Valve fitted on large GW frieght engines to moderate the application of the brake

Hi All,

Another question on GW brakes. Mathers wrote in the vacuum brake that the large engines 28/38/52 and 72xxs were fitted with a valve to moderate the action of the brake (I assume based on them working unfitted trains to reduce the likleyhood of breakaways. He says the valve is fitted with "to delay the action of the brake fitted at the entry of the branch pipe from the train pipe to the cylinder and said. The valve while it does not impeed air being removed, partially closes the opening when an application is made so moderating the action of the brake"

Does anyone know of a photo or diagram of this valve and whether any preserved locos are fitted with this. My assumption is that this would not be desireable as the locos are now normally working vacuum fitted trains.

Any ideas as ever really appreciated

regards

Duncan

 

3822 is not fitted with this and 7202 won't be either, I believe that when they left Barry these valves had been removed by the scrap man. I have not seen a drawing for these but haven't looked as not using them.

 

Thanks, the valve on 2857 was removed in the 1980s. It seams logical that on vacuum fitted trains, which is of course what most engines now work that you would not want a valve to moderate / retard the brake.

 

2818 may still have it fitted.

 

That would certainly make sense as it came straight out of BR traffic and has not been used since. Does anyone know of any fitted on engines that are running in preservation. I suspect like the small ejectors on the 56/66xx it is something which is now out of use.

 

It is extremely likely that the moderating valve is still fitted to 2818, but as stated earlier in the thread most if not all will have been removed in the preservation era. Some of you will know that the tender coupled to 4965 actually came from 2885 in Barry, and came complete with the moderating valve. That valve is still in our stores along with a number of other curio's no longer used but retained for reference samples, and I shall try to get a photo posted on here in the not too distant future. The valve itself is not particularly large and is really an old fashioned vacuum version of present day commercial pneumatic valves normally known as reverse free flow restrictors, in this case you can get the air out of the vac cylinder as normal but the admission of air back in to the cylinder is slowed or restricted to slow down the application and bring the blocks into contact with the wheels more gradually.

Regards
Bob