Thumper is a heavy-duty quarry machine with two arms and caterpillar treads. He is used for loosening rocks.
Thomas & Friends
The workmen were initially impressed with his hard work, however he proved much too powerful. Thumper's arms accidentally dislodged an enormous boulder from the mountain which chased Rusty, Skarloey and Rheneas down the line before nearly crushing Percy and running into the sheds at the mine.
Because of his large size, he often gets out of control on mining sites and causes minor disruptions. After his initial problems at Boulder Quarry, Thumper is now used strictly for slate mining.
Although Thumper never spoke, it has been said he is laid back in approach with a "cool dude" attitude, though he can come across as accident-prone. His manner is cool, and no job is too big for him.
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. However, Thumper does appears to be a Hodge-podge of various different machinery. His front-end is from a GWR 0-4-0 Diesel shunter built by Fowler. His treads appear to be based off the treads of a Kliment Voroshilov tank, albeit with the treads mounted backwards with the drive sprocket in the rear.
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 than loosening or clearing rocks, unless being lightly placed in front of the rock / cliff face to properly function, which thus means that the rock may only be lightly loosened or cracked.
Thumper is painted orange-red with his name painted on the sides of his bonnet in white. His roof is painted black.
- Thumper was never referred to by gender in Rusty and the Boulder, rather he is referred to as "it" instead. Merchandise descriptions confirmed his gender as male.