Locomotive Performance & Timing

A question that this thread might be able to answer, with some context first. I'm attempting to put together some predictions for the amount of coal & water 35011 will need for mainline running, in terms of tonnes/mile & gallons/mile, using the booked paths for recent railtours with Class 7 or 8 locomotives for the timing/distance & inclines, a formula from Andrews paper to the ILE in 1954 to convert the trailing load into a drawbar pull, and data from the Performance & Efficiency report (Bulletin 10) for the original Merchant Navy to give the steaming/firing rate needed to produce the desired drawbar pull at the booked speed. My question is, when a load is quoted on sites such as realtime trains as "Pathed as Diesel locomotive, trailing load 715 tonnes", I'm assuming the diesel is a 47 and I can effectivelly remove it's mass from the trailing load (112 tonnes), but that still gives a trailing load of 603 tonnes. A Mk1 apparently weights about 36 tonnes, even with 64 100kg people on board, that's still only 42 tonnes per coach, which puts a train of 14 coaches behind a castle in this case. Am I missing something?

 

It's a quirk of Real Time Trains, or rather Network Rail's back-end system. The load put in is chosen so that their pathing algorithm comes up with realistic paths (in terms of acceleration etc); it doesn't mean the actual load is 715 tonnes.

Tom

 

There will be some drag in the DC traction motors of the Diesel locomotive. I would estimate this as being about 2-3% of the nominal power output of the Diesel. I hope this helps.

 

Does not the 715 tons represent the weight of the train, i.e. including both locos ? If the prime mover is a
Castle ( c.129 tons ) suggests the consist is 12 Mark 1s plus support coach. ( If an 8P then 11 + 1 ). The
715 tons is a Tare figure ( i.e, no passengers ). If 12 MK1s, then allowing for catering facilities, brake,
1st class etc, then c. 500 seats, allowing 13pax/ton then c. 750 tons gross.

Michael Rowe

 

No, it's just the nearest of the various Network Rail options which simulates what a steam loco with a load within the load limits could be expected to achieve. Even then, it has to be taken with a pinch of salt. For example, the uphill times are demanding/impossible, while 30 miles downhill at 75 (eg Shap to Carlisle) will recover 6 mins on a 60mph schedule.

Maybe a chat with someone from the MNLPS re coal and water consumption might be an option for the OP.

 

Track machines are also timed at 60mph 715 tonnes due to their poor acceleration. Presumably braking isn't ideal with so few axles either, especially in poor weather.

 

Mallard was timed on the 715 ton load when moved to Grantham in 2013 for the railshow then. The train was far from that weight or length.

 

Ah-ha, makes more sense. I was spotting that all loads seems to be 715 tonnes, which seemed a lot!

 

Thanks, that's a more useful figure.

 

An unrebuilt GSN will have different fuel consumption from 35028, hence the need to try and fathom it out.

 

You must be expecting big people to go on your trains if you are working on 100kg/person. A British standard person is usually taken as 75kg. Not that it will make much difference to your overall calculation.

 

Thanks, I have never moved beyond the Network Rail report ( ‘Worley’ letter ) of 2013 i.e. for VUC calculations,
a notional 11 + 1 and an 8P weighing 150 tons.

A regular feature of actual current steam Main Line performance vs WTT suggests frequent unrealistic
requirements wrt initial acceleration from a stop and against the grade. Does the Shap pass Carlisle stop
WTT include an allowance ?

Historically, both pre and post 1948 the norm appears to have been to drop 2-3 minutes from Carnforth
pass to Shap summit pass and recover it downhill ( if there was not 2-3 minutes in hand passing Carnforth
accumulated from Preston. )

The reference to track machines assessed at 715 tonnes and 60mph somehow suggests to me a lack of
practicality ? ( but perhaps I am merely old fashioned and curmudgeonly.) But then accounts of locos driven,
apparently routinely, with controls at RFO and 45% at 70mph over Stoke definitely perturb me ! So much
for efficient running, or am I missing the point.

Regarding the un-rebuilt MN: despite the challenges of the Rugby Tests; the DBHP curves can
predict performance with an 11 or 12 coach train, ( I have not checked the Bulletin, but memory says it was
only at very high steaming rates that they aborted the Test ? ) the addition of a diesel
definitely muddies the water. Do you consider it as a dead load, ie not 11 or 12 but 14 or
15 carriages or do you assume it will assist at times I.e initial acceleration and against the
grade.

I am afraid the increasingly regular attachment of a diesel and the uncertainties as to
whether it is idling or not have left me with less enthusiasm to participate in steam
charters.

Michael Rowe

 

Tomorrow's CME has a 1 min allowance passing Penrith. Stripping that out, it has 30.5 mins for the 30m 18 ch from Shap to Upperby ie a 60mph schedule.

 

The originals had some flaws, which prompted the rebuilding, but did that make any significant difference to the coal or water consumption?

 

I think this does deserve further discussion, but let's do it on the Bulleid Pacifics - Past or Present thread.

 

Another question to help my understanding now-what's the difference between drawbar pull and drawbar T.E.?

 

They're the same thing by different names, both measured in either pounds or tons.