Junctionmad

 

 

The only purpose of the FPL is to prevent the point blades moving under a train in the facing direction. The Economic FPL achieves this by the design of the "Z" bar. The prevention of moving the point lever is by way of interlocking in the normal way.

so without a fouling bar or track circuit locking how is that achieved.  other then  either locking in the box , or slotted with signals ( which have nothing to do with the FPL per se), whats stops the signalman with an economical FPL from  just releasing lever.  If he's stopped by signal or box interlocking, he's stopped from releasing the lever anyway.

I can see the point of a seperate locking lever, as it acts as a consciousness  decision to release the FPL and then  pull the point lever.  But in an economical FPL, what additional protection is being added in the absence of any other form of locking.  It seems to me to be a " rule bender" , i.e. the physical point lock is present , but in fact no additional safety has been added.  

are you saying that the only purpose is to add a " dubious" additional protection preventing the point blades moving under their own volition , rather then an additional to locking safety 

Interlocking does not entirely prevent the points being moved as they would be free immediately the protecting signal is returned to danger (hence the Rules relating to the working of such signals).  The facing point lock bar is what physically prevents the facing point lock from being unlocked by premature movement of the operating lever - and there is no reason - apart from the weight of the throw - why an economical FPL can't work with a facing point lock bar, and of course they did.

Yes this is my point I suppose, I have seen installations with and without fouling bars.  But fouling bars as I understand it were primarily installed because of sight lines to the box, meant the signalman couldn't  determine where the train was standing.  the classic case being  engine run arounds etc 

I also understand these were phased out in favour of track circuit protection.  I can see the point of FPLs if you ALWAYS have  fouling or track circuits, but cant see the point if not.  What  protection was added, by FPLs on their own , especially since many point blades were slotted with the appropriate signal anyway 

The use of one lever is OK.  That is what happens with motor points, one lever controls the motor.  Inside the point mechanism the motor winds, that extracts the bolt, then throws the tie bar across and the final part of the motion reinserts the bolt.  Everything being detected by various detection circuits (If you look at some motor points you will see connections from both switch rails and the tie bar all going into the mechanism)

 

The important thing is that any move for passenger trains over the points in the facing direction is interlocked to ensure the points are locked before the signal can clear. 

 

I've probably not made that clear.  Let me know if you've understood.

 

Thanks

Yes I have usually seen the relevant signal slotted with the point /FPL. , though not always. I always thought the idea of the lock lever was to prevent the point lever being pulled. , ie that the tappett locking in the cabin was used. With a single lever I don't see the advantage of FPL.s.

Was it that they were always paired with fouling bars or track circuit protection ?

I think the first part of the movement withdraws the bolt (or unlocks whatever locks the points), switches are then able to move with the lever, and the final part of the movement locks them again.  Are there any of these still in existence?

 

In the late 80's / early 90's there were some hand points that were called switchlocks.  the stretcher bar was done away with and the actual switches operated with a bar that looked like the fletching on an arrow.  A novel design that unlocked, moved then locked the switches in one movement.  I'll try and find some pictures

I understand this part, But the idea of an FPL was that  the point lever couldn't be unlocked without  releasing a lock lever.  IN an economical  FPL, cant the signal man , just  release the combined lever at any stage and the point moves and re-locks.   was track circuiting rather then fouling bars then used to ensure the point couldn't be moved.

Ecomonical FPLs seem to me to be kinda rule benders, i.e. a lock is placed on the points, but infact its not in any way independent to the mechanism that moved the blades 

The reason I ask is I'm modelling irish railways  in the 70-80s and  in ireland economical FPLs were very common , right up till they were removed post 2000 

sorrr for waking up an old thread, but  in reference to the LNER drawing of an economical facing point lock, could someone explain how it actually work.  I dont believe they all came with fouling bars as well did they.  SO how does a single lever in the box , act as a lock and a point lever at the same time ????