Edward Sylvester Ellis 
The Huge Hunter ;Or, The Steam Man Of The Prairies [EPUB ebook] 

When Johnny Brainerd was a little child, he first began to tinker. He quickly adopts his mother's proposal to build a mechanical man after growing weary of creating the usual inventions. He keeps it hidden in his garage till a strange-looking man eventually sees it. Baldy Bicknell, a tracker, and frontiersman are immediately enthralled by the steam man. Johnny can try it out in the prairies, where he promises it will be very helpful for another project he is working on. Baldy is working with two unreliable gold miners! But the guys have consistently faced assaults from Indians. The presence of a massive steam man may frighten the Indians. A young prodigy creates a steam-powered robot that can walk quickly and pull a cart in its wake. He is persuaded by a frontiersman that traveling across Indian territory to a gold mine he has staked a claim to would be the ideal field test for the steam man. They engage in buffalo racing, Indian battles, and prairie exploration on the route.