Quote:
Originally Posted by Bicycle Bob
I think that the main reasons for diesel-electric drive are to avoid burning out a clutch on start-up, and to keep the whole train from jerking with each shift. The ballast is also handy for traction. Presumably, one could arrange for a separate mechanical drive for use at speed, with a burst of power from the inertia of the generator in lieu of a battery to power the electric motors during a shift on the mechanical transmission.
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Don't forget reverse. Locomotives run at the same speed and efficiency in either direction.
You also get cool benefits like slugs, which are locomotives (usually obsolete models) with the prime mover removed (and often replaced with ballast) but the traction motors intact. The slug is attached to a regular locomotive, which can power its own electric motors, as well as those on the slug. They're used in switch yards and other situations where you need a lot of tractive effort, but not a lot of top speed.