The Great Bear said:
Where does a tail load finish and a mixed train start: how many/what type of wagons then required a brake van being added? Is it that fitted vans/tanks could be tail load and no brake van because the brakes would apply automatically if they became uncoupled but unfiitted stock needed the brake van. Or is it more complex than that. Sorry if my terminology is a bit off.
Hi Jon and welcome,
You have almost answered your own question, but being fitted may not be enough (I say may as there are bound to be local variations). The essential requirement would be for the stock to be
passenger train rated, not just fitted with power brakes, and able to travel at passenger train speeds. On many branchlines that would be a fine distinction, to be sure, but there would also be a load limit to the number of vehicles, and they would be unlikely (but not definitely so) to be shunted en route. So fish vans (if rated), horseboxes, parcels vans, milk tankers and maybe prize cattle vans could all be carried as a tail load, but possibly only on certain services in the timetable as some shunting would be required at each end of the branch - think of bloaters added to the auto train on the Brixham branch between there and Churston.
A mixed train has a (goods) brake van at the end, as you rightly say, and is essentially a passenger train with any old wagons trundling along behind it. A passenger brake van (with seats or a full brake) could be used as the brake van, but it would not carry passengers and would be using the handbrake only.
To return to the OP, the extra stock would be hauled behind the auto train, this could be behind the loco or behind an autocoach, but would be a trailing load. The reason for this is that to be interposed between loco and autocoach, the vehicles would have to have the requisite apparatus for connecting up the regulator as well as brake and steam heat pipes, and probably be limited to a single vehicle in any case (I am willing to be proved wrong, but it seems that the GWR ran no more than 2 autocoaches either side of a loco). Also, on a normal days running with the freight service operated by a separate loco (think of the Ashburton branch), the coach and loco would remain coupled for most of the day, and having to uncouple, insert an extra vehicle, recouple at both ends and then reverse all this just a few miles down the line would be a right PITA...
Hope that helps,