Re: Size of air compressors *LINK*

From RGS timetable No. 5 tonnage ratings, the tonnage downhill on 4% grades was rated by compressor type.
1 - 9 1/2" compressor 30 cars 575 tons
1 - 11" compressor 45 cars 650 tons
2 - 9 1/2" compressors 60 cars 800 tons
When equipped with one 8 1/2" CC compressor:
35 cars coal or other heavy loading 1150 tons
45 cars stock and other light loading 1150 tons
45 cars mixed loads and empties 1150 tons
60 cars empties 1150 tons
Coker is right about reservoirs - the more capacity the better regardless of compressor type. Tandem pumps can be a pain if they are not in pretty much the same condition, as one will tend to take the load - especially if you have steaming problems. The up side is that you always have a spare if one goes down - unless Murphy is around.