I run a milk train on my layout and over the years I have accumulated five of Athearn's 50 foot refrigerator cars in Pullman Green which have been a large part of the milk train consist. Three of them are simply lettered as refrigerator express cars but two of them are specifically lettered as milk tank cars, one Borden's and the other New York Central. All five have ice hatches at both ends and since all are identical except for the lettering, I assumed they were all milk tank cars.
Recently I acquire Kalmbach's new book Milk Trains and Traffic. I learned that early on it was learned the milk tank cars don't require refrigeration because the tanks inside these cars were so well insulated. I think it gave an example of a 101 hour trip in which the temperature only rose 2 degrees. The milk tank cars that were shown did not have ice bunkers. Some milk was transported in cans either in dedicated can cars or express/baggage cars but these were generally top iced in warm weather. No ice bunkers were required for those either.
My question is whether these Athearn milk tank cars are non-prototypical or are there examples of milk tank cars that did use ice bunkers?
Kalmbach's new book on milk trains is an expansion of a chapter in Jeff Wilson's odler book, Industries Along the Tracks 2. In that he mentions that Class BMR cars are cars primarily used for transporting milk that have ice bunkers or ice boxes. Class BM is a milk car insulated but not refrigerated. Most privately owned milk cars were class BMT - insulated with tanks but not refrigerated
Also hauling milk from time to time were class BE - baggage express cars and BR - refrigerated express cars.
I do not have ORERs (equipment registers) old enough to see just how many ice bunker cars there migth have been in milk service. Perhaps someone else on these Forums does.
So seemingly ice bunker cars existed and were used but Wilson does not say much about them. he does mention that at one time bulk cars had interior piping for pumping in cold brine at the creamery but this was found to be unnecessary and the piping was removed in the 1930s 40s. So if even pre cooling was not needed that reinforces the notion that for the most part if the car was well insulated and the train did not dawdle, the milk would be fine with just top icing at most on hot days.
Dave Nelson