Elvas Tower: Different types of steam engine - Elvas Tower

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#11 User is offline   darwins 

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Posted 25 July 2019 - 09:34 AM

Thanks AuzGnosis

It is an interesting topic that you bring up, also a very challenging one as you point out for the programmers.
The good news for yourself and for the zig-zag route is that Peter has already had some measure of success in modelling the performance of a Vauclain type compound. This could form the basis of your Baldwin loco.
Interesting for me to note that some got to Australia (although built in USA), as I gather the Vauclain system was mostly limited to US around the turn of the century, not for most purposes considered particularly successful and never becoming very numerous.
The Mallet system was used mostly on narrow gauge lines, but there were quite a few mainline Mallet compounds in USA. As these were articulated locos then I don't think there is a case for attempting to model them in OR until we have a better way of modelling articulated locomotives in general as single units. In any case given their mode of operation, if it were possible to get a De Glehn / Du Bosquet type of compound to work, the Mallet would surely use a simple version of this compounding.
My own suggestion for developing compounding in OR is to try to model the two types of compound that were most numerous and most successful in Europe.
(1) De Glehn / Du Bosquet compounds as very widely used in France and later further enhanced by Chapelon.

(2) The Smith / Wordsell / Johnson type of compound that enjoyed a rather more limited degree of success in Great Britain and Ireland.
The success of both types were almost certainly due to the use of different cut offs for high and low pressure cylinders. Although with the latter having separate driver controls for HP and LP valve gear was abandoned quite early and replaced with a system that provided for HP and LP cylinders to have different cut offs - these being fixed for each notch on the reverser. The French retained their more complex driving controls until the end of steam.
A similar situation applied to starting - the Smith / Wordsell / Johnson system provided a more simple method of operation. The driver set off with the regulator in first valve which admitted HP steam directly to the two LP cylinders whilst the HP piston 'floated'. Once on the move the regulator could be opened further to admit steam to the HP cylinder and work in compound mode.
The French provided a range of options for starting and presumably a range of driver controls to match. These were (if I have got this correct):
( a ) HP steam to HP cylinders only - no steam to LP cylinders( b ) HP steam to LP cylinders only - no steam to HP cylinders ( c ) HP steam to all four cylinders
the three above being used only for starting trains there was also a fourth option used for getting heavy slow (freight) trains up gradients( d ) HP steam to HP cylinders with some HP steam also added to the LP steam for the LP cylinders
In all case when the train was moving faster it would then go on to full compound working.

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