Hi, can someone explain how when locomotives are lashed-up together, how they communicate with each other? Is there some sort of standard? Thanks!
It depends on the era if you are talking about the prototypes, or the control system if models. On the prototype steam engines all had crews and communicated by whistle signals and watching the air guage ( in case the conductor released air from the valve in the caboose to signal a stop). On the diesels only the lead unit has a crew and there are multiple air hoses and a multi conductor electrical cable between units that operate the rest of the units from the head engine. Also modern diesel can use radio control for Distributed Power Units further back in the train.
If you are talking models then it depends if you are using DC or DCC. If DC they will all operate although it is not possible to speed match different makes and models of engines. With DCC it is possible (but complicated) to speedmatch, but there are several easy ways to consist a lashup. I hope this helps. jc5729
For the prototype, it might help to remember that what we call “diesel” locomotives are more accurately “diesel electric” locomotives - the diesel motors generate electicity, and the electricity is used to power the motors that turn the wheels. The engines in a consist can be “m.u.'ed” (Multiple Unit) by connecting them together with m.u. cables (which you can see on the front or back of diesel engines), so all the controls of all the engines in a consist are being controlled by the engineer in the lead unit.
Not all diesels will M.U. with each other. When they started showing up, each manufacturer had their own standards–EMDs would only work with other EMDs, Alcos with other Alcos, etc. until they agreed on standards. The one exception to that, was the Baldwin Sharks. They had air-operated throttles and couldn’t MU with anything else.
The above replies pretty well answer your question. I would like to point out that “lash-up” is a totally railfan/modelRR term that I never heard used in 20 plus years working on 3 different RRs. The usual term is “engine”, “units”, or, in the context of your question, “power consist”
One more follow-up, some engines weren’t able to m.u. with any other engines. Some railroads bought diesels for a specific situation where they figured only one engine would be needed, so didn’t have the builder add the m.u. equipment to the engines. For example, the Soo Line had two AS-16 Baldwins, no. 379-380 that they bought to perform heavy switching in their iron ore yards. Neither engine could go into a consist with another engine (not even with each other) and so always worked solo.
Although rare, there were situations where a railroad would have to have two diesels ‘double-heading’ with each engine having it’s own crew, because the two engines couldn’t be run together in an m.u. power consist.