tractor , especially farm tractor . a tractor construction is disclosed which is particularly adaptable for manufacture as a plurality of independent units , shipment of same in knock - down form and assembly and maintenance by unskilled labor using only simple tools . the construction comprises a unitary frame member together with independent and separable components including a front end assembly , an engine assembly , a control unit assembly and a rear end assembly . each of these assemblies are mountable on the frame structure independently of each other and interconnection therebetween is held to a minimum . maintenance is likewise at a minimum and the above - mentioned assemblies can be replaced if necessary by unskilled labor and with use of only simple tools .