Alternative High Speed Steam?

Having been fascinated by the thread digression on Simon's Gresley section, I was wondering about the earlier designers and their high speed exploits. We know that the era of the "Singles" effectively ended with the increase in train weights needing 4, then 6 and more coupled wheels, but the designers still appreciated the mechanical elegance of the Single....and they were fast - on the GWR, GNR and MR.
Imagine therefore a modern Single with higher boiler pressure and superheating, two inside cylinders, large dia piston valves with long travel. A Kylchap exhaust, and wedge cab, high sided tender leading onto a short lightweight train and beavertail end. The locomotive already streamlined with the train, as its smaller diameter boiler and clean bodywork - hiding pipework, renders the train more bullet shaped.
This lightweight, clean, simple concept as per the Colin Chapman's approach for automotive design.
What sort of speed would be possible under those conditions?

 

If the loco and tender are to weigh as per the final form (1894) of the Stirling single and we assume a
light weight train of 90 tons then to attain 90mph on the level would require at least 850 Indicated
Horse Power. ( assuming 550 for the loco and 300 for the consist ). Within the constraints of a 49
ton loco challenging.

Perhaps a better ( slightly less fanciful . ) approach is to consider a 4-2-4 tank engine. A modernised
Bristol and Exeter loco for standard gauge. The ‘Beaver Tail’ has the hindrance of requiring to be
turned after every journey but perhaps a P&P formation with streamlining at both ends.

If steam is simply the requisite then presumably an updated Sentinel ( as provided to the Egyptian
Railways ) unit is the marginally less fanciful option.

All good fun.

Michael Rowe

 

Something close to your modernized B&ER tank?

https://en.wikipedia.org/wiki/MÁV_Class_242

 

I suspect an issue would be adhesion. All steam locomotives have more or less the same frontal area, and so the drag is going to be in the same sort of territory be it 4-2-4, 4-4-2 or 4-6-0. The 4-2-4 will have the lowest mechanical resistance , but will it be able to put enough power down on the track?
The other issue might be boiler size. If we imagine a single with very large wheels then it isn't going to have much of a boiler. The GWRs Dean singles were never fitted with taper boilers because there was no room between the wheels, so the largest boiler they had was 1540 sq ft tubes. City of Truro, in pre superheat days had 1700 sq ft . You can't have a King with 13ft driving wheels because nothing fits.
Perhaps our record breaker should be an 8-2-0T Crampton with the driving wheels behind the firebox? Or shall we reverse it completely and have cab and firebox forward, and driving wheels behind the boiler?

 

Well I have read that train speeds of between 85 and 90 mph were attained in the 1890's when steam sanders were introduced to help adhesion on Singles. So with a modern steam circuit and lighter weight modern rolling stock, significantly higher speeds should be possible. Also Drag is the product of Area x Drag Coefficient (CdA) so shape is very important and a smaller diameter boiler will help that. The Crampton concept might be a useful way of getting a low boiler and large diameter driving wheel. I did wonder about poppet valves, but are they as effective at very high speeds? How fast has the "Duke" travelled?

 

Interesting talk of a 4-2-4T... I've just started reading Denis Griffiths' book on the Gas Works Railway Locomotive Engineers, and have noticed a Dean-designed 4-2-4T, No.9. Apparently it was very prone to derailment due to the Dean frameless suspension bogies (which were later used successfully on coaching stock, and it had the Aesthetics of a scaled-up housebrick. Evidently it performed better after rebuilding as a 2-2-2 in 1884, with outside cylinders and outside eccentrics for its Joy gear. it was later rebuilt a second time as a 2-2-2 with Stephenson gear.
The book also states that Churchward at first denied this locomotive's existence, but when questioned some time later, he did admit that it had been constructed (in 1881).
Photographs are from the Locomotive Magazine, January 1940 (as built), and unknown (as rebuilt). As illustrated in Didcot Railway Centre's excellent page on GWR monstrosities below
https://didcotrailwaycentre.org.uk/article.php/484/going-loco-october-2021




Richard.

 

There's some discussion of No 9 - or rather the second GWR No 9 - here on my blog pages. https://www.rmweb.co.uk/blogs/entry/25710-gwr-9-and-10-dean-experimental-single-wheelers/

 

Thank You Jim, I'll have a good read through your page. I think No.9 as rebuilt was a handsome machine, both with Joy gear and Stephenson gear. A vast improvement on its original form!

Richard.

