Engine cradle completed and wheels fitted with sprockets. The cradle is a very clever set of laser cut parts. The petrol engine sits on the top of the cradle and drives the dynamo which sits underneath. The white pulley acts as a clutch to control pressure on the drive belt.
The sprockets are mounted onto the axles using taperlocks - fiendishly simple, and yet something I had never come across before. The engineers on this forum will probably be aware of such systems.