I have two questions I have never heard answers too.
In multi engine lashups, what determines whether 2nd, 3rd, or 4th units run cab forward or backwards. Does the direction affect drive train wear?
Air brakes. I understood that engine air was used to keep brakes open and brakes would be applied if air pressure was lost. How do brakes work in yards with car movement w/out an engine?
Usually just dumb luck–though it’s nice to have a forward-facing unit at either end of the consist. No, it has no effect whatsover on the operation.
The air is bled off from the car before it is capable of rolling freely.
…If you care to read more on the subject you might install a few words in “search” of the question of which way engines run in a consist as we had quite a discussion on this subject back a few weeks ago. Might be as long as a month ago…
LarrySmith -
There’s that word again . . .
Tell me, what does your railroad use to “lash” 'em up? Do you tie them together with rope?
Diesels, no matter what you say, are never “lashed” up. They are coupled up to make “consists”.
Pulleeze!!!
Ol’ Ed
There’s a panel on the rear cab wall w/ a switch that determines if a given unit in the power consist (lashup is a railfan term) is a controlling unit or if it’s being controlled from another unit and whether the controlling unit is coupled ahead or behind. This permits the lead engine to control the headlights for forward or backwards movement and insures that all the wheels in the consist are going in the same direction and controlls the dynamic brakes in all units. The brakes work the same for the whole train or, using the independent brake, for all the units in the consist. As noted above, when cars are being switched, the air is generally bled off and the cars are free rolling. I suppose there might be some circumstance where a car w/ air in the system might be cut loose but, as soon as the hoses came uncoupled, the brakes would go into emergency. I,ve never seen or heard of it being done (at least not deliberately) but it’s theoretically possible as long as the angle cock to the engine was shut.
Ooops! I’ll have to try to remember to type “anglecocks” as a single word to avoid upseting the automatic censor.
that wall switch you talk about has nothing to do with how the units respond to throttle or to brake applications . or if it will go forward or backwards. that switch is for the headlight activation only.
The switches on the back cab wall are for headlight control only…
Your choices are;
Controlled from a unit coupled at the long hood.
Controlled from a unit coupled at the short hood.
Controlled from a unit coupled at either end. (used when a unit is in the middle of a three or more unit consist)
Single or controling unit.
Ditch lights work on a seperate system, so if you want to PO your engineer, get on the unit behind him and turn on the ditch lights that face him.
This keeps him from using the mirrors to often to check his hair![8D]
On the bottom of the older control panel, and on the facing edge of the newer ones is a valve for the brake system, marked “Lead or Trailing” which controls both the train brake and the independent brake (locomotive brake).
This valve cuts out the control stand in that unit, and by hooking up the air hoses between units this gives control of both the brake systems, locomotive and train brake, to any other unit at either end with an active control stand.
Putting this valve in trail, setting the reverser in neutral and removing it, and putting the throttle in idle, using the back panel switches to choose which end of the consist controls the lights are all that is needed…plugging in the MU cable, the big air hose, and the other ancillary hoses pretty much sets up the trailing units…the signal from the leading unit will tell the relays in the trailing units to follow the lead command, regardless of which way they are facing, because of the way the wiring harness is set up.
The locomotives don’t care or know which way is forward…all the system does is tell them “go this way, or go that way”…
It is a simple and fairly failsafe system.
If you forget or fail to connect an MU cable, then all the locomotives from that missed connection back become nothing more than really heavy boxcars.
By removing th