section of the front frame member in a selected longitudinal relationship with the front frame member with a portion of the plate 164 overlying a portion of the channel structure 126 the lapping portions actually being secured together similarly bores 180 are provided in the forward outer corners of the rear floor plate and are adapted for alignment with selected bores 160 in angle irons 156 and 158 for further attachment of the rear frame member to the front frame section in a selected longitudinal relationship therewith it will be appreciated that the vehicle frame described allows for adjustment of the vehicle length battery compartment and counter balance by varying the spacing of rear member 162 from front member 110 and registry of bores 154 and 180 with selected bores 178 and 160 respectively in addition the vehicle wheelbase may be varied by changing the mounting of axle mounting block 144 at bores 148 in channel structure 126 however the extent to which such features can be varied will be limited to the combination of respective mounting bores provided for extended adjustment of all three features or for construction of vehicles of a larger scale using the foregoing components a channel extender structure 190 is provided the channel extender 190 includes a bottom plate 192 and side plates 194 which form a channel which is congruent with and will nest under channel structure 126 channel extender 190 includes a forward end provided with flanges 196 secured to the outer edges of side plates 194 and to triangular gussets 198 which extend below bottom plate 192 bores 200 provided in the flanges 196 are arranged to be.