At the far end of the counterbalance arm the two winding drums can be seen.
Each drum is driven by two window winder motors meshing directly onto the drum’s 8", 99 (large) tooth gear wheel as seen. These drums are now motorised and revolve at about 7 rpm. Also visible in the photograph is a servicing crane for the winding drum area, motorised by three meccano 6 volt motors, one each for slewing, elevation and hook position.
|Servicing crane for the winding drum area|
Note the extensive use of compound girders in the mainframe structure. These are slightly heavier than those used in the bucket-wheel arm (some 1" flat girders being replaced by 1½" ones). This follows the prototype. The reason is that distances between main joint knuckles are quite a bit larger than in the bucket-wheel case and, according to Euler’s theory of buckling, the tendency to buckle goes up with the square of this distance.