There were or are different styles, makes, and diameters for brake wheels, and the Railway Prototype Cyclopedia 10 goes into this in some detail. It also identifies who has made a particular wheel and housing for modelers.
Vertical brake wheels such as on boxcars are typically larger than the horizontal brake wheels seen on some older tank cars and flatcars.
The article shows many styles of brakewheels from Ajax alone.
In reviewing the article is seems many vertical brake wheels were 22" but some were 24" (Miner D-2986).
The article says that HO models of the post 1937 Ajax hand brake wheel are available from Kadee #2020, 2030 and 2040 (the one the OP has) as well as Cal Scale 351 and Precision Scale Co. 3247 and 3254. At the risk of over simplifying, the “inner” circle on the brake wheel is about the width of the widest part of the brake housing itself.
Dave Nelson