I thought about using a 1/2" electric drill and chain drive on each wheel. A generator would supply power instead of an engine. (Or get 12 or 24V battery powered tools, optional generator(s) to keep them charged.)
1 british hp is 745 watts, it's close enough to our hp.
A web search found this:
"Hammer Drill Meterk 7.0 Amp 1/2 Inch Corded Drill 850W, 3000RPM Dual Switch Between Impact Drill and Electric Drill, With Adjustable Speed for Drilling Wood, Steel, Concrete & Plastic DIY Drilling is the perfect fit for your needs"
What I like about the 1/2 inch drills is the housing usually has tapped holes for handles & things that could become motor mounts.
At 120VAC 850W would draw 7 amps theoretical, more actual.
That project is on the back burner for me but simmering.