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PatriotClass

Two Cylinder inside Engines of the LNWR

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Hello Everybody,

Hope you all are doing fine!

I am just 3D modelling the LNWR Prince of Wales and the Experimental. These engines have like many others of this time a two cylinder mechanism mounted inside the frame. I would like to try to model the inside working mechanism.

Now the photographers of this time were not interested in picturing a locomotive from below or catching some inside details. Thanks to Mr Essery's book of the Claughton class I have there a scale drawing of an inside drive - okay, this is a four cylinder but it should be similiar.

The first driver axle is a crankshaft with the two actuating rods. This is clearly visible on the drawing. The valve gearing of the Claughton - if it's not a Caprotti - is outside (Walshaerts-System?), so the inner cylinders are compound..

Now the question: Where is the valve gear of a two cylinder inside engine like the Prince of Whales? Is it connected to the crankshaft too? So does it have four rods linked to the shaft?

I searched on Google, but due to my not so good English I might using wrong words... :huh:

 

As I visited the City of Truro at Swindon, I actually examined this fantastic engine from below, but I can't remember, how the valve gear is working there.

 

Have a nice day

Chris

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The Prince of Wales and experiment 4-6-0s had two inside cylinders with Joy valve gear. This involved a two throw crankshaft for the connecting rods but the valve gear was all driven from a pin joint mid way along the connecting rod. Four of the Princes (known as "Tishies") were later fitted with Walschaerts valve gear outside the wheels but the cylinders remained inside.

look up Joy valve gear for a description of this gear.

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Joy's gear was widely used on the LNWR (and L&YR) and was also use on the 0-8-0s. You might find phtos of it on the preserved Super D.

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If you can get hold of a copy of Edward Talbot's "An Illustrated History of LNWR Engines"  (OPC 1985, ISBN 0-86093-209-5) there is a general arrangement drawing of a George the 5th from which, although a bit faint, you should be able to copy the details.

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Posted (edited)
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If you can get hold of a copy of Edward Talbot's "An Illustrated History of LNWR Engines"

Thanks for this hint. I just cought one on Ebay.uk!

 

Great links! Thank you, PenrithBeacon :pleasantry:

 

And... does anybody know, where  the Prince of Wales Class has the crankshaft axle? At the first( frontal) driving wheel set or the second one?

Edited by PatriotClass

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23 hours ago, eastglosmog said:

If you can get hold of a copy of Edward Talbot's "An Illustrated History of LNWR Engines"  (OPC 1985, ISBN 0-86093-209-5) there is a general arrangement drawing of a George the 5th from which, although a bit faint, you should be able to copy the details.

Better still, if you can find one, is Edward Talbot's self-published "Eight-coupled Goods Engines" ISBN 0-9542787-0-4 with a selection of photos taken by Peter Ward in 1952 of the under-gubbins of another G1 49151 taken in 1952, together with clearer GA drawings of various classes, which are much clearer to read.

He also notes:

"The 'G1' class originally had an indirect-action form of Joy valve gear similar to that fitted on the 'Prince of Wales' class. This was found to suffer from excessive wear and to counteract this a modified form with direct action was produced for the 'Princes' in 1920.  When this had been shown to have overcome the problem, some 'G1' class were similarly altered.  The valve travel was reduced to about 4½in by the change. This in turn made the gear slightly less efficient, as the valve no longer moved more quickly during opening and closing of the ports, which is a key feature of the efficiency of the Joy gear.The travel could only have been increased by making the Joy yoke more inclined and that would have increased the pressure on the guides and all the pins too, including the jack link in the connecting rod. (The jack link is also known as the 'prop' link or, in workshop jargon, the 'connecting' link.) Clearly this was undesirable, as the purpose of the alteration was to reduce the wear on the pins. The 4-6-2 tanks had direct motion from new and so were designed appropriately, as were the 'G2s ' later. Engines of the 'G1' class with this modification were then said to have 'strengthened motion' but the term more properly applied to the 'G2' class."

There is a helpful drawing in the book which illustrates the differences:

740275765_lnwrjoygear1.jpg.dfce90bc92a11dc094dce4f58bbeb7a3.jpg

I have to admit that valve gear is a complete mystery to me, especially when inside, but the diagram does clearly show how the direct form eliminates three bearings, and you can only wonder why Joy didn't do it that way in the first place; perhaps he did but discovered the benefits of the indirect?

I tried looking up the different types of inside valve gear in Ahrons' comprehensive guide, but, very helpfully, for both the Allan and Joy designs he merely says words to the effect that "These are so familiar that it is unnecessary to describe them" and his description of Stephenson's is so brief it is no help either.

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The indirect drive reverses the direction of travel of the valve spindle, necessary on whether you have inside or outside admission, which itself is mostly a result of using piston or slide valves.

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33 minutes ago, LMS2968 said:

The indirect drive reverses the direction of travel of the valve spindle, necessary on whether you have inside or outside admission, which itself is mostly a result of using piston or slide valves.

I don't think it does, as the position of the pivot at the top reverses the motion again to correct it.

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On 29/07/2020 at 23:21, Michael Edge said:

Four of the Princes (known as "Tishies") were later fitted with Walschaerts valve gear outside the wheels but the cylinders remained inside.

That's interesting! What was the reason for this? Is there an advantage using Walschaerts instead of Joys? Did the LMS keep these engines in service?

 

Hope, Edward Talbot has some pictures of these engines in his book. If I succeed in my project modelling a PoW with a 3D printer, a Tishie would be a nice variation on the layout, 

 

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They were not exactly pretty things:

The problem with Joy's gear was that the connecting rod was weakened where the link pin passed through its centre. In the early days, this wasn't a problem but became an increasing one as locos became ever more powerfull, placing greater stresses on the rods.

 

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Two of the Tishies were converted in LMS days (1924) and two of the five survived into WWII (one was re-instated after being withdrawn).  As @LMS2968 says, Joy's gear created a connecting rod weakness and this led to the the experiments with Walschearts valve gear A powerful superheated 4-6-0 was pushing the limits of Joy valve gear, although metallurgic issues were also found in some of the failures.  Further conversions might have been carried out, but weakness was found in the frames that made significant work to improve the locos uneconomic.  With the development of the Moguls and then the Black 5s traffic needs were beginning to be met without the expense of trying to improve a 15 year old design.  They probably would all have gone earlier if WW2 hadn't forced a swansong.

 

Alan

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19 hours ago, PatriotClass said:

....................

 

Hope, Edward Talbot has some pictures of these engines in his book. If I succeed in my project modelling a PoW with a 3D printer, a Tishie would be a nice variation on the layout, 

 

Yes he does - there is even a drawing of one.

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23 hours ago, LMS2968 said:

They were not exactly pretty things:

The problem with Joy's gear was that the connecting rod was weakened where the link pin passed through its centre. In the early days, this wasn't a problem but became an increasing one as locos became ever more powerfull, placing greater stresses on the rods.

 

Designing a connecting rod to cope with higher piston forces is not in itself a problem, but managing the trade off between strength and weight, especially when it is both reciprocating and partially unsprung is. At some point the law of diminishing returns sets in, earlier if there are more practical solutions.

 

Jim

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