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Port Dinllaen

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Re: Port Dinllaen

Unread postby tynewydd » Fri May 16, 2014 6:11 am

davidwoodcock wrote:I just wonder whether the historical background might be a little more robust if, instead of the Midland and Great Central getting involved as individual companies, the acquisition had been made through the Cheshire Lines Committee, Britain's biggest joint railway in which the Midland, GC and Great Northern were all equal partners. The facility to export coal from the Nottinghamshire and Yorkshire coalfields directly to Ireland might have been a powerful incentive for all three.


Like it - it fills a period between the acquisition and the extension/bypass to the GC/GW joint to London. Amended history to reflect this.

davidwoodcock wrote:
Incidentally, although the Cambrian Railways were grouped into the enlarged GWR in 1923, pre-grouping they had effectively been an associate of the LNWR rather than the GW.

Interesting. So the Cambrian would also be a backdoor for LNWR interests into the PD harbor - no wonder they were not treated well by the incumbents.
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Re: Port Dinllaen

Unread postby kbarber » Fri May 16, 2014 8:46 am

Sorry as if it feels I'm riding a hobby horse, but it occurs that if the diagonal emphasis is top left - bottom right you might just have room to extend P1 further into the station throat - an 1880s enhancement to cope with the increasing traffic the CLC connection brought, but with the buffer stops end constrained by the dratted Cambrian station. Which would make some of the rest of the throat just that little more 'interesting' and perhaps provide greater length in 1b?

I do like that CLC connection, it gives the Midland an entry. It was troubling me a little that the MR didn't seem to be able to access PD at all other than via the LNWR (if ever there was a recipe for trouble!!!) or perhaps via the GC after the Irish Extension was built (but they didn't get on that well either). It doesn't make much difference to the 1910 resignalling though, although it might mean a CLC design for the signalbox rather than the very distinctive Midland design.
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Re: Port Dinllaen

Unread postby tynewydd » Sun May 18, 2014 3:40 pm

Well I have made a little progress - a line drawing of the proposed new alignment is here

I am working on the schematic now. As someone noticed about the real signal box diagram at HH, its difficult to get the right balance of a rectilinear schematic and the curved shape of the real. I have also found some better symbols for signal arms and ground signals - I find I am lacking an UQ subsidiary arm and a LQ distant - but I'll get around to that at some point. I've just updated the jpg in its new half-way done state.

kbarber wrote:you might just have room to extend P1 further into the station throat - an 1880s enhancement to cope with the increasing traffic the CLC connection brought, but with the buffer stops end constrained by the dratted Cambrian station. Which would make some of the rest of the throat just that little more 'interesting' and perhaps provide greater length in 1b

I'll look, Keith, I may have slightly less constraint on the left-right having terminated the second crossing (MPD Out) at the Down - maybe i can squeeze a touch more juice and still have Pl1 - MPD In. It's all those Peco frog angles - so far I have managed without needing any custom pointwork....

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Re: Port Dinllaen

Unread postby tynewydd » Sun May 18, 2014 7:23 pm

Updated trackplan with signalling

here

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Re: Port Dinllaen

Unread postby tynewydd » Fri May 23, 2014 7:09 pm

OK. The picture is more in order now. The picture has the Up and Down properly aligned.

I tried to apply the logic of the CR Platform 1b having persisted and removed facing points from the Branch passenger approach to it, reasoning that if the CR needed to gain access, it could come onto the Up. I added a bracket at the entrance to 1b, with calling on and a subsidiary arm for the RR loop. I made the assumption that this "special" signal being squeezed into the train shed was one that the LMS chose not to replace along with its 1b starter cousin. I also added a main and call-on for Pl1a to 1b, presumably hanging from the rafters! The platform 1b starter has a bracket with an added calling on arm on the Pl1 side, I presume to allow movements to unify a 1a and 1b train. In fact that seems quite an operationally attractive idea, a train is bought into 1b and its carriages are added to a train standing in 1a, or a 4/5 coach train is brought into 1a+1b and divided into two. "the two front coaches on this train are for Pwhelli, the rear portion is for Nantlle"

I assumed that there is a GF for the 1b engine release. Hints on signaling this whole section would be welcome.

