Built: 2016-2018
Scale 1:14
A compressed air-driven tunnel boring machine built in 1880 for the first Channel Tunnel (abandoned before completion).
(Click to Enlarge)
Chosen as a subject for a Meccano model because, with its prominent medley of spur and bevel gears, sprocket wheels and chain, this machine LOOKS LIKE a Meccano model. But to represent these salient features using Meccano gears and sprockets, the model had to be at a scale smaller than ideal to reproduce all of the prototype's actions realistically and to allow use of Meccano Dredger Buckets.
The twin-cylinder main motor (which, during the Cutting phase, drives the cutting head and bucket chain, in one direction) and the reversible, single-cylinder secondary motor (which moves the superstructure and base relative to one other), are back-driven by separate electric motors, which (through lack of internal space) are mounted externally.
The movement of the base relative to the superstructure is provided by a horizontal screwed rod. All-Meccano limit switches limit its travel.
The "jacks", which raise and lower the machine at the end of each phase, are protruding round bolt heads on swivelling collars, and are moved into "up" or "down" position automatically when the base reaches its end of travel.
An external, all-Meccano controller provides the necessary one-way, and forward-and-reverse power to the motors via the limit switches. The 6-strand connecting cable is routed to the model through the "compressed air feed pipe".
The machine (built in light Red/Green) runs on a section of (cut-away) tunnel, built in Yellow/Zinc. A cardboard disk represents the face of the tunnel.