David Shepherd (RIP) and his locomotives.

Tom,
Our posts crossed! But I'm glad to have someone agree.
Andy

 

And the Tractive Effort being multiplied by the velocity (speed) is that being delivered to the rails, not the Nominal Tractive Effort, which has no place in any power calculation. And yes, no loco has yet claimed to beat LMS's 6234 power outputs of 26 February 1939.

 

It also depends where you measure things; cylinders, rail or drawbar. All will give a different result. And, yes, I'm unaware of anything beating 6234. 3316 indicated (cylinder) horsepower from memory.

 

it's ironic that so many locos bought privately were duplicated with locos from Barry later.

 

According to his autobiography "A Brush with Steam", he wanted a 75XXX because, as he says in the book: "I liked the sturdy and workmanlike appearance of the Standard Class 4s." 75029 was bought because friendly staff in the local sheds told him it was in good order.
The 9F 92203 was recommended by other BR contacts when he said he wanted one of them.
They were bought as part of a package deal by the Association of Railway Preservation Societies (now the Heritage Railway Association) negotiating with BR on behalf of David Shepherd and other groups and individuals; Clan Line, Blackmore Vale and others were involved.

 

No British loco. Just for the avoidance of doubt....

 

In the ESR stock book Second Edition I have found the following information. The Standard Class 4 was withdrawn August 1967 for purchase and the 9F was withdrawn in November 1967 for purchase.

 

And both have a little bit of interesting history, 75029 was the prototype for the testing of a double chimney on the WR, I believe Mr Ell was super confident about what he'd done (all but polished the tubes with Brasso!) and 92203 was part of the last through trains to Birkenhead, along with 4079 and 7029.

 

What tractive effort is useful for - and useful for in the rough an tumble of operating trains - is that it is
a genuinely useful indication of wether a locomotive can a start a train. To coin a Chinese proverb: "No start, no run".

Its other attraction is that it is readily demonstrably calculated, something you put in a specification and hold a
contractor to account for. The fact that it is "at 85% boiler pressure" and that it is 85% and not 80% or 90%, however,
should be an indication that it is an estimating tool - neither a scientific absolute nor a crude rule of thumb.

 

I suggest that by 1967 it was as much as anything a question of what was avalible

 

6234 managed 2,500dbhp - it is estimated that this equates to 3,333hp at the cylinders.

I seem to recall reading that some Merchant Navies got pretty close, the only limitation being that, even with two firemen, Rugby never did find the upper limit of the MN's steaming capacity... it really needed the mechanical stoker fitted to CanPac (but removed at the rebuild).

 

So, why does 85% boiler pressure come into it? And why did the Midland use 75%? And Hunslet, too.

 

But at the time did anyone did anyone know about what would become of those machines dumped at Barry. If it wasn't for Dai we'd have only 2 each of 9F and 4MT.

 

Presumably it's a rough and ready average of the pressure in the cylinder during one whole stroke. At low speed the pressure would be close to 100% of the boiler pressure for part of the stroke, reducing after the valve closes to stop the admission of any more steam. That comes some time before the end of the stroke, depending on the cutoff setting, which is always well short of 100%.

 

I came across a reference recently - I think it was in HAV Bulleid's "Master Builders of Steam" - that the choice of 85% was standardised on by the ARLE in the early years of the twentieth century, which I guess would be under the chairmanship of HA Ivatt. Standardisation allowed easier comparison of designs between companies, but as you say, it is a somewhat arbitrary figure: an estimating tool, as @Hirn suggests, not a precision characteristic. Also, as I understand, the ARLE was primarily a body of engineers for mainline companies, so the industrial builders were free to choose their own methodologies for calculation. I'm sure most literature I have seen on New Zealand locos (generally built abroad, often by British manufacturers) tends to assume a 75% figure.

My reading of primary Victorian material is that TE is rarely explicitly mentioned, or appears on diagrams. Far more common that engines are described as something like "Mr Crankpin's new 18 inch goods locomotive" and it's capabilities would largely be inferred by reference to the fact that his previous locomotive was a 17.5" design; or maybe the new one has 150psi boiler and the previous design 140psi. Explicit calculations of TE don't seem very common, though obviously the concept was understood.

Tom

 

The P2 will have essentially the same boiler as Tornado, which can be expected to produce the same maximum amount of steam, perhaps slightly more or less according to how the different valves affect the draughting. Whether it will be more powerful depends whether its poppet valves can produce more efficient use of the steam than Tornado's piston valves. That was the justification for trying poppet valves on the original P2s (and various other locos) and is a reasonable aspiration, which does indeed remain to be proven in practice.

As Tornado has the same size of grate as a Duchess and the same kind of valves one would expect their maximum power under ideal conditions to be about the same.

Edit: not that this discussion has anything whatsoever to do with the official subject of this thread!