I was out today grabbing a bite to eat, after I had stopped off at a LHS. The restaurant that I was at was situated right next to the Norfolk Southern tracks, with plenty of window tables to view the traffic.
There was a double unit that went by while I was eating, pulling maybe 50-60 cars behind it - mostly autoracks, tankers, and covered hoppers. The first 3 cars were empty flat cars which were followed by several autoracks.
I’ll freely admit that I’m somewhat ignorant about operation protocols. My understanding was that empties usually went on the rear half of a train for safety reasons. Can I assume that, since the flat cars were empty, the rest of the cars were empties, too? Is this common?
I can’t see any reason why the empties would have to be moved at the rear of the train, unless it was pre-blocked that way to facilitate switching en route. Modellers are often hesitant to run empty open cars, like flats, gondolas, and hoppers at the front of a long train, but that’s because these type of cars are often quite lightweight. With a long, heavy train in tow, our overly sharp curves can cause these light cars to derail. Since most of these cars have deep fish-belly sides, it’s easy enough to add weight beneath the floor, where it won’t be seen. Here’s a couple of photos of a 71 car train that I ran on my layout not too long ago. The four SW1200RS switchers providing the power are remotored Athearns and the grade is 2.8%, laid out over two reversing horseshoe curves of about 30" radius (one right, the next left) with an “ess” bend near the top. Total grade length is about 45’.
That empty flatcar, a Walthers GSC-type, weighs 6 ounces. Btw, because the second level of the layout has not yet been built, the train had to back down the hill after the climb. No derailments going either up or down.
Empties don’t always go in the rear. The only time its a problem is if there are a lot of empties in front of a lot of loads, or empties in front of a lot of tonnage or you are in a heavy grade area.
For probably 95% of the main line milage in the US, its not a problem. The empties fall where they may through the train and the cars are arranged by their block (destination), not load/empty.
Ordinarily the prototype doesn’t worry about mtys on the head end. The only exceptions I’ve had personal knowledge of was on the SP (circa late 60s early 70s) that had a restriction on TOFC flats loaded w/ only 1 van on the head end and the Milw that required MTY TOFC flats to be rear end over St Paul Pass (Alberton Mt-Avery Id)
I have a very vague recolection that some cars were fitted with a change-over valve in the brake line to change the braking when the car was running empty to when it was running loaded… is this correct?
As I recall (getting harder with age) if there is a TOFC car with one trailer on it the trailer should be on the front of the car. I think there was a spate of accidents blamed on single trailers being on the back end of a TOFC car making the front end light. I also recall that the PRR had a significant problem with TOFC cars derailing the caboose when switching tracks due to the longer swing of the TOFC car coupler (sound familiar to us modelers). The PRR mandated an intermeidiate length car like a 50’ box be placed ahead of the caboose to prevent this.
Generally we don’t have a problem with empties until the weight of the trailing tonnage goes up, usually no empties with trailing tonnage above 9000 tons. 9000 tons eguals a lot of loads. The bigger problem is short cars and long cars, usually the long car has long drawbars and this is a problem when stopping and going through yards. Basically the short car pushes the long draw bar to the side and derails. the other time to watch out is long empties on the head end such as auto racks when stopping, too much retarding force can pop empty auto racks out of a train, this usually happens in the yard with not well maintained track and multiple tight curves and switches.
Remember even an empty flat car still weighs in at around 30-35 tons, where as a model flat car is just a few ounces and we tend to put them through much sharper curves.