A steam locomotive is known to be able to pull more then any pure combustion engine locomotive. (Uncited)
Why didn’t oil fired steam locomotives take off?
This started when I watched: https://www.youtube.com/watch?v=Hszu80NJ438
During the runtime, it mentioned oil fired retrofits.
I search it up, and found one.
It was an overview video of a modern retrofit, and it seems to not be too difficult to retrofit, even using the same steam blaster to spread the oil in the smoke box: https://www.youtube.com/watch?v=Up1UaMVnv4M
I assume it has a lot to do with efficiency, and correct me if I am wrong, but I think it goes Diesel -> Generator -> Traction Motors
You are correct. It relates to the torque (rotational force) that can be produced at different RPM.
Diesel engines have a narrow range of RPM where the torque is highest. At low RPM, the torque of a diesel engine is low. That’s why trucks have to shift into a low gear to start moving and shift multiple times to get up to speed. The driver uses the different gears to keep the engine running within the optimal range of RPM.
Electric motors have high torque at low RPM, so they can start a heavy load moving without having to have any complicated gearbox between the motors and drive wheels.
In a diesel-electric locomotive, the diesel generator can be designed to run at an efficient speed without being affected by the mass of the train. The electricity it generates powers the electric motors which have the necessary torque to handle moving the train.
I always wondered why trucks didn’t become diesel electric or have a Prius style drive train (with diesel engine). Would be a lot easier to drive.
For anyone scrolling by and curious about this, this is caused by the combination of physical and electrical resistance. In a typical engine, RPM and torque go up together because it requires more force to get to those higher RPMs (IIRC this is called positive correlation). In a circuit, you have to kind of convince the electricity that it would be better off somewhere else (by connecting to a ground, this is due to electrical resistance), so you have to give it a heavy upfront load to get it going which causes a lot of torque due to the physical resistance