South African Loco vacuum brakes.

We've got a Class 25NC at Quainton. What puzzles me is why it has two vacuum brake hoses at each end. They are both connected to the same pipework, but no isolation cocks for each hose.

Can't see any obvious reason for this arrangement, but there must be one. Does anyone know?

 

Just a thought, are the hose ends identical. Was there stock with different ends.

Just had another thought, there is a dummy coupling for each hose? If not did they seal the circuit by conecting both hozes together?

 

I seem recall reading somewhere that when Indian railways experimented with very long freight trains they found it necessary to provide two train pipes to be able to get good vacuum at the back. Maybe that was a reason?

 

Perhaps I did not make myself fully clear. There is only one steel pipe for the vacuum brake going to the loco front and tender back buffer/drawgear beams. Both the flexible hoses are connected to this single pipe, one via a 'Tee' piece, the other via an elbow on the end of the pipe.

 

I googled 25NC and there are a number of pics on the web. Intrigingly they only show a single vac pipe. In amoungst the pics is a Garrat which does have two vac pipes.

Are the hozes still attached or just the swan-necks. Apicture would be interesting

Dave

 

Just found a picture of Quainton's loco, and there is only one vac hose visible on the front end!

Has someone altered the arrangement since arriving?

 

Will be going to Quainton this week so should be able to get a photo to put on here.

 

As in this linked image?
I was wondering if they were on opposite sides of the buckeye to facilitate coupling from one side only, but apparently not...

 

Yes, that's it. But why? There must be a reason for it.

 

Just wondering.... what size is the vacuum pipework along the loco? Is it the standard 2". If it is larger, it may be that the vac hoses are 2" because that is standard. Do some SAR wagons/coaches have a similar arrangement? As has been said earlier, propagation of a brake application is dependent on length and diameter and it might be that SAR had 3" pipes on some vehicles, especially passenger vehicles, to provide quicker acting brakes. If a 3" vac hose was provided, it would make the loco incompatible with other stock.
If it's 2" pipework, I'll shut up !

Edit:
More thoughts...Is it possible that some stock has F type cylinders and the second pipe provides the reservoir side? It would need the appropriate non-return valves in the system.

 

I have enlarged a small part of one of my pics, hence the poor quality but it appears to only show one connection.

 

Correct, only one at the front, but two at the back of the tender. No isolation cocks and normal 2" bore steel vacuum pipe...........
.

 

That's my reasoning down the drain, then!
Interesting to note that the hose couplings are iron and not aluminium.

 

Given that they would generally be hauling a load behind the tender, whatever the reason was for this twinning, it can only be surmised that it would not required at the front of the locomotive.

 

It is on the front. You can see the blanked off swan neck in the enlarged shot. I have noticed this fenominon several times and spotted only one pipe connected between vehicles and so nullifying the point but never saw the reason why

 

The NBL drawings have two on the tender rear and one on the loco front.