GWR 1930 Vacuum brakes

[GWR_Modeller]

Hi All,

Regarding gwr vans with vacuum brakes in the 1930s.  I understand that the vacuum is generated at the engine and is connected to the vacuum cylnders of fitted wagons by a pipe and the presence of the vacuum pulled off the van brakes.  The driver applied the brakes by allowing air to enter the system, this removed the vacuum and the piston in the cylinder applied the brakes.  In a simple way is this accurate? Was there some spring in the cylinder which pushed the brakes on?

So if a fitted wagon was in a siding not connected would the vacuum brake be on?  How was a wagon shunted if the brake was on?  Was there a lever or handle to disable the vacuum brake?

And presumably hand brakes were independant, albeit using the same brake blocks, and they stayed on even when the vacuum pipe was connected?

Regards, Paul

[Danemouth]

Good question Paul, I've often wondered the same.

 

I look forward to the answer!

 

Dave

[Miss Prism]

https://www.southdevonrailwayassociation.org/Brake-Cylinder.html

 

[Wickham Green]

..... or put simply, creating a vacuum in the train pipe removes air from BOTH sides of the piston but - because of the non-return valve - destroying the train pipe vacuum only allows air back beneath the piston and it's that imbalance that applies the brakes.

[GWR_Modeller]

Thanks Miss Prism, good link that explains things.  So when the van is seperated, even by accident, the vacuum on the other side of the cylinder remains and the brake is on because the pipe side has normal air pressure.  So to shunt the van the cord marked by the star on the underframe has to be pulled to release the vacuum and the brake (I had wondered what that was for).  Then the manual brake has to be applied to hold the van in place later on.  So if shunting, say, parcels vans would it take long to reestablish the vacuum afterwards.  Or would it be quicker for the pilot to attach the vacuum pipe before shunting?

 

More thoughts - did coaching stock have manual brakes? Fitted goods, Fruits, horseboxes etc had visible manual brake handles but I do not recollect seeing them on coaches?  

Could all locomotives generate a vacuum for brakes?

[LMS2968]

The vacuum brake would not be in use for a normal shunt move in sidings, it might be different within a station. It took time to create the vacuum to release the brake - time varying with the number of vehicles - and it took time to apply the brake once moving, as well as the inconvenience of bagging all the vehicles when coupling and uncoupling. Transferring coaches from one train to another within a station would generally involve using the vacuum brake, mandatory if passengers were aboard.

 

With passenger vehicles, only the brake coaches would have a hand brake. If there was a need to secure an ordinary coach, this would be done by using scotches.

 

Not all locos were fitted for working vacuum fitted trains. It became more common over the course of the twentieth century but many goods engines were not so equipped, especially those usually given to mineral train working, and many shunters were devoid also. Even the common LMS 'Jinty' 0-6-0T came as two types, either vacuum fitted or steam brake only.

[GWR_Modeller]

Hi LMS, what is bagging? PAUL

 

[balders]

5 minutes ago, GWR_Modeller said:

Hi LMS, what is bagging? PAUL

 

The process of connecting the relevant pipes (vacuum, steam etc)

 

Regards

 

Guy 

[LMS2968]

Hoses on the railway were generally referred to as 'bags'. This included the large ones at water columns, and taking water was called 'putting the bag in'.

[K14]

Further reading:—

 

Swindon Engineering Society Lectures:—

P_018 Railway Brakes - Feb 1894.pdf

P_127 Brakes for Modern Express Passenger Trains – Feb. 1921.pdf

P_145 Brakes for Long Goods Trains – Nov. 1924.pdf

 

The "Dean Dustbin":—

Description of and Instructions for Working the Continuous Automatic Vacuum Brake – Feb. 1883.pdf

Original Scan

 

The BR Handbook:—

Handbook For Railway Steam Locomotive Enginemen - 1957

 

Pete S.

