O Scale 1:43.5 (10″ pipe) … 1:48 (12″ pipe)
This elbow is part of a set of pipe fittings that are designed to connect to Evergreen tubing. Here, it is #228 tubing. This tubing has an Outside Diameter (O.D.) of 0.250″/6,3mm and an Inside Diameter (I.D.) of 0.194″/4,9mm.
Evergreen #228 tubing has a ‘Nominal’ ID. of 0.194″/4,9mm .. meaning don’t try to force the fitting but if necessary ream the tubing to the correct ID
I show this as 1:48 but it is usable in other scales. Nominal pipe size is not generally the pipe O.D. For NPS ⅛ to 12, the NPS and OD values are different. For example, the OD of an NPS 12 pipe is actually 12.75 inches. For NPS 14 and up, the NPS and OD values are equal. In other words, an NPS 14 pipe is actually 14 inches OD. To a large extent such variations in size can be ignored by we modelers as the slight difference at the scale we model is scarcely noticeable.
In 1:48 #228 tubing would represent 12″ dia pipe. The only difference being that the flange (minor differences in diameter) has 8 bolts on this British 10″ pipe flange. A 12″ pipe flange (1:48) following US practices would have 12 bolts. I address that with US standard 1:48 12″ elbows with 12 bolts which will be added to the store shortly.