Voyager/Meridian Engine Management

[richa2002]

I've always been curious as to how the engine on a Voyager or Meridian revs in relation to the driver's power handle position.

Is it directly proportional so if you select 50% power for example, the engine will rev to halfway between idle and full, or is it more clever than that as I suspect?

For example, can engine rpm vary even if the driver keeps the power handle in the same position, perhaps due to the load changing as speed is gained or lost?

Also, is there a point for example where the engine reaches full rpm and then simply the load being placed on it changes depending on power handle position?

Any information from drivers or those who know these units inside out would be much appreciated! Thanks.

 

[NEDdrv]

I've always been curious as to how the engine on a Voyager or Meridian revs in relation to the driver's power handle position.

Is it directly proportional so if you select 50% power for example, the engine will rev to halfway between idle and full, or is it more clever than that as I suspect?

For example, can engine rpm vary even if the driver keeps the power handle in the same position, perhaps due to the load changing as speed is gained or lost?

Also, is there a point for example where the engine reaches full rpm and then simply the load being placed on it changes depending on power handle position?

Any information from drivers or those who know these units inside out would be much appreciated! Thanks.

As far as voyagers go, they idle at 994rpm, 1154 I think when in forward, 1200 ish when in power notch and 1796 at full power. No set positions between power notch and full.

 

[365 Networker]

I've noticed that the engines on Voyagers seem to rev up a few seconds after initial movement - perhaps there is enough power from idle for the motors for this initial movement. Perhaps this is also the case at higher speeds, for example on a downhill gradient, the revs will reduce, due to less resistance on the motors. I can only guess of course and would also be interested if anyone can confirm this. You can see what I am referring to in this video from Birmingham New Street.

 

[Nottingham59]

I've noticed that the engines on Voyagers seem to rev up a few seconds after initial movement - perhaps there is enough power from idle for the motors for this initial movement.

At starting speeds, even full acceleration at maximum tractive effort uses very little power.

It's only when you get above walking pace that you can start to lay down the power, and only above around 10 or 20mph can you apply full power to the wheels without provoking wheelslip.

I'd expect that the engine management system is just responding to the increasing power demand as the train accelerates away from a standing start.

 

[edwin_m]

At starting speeds, even full acceleration at maximum tractive effort uses very little power.

It's only when you get above walking pace that you can start to lay down the power, and only above around 10 or 20mph can you apply full power to the wheels without provoking wheelslip.

Indeed. Power equals force (tractive effort) multiplied by speed, so at low speeds very little power is needed.

This is notcieable in electric transmissions but with mechanical or hydraulic transmission the engine tends to be at high revs to start moving, with most of this power going to heat in the transmission.