In the original petrol engine compartment, the drive shaft from the gearbox is supported with a bearing which is bolted to the engine with the aid of a bracket . With the engine removed, a cradle needed to be built to provide this support. The cradle also keeps the gearbox in the correct position between the two original rubber engine mountings.
The picture below shows the DC Motor installed inside the cradle. Note, the motor is only supported by the four bolts to the adapter plate.