In that same issue of Trains (April 2009) the article “Nice Ride!” by Tom Murray on grain cars (pp. 42 - 44) indicates that current grain covered hopper cars are about 5,200 cu. ft. capy., with an allowable gross weight for unrestricted interchange of 286,000 lbs.
Since 1 bushel = 1.25 cu. ft. (per a Ohio State University web page), the 5,200 cu. ft. hopper can hold about 4,160 bushels. So a 110-car train can carry around 457,600 bushels = 36.6 % of Milton’s 1.25 million bushel capacity.
As a check, a University of Missouri web page (and other sources) says that wheat weighs about 60 lbs. per bushel (exact figure depends on moisture content and some other characteristics). So a 5,200 cu. ft. hopper car carrying 4,160 bushels would have a payload of 249,600 lbs., leaving 36,400 lbs. for the weight of the car without exceeding the allowable gross car weight. That’s a little light - Rodney’s figure above of 60,000 lbs is more correct - so the these cars carrying wheat will “weigh out” before they “cube out” (or “bushel out” ? [swg] ).
Revising these figures accordingly:
286,000 lbs. gross - 60,000 lbs. for empty car = 226,000 lbs. max. payload per car
226,000 lbs. payload per car / 60 lbs. per bushel = about 3,770 bushels per car.
110 cars per train x 3,770 bushels per car = 414,700 bushels per train
414,700 bushels per train / 1.25 million bushels capacity of Milton = 33.2 % = just about 1/3 of its capacity.
So it appears that the Milton elevator can altogether store about 3 trainloads of grain, depending on its density. But as I previously noted above, they may not have been sure that they actually had enough wheat for this train, if they already had some bins filled with the soybeans and canola.