Locomotive braking mode

[TRAX]

Hi there

I’ve noticed that on several british locomotives (59, 66, probably others ?) you can change the braking system from Passenger mode to Freight mode and vice-versa.
If I am not mistaken, the brakes apply more quickly in Passenger mode - but why have a Freight mode at all ?
Is the difference in application rate determined by the mode itself (in which case why not benefit from the faster "passenger" mode for freight too), or is it just because of the difference in the number of vehicles to be braked behind the loco on a freight train ?

 

[4F89]

I'm no expert, but I would think it comes down to the amount of braking force required for the weight. Passenger carriages being lighter than freight wagons. I'd think you would need a slower application with freight. Unless someone can correct me.

 

[TRAX]

Yesterday or the day before I got the explanation, I think it seems correct:

The Class 59/2 is also fitted with a PBL braking system that moderates the speed in which the brakes apply force. When carrying long and heavy freight wagons it is advantageous to have a slower applying/releasing brake to give the engine time to gain traction without the immense weight behind the locomotive negating the applied power.

PBL Braking comes in two modes, Passenger and Goods. Goods is the preferred mode for freight operations as it is the slowest applied brake and is the default setting for the Class 59/2. If the driver wishes to switch to the more responsive Passenger mode they must toggle the Brake Mode switch found above and to the left of the drivers seated position.

 

[4F89]

Yeah. More succinct, but my gist

 

[FOCTOC]

Hi there

I’ve noticed that on several british locomotives (59, 66, probably others ?) you can change the braking system

Just to be a pedant: neither class are British, both being a USA designed/built machine.

The original 59s (001-005) do not have goods/pass changeover, they are permanently in goods.

To answer your original question, goods timings are obviously slower than pass to deal with the combination of wagons which may well have very different braking characteristics. It also helps compensate for train length/weight to help avoid snatches through the couplings which generally arent good news.

 

[TRAX]

Just to be a pedant: neither class are British, both being a USA designed/built machine.

To answer your original question, goods timings are obviously slower than pass to deal with the combination of wagons which may well have very different braking characteristics. It also helps compensate for train length/weight to help avoid snatches through the couplings which generally arent good news.

I see, thanks.

 

[Kneedown]

The Goods/Passenger changeover switch does indeed apply and release the brakes quicker when in the Passenger setting. The purpose of the Goods setting is to apply and release the brakes much more slowly on a freight train to reduce snatches and buffering. If the switch was set at Passenger, brakes would apply at the front of the train, but still be released at rear until the distributor's "caught up" with those at the front. This results in the rear of the train buffering to, and pushing the front, risking buffer lock and derailment. The same applies with brake release, where the the brakes on the leading wagons would release before those at the back, risking snatching and a divided train.
The Goods position put's a choke in the system, slowing the flow of air in the brake pipe. It doesn't eliminate the problem of snatching and careful driving is still required, but does reduce the effect.

 

[TRAX]

Thank you all for the great answers.