I presume that extra locos are added for temporary purposes on a long route, such as an upcoming leg requiring more power due to steeper grades.
I note that the extra power can be added at front, rear or even mid train. What dictates where to add the extra loco(s)? Are current practices different than earlier (steam) eras?
Paul
Modeling HO with a transition era UP bent
Hi,
Here's a brief summary on distributed power (DPU):
https://en.wikipedia.org/wiki/Distributed_power
...and more.
https://www.popularmechanics.com/technology/infrastructure/a5314/4345689/
Hope that helps, Ed
Ed provided some great links about what is done today.
In steam days it was much different.
No radios, no computers, only whistles and the seat of your pants.
Helpers might be applied in front, or push from the rear, but it was all done by feel.
Double headers were common, that was done by feel as well.
An example I have given before,
B&O freight train leaves Baltimore headed west, 70 cars, 3500 tons, two 2-8-2's on the point. Ruling grade to Brunswick, 1.5%.
At Brunswick, power changed to a pair of EL5 2-8-8-0's for the next leg, ruling grade, over 2%.
At Cranberry grade, over the Allegany summit, a curvy 2.3%, effectively 2.7%, the train will require two more EL5's, or a four unit set of EMD F3's or F7's to push from the rear.
Passenger trains often needed helpers as well. 12 car passenger train leaves Baltimore with a P5 or P7 4-6-2 on the point. It will require a Mikado to join in front of the Pacific for several of the steepest grades.
Passenger trains were virtually never pushed, for both safety and comfort.......
Sheldon
Short answer, locomotives are placed based on tonnage and drawbar stress.
There are a couple different strategies for additonal power. Engines can be added that have a crew on them, which are generally called "helpers" or they can be added and remotely controlled by the crew on the head end (commonly called "distributed power" or DPU).
Power in places other than the head end can be added for specific locations or it can be added and remain in train for the entire train's trip, which could be thousands of miles. If its added for a specific location its normally because of grade. If power is added for the entire trip it is done so to reduce in train forces, improve train handling and reduce fuel consumption over the length of the trip.
Since DPU only dates to the 1990's, prior to that on the UP everything was manned helpers. The helper operation was definitely different prior to that. In many cases helpers were only added when the weather was adverse (rain, snow, sleet, etc).
The original DPU set was the UP 9997, 9998, 9999, a set of C40-8's. One of the first applications of DPU was the Blue Mountains. Trains were limited to 50 cars and then number of trains were constrained by the capacity of the line. By converting to DPU, trains double the size could be handled, which doubled the capacity over the line.
The next target were unit coal trains. The UP standardized on C44AC's (while the BNSF used SD70MAC's). The C44AC's had a higher tractive effort so the UP set trains with a 2x1 configuration (two on the front and one on the rear) while the BNSF had more 2x2 sets.
Later as DPU's became more popular and common, the use was expanded into other bulk, intermodal and finally manifest (general mixed frieght).
Dave H. Painted side goes up. My website : wnbranch.com
And a mid train example from the transition era.
I have a series of photos showing a WESTERN MARYLAND coal train being brought out of one of their mine branches.
About 60 loaded hopper cars, over 3000 tons, on the point two of their large 2-8-0's, mid train, two ALCO RS units, on the rear, two more ALCO RS units and another 2-8-0. Curves very sharp, grades very steep, limited the use of larger power. Maximum speed, about 20 mph.
Think about it, one loco for every 8-9 cars.
I think the placement of the engines would relate to the situation - is it a train that requires multiple engines for the whole route, or are extra engines just added for a particular part of the trip?
Sometimes trains run an entire route, say from city A to city F, with multiple engines, because that much power is needed to get the train from A to F. The engines stay with the train the entire route in that situation.
