The 2-6-0s as seen on peticoat junction and the casey jones tv shows have a space between the center and rear drivers. I am wondering what the reasoning behind this spacing.
Bruce.
It was a way of keeping most of the weight on the drivers and still support the firebox and cab without having a trailing truck. This let the builders use a standardized boiler made for other locos like the Atlantics (4-4-2) used for passenger trains but needed another set of drivers for heavier trains. The same boiler could be used with different running gear.
Pete
That clears it up. Thanks Pete.
FYI: a ten-wheeler is a 4-6-0. A 2-6-0 is a mogul.
sfb
No. 3, as used in those shows and many other TV shows and movies, was recently overhauled and is back in steam. The current RMC has a picture of it on the Sierra RR.
in the 19th century when the 4-4-0, 2-6-0 and 4-6-0 wheel arrangements were most popular, wood was the most common fuel. the space between the rear drivers was to allow the deep firebox (needed to burn wood) to extend down between the axles. while coal burners need a large flat grate area to spread the coal on, wood burning locomotives require a firebox with a large volume generally acccomplished by stacking the wood in the firebox
In fact, the wide spacing of the second and third axles of Ten-Wheelers persisted long after the shift from wood to coal fuel. See pages 108 through120 in the Model Railroader Cyclopedia, Vol 1: Steam Locomotives for several examples dating from the 1890s and later.
In some cases the extra space between the drivers allowed for wide, sloping firebox grates to extend below the tops of the flanges. Ashpan capacity may also have been a factor, allowing extra space for the ash hopper between the two rear axles. (Usually the ash hopper wrapped around over the third axle as well.) In some of the larger examples the extra length in the wheelbase may simply have allowed for a longer boiler and firebox.
So long,
Andy
Yes, on a 4-6-0 the firebox size was limited to what would fit between the drivers. The great leap that came with the trailing truck (c.1905) was that you could move the firebox to behind the drivers and so could make it considerably wider. More firebox meant more power, so a 4-6-2 could easily outpull a 4-6-0.
Let’s insert a modest footnote here … that the Pennsylvania Railroad’s massive G5 ten-wheeler’s tractive effort of 41,000 pounds is about the same as the USRA light Pacific, and more than that of many 4-6-2s.
Dave Nelson
at the risk of sounding like a contrarian,
tractive effort has nothing to do with firebox size. Tractive effort is determined by the boiler pressure, the cylinder size and the diameter of the driving wheels. Tractive effort is a static measure which tells how much a locomotive can start.
the larger size of the firebox gives greater steam (power) at speed, in other words: power over time aka horsepower.