 

[Blandford1969]

The best way to think about it is that our vaccum cylinder has two sides to it above the piston is called the reservoir and below it is the train pipe. When we create vaccum on the engine we do this by sending steam down a converging cone which causes it to increase in speed. This then causes a drop in air pressure beyond the end of the jet and like water the air pressure in the pipe which is a higher pressure moves towards the cone and is then ejected through the chimney. You can hear the ejector when it is working. 

 

With the vacuum brake cylinder when we are removing air pressure from our train pipe which connects all of the cylinders together the air pressure is removed from both sides of our piston. In coaches and waggons fitted this is, as has already been said due to the non return valve opening to allow air pressure to come out of both sides. However once we stop ejecting the non return valve closes. In an engine cylinder there is an india rubber ring which is pulled in when ejecting which allows air pressure to be removed from both sides of our piston, this expands again when the ejector is closed. 

 

Because we have lowered the air pressure below and above our piston, gravity takes over and our brake piston falls under its effect. 

 

When we put the brake on we allow air pressure to travel down the train pipe it can only go to the bottom of the pistons (train pipe side). We now have a higher vacuum above the piston than below it. With the increase in air pressure below it is this which pushes our piston up and applies the brake.

 

In terms of wagons, as most have said few waggons were vacuum fitted at that time, most just having hand brakes. If it was vacuum fitted depending on how long it had stood the vacuum would probably have bled off . Any crew would connect the bags and blow up. If there were only a couple of vans it would only be a few seconds to create. 

 

In 1930 there were certainly pannier tanks which were not fitted with vacuum and just had a steam brake. As already said for speed though for many shunting moves the vacuum would not be used with wagons and vans where fitted as it takes longer to bag up and also take them apart.

 

 

[The Johnster]

4 hours ago, Blandford1969 said:

 

Because we have lowered the air pressure below and above our piston, gravity takes over and our brake piston falls under its effect. 

Which satisfies a requirement of all railway safety equipment in that it is 'fail safe'. 

[jim.snowdon]

7 hours ago, The Johnster said:

Which satisfies a requirement of all railway safety equipment in that it is 'fail safe'. 

Actually, no. The original statement has been taken out of context, and is referring to what happens when the vacuum is equalised above and below the piston in the brake cylinder, at which point the brake releases. 

 

When end the vacuum in the brake pipe is reduced, the piston in the brake cylinder is lifted, pulling the brake on. It isn't fail safe, but it does apply automatically, which was the requirement of the 1889 Regulation of Railways Act.

 

Jim

[The Johnster]

18 hours ago, Blandford1969 said:

The best way to think about it is that our vaccum cylinder has two sides to it above the piston is called the reservoir and below it is the train pipe. When we create vaccum on the engine we do this by sending steam down a converging cone which causes it to increase in speed. This then causes a drop in air pressure beyond the end of the jet and like water the air pressure in the pipe which is a higher pressure moves towards the cone and is then ejected through the chimney. You can hear the ejector when it is working. 

 

With the vacuum brake cylinder when we are removing air pressure from our train pipe which connects all of the cylinders together the air pressure is removed from both sides of our piston. In coaches and waggons fitted this is, as has already been said due to the non return valve opening to allow air pressure to come out of both sides. However once we stop ejecting the non return valve closes. In an engine cylinder there is an india rubber ring which is pulled in when ejecting which allows air pressure to be removed from both sides of our piston, this expands again when the ejector is closed. 

 

Because we have lowered the air pressure below and above our piston, gravity takes over and our brake piston falls under its effect. 

 

When we put the brake on we allow air pressure to travel down the train pipe it can only go to the bottom of the pistons (train pipe side). We now have a higher vacuum above the piston than below it. With the increase in air pressure below it is this which pushes our piston up and applies the brake.

 

In terms of wagons, as most have said few waggons were vacuum fitted at that time, most just having hand brakes. If it was vacuum fitted depending on how long it had stood the vacuum would probably have bled off . Any crew would connect the bags and blow up. If there were only a couple of vans it would only be a few seconds to create. 

