Just some clarification on the turny thingies.
On the trestle is an armature, the commutator is the shiny bit closest, this is where the brushes run and pass the electrickery to the armature windings. The brushes are made from carbon and the commutator is made of thin copper strips adhered to a insulating medium. One end of the strip is soldered to each end of each winding, the gaps in the strips act as micro chisels and effectively skim the brushes so that they wear down.
When the motor runs it is normal to see sparkling, fizzing, twinkling from the trailing edge, basically fine particles of carbon arcing as the comm bar leaves the brush surface.
The carbon dust permeates throughout the motor and eventually will bridge across the comm bars, the arching will grow in size and eventually it goes BANG. In learned circles this is called a 'flash over' in lay mans terms it's 'proper %$£&ed'.
The flashover can have two effects, a blown comm where big holes appear in the copper bars if the short was between the bars, the most usual kind of flash over. More unusual is the for the brush boxes to flash over but if they do then the motor is easier to repair. Finally, depending on the load, trip time and other factors there is the risk that the comm bars become so hot in the explosion that they melt the soldered connection, called 'throwing the solder out'.
If you have a flashover with burnt comm bars and thrown solder then it's a full strip and rebuild.
To prevent this motors are pulled for a 'wash and brush', basically a strip down and clean to remove all of the carbon dust. If the comm is found to be grooved, ridged or generally in a poor state (the carbon brushes wear grooves in the copper eventually) then it will be 'skimmed'. If the motor is passable and the comm partially marked or just glazed then it can be stoned in situ to smooth the comm, basically a big wooden pole with a comm stone taped on the end. Stoning is done live so it's a good idea to keep the RPM and thus voltage down, especially as the covers are open and you're poking around inside a spinning motor; big rubber over elbow gauntlets are a good measure as is a full face safety mask.
The armature on the trestle has been washed, brushed and had the comm has been skimmed, they do look nice like this. The next step will be to press the bearings on and then spin it up for balancing. The trestle is marked GE which I would assume is reserved for GE built motor armatures, not all armatures are designed the same internally.
The casing on the floor is called....yes you guessed it...the stator...because, wait for it....it doesn't turn, it's static. Inside the stator you can see two of the poles, they look like pillows, thus this is a four pole motor, there will be interpoles I suspect but I can't quite see them.
The stator has three parts, the core, head end and tail end castings, these hold the bearings. The end facing the photographer is the tail end, this is where the brushes live and is called the brush box, we know it's the brush box because we can see the cables exiting to the right by the axle bearing shell. The motor is orientated exactly as it would sit inside the traction bogie, top facing up, sat on it's bottom. To the left on the outside of the casing are the three lugs for the third fixing point, the one that stops the motor from flailing around inside the bogie.
The last photo shows the armature being lowered into the stator, the brush box is at the bottom and the brush assemblies will be fitted once the head end casting and bearing is fitted. The big bolts on the angled faces are holding the stator cores in place internally. Once the head end is on the pinion will be pressed onto the end of the shaft.
In general, DC motors are filthy, dirty, and on the whole pretty bloody scary under full load (I've seen enough flash overs up close to keep a healthy distance from them) on the other hand, AC motors are much more stable and significantly cleaner.
By far, for me, the most interesting set of images in the collection.
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