Thumper is a quarry machine with two arms and caterpillar treads. He is used for loosening rocks.
Thumper is not based upon any known quarry machine - at any rate, a machine of his type would be extremely hazardous to those around due to the lack of a window at the front of the cab, making the operator unable to see.
In addition, assuming that a window would be technically where the face would be, such a machine would be impractical in real life as well due to the end of its arms not providing a sufficient amount of area to loosen the rock on the sides and below and above the machine, let alone be capable of making a proper hole through the cliff face and properly loosening or clearing rocks. The arms appear to be on a non-flexible joint with the siderods attached to the inner arms appearing to be quite thin, thus potentially leading to the machine being more capable of damaging itself more than loosening or clearing rocks, unless being lightly placed in front of the rock / cliff face to properly fuction, which thus also means that the rock may only be lightly loosened or cracked. Thumper's treads appear to be based off the treads of a Panzer IV tank, albeit with the treads mounted backwards with the drive sprocket in the rear.
Thumper is painted orange-red with his name painted on the sides of his bonnet in white. His roof is painted black.