A variety of auto and truck manufacturers were experimenting with gas turbine powerplants in the 1950’s and 60’s. Perhaps best known was Chrysler’s extensive turbine program that produced a series of turbine-powered cars and trucks; most famously the mid-60’s bronze Elwood Engel styled two-door coupes that were provided to selected members of the public for real-world testing. But turbine applications in commercial vehicles were being looked at also – and in this category GM was the leader.
GM TDH 4512
One of GM’s first turbine concepts was in fact a bus. Built in conjunction with the Firebird I concept car in 1953, a TDH 4512 coach that had been in short term use by Detroit Transit was repurchased by GM and fitted with the company’s first generation turbine engine designated GT 300; nicknamed “Whirlfire.” Choosing a bus as an early experimental platform made sense – all the seats could be removed leaving lots of room for various testing and monitoring equipment, and the operating technicians. GM called this first generation bus the Turbo-Cruiser.
While the GT 300 turbine powerplant produced twice the horsepower of the GM 6-71 diesel then in use, it also had twice the fuel consumption – which along with emissions, were limitations never fully solved that would ultimately spell the end of vehicle turbine programs some twenty-five years later.
GM Bison Chevy Turbo Titan III
Turbo Cruiser II
GM’s turbine program continued to progress through the 1950’s and into the 60’s with the Firebird II and III concept cars, and the GM Bison and Chevy Turbo Titan series trucks. In 1964, they again mated a turbine engine with a bus – naming it the Turbo-Cruiser II. This was a GM TDH 5303 “New Look” coach, re-engined with a GT 309 turbine powerplant, that produced around 280 horsepower and 700 ft lbs of torque – about the same as the 8V-71 diesel then in use, though the turbine engine weighed significantly less. But while improved, the basic limitations still remained – cost to manufacture, fuel consumption, acceleration lag, lack of engine braking, etc.
Keeping at it, in 1968, GM updated the TC II with a new “Toric” toroidal-type continuously variable transmission (CVT) and named this bus the Turbo-Cruiser III. Though GM wasn’t able to solve durability issues, it was an interesting R&D effort – a video animation of a current toroidal variator is at the end of the article.
GM tried twice more with a turbine-engined bus – the RTX of 1968 used the GT 309 with completely new, futuristic coachwork, and in 1971, a revised RTX called the RTS 3T was a competitor in the Urban Mass Transportation Administration’s “Transbus” project. Neither bus made it to production and GM moved forward with the conventional diesel-engined RTS II series.
Today, with battery-electric slowly overtaking diesel, CNG, and fuel-cells as the future motive power of public (bus) transportation, it’s interesting to look back on some of these earlier attempts to broaden power train options for transport operators. It also again showcases GM at it’s peak in the 1960’s – manufacturing, styling, research and development – the General was “at the top of it’s game.”