Realise a proposed British steam engine

I'm sure Holcroft was smart enough to understand the thermodynamics, which is well-founded (and still in use today in industries where there is low-pressure waste steam available, from which more useful work can be extracted).

The difficulty, as with many such designs, was getting the subsidiary machinery needed to work in a relative hostile railway environment: in particular, having removed the effect of blast to create a draft on the fire, you needed a subsidiary smoke-box-mounted fan to create that draft, and which proved the weak point in the scheme.

Tom

 

Could you use some of the exhaust steam to provide draft and condense some so as to increase the range between water stops?

 

Among 4-8-0 designs that I've come across, Chapelon's engines appear to be the only ones designed as express passenger types. All the others seem to be mixed-traffic or freight types with smaller driving wheels. Maunsell on the SR and Beames on the LMS sketched-out (unbuilt) 4-8-0 designs, but both were very definitely for freight work.

2-8-2s were a much more common type with thousands built around the world, but again they were usually for mixed-traffic or freight work. Gresley's P2 was one of a select few types of 2-8-2 intended for express passenger duties.

A J Powell ("Living with London Midland Locomotives") sketched designs attached below for large and small mixed-traffic 2-8-2s, based on the Britannia and Clan boilers, (Apologies if these are already posted on another thread).

 

Cant remember where i got this, but its Powells Heavy fleshed out, the guessed driver spacing is no longer accurate for a 17ft between tubeplates, but it sure looks impressive...

 

WOW! That would be something in scale 1:1!

Thanks a lot for the drawing class8mikado

Knut

 

Well yes, and again no. You cannot use a Krauss-Helmhotz or Zara type front bogie because of limited clearances and we are now aware that the third coupled axle is the one likely to present problems when it comes to the question of the behavior of the locomotive as a vehicle but this design uses the third coupled axle as the driven axle. Welcome to the joys of trying to design within the limits of the less than generous UK loading gauge.

 

Even if it was on 5in gauge ....

There certainly seems to have been more than enough evidence the front pony truck from the 9F was already good for 90mph without the bearings and suspensión being tweaked as would doubtless have been done for a mikado designed for sustained higher speed.

 

Think this was inspired by an off the cuff musing by Riddles himself, interviewed on the occasion of a visit to Loughborough to see the Duke under restoration.
The gist was that the entire range of ' New' Standards ( 8p, 7mt, 6mt, 9f) could have been replaced with a Mikado with 5ft 6 drivers, 20 inch cylinders and caprotti valve gear...
which would move everything at a high average speed. Not to sure about the Geisl...

 

In 1914 (some say 1913) the PLM built its first 2-8-2. There were a number of variations of class 1 001 /141A which included the 141C class and these had 5' 4.96" driving wheels and in total more than 800 were built. Riddles visited Loughborough in 1981 and you have to ask the inevitable question.

It took close on 70 years before the penny dropped. The French received 1323 Mikado type locomotives in the 1940s again with 5' 5" diving wheels and they built for themselves 318 the 141P during the war and immediately afterwards and this type could very nearly equal the performance of the 240P and again on 5' 5" driving wheels.

So a 2-8-2 could replace the larger standards but I would steer clear of the Geisl exhaust. There again given the woeful attempt that BR made to design an exhaust for 71000 .........

 

The french was very serious about locomotive max speeds.
Both the US and French mikados had speed-recorders and the US 141R was allowed 100 km per hour with two cylinders and pony truck.
The domestic 141P did 120 regularly and was fourcylinder compound and had a Zara truck up front.
A 141R was tested on rollers and selfdestructed at revs that had meant 136 kmph on rails.
Inherent balance and good guiding was just as important for well-being at speed as wheel diameter.
A two cylinder 5feet 5inch british mikado with pony truck would not have been a high speed dream.
A three cylinder five feet Mikado (P1?) would have been possible with KH or Zara and would most likely not have derailed as often as the V2s.
But with five feet you migth as well make it a wide firebox 4-8-0 and enjoy better adhession and a real bogie up front.

 

The French were serious about locomotive maximum speeds because of a decree by Napoleon III which limited all forms of mechanical transport to a maximum speed of 120 km/hr. In the 1930s there were a few routes where 140km/hr were authorised but the sections did not allow for continuous high speed running. Testing did take place and in 1911 147km/hr was reached by a saturated compound Pacific which had 1.85m driving wheels and the Chapelon compound Pacifics reached 176 km/hr while engaged in conducting pantograph tests on electric locomotives. There were very good reasons why the power to maintain speeds on the inclines was so important and acceleration was important too. The Chapelon Pacifics were more sure footed when starting than electric locomotives of the 2-Do-2 type which had 80 tons of adhesive weight, much higher than the 56 tons of the Pacifics. If you can get away with a load smartly, quickly accelerate to line speed and then maintain that speed, well, the testing of the Dovre Gubben 2-8-4 in Germany against the German Pacifics illustrates the point.

