Does anyone know how the Layshaft got it's name?

[n2cbo]

This is one of those things that just keeps me up at night (Yeah, I know - get a life...). How did the Layshaft get it's name?
For all who do not know what I am talking about, The Layshaft is kind of a manual throttle for a diesel locomotive engine, and it is usually in the engine compartment of the locomotive. The reason that I am curious about the name is that the Layshaft is not a shaft nor does it have anything (that I can think of) to do with Laying down...

Any Diesel experts out there???

Thanks
Mark

[Jtgshu]

HAHAHH I had to laugh, considering I was thinking the same thing last night when I was trying to keep a GP40 running after being first started!!!!

Maybe it has something to do with how its connected to the fuel rack, and how the fuel rack "lays" determines how fast/how much fuel the engine gets???

[David Benton]

well i dont know about in diesel locomotive engines , but a lay shaft is usually a shaft seperate to a main running shaft . it may have gears or levers that work off the main shaft , or idler gears , or sometimes counter reveloution balancin weights etc .
So i would say , layshaft refers to it been seperate to the main throttle shaft , but somehow connected or influencing that shaft .

[David Benton]

actually thinking about it abit more , a layshaft in a lathe is a shaft bewtween 2 other shafts , with gears thon it that transfer between the other 2 shafts . so maybe there is a layshaft attached to the throttle that is turned by either the thottle or the remote thorttle .

[UPRR engineer]

Think this one might be better off in the EMD Forum.

[Nelson Bay]

This is one of those things that just keeps me up at night (Yeah, I know - get a life...). How did the Layshaft get it's name?
For all who do not know what I am talking about, The Layshaft is kind of a manual throttle for a diesel locomotive engine, and it is usually in the engine compartment of the locomotive. The reason that I am curious about the name is that the Layshaft is not a shaft nor does it have anything (that I can think of) to do with Laying down...

Any Diesel experts out there???

Thanks
Mark

Generally speaking an engine layshaft is a shaft that moves independently of the other parts of an engine. The layshaft (layshafts)on a locomotive engine are shafts that run across the top of each engine bank inside the top deck (valve) covers.
Each layshaft controls the fuel injector arms for a bank of cylinders. The "manual throttle" Mark refers to is a handle that allows for manual movement of the the injector arms.

[Aji-tater]

I don't know about technical engineering terms, but I'll disagree with the previous post as far as general usage of the word on locomotives is concerned. The layshaft is usually meant the rod or lever which can be used to manually alter the diesel engine RPMs. On EMDs it is on the engineer's side, at the front of the diesel engine (rear of the locomotive) and is a metal lever about 12-16 inches long (I've handled a million of them but never measured them so if that's wrong size I'm sorry). If you tell an engineer to show you the layshaft, he's not going to show you the rods inside the top deck cover, he's going to show you that lever. Maybe it's wrong in pure textbook definition, but that's the way the word is used in everyday railroading.

[Nelson Bay]

You're right Aji, in everyday railroading the "Layshaft Operating Lever" is commomly called the layshaft. I was just trying to answer Mark's question in the opening post. In my attempt to do that I felt I had to try to explain what a layshaft actually is.

Technical engineering terms???

[Aji-tater]

OK, not-so-technical terms?

I was just trying to present a different answer without saying yours was wrong. Your answer was right from a mechanical point, I was saying from an everyday use point, mine was.

To quote a certain ex-President "It depends on what your definition of 'is' is "

[Clyde]

According to the dictionary (UK), a layshaft is a second or intermediate transmission shaft in a machine. The layshaft is probably the injector control shaft along engine top deck that drives injector rack at each injector. The manual control shaft (handle) attached to left bank injector shaft been probably called “layshaft” as a mean to manually actuate the real layshaft. By the way, no part is designated as “layshaft” in the EMD parts Catalog I have used.