"Christopher Tidy" wrote in message
...
Am Mittwoch, 16. August 2017 22:52:01 UTC+2 schrieb
:
The reason locomotives are diesel-electric is that the electric
motors can deliver torque at 0 RPM - no need to slip a clutch until
the huge mass got rolling.

Interesting comment. I can see this being a key problem. Just thinking
about it, how do diesel engines scale? I mean, the bell housing on a
small car engine has a diameter of what? 30 cm? And on a locomotive
engine maybe 100 cm? So you can have something like a 25 cm diameter
clutch in a car and a 85 cm diameter clutch in a locomotive? Let's
assume it's a single plate clutch for now.

Taking this a bit further, if you have maximum engine torque and 0 rpm
at the wheels, how much power are you briefly sinking into the clutch?
Maybe 50 kW in the car and 1500 kW in the locomotive? Which means you
have 11 times the clutch area and 30 times the power. Following this
logic, I can see how clutch scaling is going to max out at about the
size of a large truck, and on top of that, trains accelerate quite
slowly. The heating might not be so brief.

Nice thought, Randall.

Chris

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