Between 1957 and 1977 Walker was a full-time inventor. In 1961 Walker formed a company called Hamilton Walker Rotary Engines Limited with the aim of producing engines for a wide range of vehicles from lawn mowers to airplanes. From 1964 to 1967 designed at least 16 engines in his farm shed. He patented many of the engines. In 1967 the Sydney Morning Herald ran an article which stated that several Australian and English manufacturers were interested in his engines. Walker also had designed an elliptical shaped car to use the engine in. Walker's engine is believed to be the second working rotary engine after the Wankel engine. A prototype engine was under construction in 1968.
Rotarymotive (alternative name: Crowther Sedan)
In the 1960s all New Zealand assembled cars, except for the Trekka, were CKD's from overseas. Even the Trekka relied on Skoda for its engine. Roly Crowther, a New Zealand speedway driver, heard about Walker's work on rotary engines. Crowther considered that an almost fully indigenously produced vehicle should be possible using Walker's engine in a fiber glass bodied car. Work began on the design and development of the car in 1965. Ferris de Joux was approached to design a two-door four seat fiber glass bodied car and Dennis Smith was tasked with designing the chassis. The car was to be rear engined and powered by a Walker Rotary engine coupled to a DAFVariomatic transmission. Toyota instruments and lighting was to be used. The front suspension was from a Triumph Herald and modified to suit. The rear suspension was independent. By 1968 the prototype was completed at Mount Wellington, Auckland but the Walker engine was still under development. As a temporary measure an NSU Prinzair cooled engine was fitted. The car was initially named the Rotarymotive and testing begun. It was slightly bigger than a Morris 1100. The rotary engine weighed under 20 kg and produced between 60 and 100 bhp. A new company Pacific Auto Industries Limited was formed with UEB's Sir James Doig as Chairman with the aim of producing the car. A second prototype was planned for later in 1970 or early 1971 using a 1200cc Hamilton Walker rotary engine. The company was formed just one month after the Anziel Nova development was dropped, but failed to raise the funds needed to start production despite an Australian firm indicating it wanted to import 5000 cars a year. The prototype was still in existence in 2011. Crowther went on make the Crowther Toiler in the mid 1970s.
Other inventions
Apart from the rotary engines and car, Walker completed a number of inventions such as the internal-head diesel and the 1965 Walker air-cushioned hydrofoil craft.
