Facing Point Locks

[richbrummitt]

I want to recreate as much of the track level detail as possible and so I've been looking for decent pictures of facing point locks, however I am left somewhat confused comparing diagrams and pictures.

 

I thought that maybe there was an earlier form of facing point lock without the lifting bar? In many photos that are reasonably clear I cannot see any evidence of the lifting bar, or the crank and spring for operating it, which according to diagrams in GWSG GWR Switch and Crossing Practice and Great Western Branch Line Modelling was not under the facing point lock cover and would be discernable if you were looking for it in some of the pictures.

 

I've since been made aware that the locking bar was not necessary if there was a track circuit (the lever being locked electrically in the box), and that an earlier form of FPL had a 'T' crank that operated both the lifting bar and plunger. This had a shortcoming in that if the connection to the lifting bar failed then the lifting bar no longer prevented the moving of the plunger. This was outlawed and so the change was made for the crank to drive the lifting bar, and hence drive the plunger but none of the sources have any dates. Anyone know?

[Guest jim s-w]

Hiya

 

It doesnt answer your question but dont forget the point numbers too (from Colin Craig)

 

 

Cheers

 

Jim

[The Stationmaster]

I want to recreate as much of the track level detail as possible and so I've been looking for decent pictures of facing point locks, however I am left somewhat confused comparing diagrams and pictures.

 

I thought that maybe there was an earlier form of facing point lock without the lifting bar? In many photos that are reasonably clear I cannot see any evidence of the lifting bar, or the crank and spring for operating it, which according to diagrams in GWSG GWR Switch and Crossing Practice and Great Western Branch Line Modelling was not under the facing point lock cover and would be discernable if you were looking for it in some of the pictures.

 

I've since been made aware that the locking bar was not necessary if there was a track circuit (the lever being locked electrically in the box), and that an earlier form of FPL had a 'T' crank that operated both the lifting bar and plunger. This had a shortcoming in that if the connection to the lifting bar failed then the lifting bar no longer prevented the moving of the plunger. This was outlawed and so the change was made for the crank to drive the lifting bar, and hence drive the plunger but none of the sources have any dates. Anyone know?

 

 

Definitely the case by 1925 but I have nothing in the way of original source information for dates earlier than that. However I have not seen any mention of it in minute books going back to 1911 so it could well be earlier than that?

 

BTW it was not Western practice to include point numbers on the ground on mechanically worked points - notwithstanding that delectable picture above.

[Guest jim s-w]

Learn Something everyday Mike

 

How were Western points numbered?

 

Cheers

 

Jim

[The Stationmaster]

Learn Something everyday Mike

 

How were Western points numbered?

 

Cheers

 

Jim

 

They weren't! (well not on the ground anyway - although in power worked areas they used the method you have modelled, presumably the 'N' letter and 'arrows' are yet to come?).

 

The idea presumably was that anyone out on the ground knew the numbers if they needed to or knowing the numbers didn't matter if you were working by handsignal. But for those unfamiliar with a place it might have been problematic - I can remember one Sunday, when we were single line working between Radyr Junction and Maesmawr, taking a Rymney Valley Relief Signalman through the crossing moves we had to make at Radyr to get a train on or off the Up Relief Line (which was the single line). I think the poor bloke had more than enough after I walked him through the double junction and crossovers giving him the number of every relevant point and signal as we went - easy if you were used to the 90 or so working levers in the 'box; not so clever if you had never seen the sky over the place before.

[Guest jim s-w]

Hi Dont know Mike

 

I will ask Colin but New Street doesn't seem to have them.

 

Cheers

 

Jim

[micknich2003]

Here's a few drawings from my collection, mainly McKenzie & Holland practise, I have several others, Saxby & Farmer etc.

I will stand corrected but I seem to recall reading of TC's being substituted for lifting bars early in the last century. Certainly the LNER was well into TC's in lue of bars by the outbreak of the last war. Locally point numbers are screwed to the point timber adjacent to the normally closed switch, this applies to both mechanical and power points. Mick Nicholson.

[LNERGE]

Here's a couple.. PM me with an email addy and i'll fire a good selection your way.

[John_Hughes]

Was there a get-out for light railways as far as the bars were concerned? I don't recall seeing them on any ng line although FPLs are fitted, though I've seen plenty on the standard gauge.

[LNERGE]

Was there a get-out for light railways as far as the bars were concerned? I don't recall seeing them on any ng line although FPLs are fitted, though I've seen plenty on the standard gauge.

 

Here is another way round the problem of locking points for a passenger move.

 

http://richard2890.fotopic.net/p36633294.html

 

This shows a Hodgson's Lock. It was mounted in the web of the rail and trapped the point blade until it was unlocked and the 'handle' pushed in. The handle could not put back with the point blade in any other position other than fitting tightly up to the stock rail. Unless the handle was once again trapping the blade the key could not be extracted.

[ozzyo]

Here is another way round the problem of locking points for a passenger move.

 

http://richard2890.f.../p36633294.html

 

This shows a Hodgson's Lock. It was mounted in the web of the rail and trapped the point blade until it was unlocked and the 'handle' pushed in. The handle could not put back with the point blade in any other position other than fitting tightly up to the stock rail. Unless the handle was once again trapping the blade the key could not be extracted.

 

 

It is not a lock, but it is a toe detector. In that it is fitted to one of the 'slide plates' and will work as a detector . The keys are for the checking if the fit of the stock rail to the running rail. the key 'B' that is in the detector will have two sides 'A' & 'B' one will be open one will be closed, the two keys (red and blue) will have to be inserted in to the checking keyholes in the power box.

When I had to check electrically powered points the distance foreclosure and non closure was 3/16". that was at the rail head, when you got down to the point lock it would not work the M/C would then move the point blades back and try the move again, if it was it would lock and all was OK. IIRC the min locking dimension was 1/16" at the rail head..