 

In 1930 there were certainly pannier tanks which were not fitted with vacuum and just had a steam brake. As already said for speed though for many shunting moves the vacuum would not be used with wagons and vans where fitted as it takes longer to bag up and also take them apart.

 

 

The GW was of the general opinion that all the locos should, if required, be able to haul any of the trains, so fitted vacuum brakes as standard; there may well have been panniers that spent their whole lives on yard pilot work that never used them.  A variant of the 57xx, the 67xx, was however built with steam brake only for dock shunting (the railway owned the South Wales ports following the grouping), and a further series of 8750, the 6750, with the later cab style was built later for the same purpose.  These locos had coupling rod joints that allowed them to be used on sharper curvature than the 'standard' 57xx/8750s.   

 

The railway also inherited a fair number of locos from constituent and absorbed companies that were not vacuum fitted, and the 'ROD' 2-8-0s were not fitted with vacuum brakes either.  There seems to have been no difficulty finding work for these engines, so by 1930 the policy of all locos being vacuum braked was pretty comprehensively compromised.  

 

A feature of the GW vacuum brake is that it applied on the locomotive as well as the train, though of course all locos had a steam brake as well and the vacuum could be isolated.

[Blandford1969]

6 hours ago, The Johnster said:

The GW was of the general opinion that all the locos should, if required, be able to haul any of the trains, so fitted vacuum brakes as standard; there may well have been panniers that spent their whole lives on yard pilot work that never used them.  A variant of the 57xx, the 67xx, was however built with steam brake only for dock shunting (the railway owned the South Wales ports following the grouping), and a further series of 8750, the 6750, with the later cab style was built later for the same purpose.  These locos had coupling rod joints that allowed them to be used on sharper curvature than the 'standard' 57xx/8750s.   

 

The railway also inherited a fair number of locos from constituent and absorbed companies that were not vacuum fitted, and the 'ROD' 2-8-0s were not fitted with vacuum brakes either.  There seems to have been no difficulty finding work for these engines, so by 1930 the policy of all locos being vacuum braked was pretty comprehensively compromised.  

 

A feature of the GW vacuum brake is that it applied on the locomotive as well as the train, though of course all locos had a steam brake as well and the vacuum could be isolated.

The absorbed classes again have interesting points. Some of the RODs had Dreadnought brakes. On the 56 and 66xx engines due to their shunting duties they were fitted with a separate small ejector for this purpose. I cannot find any preserved example which is fitted with a small ejector, just relying on the pump. Unless anyone knows any different. 

 

[jim.snowdon]

7 hours ago, The Johnster said:

that it applied on the locomotive as well as the train, though of course all locos had a steam brake as well and th

The GWR quite intentionally moved away from steam brakes on locomotives after a rather nasty collision at Slough  and all later locomotives were fitted with vacuum brakes.

 

Jim

[The Stationmaster]

10 hours ago, jim.snowdon said:

The GWR quite intentionally moved away from steam brakes on locomotives after a rather nasty collision at Slough  and all later locomotives were fitted with vacuum brakes.

 

Jim = wit n

Being pedantic not all were subsequently fitted with vacuum brakes - witness the 67XX panniers which were steam brake only.

On 14/11/2019 at 20:54, Blandford1969 said:

 

 As already said for speed though for many shunting moves the vacuum would not be used with wagons and vans where fitted as it takes longer to bag up and also take them apart.

 

 

It doesn't take any time at all to part teh vac pipes when shunting wagons because you don't bother - you just make sure the strings have been pulled and let the pipes part on their own when wagons are split (in, say, a loose shunt).  999 time sout of a 1,000 the pipes will come apart with no trouble, on the 1,00th go you finish up pulling the bag off the standpipe hence the occasional vac bags you used to find lying around in yards. 

