A small point, but the wagon in the article is a fitted wagon, but it has not been fitted with the tie bars.
(These were to check the tendancy of the brake shoes pushing against the "inside" of the wheels pushing the axleboxes, etc., outwards! Some "eight shoe clasp" brakes did not require the tie bars as much, as these had brake shoes on both "sides" of each wheel, thus balancing the brake force more effectively.)
I hope this is of interest.