How many cars could an EMD SW7 pull?

[bsteel4065]

Hi

I'm building a new layout with PRR / NYC HO in c1955. There's a switch yard at each end for which I've bought Broadway SW7's. As I'm building for reality as much as possible, I wondered as I was building, what was the real pulling power of these switchers? I mean in comes a full length train of let's say 20 cars... how would a yard with these switchers break it up? Could one a pull a whole train? How many cars could a switcher bite off and pull? Would they double up?

Cheers

Barry    

[Railway Man]

In a reasonably flat yard, an SW7 could grab the whole train, locomotives and all, no problem.

Tractive effort is ~ 42,000 lbs.  Rolling resistance is not more than 5 lb./ton of train.  A 20-car train with a pair of E-units would weigh not more than 1800 tons, so the SW7 would have to put out 9,000 lbs. to overcome rolling resistance.  Grade resistance is 20 lbs./ton of train per percent of grade, so if you had a 1% grade to lift the train up, 36,000 lbs. of tractive effort would be required plus 9,000 lbs. for rolling resistance.  I don't think the passenger train would weigh that much, and rolling resistance at low speeds is likely going to be around 3 lb./ton of train, but even so, once you get beyond 0.5-0.7%, a switch engine is going to have trouble particularly in poor rail conditions moving a 20-car passenger train and locomotives uphill.  But not too many yards or passenger terminals deal with anything like that kind of grade.

RWM 

[ndbprr]

An SW-7 can handle 20 cars.  I used to watch  a Reading SW-1 pull up to 25 cars on a branchline in Philadelphia.  Enola was switched with just about anything handy including I1 2-10-0's for the hump.

[wjstix]

If you mean c.1955 40' freight cars, I wouldn't be surprised if it could haul 30-40 cars on level track in ideal conditions.

That being said, generally our model engines are underpowered and rarely can pull as many cars as the real versions, you might need two SW-7's to move 20 model cars.

How often a switcher would move an entire train is another question. If a train is being 'broken down' in the yards, having the engine moving 5-10 cars at a time into different tracks wouldn't be unusual.

[ndbprr]

until recently the IHB was 100% switchers and pulled some pretty long trains.  I admit I am guessing but the coal trains to Inland Steel company in East chicago were probably 100 cars or longer pulled by two engines.

[bsteel4065]

Thank you guys!

As usual, fantastic detailed information. Interesting that the only piece of track I have laid so far is 0.87% incline and I tried out one BLI SW7 with 10 cars and it started to struggle after about 20 feet. I'm sure it will fine on my totally flat (with spirit level!) yard areas. No worries if I have to double up tho, that would make it all the more interesting.

Cheers and thank you!

Barry

[dehusman]

On flat and level track an 1000-1200 hp EMD can move 15-20,000 tons.

1% grade 1800 tons

2% grade 900 tons

3% grade 560 tons

Dave H.

[Sperandeo]

To back up what Dave Husman and others have said, when I was growing up in New Orleans, I often saw a single Illinois Central SW7 hauling 80 to 100 cars along the riverfront lines. They weren't going fast, but they kept long strings of cars moving.

So long,

Andy