The Caterpillar D7E is the first hybrid dozer. It was developed by Caterpillar to meet new environmental and sound regulations in the U.S. and Europe. Caterpillar showed it off at a demonstration event in California on June 11, 2009.
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The D7E is considered a midsize dozer with a broad array of applications. The D7E will replace the diesel-only D7R in the U.S. and European markets. Caterpillars range of tracked dozers goes from a D3K model, weighing 17,185 pounds, all the way up to the D11T, at 230,100 pounds. The D7E comes in at 56,669 pounds.
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The D7E is a series hybrid, using this 9-liter diesel engine to generate electricity, powering its electric drive motors. The engine runs at a near constant speed, an optimal power band for fuel efficiency. A standard tractor's engine has to change speed whenever greater power is required.
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The big metal tracks on the D7E are turned by a pair or electric motors contained in a module. They aren't directly connected to the tracks, going through a differential that lets the tracks send power back into the system. This mechanical regeneration merely sends power from one track to the other during turns, taking load off the motors.
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These are the hydraulic lines controlling the D7E's rear ripper. A similar hydraulic system controls the blade on the front. The hydraulics rely on power from the diesel engine, as there isn't an equivalently efficient electric system to replace hydraulic pistons.
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The air conditioning module on the D7E is electric-powered, and works as a self-contained unit. Keeping it largely separate from the engine makes maintenance on both easier.
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The cab of the D7E represents all the comforts of modern earth-moving equipment. The seat sits on shock absorbers, and there is air conditioning. Big windows allow good visibility all around, and there is also a rearview monitor.
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This is the main drive controller for the D7E, handling steering and movement. With a dozer, you set the speed, then push a rocker switch for forward or reverse. The electric motors driving the D7E mean there is no gearbox to worry about.
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During a live demonstration, a Caterpillar driver took the D7E over this hill, balancing briefly on the crest.
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Showing off its turning capability, the driver pivots the tractor on this slope.
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In all of its work functions, the D7E uses less fuel than its equivalent nonhybrid version, representing up to 30 percent better fuel economy.
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The D7E can actually move more material per hour than its conventional counterpart because of the greater torque afforded by the electric drivetrain and eliminating the need to change gears.
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A 40 year old D7G was also on hand at the demonstration site, showing an example of an older tractor fitted with a new, more efficient and less-polluting diesel engine. Unfortunately, older tractors won't be refitted with hybrid systems.
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