M&K Junction Railroad

M&K Junction Railroad
Another train of eastbound coal crosses the Cheat River

Monday, May 7, 2012

On Grades and Helpers

For starters, here's a quick video that I shot entitled "The Cheat River Grade Helper":

After shooting this video, I realized that I should do something about the bare backdrop on the Cheat River Grade. I cannot make a photo backdrop right now, but maybe I can at least paint the backdrop a sky blue.

 In my previous post, I remarked on the necessity for using helpers (or more head-end power) on the Cheat River Grade. This grade is 2% and nearly matches the prototype. In building my model railroad I have used Charles Roberts' book: "West End" as my "bible". My experience with needing helpers on the grade caused me to review the section in Roberts' book on equipment. Roberts compiled statistics on how many cars the prototype could pull up the grades. He used an interesting metric, number of cars puled per powered axle. Using this as a metric eliminates the differences in wheel diameter, steam vs. diesel, etc. What he found was that over the period of time from 1850 to 1991, the B&O could haul between 2.1 and 2.4 cars per powered axle up the grades. That is essentially the same result that I have obtained after testing with several model steam and diesel locomotives; between 2 and 2.5 cars per powered axle (and the latter number with a lot of wheel slip).

I believe that John Armstrong observed in one of his books on layout design that given needle-point axles model locomotives will pull more on the grades and less on the flats than prototype locomotives. He further observed that to create a helper grade that would seriously challenge model locos, 3% was about right.  I would certainly never dispute John Armstrong, but in my particular case the grades and, especially, for the combination of curves and grades, 2% seems to be about right.

It will help that most of the hoppers going up the Cheat River Grade will be empty (unlike the video above, which was just for fun) and I can arrange that most of those will be plastic models.  But the loaded hoppers coming down the Cheat will have to go up Cranberry Grade, also 2%; and these hoppers will be loaded.

During the period 1949-1952, the B&O used A-B-B-A sets of F7 diesels as pushers to help trains headed by, typically, a 2-8-8-4 articulated up both of these grades.  Assorted 2-8-8-0s and Q4 2-8-2s (as seen in the video above) were also used as pushers.  I intended to use A-A sets of diesels and Q4s as pushers.  The eight powered axles on the diesel pushers would be about 16 cars capacity, that should be OK.  The four powered axles on the Q4 would only be 8 car capacity - that might not be enough.  Matching the pusher to the train length could make the operating game more interesting.

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