"Piping" vs. dead HEP vs. batteries - what are the options?

[dbperry]

Obviously when a screamer dies, the train is completely stuck.

But other than that, are there a variety of situations to keep a train with problems moving depending on the combination of the loco and the control coach?

Is the HEP on a F40PH or HSP needed to power both the control stand in the control coach AND (or) the control stand in the loco? Is this different depending on the control coach? The K-car control stands look pretty mechanical (not much electricity needed) while I could believe that the Rotem control stands need HEP. Are all control coach control stands equipped with a battery to allow some operation without HEP?

"Piping" is the procedure of having the engineer operate the loco from the control stand in the loco, while a conductor looks out the window of the control coach to call signals. Correct? Obviously this would only be applicable on inbound trips, and I think it requires restricted speed. Is "piping" only useful if there is a problem with the control coach control stand?

Are the electrical systems not separated enough that you couldn't have a small alternator run off the main engine to power the control stand in the control coach, eliminating the reliance on the HEP for operating the train?

Although the HSP doesn't have a dedicated HEP, the alternator that is used to provide 'hotel' services power essentially functions like the HEP on a F40PH, correct? So if it fails (or if something in the power distribution), you're in the same boat as you would be with a F40PH with a dead HEP, correct?

Any insight would be interesting, and feel free to correct my inaccurate terminology.

Thanks

Dave

[Gerry6309]

I am familiar with many MU systems, though not the specific ones in question.

In most cases the locomotive's batteries are train lined to allow for multiple locomotives and push-pull operation. A control stand in a cab car is just like one in a locomotive. It should work, even if there is no head-end-power. HEP is used for car lighting and heating, air-conditioning and other loads. Controls, markers, headlights, wipers,sanders and other operation related functions are normally operated from the locomotives auxiliary power, backed up by its batteries. With the proper MU and air connections, a freight locomotive could be used to run a train from a control coach. Ordinary freight cars do not carry MU wiring and air lines, but radio signals can be used to control "helpers".

There are two extra air lines piped to a control coach, a main reservoir pipe to allow the brakes to release, and a control pipe to allow graduated release. The third, the brake pipe, controls the brakes and is the only pipe carried on freight cars. All passenger cars carry a control pipe which carries constant pressure.

MU train lines are simple on-off signals which control various signals which control the throttle position, reverser, dynamic braking, series-parallel transition and field shunting. A "screamer" would use changes in the generator field, in place of the throttle, for starting. Electronics in the HSP-46 would convert the normal signals to allow for AC traction motors, thus the screamer and HSP-46 combos used in break-in operations. I suspect that the HSPs use separate inverters to create their head-end and traction power, from a high voltage DC bus. This avoids the need for a constant 3600 RPM HEP Alternator. Correct me if I am wrong...