TomPM:
You wrote: "what kind of load would a tank car in MOW service carry? Water? Oil?"
Simple answer would be both, but the railroad would have different cars for different types of service.
Cars in water service could be broken down into two categories:
1. Those carrying potable water would be used for transporting drinking water to track crews stationed in places where it was otherwise not available. There were also examples (especially in the more arid parts of the west) where railroads would provide water to entire lineside communities.
2. Those carrying non-potable water. Most of these cars were engaged in fire supression service, in which case they would be equipped with pumps, hose reals, and tool boxes for carrying fire fighting tools. In the steam era it would not be uncommon to see some of these cars stationed at places along the route to act as emergency water supplies.
If you choose to put your car into water service be sure to put additional lettering on it specifying potable vs. non-potable water. Cars in non-potable service would have "Do Not Drink" in big letters around the car.
Tank cars could also be used in all sorts of fuel service...they were (and are) used to transport fuel oil or diesel fuel (depending on which era you are modeling) to remote or outlying places where engines were based or where re-fueling needs existed. Tank cars could also be used for such things as storing and transportation of lubrication oils. In later years track maintenance machines could also be fueled out of tank cars.
"Would there be more than one car in a work train?"
Generally yes, but it depends on what task the work train is supposed to accomplish. If it is simply delivering a single tank car of water to a track crew or taking a single load of ballast to be dumped somewhere on the line then one car trains could be seen, but they were not common.
If you are interested in learning more about the world of railroad track maintenance I would suggest the following resources:
1. There was a book titled "Railway Maintenance Equipment" that came out in paperback two or three years ago. The book is widely available at such large chains as Ma Barnes & Pop Nobles, Borders, etc.
2. Model Railroading Magazine (NOT Model Railroader) printed a fourteen or so part series in 1994 and 1995 that covered every aspect of railroad maintenance equipment. The series was authored by a former Penn Central roadmaster, and there is a lot of "this is how we did it on the PC" in the articles but the series presents a lot of pictures of different types of maintenance equipment from railroads big and small across the country. Articles were written about such subjects as bunk & outfit cars, cranes & wreck cleanup, rail and tie replacement, ballast removal, snow removal, and a couple other subjects.
Hope this helps.
JDLX
Elko, NV
http://www.trainweb.org/mccloudrails
