BigQ

On a BN line

Jay Pat Loc: Round Rock, Texas, USA

I used to wonder about the locomotives at the rear of the train.
I've been told the rear locomotive(s) sync up by satellite and add power to the front locomotives.
Pat

ghill42 Loc: Colorado

I think the main benefit of putting an engine on the rear of the train, and often in the mid-stream position as well, is to reduce the risk of pulling couplers apart. As freight trains got longer and longer, pulling all that weight from the front alone dramatically increased that problem. Now, rear motive power seems to be a standard configuration with the "heavies." Remote control locos (RCLs) have been in use with the railroads for a long time. The specifics of how those systems communicate with the engineer, I do not know. We need an experienced railroad men to educate us!

GrayGhost

Also provides quicker buildup of the air pressure in the braking system. Supposed to help stop the train quicker (as if you can stop a 7000 ft train quickly.) Also helps pushing up the hills as well so I am told.
73
walt

Jay Pat Loc: Round Rock, Texas, USA

Great, points.
Pat

Tim Stapp Loc: Mid Mitten

I've seen mid-train "helper" locomotives as well on the Canadian National trains running through Michigan (former Grand Trunk line). All of GrayGhost's points may very well apply as well.

cabunit Loc: SE Connecticut

Yes to help with the braking, because the pressure change (it's a pressure DROP that sets the brakes) comes from both the front and the rear, so more of the train applies its brakes at once. A good setup for that is to have the mid-train unit(s) two thirds of the way back with the last third behind it (them); that way, each third of the train gets equal access.

Yes to help with grades.

And yes for another reason. If a train is pulled around a curve, there's more wear on the inside curve rail from the wheel flanges (think of a string being pulled around a curved surface; all the contact is on the inside of the string). If at least some of the train is being pushed, this pressure is relieved to an extent.

Also, apropos of nothing, the second engine in the photo is a Kansas City Southern unit.

Tim Stapp Loc: Mid Mitten

On the Marquette Rail line (former Pere Marquette/C&O/CSX) line in Michigan, there are still flange lubricators that lubricate the flanges on the inside of tight radius curves. I'll try in the next few weeks to photograph the lube that has built up on the ties/ballast from the lubricators that are visible from various locations.

DickC Loc: NE Washington state

Very nice, thanks!