Saint Class 135 ish mph

2903's run was May 1906
Salisbury was July 1906.

BTW a NER Z Class Atlantic was run at 92 mph light engine. That happened, right?

 

yes and old age and poor eyesight mean typos are inevitable as are clever dicks

 

There exits a program, Perform by Prof. Hall, which contains the 2900 class data. It calculates cylinder performance. At 120 mph and 35%cutoff it tells me
that such a performance would need 75000 lbs of steam and would have both inlet and exhaust ports at sonic speed. At 15% cutoff it would need 32000 lbs
of steam, still have sonic speeds and produce 2600 ihp. I have this feeling that these are impossible combinations.
Kind regards
Jos Koopmans

 

Apologies. A good time for us both to cease to perpetuate this thread I think.

PH

 

In another thread I used figures given for bhp to calculate the c.d. of an A4 and A1/3. 120mph for the A1/3 requires 778hp to overcome air resistance. The saint would presumably have similar drag levels.

 

Is it safe to assume these accepted standards apply to continuous output? If the notion of 'mortgaging' steam supply hold true, would a short sprint of the sort described in the May 1906 run be beyond the realms of credibility?

I bow to far greater knowledge than my own regarding power requirements, but note the initial downhill gradient would overcome some degree of initial inertia. This gain would surely carry over onto level track, until overcome by air resistance. Whether that would take 60sec @ 120mph, I know not.

Regarding power required to overcome air resistance [maddog], while a 29 presents a different 'face' to HNGs locos, I couldn't imagine differences being in orders of magnitude. This, coupled with JKs observation on steam supply certainly explain why such runs were impossibilities in regular traffic, but I'd hesitate to discount the eyewitness accounts of two GWR employees of good standing out of hand.

 

Thank you for answering that one for me. I'll take my place in the dunces' corner!


Sent from my iPhone using Tapatalk

 

Lets get down to basics.

The GWR Saints were known as fast runners and equal to the later Stars on lots of jobs.

As Courier has posted there are lots of well documented runs of Saints putting in splendid performances in original condition before superheated boilers were fitted, and lots of other well documented performances with super heated boilers fitted.

The Churchward 2 cylinder cylinder casting was a complex affair but had very free passages direct to the exhaust. The later 4 cylinder locos suffered from problems on the exhaust side. A glance at the drawings of fullsize will show the comparison up very clearly.

If City of Truro went just above 100mph with slide valves and a non superheated boiler and with a moderate load on a loco that had a Dean chassis but with a Churchward boiler, I see no reason why 2903 would not have done over 100mph light engine with a far superior valve gear designed by W H Pearce, and a superior set of cylinders with piston valves.

The lack of publicity at the time of 2903's run in 1906 is not surprising - as Courier has commented the Salisbury disaster happened not long after, and the exploits of City of Truro had already been suppressed 2 years earlier.

It was only when Chief Inspector George Flewellen retired that the full story of City of Truro's epic run became public, and that of 2903 2 years later. 2903 was a much more modern loco as I have alluded to.

City of Truro had top suspended loco links. My old friend and valve gear expert Don Ashton is not very complementary of this arrangement. However, 2903 had the then most up to date piston valve design and Willie Pearce's very modern and meticulously thought out 'Churchward' arrangement of the Stephenson valve gear of launch type links. This was far superior in valve events to that fitted to the GWR 4 cylinder locos, and City of Truro.

Cheers,
Julian

 

Still very much the operative word, "if"...

There are far too many factors to take into account for the Saint run to be plausible.

I've never thought Truros run was plausible either, to be fair.

All the work done by the LNER with speed records, including the work by Gresley and his team regarding the reduction in HP needed to attain higher speeds through use of streamlining rather convinces me there's a lot of wishful thinking where the GWR runs are concerned and far too much emphasis on both perfect mathematics where the locomotives steaming rate is concerned and not enough to explain away the practicalities of actually carrying out a high speed run.

And again, just because Truro might have gone very fast it does not prove the Saint did, any more than Mallards run proves Scotsmans run.

Deflection tactics in terms of trying to beef up the GWRs argument at work. Almost worthy of an episode of "Yes Minister", this thread.

 

Where, pray tell, has anyone brought this run up, and why has it any relevance to the question "is a saint class locomotive capable of 100mph, or 120mh, or 130mph?"

Just because one story exists for another class on another railway it doesn't prove, disprove, or in fact link in any way to the GWR claims.

Treat each on their own merits.

I rather think Mr Kloopmans post above rather puts the whole notion to bed. Personally speaking, of course.

 

Whilst I completely agree with the above regarding any sustained high speed running, does the same necessarily apply to a short dash under the circumstances described?

Although the only thing steam locos share with humans, beyond having a personality, is the energy cycle (in the broadest sense: i.e. fuel in, work out), several prodigious feats were performed on occasions (I'm thinking of runs with underpowered replacement locos battling long gradients with loads which they barely had the capacity to shift at the requisite speed on the level).