Edited November 16, 2019 by The Stationmaster

[57xx]

On 14/11/2019 at 20:03, K14 said:

Further reading:—

 

The "Dean Dustbin":—

Description of and Instructions for Working the Continuous Automatic Vacuum Brake – Feb. 1883.pdf 262.17 kB · 7 downloads

Original Scan

 

 

One thing to note with the Dean version is that the whole cylinder moved up and down to apply/release the brakes, the piston itself was actually fixed in position. 

[DCB]

On models the lack of working brakes is quite a problem when modern RTR stock is used on my less than modern and less then level track.

However I expect some DCC guru to solve this and in the mean time I will experiment with Radio Control gear from really cheap Chinese R/C cars to work a brake on one bogie..

On the Full size "Brake " Coaches could be usefully renamed "Hand Brake Coaches"  as that is what they have, Hand brakes in addition to vacuum or air brakes.

There was a problem with steam brakes is they get worse with reduced boiler pressure and fail completely when the steam pressure fails as in a pipe bursting.

GW Locos had robust tender couplings so the tender handbrake  could stop them in an emergency, BR Std Locos famously had no brakes when the tender was not attached,m and at least one Britannia uncoupled its tender at speed and was very difficult to stop!

Many GW locos on original GW lines worked both passenger and goods during a single duty.  For instance Several Swindon shunters started the day on workmen's trains, shunted during the day and worked workmen's trains again in the evening. Another 57XX appears to have worked Swindon to Chippenham on local passenger, stabled at Chippenham worked the Calne branch the next day passenger and goods and shunting, and returned light to Dauntsey where it banked a freight to Wotton Bassett before returning to Swindon shed.  Quite a day and a half and very different to the shunting duties many other railways used their 0-6-0Ts for.  To quote the Rev W Awdrey's character "Duck"  There are two ways to do things, the Great Western way and the Wrong way. 

[Blandford1969]

1 hour ago, 57xx said:

 

One thing to note with the Dean version is that the whole cylinder moved up and down to apply/release the brakes, the piston itself was actually fixed in position. 

I seem to remember a couple of our coaches on the SVR are still fitted with Dean Cylinders. 

[K14]

59 minutes ago, Blandford1969 said:

I seem to remember a couple of our coaches on the SVR are still fitted with Dean Cylinders. 

 

Not according to the VCT survey - http://www.cs.rhrp.org.uk/se/results.asp

The only contender would be your 'Fruitlet', but that seems to have had its Dean replaced with a standard vac cylinder. The Dean system didn't last long (if at all) under Churchward.

 

You might well have several Churchward-era cylinders, which are distinctive in that the outer casing/reservoir is riveted together, but they work in a conventional manner.

 

Pete S.

[The Johnster]

4 hours ago, 57xx said:

 

One thing to note with the Dean version is that the whole cylinder moved up and down to apply/release the brakes, the piston itself was actually fixed in position. 

A bit like having a stationary lift in a building that moves up and down..

[The Johnster]

3 hours ago, DavidCBroad said:

For instance Several Swindon shunters started the day on workmen's trains, shunted during the day and worked workmen's trains again in the evening.

This was common with South Wales miner's workmen's as well, working as yard pilots or Control Disposal in the interims.

[LMS2968]

12 hours ago, DavidCBroad said:

On models the lack of working brakes is quite a problem when modern RTR stock is used on my less than modern and less then level track.

However I expect some DCC guru to solve this and in the mean time I will experiment with Radio Control gear from really cheap Chinese R/C cars to work a brake on one bogie..

On the Full size "Brake " Coaches could be usefully renamed "Hand Brake Coaches"  as that is what they have, Hand brakes in addition to vacuum or air brakes.

There was a problem with steam brakes is they get worse with reduced boiler pressure and fail completely when the steam pressure fails as in a pipe bursting.

GW Locos had robust tender couplings so the tender handbrake  could stop them in an emergency, BR Std Locos famously had no brakes when the tender was not attached,m and at least one Britannia uncoupled its tender at speed and was very difficult to stop!

