GWR valve gear

[hayfield]

GWR modellers do seem to have it easy with the valve gear being basic, when the other companies and BR seemed to use a more complicated version like the Walschaerts for example.

 

Can someone please enlighten me why this was   

[EddieB]

Cylinders on the outside, valve gear on the inside.

 

Edit: Here's a rather clever animation showing some of the complexity.  Of course, GWR locomotives were designed with future generations of modellers in mind - even though they were pigs to maintain.  Imagine having to oil, let alone work in the confined spaces between the frames!

 

Edited September 21, 2018 by EddieB

[The Stationmaster]

GWR modellers do seem to have it easy with the valve gear being basic, when the other companies and BR seemed to use a more complicated version like the Walschaerts for example.

 

Can someone please enlighten me why this was   

 

I don't think lots of western Enginemen would regard Great Western walschaerts valvegear as 'basic' as ii took a lot of time, and some gymnastics to oil - just imagine having to climb up among that lot from a pit underneath the engine.  Many older, and less agile, Drivers would get a Fireman to do the oiling - often with a sixpence left on the eccentric straps as a check that certain parts had been reached.  At a couple of depots (Tyseley and Old Oak), and possibly more, post war conditions saw another method of oiling which consisted of throwing a bucket of oil in between the frames in order to save time and avoid the gymnastics.

 

However in comparison with Churchward's 'scissors' valvegear there is written evidence that Enginemen must have regarded Walschaerts gear as an improvement - the 'scissors' gear was 'very unpopular' (to put it politely) and there were repeated requests from staff reps to get rid of it.

[LMS2968]

It should be pointed out that the GWR two-cylinder locos all used Stephenson's ('scissors') gear, it was only the four-cylinder types which used Walschaerts. The outside valves were driven by rocking shafts of one form or another.

[OFFTHE RAILS]

GWR modellers do seem to have it easy with the valve gear being basic, when the other companies and BR seemed to use a more complicated version like the Walschaerts for example.

 

Can someone please enlighten me why this was   

Easy. The Stephensons valve gear on GWR 2 cylinder  locos (Saints Halls Granges Manors 28xx Prairies etc) is between the frames on the real locos and therefore not visible so therefore not modelled in RTR locos.

The "motion" parts that do appear on these locos are coupling rods, connecting rods, crossheads, slide bars and piston rods, NOT valve gear - whatever any parts suppliers may state.

 

 

 

 

 

 

 

 

 rods

[OFFTHE RAILS]

It should be pointed out that the GWR two-cylinder locos all used Stephenson's ('scissors') gear, it was only the four-cylinder types which used Walschaerts. The outside valves were driven by rocking shafts of one form or another.

No. The "scissors" valve gear was not Stephensons. It was a version of Walschearts valve gear between the frames and was only used on the prototype GWR #40/4000 "North Star" .It was not used on further GWR locos as (a) it was found to be difficult to be set up and (b) Deeley the MR CME inferred  he had patented such a design

[hayfield]

Thanks for the information, I thought the inside valve gear was just for the inside cylinders. Very thoughtful for us modellers putting it out of view

[LMS2968]

No. The "scissors" valve gear was not Stephensons. It was a version of Walschearts valve gear between the frames and was only used on the prototype GWR #40/4000 "North Star" .It was not used on further GWR locos as (a) it was found to be difficult to be set up and (b) Deeley the MR CME inferred  he had patented such a design

While not arguing, I have heard the Stepphenson's gear referred to as 'scissors', rightly or wrongly, and the reference to BR suggests a period long after North Star's time. Perhaps what I heard referred to Deeley's version. It was a long time ago!

[jim.snowdon]

 However in comparison with Churchward's 'scissors' valvegear there is written evidence that Enginemen must have regarded Walschaerts gear as an improvement - the 'scissors' gear was 'very unpopular' (to put it politely) and there were repeated requests from staff reps to get rid of it.[/i]

The "scissors" gear was only ever fitted to North Star and, apart from the issues over patent challenges from Derby, a critical, and acknowledged, disadvantage was that if there was a fault that necessitated isolating the valve gear on one side of the engine, it disabled the other side as well. On the production versions of the Stars and Castles, the final section of the reversing shaft was split so that the left and right sides of the engine could be isolated independently.

 

The inside motion of the four cylinder locomotives was by repute difficult to get at, something that Churchward and the design office seemed reluctant to do anything about. Certainly, Churchward seems to have had a positive dislike of outside valve gear, partly on account of concerns over being able to design adequately strong components within the limits of gauge clearance. Bear in mind that although other designers did it, Churchward does seem to have indulged in somewhat conservative engineering, although without the modern conveniences of computers, that was probably sensible.

