Watford DC line 4th Rail.

[Ashley Hill]

Watching a video on YouTube it still shows the 4th rail in place beyond Harrow & Wealdstone towards Watford. In places it looks intact, in others it’s either derelict or missing. Since the Bakerloo hasn’t run north of Harrow since the 80s, why has there been no rush to recover it. Is it still live in places? (I know it should be treated as live if it’s there)

 

[edwin_m]

I believe it's been left but lowered onto the sleepers, to improve the return current flow.

 

[Ashley Hill]

I believe it's been left but lowered onto the sleepers, to improve the return current flow.

Nothing comes into contact with it though, does it?

 

[edwin_m]

Nothing comes into contact with it though, does it?

Not intentionally! It's presumably bonded to the running rails at intervals, possibly via impedence bonds.

 

[swt_passenger]

Nothing comes into contact with it though, does it?

It would be bonded every so often to the running rails.

 

[Ashley Hill]

Not intentionally! It's presumably bonded to the running rails at intervals, possibly via impedence bonds.

So as such it is not used as a traditional 4th rail. Do the LO units need this return as between Euston and Queens Park they only use 3rd rail.

 

[swt_passenger]

So as such it is not used as a traditional 4th rail. Do the LO units need this return as between Euston and Queens Park they only use 3rd rail.

The LO units only ever use the 3rd rail, they don’t have other central pick up shoes, so when running over LU tracks it’s only the tube stock that contacts the 4th rail, which is operated at 0 volts to put the third rail at 660 Volts for mainline trains. Exactly the same as on the Wimbledon and Richmond shared branches.

 

[Ashley Hill]

So the 4th rail north of Harrow doesn’t really need to be there, but it’s bonded to the running rail to improve the earth return. Therefore it is still treated as a live rail as such.
Have I understood this correctly?

 

[NSEFAN]

So the 4th rail north of Harrow doesn’t really need to be there, but it’s bonded to the running rail to improve the earth return. Therefore it is still treated as a live rail as such.
Have I understood this correctly?

If it’s bonded to the running rails then it should be close to 0V earth. There would be some current running through it but it should not be at a dangerous voltage.

 

[Ashley Hill]

If it’s bonded to the running rails then it should be close to 0V earth. There would be some current running through it but it should not be at a dangerous voltage.

I was considering the rule book which says that track circuit clips cannot be used in 4th rail areas and whether the line north of Harrow still counted as 4th rail.

 

[Elecman]

As it’s not a live conductor rail ( so not a 4th rail). but merely acting as an additional current return rail it’s perfectly safe to use track circuit clips

 

[Ashley Hill]

Thanks everyone for your help and replies.