Hi there,
I am wondering what the term “doubling hills” refers to with railway operations.
Thanks.
It refers to dividing a train into two sections and taking each section separately up a grade that is too steep to climb with the whole train, given the available locomotive horsepower.
The Pentrex video on Raton Pass shows this activity in detail in the 90’s.
For efficient operations, doubling a hill is to be avoided except as last recourse occurrence.
Ordinarily, yes, but C&IM doubled their coal trains as normal procedure.
Actually, they tripled their coal trains over Petersburg Hill. Since the C&IM did not operate a lot of trains, tripling the hill did not really interfere with other trains and was probably cheaper than assigning a helper.
When the C&IM dieselized they quit tripling Petersburg Hill. Their 2-10-2’s to three trips to get the coal up the hill, but their SD9’s could do it in two trips.
At their bussiest they operated 6-8 trains per day over the line so it was more efficient for them to just double the hill than to station a helper at Petersburg.
Historically, Central Pacific routinely doubled the hill from Blue Creek up to the Promontory Summit. It is one short - but steep hill in a long run of modest grades. According to the National Park Service, the Promontory grade was the steepest on the transcontinental. Even though there were helper engines at Promontory assigned to the grade, it was frequently cheaper to double the hill than to crew and supply a helper. This was one of the operating factors that led to the Salt Lake trestle. Now that is a water level route!
dd
In the days of steam power, the Tennessee Central routinely doubled some hills. Indeed, the timetable tonnage ratings had a footnote on some areas, “Doubling _________ Hill.”