Many GW locos on original GW lines worked both passenger and goods during a single duty.  For instance Several Swindon shunters started the day on workmen's trains, shunted during the day and worked workmen's trains again in the evening. Another 57XX appears to have worked Swindon to Chippenham on local passenger, stabled at Chippenham worked the Calne branch the next day passenger and goods and shunting, and returned light to Dauntsey where it banked a freight to Wotton Bassett before returning to Swindon shed.  Quite a day and a half and very different to the shunting duties many other railways used their 0-6-0Ts for.  To quote the Rev W Awdrey's character "Duck"  There are two ways to do things, the Great Western way and the Wrong way. 

All Railways worked its traffic and locos similarly, not just the GWR so little point in claiming superiority there. The steam and vacuum brakes on locos each had their advantages and disadvantages, a much smaller cylinder for steam braking was one.  If you saw the vacuum cylinder on a GWR engine you'd see what I mean: your first problem was finding somewhere to site it  where it would not be in everything else's way and still be effective in operating the linkage.

 

The LNWR used steam brakes on some Super Ds, vacuum on others. Both were pretty awful but the vacuum slightly less so. The problem was a single cylinder to operate all the brakes on both engine and tender. Things were later improved by an independent brake on the tender and two cylinders on the loco. Space constraints meant that these had to be steam. They worked, at least they worked better than the previous system.

 

Tender breakways were hardly a daily occurrence, even with Britannias. It did happen to them but the intermediate drawgear was quickly changed and the problem solved. And by the way, even with its brakes fully applied, it would take a tender alone quite a long way to stop a train.

 

There are two ways to do things, the Great Western way and the alternative. 

[DCB]

4 hours ago, LMS2968 said:

All Railways worked its traffic and locos similarly, not just the GWR so little point in claiming superiority there. The steam and vacuum brakes on locos each had their advantages and disadvantages, a much smaller cylinder for steam braking was one.  If you saw the vacuum cylinder on a GWR engine you'd see what I mean: your first problem was finding somewhere to site it  where it would not be in everything else's way and still be effective in operating the linkage.

 

The LNWR used steam brakes on some Super Ds, vacuum on others. Both were pretty awful but the vacuum slightly less so. The problem was a single cylinder to operate all the brakes on both engine and tender. Things were later improved by an independent brake on the tender and two cylinders on the loco. Space constraints meant that these had to be steam. They worked, at least they worked better than the previous system.

 

Tender breakways were hardly a daily occurrence, even with Britannias. It did happen to them but the intermediate drawgear was quickly changed and the problem solved. And by the way, even with its brakes fully applied, it would take a tender alone quite a long way to stop a train.

 

There are two ways to do things, the Great Western way and the alternative. 

You miss my point, all other railways did not work their trains similarly.   In fact the different ways different railways handled their traffic is a very interesting subject in itself.  Away from the GWR there were many hundreds of  0-6-0 tanks with no train brakes and unbalanced wheels limited to freight and shunting.  Most J72s modelled by Bachmann had no train brakes, many J50, Lima, had unbalanced wheels, the E2 modelled by Hornby (and Thomas) had train brakes and balanced wheels but feeble coal capacity so were restricted to yard work.   The GWR was unusual in that it had large numbers of small vacuum braked tank locos with balanced wheels capable of running at up to 60mph , not just post 1923 but pre 1900 as well.  It also had a fleet of 5ft wheeled, later 5ft 2" Dean Goods and 5ft 6" wheeled Dukes etc for service in the hills of Devon and Cornwall and was well equipped when demand for fast Vacuum braked goods services increased dramatically around 1900.   That demand caught many railways by surprise and they had to use express passenger locos on them, even the latest 4-4-2s and on the GC and NE the latest express 4-6-0s were quickly diverted to express freight work.  The GW met that demand with existing Dean Goods and Duke locos and new build Bulldogs and 43XX  with Halls following in the late 1920s.   I don't think I have ever seen a 4-4-2 on an express goods on a model or a large wheel 4-4-0 except in pictures of "Heckmondwyke"