NASA's Crawler-Transporters are the biggest, baddest, most kickass six million pounds of tracked vehicle in the known universe. There are two, Hans and Franz, but I shall refer to the Crawler in the singular as they are identical and it makes it easier mmkay? It's big, it's old, it's damn near Pharaonic. The "Crawler" is actually a platform full of generators and engines resting on 4 tracked "trucks". The height of the Crawler can be adjusted independently between 6 and 8 meters by each of the four trucks. The crawler is rectangular, 40 meters long and 34.5 meters wide, but the cargo contact points are positioned in a square 27 meters to a side
Since words can not be used to adequately describe its dimensions, let us break it down. The four trucks are 3 meters high and 12 meters long with two treads each. Each tread has 57 shoes per track. Each shoe weighs over one ton. This is all just to support the load, not to move it. The moving is done by 16 375 horsepower electric traction motors, two to a tread, four to a truck. These are powered by four 1,000 kilowatt generators in the main body, which are turned by two 2,750 horsepower diesel engines. This is all just to move the thing in one of two directions, forward and backward. Jacking, steering, lighting, ventilation, and the onboard systems are powered by two additional 750 kilowatt generators turned by two more 1,065 horsepower diesel engines. Two additional 150 kw generators are needed to raise and lower the platform. In case you didn't keep tally that's 7630 horsies of Diesel power being made into 5800 kilowatts of electricity.
This thing pokes along at 3 kph, 1.5kph loaded, and gets a full 0 mpg. That's right, 0 mpg. Because when you round 0.007 mpg, it becomes zero. Back on track, this means that the Crawler gets 42 feet per gallon, at 125.7 gallons per mile. It takes about 1,000 gallons to move the Shuttle and MLP between the Vehicle Assembly Building and the launch pad. This drinks from the combined 5,000 gallons of onboard fuel storage. All this makes things hot, so 500 gallons of water circulates through six radiators each with up to a 75 hp pump. The crawler is also said to be the loudest vehicle on earth, even after taking into account it's six 9 foot long 3000 pound mufflers.
The Crawler is controlled from one of two cabs on opposite corners of the Crawler. They don't try to back this thing up, they just reorient themselves and switch control cabins. The crew consists of one driver, four observers advising the driver, and six technicians minding the many systems. When the Crawlers where first used during the Apollo missions, the crew were all actually supplied by the Bendix Commercial Vehicle Systems company, which seems to specialize in heavy trucks, but I can find no data on the current crew. The driver's cabin has the regular instrumentation of gas pedal, brakes, speedometer. air conditioning, two way radio. The ignition process is no simple turning of key. There is a 37 page checklist to be followed that involves charging circuits, pressurizing pnuematic and hydraulic systems, and setting up the generators. But I must wonder, what kind of acceleration does a 6 million pound vehicle get when carrying 12 millions pounds of cargo? Does he just tape the gas pedal to the floor and read the paper until the speedometer jumps from '0' to '1'?
A day in the life of Hans (or Franz)
Well, first they decide who has to go to work today based on either a past wrestling match or an immediate coin toss. Then whoever loses makes a laser guided entry into the Vehicle Assembly Building and parks under the Mobile Launch Platform, lets say Hans lost. All entries and exits are laser guided, as this is a big bull in a big China shop, and precision is required. The MLP usually has the Space Shuttle sitting on it and itself sits on five pedestals in the VAB, so Hans has to use his two 150 kw generators to lift his platform to meet the MLP. Then he has to keep pushing to take the 12 million pound load and lift the MLP off the pedestals and begin moving forward.
Then it's a leisurely 5 hour drive at 1 kph to the launch pad. During this whole drive and the 5 degree incline it involves, Hans keeps himself and his cargo safely level to within 10 arc minutes with a fancy laser measurement system and the JEL Cylinders, which raise the rear end precisely as much as needed to stay within the 10 arc minutes of deviation. Upon reaching the launch platform, Hans drives in and lowers the MLP unto another set of pedestals (to the precise tune of 2 inches), then makes his way to a sheltered location to wait out the fiery launch. Upon departure, Hans makes his way back to the launch platform and takes the now 3.2 million pounds lighter MLP back to the Vehicle Assembly Building, then goes back to bed. All in a days work, if it's that time of the month he switches out his 400 gallon oil drum.
These two kids were built over three years for the exorbitant sum of $14 million 1967 dollars by Marion Power Shovel Company of Ohio with the original purpose of transporting Saturn V rockets as were used for the Apollo missions. They where assembled on-site instead of attempting any crazy stunt like going cross country in a vehicle wider than the New Jersey Turnpike. In 1977 the Crawlers were named National Historic Mechanical Engineering Landmarks by the American Society of Mechanical Engineers and modified to serve in the Space Shuttle project. Since their creation the Crawlers have racked up a grand total of 2,526 miles of travel, all at either 1 or 2 miles per hour.