Bahamas

Fiddling with the brake valve is n0t good practice. I once had a drive of an EQ braked loco on a train of ballast hoppers, and my instruction was don't drop her below 18 inches unless you want to stop. I recall many old hand and not so senior drivers on DMMUs, and actua;ly have a few drives myself . Obviously the high vacuum gave really quick brake release, but if you had zour braking points you could achieve some really could stops, and shave minutes of delay if you knew what you were doing.

 

Dropping the vacuum to 18” is doing nothing more than taking up the clearance between the brake shoes and the wheel. You need to go below that to get any braking. I always preferred vacuum to air brakes but that may simply be due to the fact that most of my driving has been on vacuum braked trains. When riding with other drivers I’ve noted that a lot of them see-saw the vacuum brake application valve which I consider to be a poor practice.

 

My comment was of course based on what I’ve seen drivers do as an observer on the footplate, can you actually maintain a level of vacuum without constant adjustment?

 

The traditional vacuum brake system used on the pre BR and subsequent railways was 21 inches of vacuum in the pipe, except for the GWR and BR(
WR) which was 25 inches. Steam locos had a vacuum ejector (actually a small and a large) - one to "blow up" ands one to maintain the level. Western locos also had a vacuum pump generally driven from a crosshead shaft on the driver's side (right hand side facing forward) andwhen in motion you hear the Western loco "spitting" as it moves.

Diesel and electric locos had electrically powered vacuum exhausters which created the vacuum in the reservoirs and the train pipe. Some locos had an exhauster speed up button to hasten the creation of the train pipe vacuum. If a "standard" loco replaced a western loco, the cords would need to be pulled on each coach or wagon to release the high vacuum, then create the 21 inches.

Hope this helps

 

Not really, I knew all that, it wasn’t the question I asked it was about maintaining a level of brake force eg 15 in of vacuum without constantly adjusting the brake valve

 

I found it fairly easy to do so. Descending the bank from Goathland to Grosmont, once up to speed I’d drop the vacuum to about 15-16” which would be about the balancing braking to keep the speed steady. Some slight adjustment was always necessary to maintain a steady speed but it was never a case of heavy applications unless I wanted to reduce speed significantly. With a Deeley brake it was a question of having your palm resting on the plunger and, as soon as you felt it move, move the application handle towards the off position. Letting the vacuum go low would bring the loco steam brake on and make the overall braking greater. The gradual steam brakes fitted to the BR standard steam locos were much easier as the loco brake force was more variable.