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Originally Posted by jamesqf
That would give it two distinct power paths, so it'd be a hybrid.
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Even though all the energy still goes through the same electric drive motor in either mode?
Even if the source of that electrical energy is just another diesel generator?
Even if the source of that electrical energy is just another train braking?
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Quote:
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Originally Posted by dcb
No, because you can add a "granny gear" to a regular transmission, with a lot greater transmission efficiency than driving a generator driving a motor. The inefficiency of such a setup will marginalize/negate your ability to downsize the engine.
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Something else occurred to me this morning ...
The GE Dash 9-44CW Diesel - Electric ( an older design ) produces Starting torque of up to 142,000 lbf from it's 4,400 HP electric drive motor.
That seems like a very tall order to me for a mechanically connected Diesel engine ... especially if we insist on not up-sizing the diesel engine any from its roll as a generator engine ... sense the Diesel literally has zero torque at zero RPMs... the initial breaking of rest mass inertia of the entire locomotive comes from a build of of rotating mass being connected to the stationary vehicle and all the mass of the load.
The clutch , flywheel , gear ratios , massive transmission components , enormous complexity of such a massive complex transmission ... that not only has to pull out from zero , but also shift gears smoothly and accelerate up to full speeds.
A mechanical transmission capable of performing this task ... I would anticipate not only being more expensive than the electric drive motor option ... but would also be much less reliable in the operating life of a locomotive.
Just like automotive engines that are mechanically connected the diesel engine such a design would no longer be operating the engine at it's peak efficiency , and the average operating efficiency of the diesel engine itself would drop considerably from the varying loads.