Grade Question

[Conductorphil]

I've just got a few design questions for those who work around in surveyor.

I'm designing a fictional UK based route, a small branchline for containers, general goods, passengers and coal.

What would you consider a maximum average grade to be when going up or down on track? I've looked at the usage of 2 and -2 and while it seems good, it seems to be a little too far angled.

 

[cascaderailroad]

I would think that a 2% grade would be an absolute maximum for a mainline, and 1.50%, or 1.75% would be prefered. Most grades are kept below 1.00% or much less.

Branchlines and backwoods railroads oftentimes had very sharp curves and steep gradients

 

[oknotsen]

Hi,

This list might be helpful with giving you a feeling:
http://en.wikipedia.org/wiki/List_of_steepest_gradients_on_adhesion_railways

For freight trains, gradients should be as gentle as possible, preferably below 1.5 %.

 

[Conductorphil]

Thanks for both of your replies. It does seem logical to have a maximum gradient of 1.5% on a freight based track. The link was also helpful.

Another question then, though I don't really know if this is really an applicable question. Would it be likely for a track to be forcibly leveled out so as to reduce the strain on an engine? I mean, obviously it is logical that you'd want the grade to be as low as possible, but what I am referring too mostly is what would be a maximum preferred length of track on a rising gradient of roughly 1.5% before leveling out so that the engine can temporarily reduce strain and build up more steam? Or would a grade like this not really be that big of a problem?

 

[Dermmy]

That depends a lot on the local topography. There are two issues - minimizing the grade and getting over the hill. I see from the OP that you are doing a UK route. When the Midland Railway struck north to Scotland in the 1870s management insisted that the ruling grade would be 1%. It took a while to find a suitable route and I forget the surveyor's name, but management did get their 1%, problem was that they got over 60 miles of it - hence the route's nickname The Long Drag! The problem with your idea to ease the grade for a bit on one section only means that (assuming we are still going up hill) the next bit will be steeper.

There are plenty of exceptions, but about 1% would be a fair max grade on UK main lines, however the 'small branchline' you are contemplating could go double that, even more over short lengths if necessary...

Andy

 

[Conductorphil]

This is why I like this forum: Very good answers.

Thanks for your help. I'll start realigning my track and see what turns up.

Final question then, which relates to what you said in your most recent post: Just how difficult would a 1% grade be? From what I know of mathematics, 1% seems to be a miniscule change in height (Or is there a distance over height calculation that I am missing?) which should not really be that big of a deal for a locomotive.

 

[Dermmy]

...1% seems to be a miniscule change in height ... which should not really be that big of a deal for a locomotive.

For every 100 feet moved forwards the loco is exerting the force required to lift many hundreds of tons (and on some modern railways many thousands of tons) one foot vertically. That's over and above the force required to move the load horizontally. That's a huge expenditure in energy! 1% is an acceptable main line grade, but that doesn't mean it's not steep...

Andy

 

[BLACKWATCH]

As an extra bit of information on this (for comparison), the 'Great Central Railway' was around 1 in 130 at it's steepest, with 1 in 176 being the most common gradient, so you can see that 1% (1 in 100) might be described as steep in gradient terms.

 

[Bill69]

Hi Conductorphil,

Here is a link to a handy grade calculator.
http://www.trainman.id.au/grade.htm

Just as a note, there are quite a few areas in New Zealand where the main line has a 2% grade, like up through the central plateau.

Cheers,
Bill69