A shipping crate consists of a crate base to which the engine is fixed, with side walls and a cover. All parts of the crate are made from spruce and plywood. That is because wood has the ability to flex when the heavy crates are lifted. However, since the wooden battens could still be cut in half by the steel lifting cables as the crate is hoisted up, metal corner plates are needed for reinforcement.
The construction of a shipping crate starts with the measurement of the engine's external dimensions. Every day, Siegfried Keller pays a visit to the paintshop next door. Here, in front of the spray booths, staff prepare the engines for receiving their final paint-finish. In the middle of the room is a Series 4000 marine engine. Siegfried Keller measures its external dimensions and marks them off on a wooden slat. Besides the length, height and width of the engine, he also marks the positions of the holes to be drilled for the engine mountings. With the help of this slat, his staff make up the finished crate for the marine engine. The base is formed by two solid wooden beams. The joinery workers nail planks to their underside to form the bottom of the finished crate. Onto the base, they then nail wooden battens called cross-runners to which the metal corner plates are then fixed. Across the top of the cross-runners they attach three more battens – the length runners. These are what the finished crate will stand on. The crate-builders then turn the base over with the help of a crane and fix wooden blocks in place for attaching the engine mountings. They then screw threaded rods into the blocks so that the engine can be bolted onto the crate base. "We use about one and a half million nails a year," says Siegfried Keller. In one month, the joinery shop gets through as many as two or three articulated truck-loads of solid timber and one truck-load of plywood. But the wood has to meet an important requirement if it is to be used for making mtu crates - it has to have been heat-treated. This is what the International Plant Protection Convention (IPPC) specifies and what most countries outside Europe demand. Otherwise, undesirable insects lodged inside the wood of the crates could be carried into other countries and continents. Siegfried Keller points to the official black stamp on the wood. "That has to be visible on every piece of wood used, or else we have problems with customs," he reveals.