The hybrid technology also allows adaptation of a few unique features, one of which is coast control. With a torque converter machine when you let off the throttle, the loader free-wheels. With a hydrostatic machine, when you let off the throttle, you get dynamic braking. With coast control, you can select from four settings – from no dynamic braking to dynamic braking similar to a hydrostatic machine.
Another unique feature is Full Rim Pull Control. John Deere wheel loaders currently come with Spin Control. “It is a reactive system,” says Chesterman. “It has four different settings.” When a conventional wheel loader starts digging, it drops engine rpm to keep the wheels from spinning. For the 644K Hybrid, the system has been expanded to Full Rim Pull Control. "We are not changing the speed of the engine. It is just not going to generate as much pushing force or rim pull in certain settings."
Similar but Different
The 644K Hybrid uses many of the components of the conventional 644. For instance, the frame is basically the same.
“The axles and brakes are identical to the conventional drive machine,” says Chesterman. “We do some things to the counter-weighting of the machine, but this particular model we manufacture in Stage II emissions, Tier 3 emissions, Interim Tier 4 conventional and now Interim Tier 4 hybrid. We always have to do some juggling based on the engine and the aftertreatment device.”
John Deere teamed up with industry leading suppliers for the electric motors and drives, but it manufacturers its own inverters, as well as the transmission to which the electric motor is attached.
Will this technology be applied to other loaders in the John Deere wheel loader line? Chesterman indicates that this technology is scalable. “We are going to apply the correct technology to the right machine. This technology is flexible.”