Bakerloo Resignalling - Treadles, Deltas etc.

The track circuits installed are of the Jointless Track Circuit (JTC Model FS2500) indeed delta position detectors are not compatible so indeed they use the Silec Treadle which is a arm depressed by the train wheel which operates a pair of contacts in the unit. As far as I'm aware the Bakerloo has no position detectors of the newer type be in the Siemens design or the Frauscher Design but I'm not 100% on that.

So Queen's Park is entirely 'Treadle' with no other type of Position Detector in place at all in the area?

Many thanks DistrictSOM and Tom for your replies - they are much appreciated.

Only fault we have experienced of them is when the arm breaks and it fails to detect a train. But the contacts revert to there open position. The arm is slugged by approx 8 secs when depressed by a train before it comes back up

There is always a back up timing section known as a 2nd shot in case they do break. Not 100% on the Bakerloo as Tom was a T/O over there but other lines its used in the release of the signal lever lock in most situations so the signaller would need to take a release on the signal concerned 1 minute for manual releases and 2 minutes for automatic releases. As the 2nd shot system is only used in speed control situations and not releases of signal locks. Again going from memory the treadle is proven to be ok in the signal in the rear of it as its in the selection circuit with the relay proven down first which is fed from the treadle. Another thing we have realised and LU could be causing problems for them selves is that company which makes them states only 24v maximum should go through the contacts but we have 100v going through them, but I've never known one fail due to worn out contacts just the arms wearing or breaking off.

My experience was that they tended to fail mechanically rather than electrically too, and it wasn't uncommon for a number of treadles to all fail around the same time. We fed them at 50v DC and I don't recall any problems with them (I would expect NR to use a similar voltage).

Certainly not all of the treadles at Queen's Park had a second shot timer; from memory the ones in the North Shed specifically were 'one shot' applications.

A second shot is where the treadle does not detect the train for any reason and then its proved via timing sections and track circuits being down for a set amount of time.