This being so, might I point out that were it possible to run the marathon at the current world record pace for the 100mtr sprint, the record would stand at 1hr 7min 26.7sec rather than the current 2hr 2min 57sec (source: IAAF website).

I wonder if, at some future point, the owners of 2999 and Network Rail would be..... naah, forget it!!

 

The volume of steam required per revolution, and the consequent flow rate of steam through the valves, would surely still be the same for a "dash" which might not have been for hours but would have been for minutes.

 

I'm making a stand. I'm saying it is true with the caveat that the actual speed was between 100 and 120 mph. C.b. Collett jumped on the footplate with the Robinson fellow, and a Swindon engine crew that he knew was game and said, "C'mon lads, the boss is away, I've got us some clear track, let's go do some "testing"!.

We have some testimony from two sources at least that it happened. I'm not sure about the signal box timings - were they from a third party? So maybe three sources of back in the day...

I believe a saint was capable of doing 100+ mph. 6ft 8 1/2 inch drivers - the same as Truro. More HP than Truro. I'm confident that the good reputation of Swindon engineering tolerances would have prevented the driving components from physically grenading for spinning themselves into oblivion in order to get to 100+. Unless there is some evidence that saints were notoriously rough riders and that they would have without a doubt ended up down an embankment once they hit such and such a speed - not saying it wouldn't have been as scary as hell...

A couple of limiting factors that have been brought up that I can see carry merit;
~Wind resistance. An Unstreamline engine is going to top out somewhere no matter how good it is. This factor alone causes me to err conservatively closer to 100 than 120.
~The Saints steaming capabilities will also restrict performance at some point. But if Truro could do 100 mph then why not her big brother with the next generation of steaming technology? Surely this alone should theoretically take a Saint a comfortable margin over 100mph.

So I say it happened but the details will clearly never be worked out to unanimous agreement. Perhaps if the the story said "over 100 mph" then there may be be less bees in bonnets?

Still a cool story.

 

This debate reminds me of one on an American forum where people were claiming the Pennsy T1s regularly ran at speeds over 130mph - way over the max line speed in force. In spite of the level headed contributors raising many valid points why these speeds were almost certainly not achieved - the "believers" simply ignored such reasoning and based their claims on a guard's journal timed with a wrist watch to the nearest minute.

 

And as, in the absence of a time machine, proof is the one thing we will always lack, so we will go round in circles.

I'm surprised not to have heard mention of the impact of cross sectional area, and tge effect that has on air resistance. I've heard drivers comment that a single class 153 has significantly worse performance (acceleration and speed) than a pair, yet the pwer weight ratios are unchanged.

I will also note that the antis are applying a more modern sensibility to a very different era.

 

I think with some of these GWR claims you don't need a time machine, just an accurate tape measure ...

More seriously: there seem to be two key hurdles to cross that are being ignored.

The first is that to measure speed, you need to measure distance and time, and both are subject to errors of measurement - so you can't give an absolute speed, simply a range - i.e. the loco went at X mph, +/- y mph. As @Jimc has pointed out, the times from the signal boxes don't support a claim of 120mph, but rather that the loco was travelling at somewhere between 75 and 200mph. Essentially, the error in measurement is so large as to be useless. Timing quarter mile posts at 120mph means they have to go past every 7.5 seconds. Hand timing would be very hard to even within 1/2 second, which is a big error in 1/4 mile. (A quarter mile somewhere between 7 and 8 seconds is somewhere between 112 and 128 mph; I suspect the timing error could easily be greater than that over such a short distance).

The second point, touched on by @JJG Koopmans and others is what is physically reasonable, taking into account the power required to achieve a certain speed; the rapid increase in power required to overcome drag (a cubic relationship with speed, i.e. whatever power is needed to overcome drag at 100mph, the amount at 120mph is about 175% as much); the fact that the tractive effort will drop with speed and ultimately you have no available force to continue to accelerate the locomotive; the physical ability to actually get steam in and out of the cylinders given very short time periods the ports are open etc. For me, the relationship between speed and drag is the killer: I can believe round about 100mph, given what the locos achieved pulling service trains, but every small increment over that becomes steadily less and less physically reasonable.

Ultimately, "newly outshopped Saint on test travelled at a speed somewhere between absolutely day-in, day-out routine and physically impossible" isn't much of a juicy story for Tuplin to work his special brand of magic on. "Saint did 120mph on test" makes for a nice page or two in one of his novels erudite discussions of locomotive practice.

Tom

 

This is getting rather silly.

The claims that the GWR cannot have conducted high speed light engine runs are ridiculous. Such tests are well documented by numerous sources over decades.

So we are left with the statements from Collett that there were signal box timings and basic stopwatch timings as stated. Do I believe those statements. Well yes. All those numbers in such circumstances really tell us is that the locomotive was travelling at some unknown speed, significantly in excess of 100mph, down an appreciable bank. Calculations to prove that it could or could not do exactly 120mph on the level are beside the point, because Collett was claiming neither. He made a careful statement that the speed recorded could not be regarded as accurate and that the maximum record speed remained as COTs 8.8 quarter mile.