Can you mue 100 locomotives?

[Trainman101]

Is there a limit of how many con work together? Thanks

[DutchRailnut]

no the amount of control relays activated would trip the Control circuit breakers on lead unit.
8 is about the most before problems start.

add to that that most railroads have rules on how many active traction motors in a consist, on most railroads its limited at 24.

[Allen Hazen]

Couple of questions.
The Pennsylvania Railroad, to balance power at different terminals, used to run whole trains of locomotives (no cars). Would most of these have been dead-in-tow rather than m.u.'ed?

And the Chicago Great Western, I think, was noted for running long freight trains with massive numbers of F-units: I think I have seen reference to their using up to ten units on one train. 10>8, so… does anyone know if they did something special to allow reliable m.u. operation of locomotive consists of this size.

(See what happens, Dutch, when you give helpful and informative answers to questions? People just ask more! (Grin!))

[DutchRailnut]

they probably only MUed the air , no jumper to rest of consist.

[BR&P]

they probably only MUed the air , no jumper to rest of consist.

I presume he is talking about the PRR part of your question. If the CGW was using 10 units to pull the train, they would all be fully MU'd. I don't know whether they did anything special or not. I suspect they just set them up and crossed their fingers.

The PRR also may have towed along the trailing units at idle, especially in winter when you would not want the engines dead account freeze-up.

[John_Perkowski]

Is there not now a FRA limit on the number of powered axles for a consist?

[DutchRailnut]

no, just individual railroad rules. most limit it to 24

[mtuandrew]

And the Chicago Great Western, I think, was noted for running long freight trains with massive numbers of F-units: I think I have seen reference to their using up to ten units on one train. 10>8, so… does anyone know if they did something special to allow reliable m.u. operation of locomotive consists of this size.

I think in regards to the CGW, if there were ten units on some trains, at least a few of those ten would have been manned helpers for the grades out of Dubuque & the Winston Tunnel. I haven’t seen pictures of that many units MU’d together in operation (I can’t imagine how many drawbars they would have broken with more than 8 units/12,000 hp fighting 200 cars on the rolling CGW route profiles), though Don Hofsommer or John Luecke would be much more definitive references.

[Engineer Spike]

CPR has a limit of 8 locomotives in a consist. I agree with the point of control breakers tripping. There might be air problems too. We have a rule about using the automatic brake to control large consists, since the lag time is so long, when using the independent brake. One leak may prevent the rear unit from getting enough air to bail off the automatic applications too.

24 axles, or its equivalent had been the norm. First, I said equivalent because the railroads base 6 axles off of the output of SD40/C30-7/U30C/C630. They know that newer units, such as -8/9 GE, and SD60/70 can equate to about 25% more TE. The AC motored units rate even higher. Some late 4 axle units, such as GP60 can produce the effort of a SD40. Second, some western railroads allow much more than 24 equivalent axles of power. Again CPR allows more axles on the SOO, vs. the D&H. This is because of the steeper hills, and tighter curves in the east, as opposed to the flat prairie. Some has to do with the types of cars. A mixed train might have empty cars, which could be ripped right off the track. This is most likely on a curve, and is called string lining. Many general freight cars aren’t designed for the high forces. Some coal cars, for example have higher strength couplers. Also a unit train can have less problems in other ways. All the cars are the same, and are loaded uniformly. This eliminates some in train forces, which are present in mixed trains, where cars react differently.

This topic is becoming somewhat moot. Most of the newer power comes with distributed power gear. This way the power is spread through the train. There isn’t the strain on the head end, and no need for a large head end consist.

[litz]

while not a freight railroad, there are examples of many more powered axles on trains, mostly in commuter/subway setups. In most 3rd rail concepts, each car is basically its own "locomotive", with powered trucks.

a 10-12 car long train, each with 4 axles, and each axle powered, works out to quite a few traction motors all pushing things along.

The limit, in those cases, works out to whatever the power supply for the rail can deliver.

[Gadfly]

while not a freight railroad, there are examples of many more powered axles on trains, mostly in commuter/subway setups. In most 3rd rail concepts, each car is basically its own "locomotive", with powered trucks.

a 10-12 car long train, each with 4 axles, and each axle powered, works out to quite a few traction motors all pushing things along.

The limit, in those cases, works out to whatever the power supply for the rail can deliver.

Southern used to use "radio cars" mid-train to control mid-train slave units. Theoretically, I guess one could "MU" that many units, but why would anyone WANT to. Just makes for an unwieldy, possibly un-controllable mess!

When I was walking the yards in the 80's, one could always tell the radio trains because of the "CHIRRRRRRRRRR-UP, UP, CHIRRRRRRRRR-UP", UP coming over our walkie talkies.!

[John_Perkowski]

That was in the days of big radios. Those days are long past. I've seen coal trains on the front range with 3 leaders, 3 mid train units about 70-80 cars into the consist, and 3 trailers.

Amazing thing, modern radio technology.