The selected illustrations are from a story Todd wrote called “The Warbots: The History of Armored War from 1975 to 17,500 A.D” published in Galaxy Science Fiction (October, 1968). The first “mecha“—a robot or machine of humanoid appearance controlled by a smaller humanoid from a cockpit—is generally considered to be Mazinger Z, from the manga of the same name written and illustrated by Go Nagai. Perhaps that designation needs to be reevaluated. Todd’s designs are reminiscent of a number of mecha from the 1970s and 1980s, including the Zentraedi Battlepod in Robotech.
Todd updated his illustrations (below) for 1986’s Body Armor: 2000, edited by Joe Haldeman.
(Images via archive.org and iamanangelchaser)
2 Warps to Neptune 
Wow, Maschinen Krieger might have some ‘splainin to do.
The blogger who posted the later series of illustrations mentioned something to that effect as well.
Nice!