This is based on the "Kirow Bridge Building Machine " shown working in China. It can be seen on Google and You Tube.

Assisted by Edmundo Veiga this is a fully working model as far as I could see at this scale reduced to be not too long. This is my own design.

See the real machine video here :- https://www.youtube.com/watch?v=hrTL8_42rLs

This is a video of the model taken at Skegness by Tim Surtill. https://www.youtube.com/watch?v=BmCGPzr07aE