The gwr combined ejector as fitted to steam braked engines

Dear all,

This is a bit of a long shot. I am working on a paper on the GW vacuum brake, In looking at this subject there are some parts which have changed since the original text was written as a result of BR practice. The type I am working on at the moment is refered to as the combined ejector type(as fitted on panniers/ praries.)

The drawing below shows a front view of the ejector. At the top is the setter cylinder which is attached to the ejector by a U shaped attachment and as shown in the photo below that.





In the drawing it is possible to see a small release valve at the bottom of the setter cylinder. I am trying to find a clear photo this valve fitted on any engine. Those steam braked engines we have on the SVR do not have these valve and I am wondering anyone knows of any engine still with this valve fitted and if so do they have a photo they could let me have a look at?.

Of course many steam braked engines had a small reservior fitted separatley such as here on 7714
with its own release valve but that's a whole diffferent topic.


Any help or suggestions would be really appreciated

kind regards
Duncan

 

I can't see a release valve in that drawing, but there is a union for the pipe to the reservoir as also seen in the photo.

 

My understanding is that originally reservoirs were not fitted (they came with the fitting of ATC).Therefore a release cock was fitted instead of the union to reservoir,

I'm sure I've seen a pic of one somewhere.

Stephen

 

Hi I agree there is an attachment that goes to the res - see this image of 5764 that shows that connection

I will dig out the other drawing which shows this mysterious release valve which is refered to in Mathers work on the GWR Vacuum Brake and he says the following:
"
If it is required to apply the steam brake with full force , (whilst hauling a vacuum braked train,), the handle must be put right over to the “Brakes On” position and the release valve F opened (on the reservoir). Piston C will then rise again and the large valve ‘E’ opened thus admitting steam more freely to the brake cylinder.



If it is required to apply the steam brake with full force the handle must be put right over to the ‘Brakes on’ position, however the driver must clearly be aware of the risk of the wheels locking. The system is fitted with a reservoir release at F (on the reservoir) If the setter valve sticks and the steam brake is not released a quick release of the reservoir by this valve can result in the setter re-setting.



In some cases the reservoir is not provided (such as on 5764(my addition)) and a small button ‘G’ is placed under the cylinder. This takes the place of the release valve ‘F’ (for engines with a reservoir)"

here is another copy of the diagram showing valve G
,

Regards

Duncan

 

That would make sense based on the differences between 5764 which as far as I can find out did not get ATC and 4566 / 7714 which did. Hopefully the additional diagram helps as well.

If anyone knows of a pure steam braked engine with this valve I would love to know about it.

On a separate note I don't quite understand why you would want to release the res totally as it would then release the engine brakes and so reduce the braking capability (unless of course they were already locked)

regards

Duncan

 

My understanding was that if the loco wheels locked up when braking hard, using the reservoir release valve to over-ride the setter meant that they could be released without releasing the vacuum brakes on the train, and then re-applied using the direct steam supply controlled by the application handle rather than the setter.

If the reservoir could not be released, then the only way to ease the loco brakes would be to re-create vacuum which you would not want to do if trying to stop as quickly as possible.

(I seem to recall a RAIB report into a level crossing colliion on the Dean Forest mentioning that the driver in the cab of the Auto-Coach, having applied the vacuum on the train using his application valve, had no way of easing the loco brakes, relying instead on an experienced Fierman releasing the reservoir and using the loco's application valve to make a graduated application.)

 

Only if the brake handle is in the running position or apply a small amount of air into the trainpipe.

With the brake handle fully in the on position, steam is supplied to valve E in addition to valve D (which is always supplied steam). Steam will therefore be supplied to the brake cylinder with either valve D open (setter valve in the lower position), or valve E open (setter valve in the upper position). Valve E supplies more steam than valve D, thus increasing the brake force. The setter valve moves to the upper position, only if the res is equal to (or lower) than the train pipe.

Stephen

 

Correct if the brake valve is in the running (vertical) position.

By opening the reservoir release valve - the setter valve moves into the upper position, shutting valve D and thus (with the brake valve in the running position) stopping steam passing to the brake cylinder(s).

Stephen

 

Yes, that's right in terms of its use. Thanks for the suggestion on the fitting of ATC to the difference on where the res release is. Now the remaining part is, is there any steam braked engine with the original release valve G?

 

Can anyone help with a cutaway or schematic drawing and description of this GWR brake valve, other than the ones posted above? I'm doing a presentation on vacuum brakes at the W/E and would like to include this in it. None of my reference books have any info.

 

These two Swindon Engineering Society lectures might be of use...

Railway Brakes - Feb 1894 which includes a drawing of the valve, &

Brakes for Modern Express Passenger Trains - Feb 1921 which doesn't.

I have another article from around 1902 which has a drawing, but like the 1894 lecture, relates to the Dean brake cylinder. PM me if you want a copy of that.

Pete S.

 

Thanks. That's great.