Skidders pull logs from the woods. They may be propelled by rubber tires , as this John Deere skidder with a skidding grapple shown below. Wheeled skidders can generally travel faster than tracked machines, but can not pull as large a load per turn. they are cheaper to purchase, maintain, and operate, however.

A good discussion of rubber tired skidder development can be found at these links:

http://www.aone.com/~robert/skidder.html

http://www.aone.com/~robert/skidder5.html

 

Tracked skidders can be of two types. The first type is the familar bulldozer-type skidder like this Caterpillar 527, with a skidding grapple and a high-roller track arrangement. These tracks are semi-rigid and have great pulling power.

The second type of tracked skidder is the low-ground pressure, torsion suspension vehicle shown below. This machine is now made by KMC of Canada, but is a U.S. design, originally produced by FMC Corp., who made armored personnel carriers. In fact, the tracks are adaptations of the boggie wheel, torsion suspension system of the M-113 APC. Note the difference inthe grapple setup on this machine compared to the other two types above. This grapple can reach out to grasp logs and bunch them together for a load. This ability to move from side to side leads some people to call these swing-graples or bunching grapples.