If you apply the AAR rule for maximum rotational speed of the driving wheels for a 5'5" diameter you get a maximum speed of 97.47 mph (156.86 km/hr). The 9F 2-10-0 design did achieve in excess of 90 mph and this was with 5' diameter wheels and if the Gresley Pacifics had been restricted to the AAR limit they would not have set the records that they did. Speed should not be a great concern. The Americans could be good at balancing their large two cylinder locomotives and they were also prepared to use special grades of steel to allow them to achieve this. When these special grades were in restricted supply locomotives could be built using more conventional materials for the motion work with these engines being a little more limited while working and waiting for the special alloys to be come available again. Being a wartime build I don't think that the 141R will have benefitted from Timkin High Dynamic, even the N & W struggled to obtain this.

Have a look at some drawings of the British locomotives. You don't have the space to allow significant lateral movement of the leading coupled axle so you have to find another way of doing things. The V2 with modified leading truck gave little trouble and a modern application of the design has proved to be most satisfactory when included in the design of 2007 when that chassis design was run through VAMPIRE.

 

A two-cylinder 9F doing 90 rotates 8.4 rev per second.
A three-cylindered A4 did 8.82 and started to selfdestruct as did the two cylinder US made SNCF 141R at 7.28.
Some numbers here are not reasonable.


We are discussing post WW2 steam locomotive engineering when 250 psi was state of art

A P1 with 18 inch times 28 cylinders and 250 psi would have been just as powerfull as the originals and the first of these managed to get 20 inch cylinders through LNER loading gauge.
If we can place an 18 inch cylinder one inch further out from midplane we gain more than enough freedom for lateral movement of first coupled axle in a K-H/Zara arrangement like the Prussian P10 that had plus/minus 25mm freedom.

Gresley and the P2 people went one foot to big.

 

Hmm, I’d have to go with that proposed LMS 4-8-4.

 

Back in the day those would have had a serious issue with turntables. That would actually be much less of an issue now that most turntables have gone and you need to use triangles anyway. Some of the existing Class 8 Pacifics are about as large as you can squeeze into the British loading gauge, but adding length would allow a significant increase in power (as, of course, would other design improvements without going any bigger). The 4-8-4 would however need two firemen or a mechanical stoker.

 

Adding length to the boiler would not necessarily increase its steam generating capacity. The maximum boiler diameter fitted to pacifics and the P2s was 6' 5.5". This limits the cross sectional area of the tubes. When this area falls below 15% of the grate area it restricts the gas flow. To counteract this an increase in smkebox vacuum would be required and this could increase the back pressure.

Sent from my SM-A105FN using Tapatalk

 

A thought occurs .... were a gas producing grate to be added to the list of clever suff .... might the reduction in solid particulates permit use of (something along the lines of) Sevres section tubes, thereby mitigating the issue you raise?

 

The answer is probably a garratt as it's the only way to get a fatter boiler in. But built following Beyer Peacock advice. If you took one of the bigger african ones and re-gauged it, it would probably do well as is.

Ok, the length would be an issue, but that could be designed out to some extent (on high axle-load track do you need all those wheels? Put a scoop on to cut down water capacity needed, etc etc).

According to wiki
TE of an EAR class 59 83350lbf
9f 39667lbf
Duchess 40000lbf

That's clearly not the whole story, but you stand a bigger chance of fitting that in the british loading gauge (sideswipe apart).

Back to topic, the LMS garratts, but without LMS insistance on LMS parts

 

The big US locomotives (Big Boy etc.) seemed to have longer combustion chambers, rather than longer tube length.

 

250 psi was in no way state of the art. Baldwin had 350 psi in 1926 though this was what we might call a bit of an outlier, 300 psi was in use on the N & W in the 1930s and the French were using 20 atmosphere/293.92psi certainly from 1930 on the PLM. The Bulleid Pacifics were rated at 280 psi when built but this was later reduced to 250 psi but there was a history in the UK of reducing boiler pressures in order to save on maintenance costs. The French applied feed water treatment and found that they could close some boiler repair facilities because they were no longer needed.

The A4 did not start to "self destruct" it simply overheated a bearing and it was not the only design which did so when railways were looking at running faster trains and also setting speed records. It took a little while before the reasons for the failure were understood. Don't shut off the steam supply quickly and completely when easing down from high speed, you need some steam in the cylinders to be compressed, to cushion the reciprocating masses. The A4 was calculated to be able to go faster than the record that was established but WW2 came along and the LNER was never able to make a further official attempt. What these engines could achieve we will never know but Bill Hoole was quite certain that 60007 would have broken the established record on 23rd May 1959 if he had been allowed to. In terms of the number of trains that these engines worked not that many were recorded but it is clear that rotational speeds well in excess of the AAR limit presented few if any problems.

The 141R was built in war time and was satisfactory for the services and conditions it was expected to face and the maximum speed it was expected to reach was 80 kmh. The sample (of one) failed at 136 kmh, it did not equal the AAR standard but it didn't need too.

 

Re boiler maintenance: Didn't Bulleid employ the TIA system?

The French closure of boiler facilities is a subject I'd be keen to know more about. Beyond noting the SNCF had been around for a decade by the time BR was formed, I know precious little of it's structure or objectives. Count how steam operations were managed against the backdrop of modernisation among areas in which I'm woefully ignorant!