 

The North Eastern J class singles could and in fact did do it...

 

Depends most on total lenght of train and total mass.

https://www.national-preservation.com/threads/steam-train-power-calculator.1193201/

With a horsepower demand known it will be possible to calculate area of grate,heating surface etc.
The singles had very big wheels and instead of that a three cylinder compound will allow smaller wheels and bigger boiler diameter.
What was the fastest and most powerful single?
The power model can be checked on streamlined trains if we can get more information on the Belgian class 12 with streamlined waggons that was the fastest regular european steam train

 

According to published figures the most powerful single in this country was the North Eastern J class mentioned above, and certainly in terms of power output at speed (90mph) though in fact there is very little published about power output from other singles. The best high speed run from a single is probably "Duke of Connaught" on the Plymouth mail train in 1904.

 

...You are claiming that this locomotive could do 90mph.

I see we have learned nothing from the previous debates in relation to claimed high speed runs.

 

I'm not able to comment on whether this happened or not but reciprocating steam engines were traditionally designed about a maximum speed of 360 rpm as this was generally attainable with conventional valve gears. With 7'-7¼" driving wheels, 90 mph would equate to 332 rpm so well within that design parameter.

 

I understand that Steve, but that does not take into account rolling resistance of rolling stock, air resistance, the quality of the track, etc etc...

In my tome on Gresley I have had to look at so many different claims on Stirling's singles and I came to the conclusion quite rapidly that 70mph was possible. Over that? 80mph? A real push I think. 90mph? No, not possible, from my point of view.

One of the things I think Gresley doesn't get enough credit for, but probably should, is that he recognised in the 20s that streamlining the entire train and maximising power whilst shortening the overall train length would give increased speeds. The Silver Jubilee regularly running over 90 and 100mph average speeds during its run, and the Coronation/West Riding trains doing the same is testament to his scientific development.

For the purposes of this thread (apologies for going off topic!) but I feel alternative high speed steam would likely have required a recognition of the steam turbine more. Stanier's Turbomotive is a good example. Imagine if that had in fact been streamlined rather than conventional in shape...

 

In middle Europe it was accepted that two cylindered locomotives, that did not hammerblow more than 15%, would be allowed to run 5 rps/300rpm and three and fourcylindered 6 rps/360 rpm.
An LSWR S15 doing 5 rps is 60mph or 93kmph.
Mr Ramsey ,of this site, claims from personal observation that a S15 was very unpleasant at 45 mph and impossible to fire at 50mph.

 

As ever, Simon makes good points about the claimed Maximum speed of Singles, but there are good records of sustained very high average speeds and so 90 mph maximum speeds are still possible I would have thought. Also didn't Mr Gresley also work on the "streamlining" of ports and steam passages for the A4, which was another factor in their high speed exploits.

 

The Indicator diagrams for the North Eastern J class single 1518 were published in The Engineer in March 1890 and include a maximum IHP of 1086.6 at 86 mph. I might suggest that giving the result to five significant figures is somewhat optimistic, but as stated above, this is the greatest power output reported for a single in this country. O.S. Nock has reported 90 mph for 1517 of the same class (not sure where the original data comes from) and Rous-Marten has given 90 mph for Midland single 117 down 1-in-200 before Bedford with supporting quarter mile timings and also 90 mph for a Dean Single down 1-in-1320 but never seems to have provided any further details except that 3 miles were covered in 2 minutes.

 

I note that is still not 90mph.

I feel like I need a timekeeper bingo card. On it needs to be Nock/Allen/Rous Marten/speed claim/city of truro/saint/flying scotsman/mallard/stopwatch!

So to sum up:

We have a report from the The Engineer which doesn't prove 90mph, but gives a high speed in the 80s.
O.S. Nock reported 90mph for the same class but provided no data or evidence.
Rous-Marten has given 90mph for a different class to quarter mile timings (so no scientific data to back that up with either)
Rous-Marten also claimed 90mph for a Dean Single but his only evidence was saying 3 miles were covered in 2 minutes.

It's not exactly the best data for analysis is it?

 

Nor is it proof that they didn't or couldn't.

 

Actually it makes it far less likely they didn't - because we're dealing with unreliable evidence. We have the laws of physics to show they couldn't in the first place.

We haven't even touched on the adhesion issues of large wheeled locomotives travelling at speed, whereby the actual driving force for propelling the train is smaller than a 50p piece on each railhead. Singles did not have great adhesive weight historically (if at all?)