The new throat adds extra distance such that the gantry is now "one-way" in front of the left hand road bridge and only has arms for the exit roads outbound. In each case there is a branch and up signal pair and a smaller arm for access to the down to shunt except for the branch which has no access to the up. I assume this branch pass arm could be dispensed with actually. All branch pass clearances either way would lock out the signals that would allow access from the branch to the Up and the crossovers between up and Goods.

The lack of access from the branch passenger to the goods facilities means that they are reached by plain crossovers from the up. There is a crossover from down to up just before the double slip pair to the branch that could have been combined with the line from the Gds In to Down, but having them separate gives positions on the Up and Down where a loco (e.g., pilot) can wait before being called on, or with a few wagons during run-round of the goods train in the Gds In side without fouling the other lines.

I removed the Pl4 arrangement as "70s" and left it as a ground frame and some simple ground signal signaling to protect shunting movements in Gds Out.

The lever numbers shown are all "nominal" right now.

Question - how would token exchange work on the branch? While there was a box at the end of the single track, it was easy. Now with a large semi-automated (pneumatic) box on the other side of the tracks - how would that function be done, or would the old box be retained for that and have control over the branch signaling up until the station throat? In model terms, this gives the possibility of something else for the person operating the goods yard, WR Shed and Gds Yard to do!

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Re: Port Dinllaen

Unread postby Mike Hodgson » Sat May 24, 2014 5:27 pm

Token exchange could be carried out using auxiliary token instruments. That is, the signalman would obtain a token in co-operation with the other end of the section in the usual manner, but instead of giving it to the driver, would insert it in another instrument which is connected to a similar instrument probably located on the platform. The train crew (or the platform inspector) would be required to obtain the token from that instrument. Incoming trains could surrender the token in like manner.

However I think it more likely that a replacement box would have been sited in a position convenient for token operation. Signal box position was originally determined primarily by point rodding constraints, but in later years point motors allowed greater emphasis to be put on factors such as proximity to level crossings or practicality of token working. Using an auxiliary pair is a way of getting round the problem if you can't put the box somewhere convenient for token working for some reason (for example if it can't be close to both the crossing and the single line)

For more info see:
viewtopic.php?f=6&t=3786
and
http://www.railsigns.co.uk/info/etoken1/etoken1.html
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Re: Port Dinllaen

Unread postby tynewydd » Wed Aug 20, 2014 5:47 am

I have been trying to reduce the PD signaling a bit. The latest attempt is here.

Changes -
  • removed the signaling for the engine run-round loops at platform 4 and Platform 1a and replaced them with a GF release lever.
  • removed the signals for the branch passenger line from the gantry as I reasoned that would be cleared all the way out and treated as a single TC so that there is no reason to have a train stand blocking the access to the Goods In and Yard.
  • removed signals for access to the Down to shunt from the Up/Dwn Passenger and the Up line. Reasoning that you can use the Up and then the 42/44 leading crossover.
  • tried to tidy up the signaling on the gantry - but this led to the following question - what is correct for the signal 79 that allows a train out onto the Down line up to the shunt limit? I had a subsidiary arm but then I realized that there was nothing to be subsidiary to. (Even if I thought of it as a "draw ahead" signal - which i don't think the LMS or MR or GC even had). So I changed to a miniature arm but that seems like it isn't right either. Is the thing I really need a ground disc mounted on the gantry?
  • added indication of the automated signaling between PD and PLJ at 1 and 87 (not decided if those will be 3 position or home and distant combos).
  • added a catch point 27b to the Goods In line to protect the passenger lines from runaway wagons from arriving goods when the engine is running around.
  • Made 69 into two linked ground discs between Goods Out and the Engine Spur - selected by virtue of which way point 26 is set. And moved and split up the Goods Out signals 87,86 to have two LQ ringed survivors and two ground discs 70,71 controlling exit - this eliminated two theaters.

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