"Physics" Question

I just read that three men could, allegedly, move a B&O EM1, 2-8-8-4, on level track.  

At the trolley museum I volunteered at, the documentation for rapid-transit car operation mentions the one car with roller bearings, should always be chocked when unattended since "it can be made to roll simply by climbing upon it". I've heard stories that six men were able to push that car (weighing in at about 72,000 pounds empty) when it was disabled by an electrical failure. But that may not have been level track, and the car has traction motors on each axle. It wasn't mentioned how many were needed once it was in motion.

 

I myself pushed a truck mover called "The Shunter" when it got stuck on an insulated section of contact wire and couldn't swing its pole owing to a pair of barn supports flanking the tracks at that point. All it took was to nudge it with a crowbar under a wheel, then brute force on my part did the rest. But that car had friction bearings and two traction motors on its axles. I found out later that it weighed 8000 pounds.  It was much easier to shove a PCC trolley with just two people, so much so that one person could have done it.

 

No personal experience with a freight car, but it seems at least plausible that a car sitting on the slightest of inclines without handbrakes engaged could be nudged into motion by a seemingly insignificant bump.

 

---PCJ (ironic signature below)

I have seen videos of strongmen moving cars. I was able to find this one:

 

http://www.youtube.com/watch?v=hP00VmKx_No

 

Pete

The Answer is "YES" • See Photo of it being done.

 

When I worked in Columbus,Ohio at NS's Watkins Yard as a brakeman/conductor,we would cut cars off in motion and sometimes have one hang up (not roll).

 

 Now Watkins was a bowled yard, but pretty level near the switching lead where the cars would hang up.But two of us on the ground would lean onto a car with our backs and start walking the car till it got off the level and it would start rolling .I've done this with loaded and empty cars,not always successful but a lot of the times.

 

Two other people and I were able move a caboose by hand when I used to help out at Black River & Western.

That makes me wonder about the bearings (?) between the wheel axle and the hub. Whatever is there must be very low friction I would think.

Not sure what you are asking, or are YOU even sure? There is no Bearing between the wheel and the axle. the bearing/bearings are between the axles and the truck frame.

The question posed is this: On level ground, could a single 200-pound person get a freight car moving by simply by leaning up against it and pushing it with his/her legs.

The Force to be overcome is the Coefficient of Friction X the Normal (Perpendicular to the surface) Force.  On the level the normal Force is the Weight.  Friction is the force to be overcome. In most cases, with roller bearings, a very small fraction of the weight.  A small grade can quickly reduce the Normal force and in turn the friction. At the same time adding a Force component in the downhill/uphill direction.    

 

Yes, it is possible, but a lot could depend on:

 

1) The temperature of the day and the corresponding temperature of the roller bearings.

 

2) The condition of the grease within the roller bearings.

 

3) The condition of the rail surface, i.e NOT all rusty as most industrial sidings are.

 

4) Absolutely NO dragging brake shoes.

 

5) Whether the car is empty or loaded.

 

6) How long the car has been stationary.

HW, no I was -- clearly -- not sure. Thanks for clarifying.

One of the selling points Timken used with the 4 Aces Northern, was that 3 women in high heels could get it rolling.

 

 I believe Ed King wrote in his book about the N&W class A engines, that the engineers were told they better be getting on the brakes going down a particular grade, or they'd have a runaway, VS. friction bearing engines that would just coast down hill or actually slow down on the grade from the drag.

Now THAT is just not logical! We have come down some really serious grades with SP4449, and those plain bearings NEVER slowed us down a bit. Besides, if plain bearings provided THAT much friction, there should be one heck of a lot of heat.

Two factors to consider also are wind and grade. 

Wind can easily blow cars when no air is on the cars.  Empty center beam flats are especially problematic.

Also, cars are pretty sensitive to grade.  It is believed that the best rolling cars will not accelerate unless the the grade exceeds .0010.  Roughly 10' of rise over a 2 mile length

The engineers that I worked with that were around when the Y6 came on the scene directly told me that they had to learn to run all over again because of the new roller bearings. The engines rolled much more freely than the plain bearing versions.

