An email from Geoff
I obtained an old and original rack for my 1925 Big Four...trouble is it doesnt fit! I think it is from a 16H but I don't know what year bike the rack came off. The arms on this rack are too close together and too short where they bolt onto the frame for my Big Four so I reckon on the Big Four rack the arms are slightly longer and angle slightly outwards at about 15 to 20 degrees so as to fit onto the studs on the outside of the rear downtubes which must be wider apart on the Big Four than the 16H. Another reason it doesnt fit could be that pre-1925 model racks have a different part number to 1925 onward models. If anyone can send me the dimensions of a 1925 to 1927 Big Four rack from the fixing bolt holes just above the spindle vertically to the topside of the platform where the luggage fixes and the length of the front arms I would be very grateful!