there were particular reasons at Reading which related to the possibility of Main Line East having its signals at danger and the fact that the slip took place at the entrance to the platform) but I think Reading was probably the last place to have them.  The Reading Slip Distants were in fact a splitting pair so in theory slipping could also take place on the Up Main Through Line although as far as I'm aware it certainly wasn't booked to take place there in later years (and would have been a right nuisance if it did.

 

There were also copious Instructions regarding the need to stop instead of slipping as a stop could happen for all sorts of reasons (e.g. defective slipping coupling) or even a train stopping for water when it was not booked to do so.

  • Like 1
  • Friendly/supportive 1
Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×
×
  • Create New...