Matt Denton, from Hampshire, estimates his "very expensive toy" has cost him hundreds of thousands of pounds.
He says a mining company and a marine research organisation are now interested in his design and he hopes it might be used at science fairs.
During its development the machine had one outing, at a music festival, where Mr Denton says it was well received.
"It's an entertainment vehicle," he said. "But I hope it will inspire people."
The project was only initially intended to take 12 months, Mr Denton, who usually specialises in small-scale animatronics for the film industry, said.
"After 18 months we tried the model out. We had to completely strip out and rebuild the legs. They were too heavy and complicated.
"I'm a software and electronics engineer so this was out of my area - I had to learn fast."
The robot, driver-operated by joysticks within a cockpit, can only travel at 1.5km/h (1mph) and manage a distance of 5km on a 20-litre (4.5-gallon) tank of diesel.
"It's not about miles to the gallon, it's about gallons to the mile," he said.
"It wasn't built to be efficient and fast. It was built to look cool and insect-like and fun."
Mr Denton said he was inspired by science fiction to create the "walking" machine.
"But legs are very inefficient - the wheel was invented for a reason," he added.
A giant-mantis robot with hydraulic legs has been unveiled by a designer who spent four years creating it.