Lower quadrant signal bounce

[ibthorpe]

Can anyone tell me if there is signal arm “bounce” with lower quadrant signals? When the lever is pulled to set the signal I presume it should be a two stage motion as the arm lowers. When the signal returns i.e. arm travelling back upward, is there any bounce? I can’t see why as the arm is not returning under gravity.

 

Any guidance welcome.

 

Paul

 

 

 

[Penrhos1920]

Although the arm isn’t returning under gravity, there is a bl**dy big counterweight at the bottom of the post that is returning under gravity and is rigidly connected to the arm.  So there is bounce.

[royaloak]

When the signal is pulled off the signaller will be pulling the lever with a fair bit of force so the arm (and weight) will build up momentum, then when the wire reaches the end of its travel the arm (and weight) can continue on before returning to the maximum wire length under gravity, the more force put into the wire the more continuation and 'bounce'.

 

When the signal is returned to danger it will do so entirely under gravity and can bounce against the stop.

 

A lot of semaphores which are some distance from the signalbox are now electrically operated so no bounce on those.

Edited January 16, 2020 by royaloak

[ibthorpe]

Many thanks. I fully understand. I had forgotten about the big balance weight!

 

Paul

[phil-b259]

Three improbant things to remember:-

 

(1) The signallers technique - depending on whether they throw the the lever back or try and ease it back gradually will have a direct result on the force with which the signal arm moves and therefore the amount of bounce exhibited

 

(2) The condition of the equipment - a worn rubber stop will have much less energy absorption properties - or indeed less ‘springyness’ and that will affect the bounce of the arm.

 

(3) The distance from the lever frame - the longer the wire run the grater the forces and the grater amount of ‘slop’ and overall energy in the setup.

 

Ultimately in a well maintained system and with a top notch signaller operating it then the bounce will be minimal.

[Argos]

There is a topic on here somewhere (Signalling and trackwork?) That discussed this and includes some videos of lower quadrant signals bouncing.

[Argos]

Here we go:-

 

 

[Caley Jim]

On CR (Stevens) signals the cast iron spectacle plate weighed 30lbs, much heavier than the arm, and so returned the signal to danger.  The arm was connected by a rod to a lever with a balance weight on it around 4'6" below the arm.  the purpose of the balance weight was to maintain tension in the signal wire when it had been returned to danger.

 

Jim