That is a different situation where say one steam engine would be sufficient to get the train from A to F except that there is a steep grade between C and D that requires a 'helper' engine or engines to be added for just that section. Adding a helper or helpers at C and removing them at D is going to be easier if the helper is coupled to the front of the main engines, or coupled behind the train. It would be more difficult to add a helper in the middle of the train, since more switching would be required to add the helper at C and remove it at D.
BNSF and UP might have some freight trains were three diesels are on the point, two mid train, and a helper on the rear. The mid train helpers and rear helper are used for a tough segment of the run, then removed as needed.
You might see this with coal drags.
ATSFGuy BNSF and UP might have some freight trains were three diesels are on the point, two mid train, and a helper on the rear. The mid train helpers and rear helper are used for a tough segment of the run, then removed as needed. You might see this with coal drags.
Distibuted Power helpers tend to stay in a train for it's entire journey. Even outside of the mountains, in so-called "flat land" territory, you can have significant grades and harsh "hog backs" and sags. On the longer trains and heavy bulk commodity trains, the DPs help to control slack action and excessive coupler strain.
Jeff
jeffhergert ATSFGuy BNSF and UP might have some freight trains were three diesels are on the point, two mid train, and a helper on the rear. The mid train helpers and rear helper are used for a tough segment of the run, then removed as needed. You might see this with coal drags. Distibuted Power helpers tend to stay in a train for it's entire journey. Even outside of the mountains, in so-called "flat land" territory, you can have significant grades and harsh "hog backs" and sags. On the longer trains and heavy bulk commodity trains, the DPs help to control slack action and excessive coupler strain. Jeff
All reasons why trains were kept shorter back in the day. And why the longest trains moved very slowly.
Standard power on a UP coal train operating out of the Powder River Basin was a UP or CNW C44AC on the point, DP equipped, a C44AC trailing on the head end. The trailing head unit was commonly an SP C44AC because they were not equipped with DP or cab signals, then a UP or CNW C44AC on the rear (DP equipped). The coal trains varied between about 135 cars to 110 cars, depending on the route and how big the loop was at the plant. There were a few 100 car trains with two C44AC's that operated to the Chicago area.
The trains operated in DP configuration the entire trip, loaded and empty.
The longest train operated by the UP was a test train from Dallas Intermodal Terminal to Los Angeles. It had 3engines, 6000 ft of train, 3 engines, 6000 ft of train, 3 engines, 6000 ft of train and 3 engines. 12 engines and 18,000+ ft of train.
Back in the 1970's when I worked for the government out in California, my best friend and I would chase the SP trains over Donner Summit. 10 SD45's, front, midtrain and rear in various combinations. BNSF rules state that heavy trains require DPU and specifically states all grain trains on the Pikes Peak Subdivision which I model.
Interesting reading.
In 1967, the PRR operated a 342-car, 35,805 ton ore train from Cleveland to Pittsburgh to test the feasibility of long trains. Evidently it wasn't successful, as 13 knuckles were broken during the run, and it was never repeated. I have never heard of the power assigned to this train, and whether it was distributed or not.
Some Railroads would not use a pusher on the rear with certain Cabooses/Cabin Cars, whatever. The Caboose had to be cut out of the train and the pusher was cut in between train and Caboose.
The Norfolk and Western Railway in the 1960s also experimented with long trains.
https://www.railserve.com/stats_records/worlds_fastest_trains.html
500 cars, 48000 tons, 4 miles long with 3 engines in the front, 3 in the middle. They only got one knuckle. I read articles in an old Railroad Magazine issue from that era that they ran a few test trains, each a little longer until this one was ran.
UP currently is running 294 car, 16000+ feet, 42000 ton coal trains between the Powder River coal fields in Wyoming and the Oak Creek Wisconsin generating plant. It usually has 2 engine in front, 3 in the middle and one at the end. Not every Oak Creek coal train is ran this way. Most are still in the 147 car range, 2 engines in the front and one at the rear. (The monsters are just two standard trains put together.) They run empty on the return trip in the same configuration.