Expanding on the Logging Crew theme that I introduced earlier (see the Logging Crew
idea), I have created a tracked harvester. If you've never seen a harvester in action, you can get a pretty good idea about what it does by watching this video
. They are pretty awesome machines. Note though, that the harvester in the video is a Cat 501, while this model is based (loosely) on the newer Cat 541/551/552 family.
As the video demonstrates, the job of a harvester is to fell trees, strip them of all their limbs, cut them to length, and then deposit them in a pile with the other cut logs. At their core, tracked harvesters have a lot in common with tracked excavators, since they both have the same boom-and-stick configuration, but harvesters have a harvesting head at the end of the stick, rather than an excavator bucket.
Most tracked harvesters also have a special feature that most excavators lack: The cab can be tilted, allowing the harvester to work in steep terrain while the operator remains level. I have included this feature in the model with a Technic-like control knob in the undercarriage. Turning the control knob drives a worm gear that tilts the superstructure forward or backward up to about 20 degrees.
Here is a sequence of images that show how this model can perform the harvesting task in a LEGO forest. First the grappling arms of the harvester head grab a tree near its base.