One of my favorite train watching sites is the Alpine, TX station platform. Alpine is a crew change point for Amtrak and the UP.
Whilst in Alpine this week I watched two UP freights get underway after changing crews. They were westbound. The engines and first few cars were located on a slight upgrade; the remainder of the train was either in a slight swale or downgrade coming into Alpine.
I remember reading that starting a freight trains consists of moving one car at a time approximately six inces, i.e. the first car moves six inches; the second car does likewise, etc. Is this true? Also, what throttle setting would the engineer usually use to get the train moving. The locomotives on the trains that I observed were SD70Ms.
What you’re talking about sounds like what’s called “taking out the slack”. Because of the way couplers work, there is a bit of slack between cars - the train isn’t one solid unit, so when the train starts, the first car moves a few inches before it’s rear coupler begins to pull the second car, and then they go a few inches before the second car begins to pull the third car, etc.
In steam days, engineers often would just open up the throttle full blast, as steam engines tended to take a long time to get up to speed. When diesels came in, the instructors had to warn the engineers not to do that with diesels, as the diesels had much more power at the start. If you went from a dead stop to Run 8, you could jerk the coupler off of a car. I think normally you would start at a lower setting like Run 2 or 3 to get things moving, then slowly work your way up to more power.
Starting a train depends on factors like your undulating grade in Alpine, TX. Withthe raw power of diesel-electric locomotives, power is applied slowley. Back in the 50’s/60’s, there was a lot more ‘slack’ in the couplers/draft gear. Modern trails have a lot less ‘slack’, although it is still there. Depending on the current company rules, advancing the throttle one notch at a time until all of the slack is taken in is usually done before the engineer can accelerate the train up to track speed.
If the braks are set on the part of the train on that down grade, there is going to be quite a ‘kick’ as the train brakes release and come in on the engine. Train handling can be an ‘art form’. When I worked for the ‘Q’ back in the late 60’s, we would ‘power brake’ and drage the train onto the level - something frowned upon these days.
There’s waaaay more slack today than ever . Free slack is the slack only in the couplers themselves, this is mostly unchanged. Spring slack is from cushion devices and can be 5-6 feet per car if the train is bunched. Mutiply 5-6 feet plus 6 inches free slack times 100 car train , fun when the slack runs out and the train is moving in both directions.
Considering all the free slack that is running throughout todays 9000+ foot merchandise trains, I find it all the more amazing that todays engineers are able to move these trains over undulating territory with the train on multiple crests and sags at the same time - with slack running in and out on various portions of the train at the same time and not tearing the train in multiple pieces.
If memory serves, the reason for “taking out the slack” had more to do with friction bearings than anything else.
A standing car with friction bearings will squeeze the journal oil out from between the axle and the bearing. As a result, the first motion is nearly dry metal to dry metal (unless the car has moved recently, and even then).
Starting an entire train all at once in that situation would require some pretty hefty tractive effort.
Bunching, then pulling out the slack spreads this out - per Randy’s number of 6" per coupler, that’s upwards of 50 feet for a 100 car train, which means the first car (and the locomotives) would have moved 50 feet (and the wheels thusly several revolutions, bringing the journal oil into play) by the time the last car (and caboose) saw any motion.
I remember seeing what was apparently a stalled C&O train bunching and stretching several times (and around a curve at that) in their efforts to get back underway. Inasmuch as I think the hoppers were empty, they were likely trying to get started on a downgrade.
Depending on the length of a train you start out in notch one and hold it there for about ten seconds or so. Then you go further up the notches. For your average 5000-9000 foot train usually putting the locomotives in notch one results in nothing moving. Sometimes even in notch two or three nothing moves depending on the grade or weight of the train. With smaller trains with less than 20 cars you will usually go from notch one and then notch 2 in just a few seconds since the slack will be pulled up quickly.
Taking out the slack is critical when starting a train. Considering some trains are way over a mile long, those last few cars can move from 0 to 20mph in a split second if a engineer just opens the throttle and takes off. You deferentially feel the slack being pulled up when you throttle up as it feels like a tug of war with the locomotive and the train. Locomotives have a distance counter in the cab and when you leave you set it at zero. Then when you have moved the length of your train you know all the slack is gone and you can proceed at normal speed.
When drifting down a hill the slack can bunch up from the rear to the front and hit the locomotives and push them forward. I remember several times rolling down a hill with a long train and hearing the slack start to bunch up and coming towards the locomotives. Let me tell you there is times that slack action hits you so hard it will knock you out of your seat. I remember another time the we were doing about 20 mph down a hill and the slack action caught up with us and sent us from 20mph to about 35mph in about two seconds. It was like the locomotive hit the nitro button.
Common sense says that no matter how much power you have on the head end a string of 100 cars is more difficult to start 100 at once than one at a time. When a train stops, brakes are applied from the head end to the hind end so the rear cars will push into the lead cars, thus all be bunched together so starting will be one car at a time, slowly and carefully so as not to rip the train apart., Sometimes a train can be stopped all stretched out with no slack and the power must pull all 100 cars at once. Curves, dips, humps, upgrades, downgrades, one or more of the above, are all possible Both the stopping engineer and the starting engineer…assuming a change of crews…has to be expert enough to make the right stop for the right start. Its not like driving a car or truck. It takes skill, expertise, knowledge of the locomotives, of the types of trains, the terrain, the location, the railroad, the cars, the engineer himself, to start, run, and stop a train. The bigger trains, the more power, the computers of today, have only changed the dynamics not the engineer’s need to be what he needs to be.