I’m farely new to this hobby and I can see why it can be addictive. But I have questions, mostly from actual observations locally as well as watching youtube videos.
Why do some locomotives use the bell when going over grade crossing and some don’t? Company policy?
If a train has more than one locomotive and are using both for power, can the lead loco control both? Are they electronically coupled?
As above, why would a loco be pointed the opposite direction? Can they still help move the train or are they put in “neutral” and just towed along?
It can, through a system initially developed by Frank Sprague called multiple-unit control. If you look up ‘diesel MU’ you’ll find much more detailed accounts of the details, and the various ways the systems could be provided. Usually the lead locomotive can control more functions than just ‘power’.
DPU is a later version of MU that allows control of power that is ‘remote’ from the lead locomotive’s cab.
Older versions of the system were electrically coupled (through wires in special cables). Sometimes different systems assigned different wires in a cable to ‘non-standard’ functions and you’d have to be careful when connecting them. Baldwin and some other systems used air control for the throttle, which had advantages and disadvantages, but could be equipped with a compatible system to run with ‘normal’ electric MU systems. More modern systems do use electronic components for some of the functionality.
Modern engines are fully bidirectional in terms of making power, with the caveat that if the exhaust ‘leads’ the cooling fans or radiators in tunnels, there can be a problem with heat. Note that before a consist is put into service, the direction for each unit has to be carefully set to “forward” or “reverse” depending on which way it is pointing – you may have noticed a little “F” painted on one end; this signifies ‘front’ for MU setting purposes. Once that is done all the locomotives happily pull together.
Locomotives are coulpled together to operate in MU or Multiple Unit control. The locomotives are connected with a 27 Pin electrical cable between each unit as well as four pneumatic hoses in addition to the air hose that connects to the braking system of the train they a
I hope the folks on here will correct me, but I believe the traction motors need to be electro-magnetically engaged otherwise they will just spin — so they’re kinda automatically disconnected.
I believe this is because there are no permenant magnets in the trucks that would cause constant wear for a locomotive that is dead in tow.
When a locomotive is DIT - it has been configured (with the prime mover shut down or operating) so that no electrical power is being sent to the traction motors - the commutator of the traction motor does revolve as it is geared to the axle upon which it is mounted - there is no electricity working through the traction motor.
The only wear is on the ring gear on the axle and the pinion gear on the traction motor. Such wear is negligable.
So the brakes would be like a semitruck, where they need air applied to move the cars, right? No air and the brakes lock up… I would imagine… (you guys are gonna get tired of my questions soon!)
The thing to remember - in a train, that is required to have a fully charged air brake system - removing air applies the brakes. Increasing air pressure works to release the brakes and recharge the system.
In a railway brake cylinder the spring pushes to release the brake. Air pressure applies the brake. If the entire air brake system on a railcar or locomotive has been bled off to 0 PSI the air brakes are released (this is done on a daily basis when cars are switched). Brake cylinder air pressure may take anywhere from minutes to months to leak off completely, but it cannot be depended on for long periods of time. This is why handbrakes (manually applied parking brakes) are needed, nearly every car and locomotive has one.
Locomotive (known as the indpendent brake) and car (known as the automatic) air brakes work slightly differently, and while they are interconnected the Engineer can control them together or separately. Locomotive brakes are straight air, increasing air pressure applies the brake, it’s that simple. Cars are more complicated.
A car’s air brake system has been designed so that after the system is charged a drop in brake pipe pressure at a rate of at least 3 PSI per minute will cause a brake application. And if the brake pipe pressure drops at a very high rate a emergency brake application is triggered, which involves all the cars applying the maximum air braking effort possible at that point. This is the fail-safe part of the railway air brake system, if a problem occurs (busted air hose, broken coupler, derailment, etc) all the brakes apply automatically and the train comes to a stop.
Understanding why this happens requires a bit more of a detailed explanation of how a car’s control valve works internally.
The air brake application depends on the difference in air pressures on two sides of a slide valve, the reservoir
So locomotives needs air to apply brakes, but cars need a happy balance? I would imagine that a 100-car train would take quite a long time fill all those lines and tanks.
Steve, welcome to the wonderful world of railroading.
Yes, the engine brake can be controlled separately from the train brakes. Ordinarily, when the train brakes are applied, the engine is also braked–unless the engineer stops that braking (“bails the engine brake off”), and the engine can be braked separately.
As you can see, having the cars braked by reducing the brakeline pressure is much faster that having them braked by applying more pressure in the brake line. Indeed, the reduction in pressure travels much faster through the line than an increase in pressure is able to travel.
George Westinghouse’s first brake system was "straight air,"which worked fairly well for short trains, but he soon realized that the genesis of the current system was far superior in braking time, and developed the first version (maany times improved) of the current system…
Yes, it takes time, especially in cold weather, to build the brakeline pressure up in a long string of cars. There are tails of yardmasters or other superior people who insist that a mewly made up train be taken out immediately–and such are instructed in the facts of pumping up.
I may be mistaken - but I believe the operation of railroad Air Brakes comprised about two to three WEEKS of the Engineer Training cirriculum at CSX’s REDI training center before REDI was eliminated by the PTC putsch at CSX.
The classroom portion of CN’s Engineer training program now takes 3 weeks. Many things are skimmed over and others are not mentioned at all. I am given to understand that at one time new Engineers spent nearly 2 months in the classroom, and older heads were given the opportunity to take additional trainer or refresher courses. None of that happens anymore.
Yes, as long as it was charged with air first and its air brake system is working properly.
Cars that have been bled off or have defective air brakes will continue to roll if they are uncoupled from the train. Yard crews take advantage of this when switching by kicking or humping.
This was the main drawback of Westinghouse’s original straight-air system. If anything happened to cause the brake pipe pressure to drop to 0 PSI (busted air hose, broken coupling, derailment, etc) then the train had no brakes, and the tail end could run away backwards. The crew then had to go ‘over the top’ and stop it with handbrakes.
When I went into engine service 15 years, we started out with one week of classroom training at my home terminal, mostly basic mechanical items. Then a month or so of field OJT, then two weeks of classroom training at Salt Lake City. That was mostly rules and running a simulator. They had a working air brake mock-up, but that probably used up a day or less of the classroom time. After that back to OJT until they felt you were ready to be qualifed. About 6 months total, give or take. Those who paid attention as a conductor to what the engineer was doing, where and when he was doing it had a bit easier time in training. {Most of our modern engines have a duplicate operating screen on the conductor’s side. It shows the same thing the engineer sees. At least until that screen was taken out and replaced by the PTC screen.) Some who spent more of their time on inspecting the inside of their eyelids for cracks had it a bit harder.
steve-in-kville
If a train has more than one locomotive and are using both for power, can the lead loco control both?
It can, through a system initially developed by Frank Sprague called multiple-unit control. If you look up ‘diesel MU’ you’ll find much more detailed accounts of the details, and the various ways the systems could be provided. Usually the lead locomotive can control more functions than just ‘power’.
DPU is a later version of MU that allows control of power that is ‘remote’ from the lead locomotive’s cab.
Are they electronically coupled?
Older versions of the system were electrically coupled (through wires in special cables). Sometimes different systems assigned different wires in a cable to ‘non-standard’ functions and you’d have to be careful when connecting them. Baldwin and some other systems used air control for the throttle, which had advantages and disadvantages, but could be equipped with a compatible system to run with ‘normal’ electric MU systems. More modern systems do use electronic components for some of the functionality.
As above, why would a loco be pointed the opposite direction? Can they still help move the train or are they put in “neutral” and just towed along?
Modern engines are fully bidirectional in terms of making power, with the caveat