Of the millions of rotating electrical machines sold each year, the majority are assembled in the ideal conditions of the maker's factory and shipped to the customer in one unit. At the large end of the range, however, when ratings are in tens of megawatts, a size is reached when transport and site handling limitations prevent this. The machine then has to be broken down for shipment into main components such as rotor, stator, baseplate and bearings. For very large machines even this division into components in order to solve the shipping problem, either to modify the design of components, possibly to their detriment, or to assemble them at site where conditions and facilities will not normally be as good as those available at a manufacturer's works. This article describes the special problems that arose at site with two projects, Dinorwig and JET where the option to build at site was chosen, and those that still arose with the QEZ refit when the ideal design of propulsion motor was modified to produce shippable elements.