There have been some large Meccano models built – the construction toy invented by Frank Hornby over 100 years ago, but retired applied mathematics lecturer Graham Shepherd believes he has built the largest one so far, a 1 250 kg model of a giant coal mining machine known as Bagger 288, built by Germany-based Krupp in the seventies.

The machine is an example of a bucket wheel excavator, the 288 being one of a class of machines, capable of mining 240 000 m3 of coal a day. This is the largest such machine class in the world, the prototype being a behemoth of 13 500 t, 95 m high and 220 m long.

Shepherd tells Engineering News the model is built on a scale of about 1:18, resulting in a model with a length of about 41 feet, a height of over 16 feet, and a width of 7 feet (quoting in the units most Meccano enthusiasts think in!)

He first began thinking of doing something like this four-and-a-half years ago when wondering what to do in his retirement. As a boy, he had been a keen Meccano modeller but the demands of working and family life, and some major house building projects, had resulted in his set being mothballed for nearly four decades.

Shepherd says that one thing led to another until he found himself thinking seriously of a world record challenge.

His set was nowhere near big enough for the task, so he began looking at ways of making replica parts. With the help of a laser cutting facility (which he also needed to do the bending) and a small metalworking shop in his backyard, he began turning out parts in mid-2009. With a rueful look, Shepherd recalls drilling the equivalent of one-million holes in 1 mm steel with a small Ryobi bench drill. “It’s still going,” he says.

Gradually, the parts were converted into the model shown in the picture, using over 250 000 bolts, nuts and washers. Realistic actuations are achieved with some 55 electric motors, most of which are factory redundant automotive window winders. Gearing is by means of a heavy-duty system specially designed to take the large torque transfers. In like manner, many of the standard Meccano parts have been made in heavier gauges as the lighter gauge ones would simply buckle under the weight of the huge machine.

The main components of the bucket wheel system are visible in the picture. The 44-inch-diameter wheel rotates against the coal face, filling the buckets as it does so. The coal then falls out onto a conveyor in the arm holding the wheel, which carries it into the central unit where it falls onto another short conveyor, which takes it out onto a long transfer arm (19 feet long in Shepherd’s model). The latter transfers it to a second unit, which rides on three crawlers, where it is finally moved out on a cross-slider conveyor from where it falls onto a ground-based conveyor, which is represented in the model by a 20-foot-long unit driven by three motors.

Included in the model are the cranes that the machine uses to service itself. All these (five in all) are also actuated by small electric motors controlled from the main control panel.

He tells Engineering News that final assembly of the model involved three main lifting sessions and ten or eleven strong friends each time, as well as a considerable amount of bespoke carpentry for each session. Fortunately, all went well.

The interest in the project from the global Meccano community is evidenced by hits on the Bagger 288 blog, which traces construction of the model. The most interest has come from enthusiasts in the Netherlands followed by the US, the UK, Germany and South Africa.

When asked what will eventually become of Bagger 288, for which, clearly, his wife has shown extreme patience in allowing the model to be assembled in the lounge of her home, Shepherd replies: “You can’t just take a screwdriver to it and pull it all to pieces. After four-and-a-half years’ building time, you get rather attached to it. So, I will probably put it up for sale. I’d like to see it in a situation where people can enjoy watching it go through the motions. After all, there is only enough room for it to traverse one foot backwards and forwards in the lounge! And Eileen really would like the lounge back!”