Niels

A King had four 16.25 inches cylinder stroking 26 inches fed by 225 psi and had 78 inch drivers. Substitute with 250 psi,60 inch drivers needs two 21.5 inch dia cylinders stroking 30 inches. This is very close to the two times rebored LMS Crab that had cylinders six feet eigth apart.

The ground rules for my imaginary ,late pre,early post WW2 UK universal 2-6-0 locomotives are : Driver diameter 5 feet (like 9f that did 90 mph everyday) Wide steel firebox 250 psi (round topped outher shell) Frames can then be 2 inches closer together without catastrophic concequence for narrow grate dimensioning. Boiler can be pushed sideways for mass balance. Stays of wide fireboxes over wheels are easy to inspect and repair. First driverset can then can move an inch each side. Let us start to se if we can substitute a GWR King and use say up to 18% less steam. If,then all future 4-6-0 were unnessecary.

Let us try to make the two cylinder compound 2-6-0 scheme work witin the LMS loading gauge. The single outside high pressure cylinder wil be moved forward so that no conflict between croshead and coupling pin can occur with 3 feet four from centre plane to cylinder centre. This gives us easily the requested side freedom for front driver of one inch each side to make a Krauss-Helmholtz or Zara truck possible. It takes 7-8 inch forward placing of cylinder. The LMS crabs had 21 inch dia cylinders placed 3feet 4 inches out ,lifted so high that they cleared the platform edge corner. So do we with the single outside high pressure cylinder. What shall we try to substitute? B1,B12 orB16?

They ran very close to limit

The front drivers on the WD 2-10-0 had a quarter inch play to each side and the 19 inch diameter cylinders were 6 feet 7.875inch apart.

4-6-0s went out of fasion in most of Europe around 1925 and new builds were something with Krauss Helmholtz or Zara trucks up front. The P10 or Baureihe 39 did 138 kmh on level track when tested by police in 1925 or there around. More than 200 were built that worked to end of steam,and had KH up front. The P2 had Gresley patented swing link pony truck and was clearly not the way to do it. I wonder why not a single UK locomotive used it and think it has something to do with the loading gauge. On continental KH locomotives , first driver is allowed a 1 inch moving freedom to each side in collaboration with the leading small wheel that can move more. Then crosshead pin is very close longitudinally to the leading coupling pin that shall not smash croshead slides or worse when being 1 inch out of line. It is an interesting thougth if the myriad of UK two cylider 4-6-0 had not been cheaper and just as usefull if built as two cylinder compounds 2-6-0s with extra balancing? The LMS crab was not a mile of performance -wise relative to black fives (I have read somewhere)

A cheap way to test if it works is to borrow a scrapworthy Schools class and weld up two new cylinders. A LNWR George the Fifth will also be possible or a Modified Hall plus crankshaft parts from a Castle.

Let me calculate how big cylinders we need for the 9F modified and P2 mutilated using the numbers from Chapelon 242 Three Cylinder Compound The outside 242 low pressure cylinders were 270 litres. Adhesive mass 84 tons and ours are 66 tons 242 drivers was 1950mm and ours are 1890 and 1520mm 9F as threecylinder compound needs low pressure cylinders of 165 litre P2 modified ditto needs 200 litre per LP cylinder. Both can have 24 inch outside LP cylinders without harming surroundings and this is met by 27.5(P2) and 22 inch(9F) strokes and make identical piston velocities for same speed over ground.

We need 90 degree between Hp and LP for most even pull. The uncylindered side pin can be inline or opposite the LP pin. This is ideal for the coupling rods ,but not for balancing. Three cylinder locomotives had 120 degrees between out side pins and coupling rods worked well for many locomotives. Let CME and Civil and locomotive union people agree how much hammerblow and fore and aft shuttling can be allowed ,and do the rest by the funny looking conrod thing and pin angling. Some Yawing/swaying couple is ,as proved by Bulleid ,not a dissaster. It is often claimed that LP pistons are much more heavy than HP ditto. Forces are the same and LP piston and rod lives in much colder and nicer temperature

The HP valvery be it piston or poppet moved so far inside as possible The LP cylinder as far from mid-plane as possible Reduce boiler and use saved mass for preheater and put that on ligth side footplate. Move boiler a couple of inches sideway. Bulleid modified a Schools to have no hammerblow and being three cylindered therefore had a rather big yawing couple.Was not changed back. It does not matter much on a long locomotive evidently.

Cox stated that SNCF 141P was worlds most efficient Stephensonian. 76 tons adhesive 1650mm dia drivers 20 bar boiler pressure (like Bulleid pacifics with steel fireboxes) 185 liter high pressure cylinder volume 450 liter low pressure Four cylinder Compound. Rebuild of 9f to 4-8-0 as two cylinder compound can have a single outside 146 litre cylinder or 20/30 inch bore and stroke and a single inside low pressure 355 litre or 30.5 bore and 30 stroke No tunnel or platform interference for the 4-8-0 LNER P2 to pacific rebuild needs 180 litre high pressure and 437 low ditto. 22 inch diameter 30 inch strokefor outside high pressure 33.5 inch and 30 inch for inside low pressure

Four simple cylinders used around 10% more steam than corresponding two simple. Size matters. Two cylinder simples self-destruct at speed .That was Ravens reason for three cylinders at NER. This leaves as sensible configuration three cylinder compound or two cylinder compound with extra balance components. Two cylinder compound with extra balance is almost unproven and interesting so that is what I am dreaming of. The three cylinder compound with 24 inch outside low pressure is not in problems with gauge.