The F.P.L. bar has a tolerance of about +/-1/16". So you do not have a lot of movement at the toe end of a point.

 

OzzyO.

[ozzyo]

Hiya

 

It doesnt answer your question but dont forget the point numbers too (from Colin Craig)

 

 

Cheers

 

Jim

 

 

Can one ask for a larger photo please.

 

OzzyO.

[johnw1]

Mech FPL - Barnham

 

http://pics-by-john.photoblog.org.uk/p49326819.html

[LNERGE]

It is not a lock, but it is a toe detector. In that it is fitted to one of the 'slide plates' and will work as a detector . The keys are for the checking if the fit of the stock rail to the running rail. the key 'B' that is in the detector will have two sides 'A' & 'B' one will be open one will be closed, the two keys (red and blue) will have to be inserted in to the checking keyholes in the power box.

When I had to check electrically powered points the distance foreclosure and non closure was 3/16". that was at the rail head, when you got down to the point lock it would not work the M/C would then move the point blades back and try the move again, if it was it would lock and all was OK. IIRC the min locking dimension was 1/16" at the rail head..

The F.P.L. bar has a tolerance of about +/-1/16". So you do not have a lot of movement at the toe end of a point.

 

OzzyO.

 

It's is a lock. The sectional appendixies refer to it as such. Could you clarify what you mean by 'side plates'? I doubt very much if any of these made onto power boxes. There is mention of one at Hackney Downs in the 1950's.

[The Stationmaster]

Was there a get-out for light railways as far as the bars were concerned? I don't recall seeing them on any ng line although FPLs are fitted, though I've seen plenty on the standard gauge.

 

There was a get-out for light railways. It was recommended that they use economical FPLs (one rod to work both the FPL and the switch rails) but the real get out was that if the lever operating the points was alongside them there was no need to provide a lock bar.

[The Stationmaster]

Here is another way round the problem of locking points for a passenger move.

 

http://richard2890.fotopic.net/p36633294.html

 

This shows a Hodgson's Lock. It was mounted in the web of the rail and trapped the point blade until it was unlocked and the 'handle' pushed in. The handle could not put back with the point blade in any other position other than fitting tightly up to the stock rail. Unless the handle was once again trapping the blade the key could not be extracted.

 

I don't see it so much as providing an FPL function as providing a lock to prevent unauthorised operation of the points (i.e. you have to have a key to release the points). It - as I understand your description - will only work on the closed switch rail (to keep it closed) but has no effect on the open switch rail or the stretcher bar. Thus, in extremis, the stretcher bars could be damaged and the opposite switch rail could move, and possibly close (and I have seen that happen on badly maintained handpoints).

[LNERGE]

The Elsenham and Thaxted Light Railway used them extensively. They did run passenger trains.

[LNERGE]

I don't see it so much as providing an FPL function as providing a lock to prevent unauthorised operation of the points (i.e. you have to have a key to release the points). It - as I understand your description - will only work on the closed switch rail (to keep it closed) but has no effect on the open switch rail or the stretcher bar. Thus, in extremis, the stretcher bars could be damaged and the opposite switch rail could move, and possibly close (and I have seen that happen on badly maintained handpoints).

 

In this arrangement there is no means to detect the position of the open switch rail.. I installed this fairly recently and it got past the new works testers and a pretty good prodding from Network Rail.

[meple]

An economic facing point lock.

[Guest jim s-w]

Can one ask for a larger photo please.

 

OzzyO.

 

Bigger? Like higher res? What for?

 

Cheers

 

Jim

[richbrummitt]

Thank you all for your pictures. I have plenty of pictures, but many do not give the dates. All the diagrams are of the later (more standard?) arrangement.

Definitely the case by 1925 but I have nothing in the way of original source information for dates earlier than that. However I have not seen any mention of it in minute books going back to 1911 so it could well be earlier than that?

 

BTW it was not Western practice to include point numbers on the ground on mechanically worked points - notwithstanding that delectable picture above.

 

 

How high are the letters at 1:152 to be visible in the 4'?

 

Back on topic Are you are saying that these dates are for locking bars and FPLs being linked up the latter way, or the initial provision of locking bars with FPLs?

 

 

 

 

 

[The Stationmaster]

In this arrangement there is no means to detect the position of the open switch rail.. I installed this fairly recently and it got past the new works testers and a pretty good prodding from Network Rail.

 

 

Looks like a fairly normal arrangement to me - typical ground frame operated with no signals reading through it (or indeed lever frame operated with no signals reading through it) with the FPL bolt locking the type of front stretcher provided for precisely that purpose, just as has been around for years (albeit with different types and styles of material).

 

The quopte from the Appendix also seems fairly clear - the purpose of the Hodgson's Locks was to lock the points to prevent them from being operated without a key. Obviously much cheaper than a ground frame with, say, an Annett's Lock. But the arrangement still didn't lock the stretcher bar although one presumes it was accepted by HMRI in the circumstances of that particular light railway?

[micknich2003]

The attached ex Saxby catalogue may help to clarify the use of an "Hodgson Lock". Best Wishes, Mick Nicholson.

[LNERGE]

Thank you Mick. I have nothing in my collection to show how a Hodgson's lock was mounted.

[John_Hughes]

There was a get-out for light railways. It was recommended that they use economical FPLs (one rod to work both the FPL and the switch rails) but the real get out was that if the lever operating the points was alongside them there was no need to provide a lock bar.

 

That makes a lot of sense; the VoR for one was a great user of the Pease Economic Facing Point Lock, the last one of which failed rather interestingly at Devil's Bridge some time in the BR period, leaving an up train strewn all over the station throat.