NEED A LITTLE PUSH HERE

[louisnash]

I have read here about RR grades and knew how they were figured. The question I must ask now if it hasn't been already is how is it determined when you actually need a helper on the rear to push.

I know that weight is a major, if not the only factor in determining this,but are there others? Is it also for safety reasons? I know that the grades here aren't near as steep as the ones out west.

I was in Ford,KY one time just south of Winchester,KY and they add helpers there to get to Richmond,KY but I can't remember if they hook all the lines from one loco to the other. Or do they just couple up and go?

Thanks to all that respond.

Brian (KY)

[Anonymous]

To Jackflash and Wabash: I finally read some Powder River Div. General Notices (yeah, I was really bored) that outlines the functions of Helper link that we talked about. I'll post the high points when I'm not being so lazy. I said that when I got more info that I would share it with y'all. I even loaded it on my Palm Pilot so I can refer to it just for you guys. But, hey, that's the kinda guy I am. Hehehe
Ken

[JoeKoh]

gravity what goes up must come down.they use the engines not only to push but to help brake down the other side.
stay safe
joe

[oltmannd]

Whether or not you need a pusher to get up a hill is entirely a matter of grade, train tonnage and drawbar strength. Here's the method for figuring it out:

It takes 20 lbs of pulling force per degree of grade to move a ton of freight up hill.

The max strength of the drawgear in frt trains is (usually) 250,000 lbs. (up to 400,000 for some unit trains)

A hypothetical: Train weighs 5000 tons. Needs to get up 2% grade. So, 5000 x 20 x 2 = 200,000 lbs of pulling force. Since this is less than 250,000, you can do it all by pulling from head end. A 400,000 lb locomotive with 25% adhesion can pull 100,000 lbs (typical C40-8 or SD60), so two would get the train up the hill.

If the train was 10,000 tons, you'd need 400,000 lbs tractive effort which would require four C40-8s. Too much to apply at the head end (you'd break a knuckle, for sure!) so you'd have to put two on the front and two pushing.

Coming downhill is a different matter. Additional locomotives can be added at the front or the rear if it is desired to control train speed primarily with dynamic braking. There are often limits on how much dynamic braking can be applied a the head end in order to keep the train from derailing, but it is not as straightforward a calculation as getting up the hill.

-Don

[bfsfabs]

Donald, Is it as straight forward to figure for curvature ? In your example are the curves presumed to be compensated to 2% ?
Curiosity overwhelms me.

Lowell

[alangj]

Don,

What would be the factor used to calculate the necessary pulling force on level track? Obviously, you can't use the same formula in your example, since on level track the grade is 0 degrees, and 5000 x 20 x 0 = 0, which doesn't quite match what we know as reality.

Alan

[Anonymous]

Brian,

There are a couple of ways to take your question, and I will answer what I think you asked which is why does one railroad use helpers on a 2% grade but another uses them on a 1% grade.

The reason has to do with the ruling grade on the rest of the territory. In the Western mountains helper grades are generally 2% or so. The ruling grade, setting aside the helper grade, will often be about half the helper grade. For example, GN Stevens Pass is 2.2% both ways with 1% on the approaches. You size the train for the speed you want on the approaches, say 1.5 HPPT but if real drag operation you could get by with 1 HPPT. Use the 250,000# drawbar rule and you could have 25,000 tons and 25,000 HP, which is much more than would typically be operated in this territory. More realistic would be 12,000 HP with a 9-10,000 ton train. That will give you a speed greater than minimum countiuous speed. And there is about 1.3 #/ton rolling and air resistance.

For help need to double the power if double the grade. On a mountain railroad with 10 degree curves helper would likely be cut in to reduce in train forces. Rear helpers OK with unit trains.

Now consider a line in the east with a short 1% grade on an otherwise .5% territory. Choice is to either power every train for the 1%, or power for .5% and help. Here pushers more likely as amount of power in your helper will probably be less than in the 2% case. This is the kind of territory where diesels eliminated a lot of helper operations. Most western railroads count 1% or less as flat, they just power for them. Helpers are an operational pain.

The point is "it all depends", on the traffic, how fast it has to move, and on the relative costs of powering through for the steepest hill, vs under powering with helpers.

I hope this answers the question you had in mind.

Mac McCulloch