Push-Pull operation

It would depend on whether he needs the power of both engines to get over the road with the new train. If he needs them both, they both stay running and on line.

If he only needs the power of one engine, he would typically shut down the trailing unit and run from the operating unit...unless it is in the dead of winter. In that case he would leave the trailing unit idling and just take it off line.

There is no traction  advantage or disadvantage having the lead unit providing active traction rather than being pushed from second unit.

Thanks Rich.  Just what I assumed the answer(s) would be, but never hurts to ask the experts.

There is one difference when the leading locomotive unit is isolated.  It is neither an advantage nor a disadvantage.

When the leading locomotive is actually being pushed by trailing units, it does not track as well, and tends to bounce vertically and hunt horizontally in response to track irregularities.  This is in contrast the tracking when the unit is on line, creating draft or buff force at the rear drawbar, in which case the higher the amperage is, the less it will respond to track irregularities.

Thus, although I have never ridden on one, I would expect that the Amtrak "cabbage" F40PH units that have been converted to unpowered control cab baggage cars probably bounce and hunt when moving at passenger train speeds.

I might be missing something here. You have two engines coupled together back to back. The train arrives where it's going, and the consist is uncoupled so it can haul another train, in this case, in the other direction. Then the question is, which of the two engines would be running? Why would the railroad have two engines in a consist and only have one running and the other just "along for the ride"? Unless we're talking F-units or something. A big selling point for road switchers (GPs, SDs) is/was that they could be operated in either direction without needing to be turned. I would think if there were two engines, both would be needed and both would be powered.

I know some railroads run local freights with an engine at each end of the train, and only use one at a time as needed to switch trailing or facing point spur tracks. But not two engines coupled back to back in a consist AFAIK?

Stix,

I think the reason is for safety.  Engineers have a better 180 degree view from front cab windows than out one window facing along the long hood ahead, with no visibility to other side (and yes conductor/brakeman/whatever is suppose to be those eyes).  Also if running one unit, it might need turning to comply with RR rules, and nearby turntables are pretty much things of the past AFAIK.

Plus I suppose, you have spare unit in case your prime mover fails in middle of no where.

Number 90 posted:

There is one difference when the leading locomotive unit is isolated.  It is neither an advantage nor a disadvantage.

When the leading locomotive is actually being pushed by trailing units, it does not track as well, and tends to bounce vertically and hunt horizontally in response to track irregularities.  This is in contrast the tracking when the unit is on line, creating draft or buff force at the rear drawbar, in which case the higher the amperage is, the less it will respond to track irregularities.

Thus, although I have never ridden on one, I would expect that the Amtrak "cabbage" F40PH units that have been converted to unpowered control cab baggage cars probably bounce and hunt when moving at passenger train speeds.

I wondered about how well the lead unit tracked when "dead" and being pushed by rear, which is why I wondered if having the lead unit wheels actively pulling rather than passively pushed was best thing to do

I know on my layout having the trailing engine pushing the un-powered one is asking for trouble especially at switches.  Yes, of course there is a significant weight differences between powered and un-powered layout units, compared to real RR where similar class/make units will weigh about same.