[Animats]

> Mechanical transmissions like in cars were only in use for a very short time.

Fortunately.[1][2] British Rail tried in the 1950s. Four 12-cylinder Diesel engines driving the the wheels through three differentials and four hydraulic clutches. The engines were geared such that the speeds added. As speed increased, more engines were turned on. Since startup only used one engine, starting pull was rather low for the engine power installed.

Only one was ever built.

[1] https://en.wikipedia.org/wiki/British_Rail_10100

[2] https://www.youtube.com/watch?v=oYRZIQKMmWo