Rapido Trains F40PH-2D Operating Instructions Manual - page 9

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engine) via a 2:1 ratio gearbox.

In order for the HEP alternator to turn at the needed speed of 1786 RPM, the prime 

mover must always be running at its maximum speed of 893 RPM. So rather than hear 

an F40PH-2D labour through the notches from idle to eight, it always sounds like it is 

screaming at notch eight.

The throttle does not control the prime mover’s speed; instead, it controls the flow of cur-

rent in the Traction Alternator, which in turn controls the amount of power delivered to 

the Traction Motors. From our perspective as model railroaders, the locomotive sounds 

pretty much the same no matter what speed it’s going or how heavy a load it is pulling.

HEP MODE: IDLE, STANDBY AND RUN

Inside the cab of a real F40PH-2D is the Head End Power Mode Switch. The three posi-

tions are Idle, Standby and Run. This switch is key to how the locomotive sounds and 

operates.

IDLE: When the HEP Power Mode Switch is set to Idle, the F40PH-2D operates like a 

freight engine – as you increase the throttle, the prime mover speed increases from its 

idling speed of 460 RPM up to its maximum of 893 RPM. The locomotive power is di-

rectly tied to the prime mover speed.

By default, your model is set to Idle. If you put it on the track and advance your throttle, 

the HEP alternator is not engaged and the locomotive will operate and sound like a 

freight engine. If you are running your locomotive in freight service or you are pulling 

steam-heated passenger cars (such as VIA’s blue and yellow cars), then you will want to 

keep the Head End Power Mode Switch at Idle. 

STANDBY: Standby is meant to be used when the train is idling for a long time at a 

station, such as between runs. The HEP is provided by the Traction Alternator rather 

than the HEP Alternator. Since the Traction Alternator is being used for HEP and not for 

the Traction Motors, the locomotive cannot move. The prime mover rotates at 720 RPM, 

which roughly sounds like Notch Six. 

RUN: Once the F40PH-2D is in Run, the prime mover is rotating at 893 RPM and the 

second engineer can turn on the HEP to the passenger cars. From a railfan’s perspective, 

there is no noticeable difference in the sound of the locomotive between Run without the 

HEP turned on and Run with the HEP turned on. So we don’t have an extra button for 

that. In general practice, the locomotive is kept in Run for its entire trip – i.e. from termi-

nus to terminus — even if it is making several station stops along the way.

Note that the locomotive must be stationary when changing between Head End Power 

modes.