Usually, installation of a crane of this type involves lifting the disconnected end-carriages onto the gantry, then attaching the girders to form the frame of the crane, finally lowering the crab and hoist into position from above.
The problem in this case was there was not enough factory headroom to do that, even though Condra designed the crane with a lowered profile to achieve maximum lifting height.
Condra’s solution was to fit both 12-metre-span steel girders with bogeys at each end, four bogeys in all, and develop a different installation sequence. Fitting the girders with bogeys frees up an additional 20mm of headroom through reduced wheel loading and smaller-diameter wheels on the end-carriages.
Integral bogeys also allow placement of the girders on the factory gantry as the first step. Moving the girders apart then delivers space to allow lifting of the hoist into position between them, instead of lowering it into position from above. Closing up the girders, then linking and fixing their bogeys results a completed crane with two double-bogey end-carriages.