A Diesel Locomotive's Traction Motors

[Anonymous]

A deisel-electric locomotive's drive train goes from its diesel engine to a generator, then to an (or is it some?) electric motor(-s).

How is that final electric stage of its propulsion arranged? Is there one, large traction motor to propel the whole thing? Or more than one, but smaller? Are they one per axle? One per truck? How do they usually do it?

[Anonymous]

David,
They are mounted on the trucks and connected to the axle via gearing that is enclosed to seal the unit from the debris that kicks up while at speed. The number of electric motors depends on the type of truck ie; passenger, freight and the number of axles. Alco PA's nand EMD E units have two per truck with a center idler axle for a total of four per engine. Your four axle freight and switcher units have one per axle for a total of four. Your big SD's, Century's, CW's all have six axles with one motor per axle. I hope that answers your question.

Mike M

[Anonymous]

In the diesels' traction motors' geared mechanical linkage to the axles, what is typically the gear ratio? Is it 1:1, giving the axles the same RPM as the motors supply, (a mechanical advantage ["MA"] of 1)? Is it a reduction ratio, where the axles turn slower (but with increased force i.e. MA greater than 1), or a ratio, where axles turn faster than their driving motors (but with less force -- MA < 1)?

[Anonymous]

It all depends but usually around a 60:1 ratio.