How do train engines have enough traction to pull a mile-long train with less then 2 sq in of wheel contact?

Question

Both the wheels and track are polished steel with hardly any friction, and the train weighs more then the locomotive.

Answer 1

Geez, hold up here... There is so much mis-information here its amazing.

1: There is NO magnetism to the rails. (Paul G)
2: Grades can be up to 3%. (marren*)
3: Trains always have carried sand even steam engines -- its not just modern engines (c_c_runner88).

Now, the very first answer here summed it up well..

Tractive effort or track adhesion -- whatever you wish to call it.

Horse-power doesn't mean jack unless theres traction.. So a locomotive may have have over 150,000lbs of tractive effort.
This is the force applied in moving a train.

When the engineer moves the throttle to the first notch, the amperage to the traction motors will climb and they begin to turn the wheels. Wheelslip is indeed countered with sand from the locomotive's on-board sanders. Oddly enough, its not just wet or icy rails that cause problems -- the biggest trouble maker for trains is wet leaves on the rails in fall especially. These hamper traction big time.

So in short, the tractive effort/adhesion of a locomotive is what pulls the weight.

Answer 2

I have to agree 100% with the last answer! I've been an egineer for 3 yrs now and didn't know this until recently....a locomotives wheels only touch 1/8 inch of the rail! All the weight of the locomotive forced down on 1/8 inch gives it is true traction effort!
Steel on steel there will be slipage at times, and sometimes the computers don't pick it up and you can manualy sand the rails by a switch on the control panel on the engineers consol. Now the cars have no effect on helping they are dead weight and they do touch nearly 100% of the rail.

BA/ KCS

Answer 3

I'm a locomotive engineer .. her es how next to the wheels are traction motors and they produce force down on the wheels also to get moving we use sand to get traction most trains are giving enough engines with horse power to pull the train

Answer 4

Engine weighs 200K pounds, and a good one can exert 75k-100k pounds of pull (tractive effort, it's called). This engine can pull a train of about 6,000,000 pounds on level ground.
Polished steel is hardly frictionless - you can walk on it without slipping. Of course, when it's wet then it gets slippery, and engines will spray fine sand on the rail to aid in traction when this ocurs.
However, there is some slippage all the time, so this is why train tracks are as level as possible.
EDIT - there is no magnetism to the tracks, trust me. There's so much steel junk lying around on the rail bed that it would be a total catastrophe.

Answer 5

on each engine there are sanders which spray out sand between the steel wheel and the steel rail. This is applied on start up, grades and emergency stopping. The sand is stored in large bins or towers inside the locomotive.

Answer 6

About some 20 tons of steel pressing down on the wheels. Of course, it has to start out slowly. It won't be doing 45 mph in 6 seconds, EVER! Not a FREAIGHT train anyway!

Answer 7

there are sand reservoirs that are electronically controlled. When the computer senses slippage, sand is released from the reservoirs so that it goes onto the rails and the wheels can get more traction. Of course, this is just on modern engines. Plus, they weigh a LOT, which adds traction, and they start off slowly to get better traction.

Answer 8

I think the weight of the box cars and the engine itself and the engine are Desil-electric engines that put out ease over 1000 hp It is one giant electro magnet it has to magnetiize the wheels to the track and I think that is your answer that and have you seen a train start out there is a sharp shock joilt through all the cars to break away from a stand still well the two combine and you got my answer

Answer 9

From my understanding the grade is kept to 1% so you will never see a train going up a steep hill . They assign the number of units
(engines) in proportion the the weight of the train . Also used to slow going down hills as all those tons of steel pushing you.

Answer 10

that what seven diesel locomotives, each with a V-24 engine, each cylinder measuring 9 inches across, can do.

same way your car can carry itself and several passengers....only on a much higher scale.