operating multiple engines

[Awesome!]

GM "General Purpose" diesels ("GP's" or "Geeps") ride on two two-axle trucks, with all four axles powered. GM "Special Duty" ("SD's") ride on two three-axle trucks, with all six axles powered.

This would be the same for GE "B" units and "C" units respectively (as in C-44-9W).

Switchers use two two-axle trucks, all axles powered.

In the "Glory Days" passenger diesels like Alco PA's or GM E-units used two A-1-A trucks, meaning they rode on two three-axle trucks, but the middle axle was an unpowered idler. It gave a smoother ride at higher speed that way.

If you run multiple engines with a configuration 6-axle and 4-axle would that be efficient? What about the steady 2% grade what configuration is more efficient?

[wjstix]

GM "General Purpose" diesels ("GP's" or "Geeps") ride on two two-axle trucks, with all four axles powered. GM "Special Duty" ("SD's") ride on two three-axle trucks, with all six axles powered.

This would be the same for GE "B" units and "C" units respectively (as in C-44-9W).

Switchers use two two-axle trucks, all axles powered.

In the "Glory Days" passenger diesels like Alco PA's or GM E-units used two A-1-A trucks, meaning they rode on two three-axle trucks, but the middle axle was an unpowered idler. It gave a smoother ride at higher speed that way.

[Awesome!]

What is the different 4 axle or 6 axle tractors?

[cleo3]

Thanks for the explanations.  Now I understand.  I was looking at it as if the diesel was the power to the wheels.  It makes sense now.

[ndbprr]

When diesels first started to take over not much was compatible.  Baldwin used a pneumatic control system for example.  Once the unions allowed one crew to operate several engines standardization soon followed.  There are also some switchs in the cab to make an engine a lead or follow engine.  There are is also a switch to disable the dynamic braking as it is possible for a train to have too much braking power.  ICG limits dynamic braking to 16 axles (I think).

[wjstix]

Diesel engines are really Diesel-electric engines. The diesel motors generate electricity, which powers the electric motors turning the wheels. Because of the electrical nature of it, it's pretty easy to hook up several engines electrically with cables so all of them respond to the cab in the lead unit of the consist. The engines all respond to the throttle of the lead unit; the engineer doesn't have a separate control for each engine. When referring to this we often use the term "m.u." for Multiple Unit. 

On some long trains, separate helpers are used at the rear, which could use their own crew, or be remotely controlled via radio from the lead unit at the head of the train. 

 

[cleo3]

I'm new to this train stuff.  I've been wondering how one engineer controls several locomotives.  A lot of times I see a train with different types of engines, even 4 axle with 6 axle engines.  How do you get all the locomotives to give maximum power with only one engineer?  For example, a pilot flying a multiple engine airplane has separate controls and guages for each engine.  How does that work with 2 or more locomotives connected together?