Reply to post:

Please, re-read your own post before being so daft as to claim I *make* your point. I'll help you out:

"Engines are not trivially scalable, and in any case a jet engine can have problems in a ground vehicle due to the considerable centrifugal forces of the high speed turbines causing problems when cornering. Although those can be alleviated by mounting it vertically."

The "considerable" centrifugal forces obviously aren't, as none of the examples mentioned had a) any cornering issues, or b) turbines mounted vertically. Scalability isn't a problem either, as there are plenty of examples of gas turbine applications ranging from the micro-turbines used in the C-X75 through to the larger turbines used in the Rover JET1 and APT-E.

There is an issue, one you completely fail to mention, which is throttle response on gas turbine/mechanical drive systems. It was this that caused issues with the JET1 (for example). The Jaguar C-X75 didn't go in to production as the market for an £800,000 - £1,000,000 million niche supercar was considered non-existent in 2010, less than 2 years after the financial crash.

APT-E worked fine, with the gas turbines driving electrical generators, but was not adopted for production as Leyand stopped manufacture of the turbine it used. An additional concern was that BR have had to maintain a fleet of diesel, electric, and gas turbine powered rolling stock. The same issue that caused BR to eventually scrap diesel-hydraulic locomotives and instead use diesel-electric. In France SNCF operated the Turbotrains, two classes of turbine powered trains that were production models rather than one-off prototypes.

The issues around the widespread adoption of gas turbines comes down to infrastructure and economics. So yes, there were good reasons why none of the vehicles mentioned went in to production. However those reasons had absolutely nothing to do with the points you made.