 

Jim

[The Stationmaster]

The "scissors" gear was only ever fitted to North Star and, apart from the issues over patent challenges from Derby, a critical, and acknowledged, disadvantage was that if there was a fault that necessitated isolating the valve gear on one side of the engine, it disabled the other side as well. On the production versions of the Stars and Castles, the final section of the reversing shaft was split so that the left and right sides of the engine could be isolated independently.

 

The inside motion of the four cylinder locomotives was by repute difficult to get at, something that Churchward and the design office seemed reluctant to do anything about. Certainly, Churchward seems to have had a positive dislike of outside valve gear, partly on account of concerns over being able to design adequately strong components within the limits of gauge clearance. Bear in mind that although other designers did it, Churchward does seem to have indulged in somewhat conservative engineering, although without the modern conveniences of computers, that was probably sensible.

 

Jim

 

One of Churchward's reasons for going for inside valvegear was that it generally allowed space for larger and more robust bearings on some important parts (hence the 'finding' that it could still be reliable if oiled by throwing in a bucketful of oil).  However lest we forget two cylinder engines preceded 4 cylinder designs from the Swindon Drawing Office and inside Stephenson valvegear makes it simpler to arrange the necessary eccentrics between the frames than outside them (just look at a picture of the Black 5 with outside Stephenson gear).   Churchward was starting in any case from an inside valvegear arrangement on his large engines and all that was essential was finding a method to drive the valves of the outside cylinders from valvegear that was placed between the frames although his initial approach of using an arrangement based on Sievert's design was not a success.  

 

More in my post (29) in this thread - 

 

http://www.rmweb.co.uk/community/index.php?/topic/83925-the-reversing-rod-on-north-star-4-4-2/page-2 

Edited September 22, 2018 by The Stationmaster

[The Johnster]

I am finding this thread very informative; thanks, everyone!

[62613]

One of Churchward's reasons for going for inside valvegear was that it generally allowed space for larger and more robust bearings on some important parts (hence the 'finding' that it could still be reliable if oiled by throwing in a bucketful of oil).  However lest we forget two cylinder engines preceded 4 cylinder designs from the Swindon Drawing Office and inside Stephenson valvegear makes it simpler to arrange the necessary eccentrics between the frames than outside them (just look at a picture of the Black 5 with outside Stephenson gear).   Churchward was starting in any case from an inside valvegear arrangement on his large engines and all that was essential was finding a method to drive the valves of the outside cylinders from valvegear that was placed between the frames although his initial approach of using an arrangement based on Sievert's design was not a success.  

 

More in my post (29) in this thread - 

 

http://www.rmweb.co.uk/community/index.php?/topic/83925-the-reversing-rod-on-north-star-4-4-2/page-2 

There are a few pages, with a side elevation, in the book  Midland Steam by Professor Tuplin, which describe the Stevaert valve gear as fitted to the '990' class, and there is also a mention of the patent disputes.

[jim.snowdon]

There are a few pages, with a side elevation, in the book  Midland Steam by Professor Tuplin, which describe the Stevaert valve gear as fitted to the '990' class, and there is also a mention of the patent disputes.

And a good isometric drawing of the Swindon version, from memory, in O S Nock's "Stars, Castles & Kings", as well as some words about why it ended up not being perpetuated.

 

Jim

[Coach bogie]

It should be pointed out that the GWR two-cylinder locos all used Stephenson's ('scissors') gear, it was only the four-cylinder types which used Walschaerts. The outside valves were driven by rocking shafts of one form or another.

Except 4000 North Star which built with Scissors. Replaced later.

 

Mike Wiltshire

[jim.snowdon]

Except 4000 North Star which built with Scissors. Replaced later.Mike Wiltshire

And the (much later) Hawkesworth 15xx, but then, he was arguably the first GWR CME to move forward from Churchward's design tenets. So did Stanier, albeit once he had achieved independence from the GWR by going to the LMS. When his team designed the Coronations, they did the sensible thing and put the valve gear on the outside and transferred the motion to the inside.

 

Jim

[Wickham Green]

And the (much later) Hawkesworth 15xx, but then, he was arguably the first GWR CME to move forward from Churchward's design tenets. So did Stanier, albeit once he had achieved independence from the GWR by going to the LMS. When his team designed the Coronations, they did the sensible thing and put the valve gear on the outside and transferred the motion to the inside.

 

Jim

............. which Holcroft and Gresley had been doing for years - albeit on three-cylinder locos.

[The Stationmaster]

Interesting this black 5 is reputed to be the strongest of all the black 5's.

 

In theory it should be the strongest in starting away and at low speeds because of the nature of Stephenson valvegear.  No doubt one of the reasons for the enduring popularity of that valvegear in British designed 2 cylinder engines - don't forget that inside cylinder engines using it were built by BR as late as 1955.