Detailed Product Description Crawler tractor1, track the use of Direct-coupled drive VVVF control. ... 2, the upper part of the flexible cylinder compact crawler used to automatically adapt to changes in specifications for pipe ... pipe specifications. 3, using V-high coefficient of friction rubber.Crawler tractor parameters:ModelQY125/3QY250/4QY450/4QY630/6QY800/6Traction range/mm ...