Problem with the two wonder schemes is that cylinder front starts to foul platforms on curves. Raven Pacific had 19 inch cylinders 3 feet 4 from centerplane and ran over NER rails. Fixed wheelbase was comparable to proposals as were cylinderfront distance from first driver. The Raven Pacific and proposals can have 24 inch dia cylinders if placed 3feet1.5 inch from centreplane. The Question of sensible max tractive effort for 66 ton adhessive weigth is more difficult. Blue Peter had factor 3.67 and came to grief slipping. A1/1 was 4 as was Peppercorn A1 Britania 4.23

I do not build models but dream locomotives. Cheaper and easier for my eyes. Ultimate British Pacific versus 4-8- 0 based on modified 9f. Interest is to see how much power considering the smallness of UK loading gauge. Both have drive to first driver and thus of nessecity longer between aft boggie wheel set and first driver. Instead of 5 feet six we need something like 8 feet. The gain is that outside cylinder can have centerline 3 feet 1.5 from midplane by having conrod inside coupling rod. For conrod outside coupling rod 3feet 4 is the smallest I have seen.

Mr Adrian Tester has written a book comparing Lms 4f o-6-0 and Ivatt 2-6-0 and the Ivatts were not best. Very interesting book. ISBN 978 0 9570779 0 4

As I read the drawing it was a single upper wide bar and two lower narrow bars.Still not very much clearance possible between decent size pins

Having croshead pin and front coupling pin passing each other,very closely, two times per rev gave Webb problems on 0-8-0 compounds

B16/1 rebuild The picture above was made to explain how i would rebuild B16.The 18.5 inch outside cylinders were 6feet 8 apart and used on both B16 4-6-0 and T3 0-8-0 as was also the boilers. If we put the remaining outside conrod inside the coupling rod we can increase diameter 5 inch that is having a 23.5 inch cylinder acting on high pressue and give more tractive effort than a King. Overkill so 20 inch outside and a 30 inch inside low pressure will be rigth.

All GWR 4-6-0s ,apart from Kings,had same wheelspacing. Take any two cylindered and remove one outside cylinder. Fit first driving set with a single crankthrow a la LMS,LNER, or SR. Put a single low-pressure cylinder where Stars,Castles or Kings had two inside cylinders. Put a balancer connecting rod on outside without cylinder. This gives around 10 to 18 % more power for same amount of steam and a more even pulling force than the fourcylindered GWR locos and almost perfect longitudinal balance without hammerblow. The picture shows a B16 rebuild but on GWR the connecting rod will go from high pressure,outside crosshead to second driver

Most british outside cylinders where sitting 6 feet 8 apart and driving on to secord or third driver. If You drive unto first driver they can sit 6 feet 3 apart as on the LMS 4-4-0 compound. Many british second or third driver locomotives had outside cylinders bigger than 17,25 inch. Problem is greater throwout on curves . It is not really good to have connecting rods shorter than 6-7 feet.

Is this a Trethivic thing from Egypt? An interesting way of extracting last heat from smoke like in a Franco-Crosti,where it did not really work either

Because its a reason for feeling shame being danish. https://www.jernbanen.dk/Fotos/Damp/DSB_E975_1942.jpg https://www.jernbanen.dk/artikler.php?artno=27 They were designed 1914for the Swedish mainline between Stockholm and Gothenborg. 1938 they were sold as surplus(very cheap) to Denmark due to electrification in Sweden. They wee so well liked here and during the war it was decided to build 25 more to the original drawings. They were used until early 70ies Chapelon? Never heard about it. They have one common glider for both high and low pressure on one side and the most crooked ports foundry could make. They were lovely to look at. One of my most cherished boyhood memories was about 1955(10 years old) An uncle was chief engineer on a small daily boat from Copenhagen sailing under the Little belt Bridge http://billedarkiv.mfs.dk/fotoweb/cache/5001/archive/Arkiv-97/000028316.t480c6a93.m800.xBQjpEDH6.jpg and two trains with class E pacicifs(in Denmark) crossed slowly mid bridge in sunshine. Lillebaelt Sans Es They could have been build as three-cylinde compounds and being worlds best

Talbot on page 246 repeats the Nock Precursor nonsense of Whale being ordered to make it a mixture of Jumbo and Caulifloors. Whale used the Alfred the Great class as model.No outside cylinders,bigger boiler and better cab. He later modified some of the Alfreds this way but stopped when they were not asked to run fast. At slow speed a compound is often more frugal than a simple.

Mr Nock was responsible for a lot of words. His stories about Whale making locomotives look suspect to my eyes. In Edward Talbots book page 199 there is a weigth diagram signed by Whale august 05 showing Bill Bailey. First picture of Whale experiment was taken june 05.They knew each other. For my eyes it is evident that Experiments were streched Bill Baileys. Remove outside cylinders(This removes more than half the load on the inside Joy gear.It must have been extremely troublesome at speed and Whale was responsible for maintenance). The geometry between inside cylinders and crankshaft and boggie is almost unchanged. Six feet drivers is better than five on a two cylinder locomotive going fast so the plain driver shafts have to be put a little aft.The saved mass can be used for a bigger boiler and that is a nice thing. Experiments were not rebuilds but family.

Trains are long things and air resistance comes from total air-wetted areas.The DSB environment boss once stated that fuel consumption per unit was unchanged wheter one ,two or three were coupled up. The main air restance from steam locomotives comes from driver spokes when going fast. Streamline locomotives below 75mph are marketing stunts making maintenance difficult.