Tower cranes arrive at the construction site on 10 to 12 tractor-trailer rigs. The crew uses a mobile crane to assemble the jib and the machinery section, and places these horizontal members on a 40-foot (12-m) mast that consists of two mast sections. The mobile crane then adds the counterweights.

The mast rises from this firm foundation. The mast is a large, triangulated lattice structure, typically 10 feet (3.2 meters) square. The triangulated structure gives the mast the strength to remain upright.

To rise to its maximum height, the crane grows itself one mast section at a time! The crew uses a top climber or climbing frame that fits between the slewing unit and the top of the mast. Here's the process:

1.The crew hangs a weight on the jib to balance the counterweight.

2.The crew detaches the slewing unit from the top of the mast. Large hydraulic rams in the top climber push the slewing unit up 20 feet (6 m).

3.The crane operator uses the crane to lift another 20-foot mast section into the gap opened by the climbing frame. Once bolted in place, the crane is 20 feet taller!

Once the building is finished and it is time for the crane to come down, the process is reversed -- the crane disassembles its own mast and then smaller cranes disassemble the rest.

Scania (part of Volkswagen) builds modified, heavy-duty diesel engines designed to run on almost pure ethanol (E95, or 95% ethanol, with a 5% ignition improver).

If that sounds weird, that’s because it is. US auto manufacturers make a big deal out of converting cars and trucks to run on ethanol/gasoline blends of up to 85% ethanol. Scania has done better than that for 15 years, and guess what, their engines can run on 100% biodiesel too, without any modification.

Scania’s compression-ignition (CI) ethanol engine is a modified 9-liter diesel with a few modifications. Scania raised the compression ratio from 18:1 to 28:1, added larger fuel injection nozzles, and altered the injection timing. The fuel system also needs different gaskets and filters, and a larger fuel tank since the engine burns 65% to 70% more ethanol than diesel (whoa! see below). The thermal efficiency of the engine is comparable to a diesel, 43% compared to 44%.

While Scania originally introduced this technology for “heavy commercial vehicles in urban operation” (city buses), they’re now extending it to trucks as well. Scania maintains that with existing technology, the transition to renewable fuels can be painless. Since in the last 15 years they’ve put 600 ethanol buses on the road (mostly in Sweden), the company seems to know what it’s talking about.

Scania is also working to develop ethanol refueling infrastructure, which should make it easier for smaller transport companies to invest in ethanol-powered vehicles.

But why not use biodiesel, since ethanol requires about 1.5x more fuel usage? Scania’s answer may raise a few eyebrows: “the farming capacity [for biodiesel] is insufficient for the huge need foreseen for the transport industry.”

Unless you take EU spokesman Michael Mann’s comments seriously (he said that Europe can grow enough fuel to meet 10% of it’s transportation fuel), Scania must be betting on cellulosic ethanol. The intensifying food vs. fuel debate isn’t taking this issue lightly, as I’ve written about here and here.

In any case, Scania’s work seems to indicate it might not be as hard to create engines that run on alternative fuels as auto manufacturers maintain.