reaperexpress
Senior Member
Is the MP40's speed limit engine horsepower or a limit of the wheelset etc?
Im curious because the current MP40 fleet is being converted to dual cummins Q60 engines with a total of 5400 hp, much more than the current 4000 hp. http://www.railway-technology.com/news/newsmotivepower-repower-metrolinx-locomotives-new-engines
Even more curious is that wikipedia states that the max speed of the MP40 is 108 mph (174 km/h) http://en.wikipedia.org/wiki/MPI_MPXpress
Here is my source for GO's MP40 top speed.
Locomotives can be equipped with a variety of final drive gear ratios (the ratio between the electric motor and the wheels). A ratio that has the motor spinning faster for a given ground speed will provide more torque and acceleration, whereas the opposite would provide a higher top speed.
For example, when VIA's F40PHs were overhauled, I'm guessing they had the final drive ratio changed to reflect that they were getting an increase in useable horsepower, which in turn allowed their top speed to be increased from 90 mph (145 km/h) to 95 mph (153 km/h). But I'm having trouble finding sources to support this notion.
In any case, I'm also guessing that GO opted for a gear ratio that would provide the best acceleration while still being able to (approximately) attain the highest speed limit. I assume that the new more-powerful engines will have the gear ratio set such that all of the extra power is put toward acceleration rather than top speed.
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