Power Reversers

[darwins]

I am trying to find out more about power reversers used on steam locomotives in UK, if anyone can point towards diagrams and explanations, particularly of how the controls were operated by the driver, I would be grateful.

So far I have been made aware of three main variations, two of which are described briefly in Hodgson's book on locomotive management.

1. James Stirling's "steam and cataract" steam reverser. First used on GSWR in 1873, later used on SER, SECR, SR, and also on NER and GCR.
The driver had two controls, the mini reversing lever and also a combined steam and cataract valve (rotary). How were these used to adjust the cut-off?

2. Drummond's steam reverser. First used by Dugald Drummond in 1903 on LSWR. Was this the same as the steam reverser introduced by Peter Drummond on the Highland Railway in 1900?
There is a brief description of operation here: https://janfordsworld.blogspot.com/2017/09/on-footplate-drummond-t9.html
Does anyone know more of how this one works?

3. GER compressed air assisted reverser. When was this introduced? Which locos were fitted with this? Hodgson says the controls could be used manually or power assisted. Was there any difference in the way that the controls were used between manual operation and power assisted operation?

 

[Rescars]

D L Smith in his "Locomotives of the Glasgow and South Western Railway" records this "newly invented" gear being fitted to five of Stirling's 6 class 4-4-0s and ultimately all of Stirling's 221 class 0-4-2s. Some of the 221s were built with screw reversers, but were converted later - which suggests the system was efficient and effective. Although he has much to say about the allocations and workings of these locos (including the use of the 221s on passenger trains despite the lack of any continuous brake!), sadly he says nothing about how the reversing gear operated. Smith of all people should have had some anecdotes.

In regard to the GER, this is just a guess, but a power reverser seems likely to have been the work of James Holden. His work with oil firing (Petrolea) and steam out-accelerating electric traction (Decapod) prove he had no fear of innovation. Power reversers might have had a particular appeal in operating the intensive suburban services from Liverpool Street. Holden was in office between 1885 and 1907. Compressed air would have been readily available as the GER used the Westinghouse brake.

 

[Taunton]

USA quite commonly used compressed air reversers as well. Obviously more practical on a locomotive with air brakes (like the GER) than vacuum.

The trouble with power reversers is they tend to "leak off", and the setting slowly moves away from that intended, especially when worn, such that the driver has to pay attention and periodically apply small movements of the control to keep it set as required. They also need power available in the first place, so are a nuisance on shed when boiler pressure has been allowed to fall away.

 

[Rescars]

With regard to James Stirling's "steam and cataract" steam reverser, it seems likely that the cataract gave a finesse to the control which could not have been achieved with steam alone. In this context it seems probable that the "cataract valve" was some variety of dashpot or damper (as opposed to the type of cataract valve used to control the time interval between the working strokes on a Cornish beam engine). Presumably the mini reversing lever set the cut-off required and the steam provided the power (suitably damped) to adjust the valve gear accordingly.

 

[D Williams]

I was told by an ex BR driver that the steam reverser on the West countries was as reliable as the proverbial baby's' backside to the extent that most drivers wouldn't attempt to vary the cutoff once set. When this was attempted it wasn't unknown for it to move into the reverse position , which livened up things when working stone trains from Meldon. It is likely that the early applications ( Stirling and Holden) were to locos fitted with slide valves which require a great deal of effort to adjust the gear setting when the regulator is open. With a lever reverse this is difficult and ill-advised (as well as life-threatening). A screw reverser solves this problem but wouldn't be popular if the loco was required to make frequent changes of direction eg shunting. Piston valves are balanced and require far less force to be driven by the valve gear and hence are much easier to move from front to back position or to adjust the cutoff. So, freight locos ( on the GWR) usually had lever reverse and passenger screw . Why OVSB decided to fit power reverse to his brain children must remain one of life's mysteries.