tractor pulling small version

If this is the one I think it is I saw it on a forum awhile back in it's first stages of a brain storm someone posted one he was mocking up
electrifying aint it .

That is pretty neat! A lot of potential from those DC traction motors. The reason direct diesel drive never caught on in railroad locomotion.

Hey, finish that statement. I always wanted to hear why they switched to A.C. I was told it was an efficiency issue, though the teller wasn't sure thanks,Fritz

There are still a lot of DC drive motive power out there. If I'm not mistaken AC drives came of age in locomotive power with the advent of power inverters that work by altering AC sinewaves to the motors. Couple these with computer control (that's working correctly) and the whole system works to maintain programmed parameters hundreds if not thousands of times a minute based on feedback from a zillion sensors. This continually tweeks everything from fuel feed to wheel slip to maintain peak efficency. The engineer basically blows the horn at grade crossings and catches h**l if his train is 2 milliseconds late. DC drive is very powerful but woefully inefficent.

I read in TRAINS magazine that some company is now rebuilding older locos into dc drive units basically reusing the old frame and car body.

Without doing a lot of hunting on the DC vs AC power in locomotives ...
The majority of locomotives in service (and even being ordered) are still DC driven. Cost being a major reason.

Limited clarification about the following ... on a locomotive you have an engine turning a power supply (generator or alternator) and each axle has a motor.

Significant difference in pulling utilization... with a DC motor you can only operated it so long at max amperage before you start burning out components (I don't recall brushes/commutators?). So if you've got a heavy train on an uphill grade and drop below certain speeds you can't apply more power ... you can't crawl up a grade.

Because the A/C motors are built differently... you can crawl... forever with the throttle wide open without impacting the motors. So if you're the engineer and have a train that is underpowered it just takes longer to get that but you can with patience. On a DC unit you either take the train over the hill in two parts... or you wait on an additional locomotive. Fancier hardware though adds significantly to the price so most RR's have opted to manage their DC units better up to this point.

There's a couple of RR guys on here that can probably speak to it better... and some of the electrical guys can too.