And the wind velocity and direction.  Really, I'm not kidding.

 

Yes Matt, it can be done I know for a fact.

 

Spotting cars without a switcher again, eh Doug?

Well I won't lie..... I'm not 200 lbs

My father worked the car shop for the Pittsburg and Shawmut Railroad, Brookvillle, PA many years ago.  They would use a pry bar, between the rail and a wheel, to get the car rolling. Once rolling it moved easily.

Car movers are used all the time.

 

I've seen unsecured single cars in the yard start moving by themselves on a windy day.

It took 4 to move a Niagara, must have been the centipede tender.

 

I love everything about this photo and would not have believed it without seeing it. Says a lot about how well they were able to engineer these machines.

Some rather excellent engineering went into those young ladies as well.

 

Here's a Timken ad:

 

If these ladies were trying to drag me off somewhere I wouldn't offer much resistance either.

 

hahahahah

Well...maybe. A slight downgrade also helped. 

 

These staged shots were always done on a very slight grade. On level track or even .1% up - no chance.

I suspected the same thing about the slight downward grade but didn’t want to disagree with the last few posts. When I used to watch World’s Strongest Man on ESPN, (the only time I watched ESPN) I remember effort the athletes had to expend to get a freight car, truck or aircraft moving & they weren’t smiling. It was hard to believe that a few models standing almost upright could initiate the movement of that locomotive or the freight car on a flat terrain.

http://www.youtube.com/watch?v=WFi0hNC2rsA

These are just my opinion.

Thanks,

Naveen Rajan

I really laughed when I saw this post Rich. Oh well, never let physics get in the way of good marketing.

Yes, they are.

I could do it.  I could also eat fifty eggs in an hour.  And drink fifty beers in twelve.
Back in the day...

I think Jack LaLane pulled one with his teeth.

Back in the 80's while they were rebuilding the Northeast Corridor, Amtrak parked their equipment on the old rail yard in the Edgewood Area of Aberdeen Proving Ground.  Sometime over the weekend a hopper car full of ballast started rolling through the yard and continued about two miles until it ran out of track.  Lucky thing it was on the weekend, because the tracks crossed a major road and tracks along the old loading dock was used as a parking lot.  The only damage was a trash dumpster and a smashed car stop at the end of the track.

I don't know Rich,, it looks like those ladies are going lash that locomotive up to the hopper in the other photo.

 

Clem

It is very hard to find track that is perfectly flat in order to run this test.  I did drift tests on transit cars, and on a 120 mile system there were only two places that the track charts claimed the track to be both level and straight.  On a railroad the track is actually the primary suspension with a spring constant of about one million pounds per inch.  So on level track, every car is going to be climbing up some small grade all the time.  If you look at a stress strain diagram for steel you will see that for any stress there is some strain.  So for a car sitting on level track, the wheel has a small flat spot where it contacts the rail and the rail has a small depression where the wheel sits on it.

 

All that said, over the years I have been invloved in pushing many cars to move them a short distance.  As to all the pretty girls pulling around Timkin equipped equipment, above fifteen MPH, or so, the rolling resistance of rollering bearings and plain bearings is about the same if the lubricant is up to temperature. Timkin actually sold ther bearings based on savings in oiling and maintenance.

The last 10 Reading T-1 4-8-4's had roller bearings on all axles. Hostlers and crewmen were warned that they rolled more freely than other locomotives.

 

Answer is on the blackboard..............

 

Force to overcome on the level is Friction.

Frictional Force is the coefficient of Friction X the Normal(Perpendicular to the surface) Force, on the level, Normal force is the Weight.

Grades, relatively small in the railroad world 1 to 2%, at the most, add or subtract, another component to the force, determined by simple trigonometric functions of the angle Sine and Cosine. 

 

A lot of engineering time is spent on friction.  

The Lac-Megantic, Quebec tragedy, would be an example of under-estimating forces.