traction motor blowers

[train18393]

I was in a discussion yesterday with a guy who worked at the SanBernido shops on the AT&SFe back in the 80. He Painted, hostled and did general mechanical work on the locomotives there. We got to discussing traction motors and he said that the motors were filled with a thick black greese, and that there was no room to blow air through them. I was of the oppinion that there were traction motor blowers and ducts going to the traction motors on most, if not all, traction motors.

I checked the 1947 Locomotive Cyclopedia that my dad gave me about 40 years agoand most of the diagrams therin did indicate that there were blower motors. EMD, FM, Baldwin...they all showed blower motors. In the section on trucks and traction motors they did show flanges  where I think the ducts mounted but I could find no reference for later models. Did they discontinue using them or is the guy that worked on them forgeting something? I model the NYC in the 60s so I have no references for engines that they may have been working out there in California in the 80s. I would think that even the mighty SantaFe still had plenty of first generation and second generation engines they would be working on then.      Thanks.

 

Paul

[BigJim]

Your guy is wrong, at least in a way.

 The motors themselves do have duct work going to them and air circulates through them to keep them cool.

There is a gear case that encloses both the pinion gear on the motor and the driven gear on the axle. This gear case is filled with grease. We called it "gear tack", because when it leaks out on the ground and you step in it, well it's kind of like the stuff tar babies are made of. Very hard to get off.

In order to fill the case with grease; The gear tack came in polybags that we put in a big bucket and then poured oil over them to make them slippery. Take the cap off of the case and start stuffing slippery bags of grease into the case. No need to worry about the plastic bags.

[Mimbrogno]

Sounds like he was confused about how a traction motor is layed out. These motors have two parts: the electrical windings and the gears. The actual motor part is the windings, which are housed along with the commutator in what basically amounts to a massive can motor with openings on the side and on one end to let air pass through it. Air is pushed either by the top or the side of the motor casing to blow across the windings and absorb their heat before exiting at the end.

The motor itself is craddeled in the rest of the traction motor assembly which consists of the main support frame, the gears, and the mounting assembly. The frame holds everything in place and supports it across the mounting points, which can consist of various types. Some examples of different mountings are the "Twin Motor" style (used on the GG-1) with two motors sitting side by side above the axle, attached to the truck frame above. This motor uses 3 or 4 gears to transmit the power to the wheels. Then there is the "Gearless" style, which has the motor armature windings built directly into the axle, with the field windings mounted on the frame; so that the wheels themselves are actualy part of the motor and no gears are needed. The most common style by far today however, is the "Nose Suspended" or "Axle Hung" motor. In this arrangment, one side of the motor is mounted on a bearing sleeve that rides on the axle, while the other side is mounted on the truck frame. Two gears, mounted in a closed lubrication chamber, connect the end of the motor to the axle.

The lubricant used for these gears is basically what amounts to road sealling tar, and is officially described as follows:
"Traction Motor Gear Compound = An extreamly heavy bodied black adheasive mineral lubricant with Saybolt Viscosity of 2000 seconds at 210*F; Also known as Texas Crater Compound."

The way this lubricant was applied (officially called "Cratering a motor") in the old'n days was a couple of men would, after coating their hands and arms with benzene or other very light petrolium, reach into a bucket of the stuff and pull out a big globby handfull to spread on the gears. I'm told it was more like glue than a lubricant, and it had to be applied in a thick coat to every square inch of every tooth on the gears. If the men didn't put benzene on their arms beforehand, the lubricant would either not be removable, or it would take the top layer of skin off when it was pulled off. Because the gear compound was made for high temperatures (around the boiling point of water), it was very stiff when it was cold. pushing a dead engine with cold motors, especially in chilly weather, was very difficult and sometimes it would take a locomotive of equal size and power just to move that dead engine alone. You could imagine the difficulties of pulling those PA's out of the snow after the Daylight got caught in a Blizzard for three days in 1952. This is one reason why locomotives must be treated tenderly in cold weather just after starting up. The resistance of the cold gear compound can put more strain on a motor than even the heaviest train on any hill, and burn it out before you get a houndred feet. (Remember, the gears and the motor itself are in two seperate housings, so the heat from the windings doesn't warm up the gears much because the blower air doesn't come into the gear compartment.)

As for the blower's themselves, they are generally in the form of a large fan or centrifical blower mounted on the fram inside the engine compartment. They blow air down through passages in the frame to ducts that direct the air into hollow chambers in the trucks that sends the air to the motors. The air moves across the motor windings, and is finally expelled out the end of the motor housing opposite of the gears (aka the commutator end). The blowers can either be driven by a seperate motor or by a "Vee" belt connected to the engine driveshaft.

-Matthew Imbrogno
Mechanical Vollenteer, Arizona Railway Museum
www.azrymuseum.org

[Anonymous]

I learned something today. Thanks.