Gradients

 
  whiskymac Beginner

Just trying to plan out my layout. If I take the track to a height 78mm over a distance of 2035mm am I correct in working out that the gradient is 2.6. I have just ran a train with six carriages and dummy diesel loco for extra weight and it seems to handle it OK.

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  alantrains Train Controller

Location: Brisbane Qld
Just trying to plan out my layout. If I take the track to a height 78mm over a distance of 2035mm am I correct in working out that the gradient is 2.6. I have just ran a train with six carriages and dummy diesel loco for extra weight and it seems to handle it OK.
whiskymac

I think you did the division the wrong way around.
If 1 mm in 100mm is 1% grade then 78mm in 2035mm is 3.8% grade.
cheers
Alan
  Kevin Martin Chief Train Controller

Location: Melbourne
I think you did the division the wrong way around.
If 1 mm in 100mm is 1% grade then 78mm in 2035mm is 3.8% grade.
cheers
Alan
alantrains

Or 1 in 26 (divide 2035 by 78 ). The OP got his decimal point in the wrong place. Quite an acceptable grade for a model railway, many come here with far steeper grades.

edit. Sorry I got it wrong. 1 in 26 is NOT an acceptable grade, its too steep.
  alantrains Train Controller

Location: Brisbane Qld
Or 1 in 26 (divide 2035 by 78 ). The OP got his decimal point in the wrong place. Quite an acceptable grade for a model railway, many come here with far steeper grades.
Kevin Martin

Normally percent grade is calculated by dividing the rise by the run (either run or hypotenuse as Hypotenuse is easier to measure and over a long distance it makes little difference) then multipling by 100.


78 /2035 *100 = 3.83% which is 1 in 26

regards
Alan
  LaidlayM Chief Commissioner

Location: Research
Or 1 in 26 (divide 2035 by 78 ). The OP got his decimal point in the wrong place. Quite an acceptable grade for a model railway, many come here with far steeper grades.
Kevin Martin

Crikey Kevin, I reckon that is pretty steep.  I don't know if "far steeper" would work, I would discourage anything steeper.

Mark
  a6et Minister for Railways

Crikey Kevin, I reckon that is pretty steep. I don't know if "far steeper" would work, I would discourage anything steeper.

Mark
LaidlayM

I have 1:40 grade on my layout which is also on a 28" curve, not too much of an issue with a diesel but as I model steam era, it tests those models very much, which means you need well weighted loco's as well as the R/S being free rolling.

One thing for sure, is that I would not have a 1:26grade on a layout if I could avoid it. 1:30/33 is very steep for main line & even was for the 1:1 gauge as well.
  Kevin Martin Chief Train Controller

Location: Melbourne
Crikey Kevin, I reckon that is pretty steep. I don't know if "far steeper" would work, I would discourage anything steeper.

Mark
LaidlayM

Yeah, I made a mistake. I know I typed the right answer of 1 in 26, but the brain went wrong at what that meant! Definitely something to avoid, although plenty of question get asked here about 'What is the steepest grade' etc.

Sorry Mark, a6et and others.
  a6et Minister for Railways

Yeah, I made a mistake. I know I typed the right answer of 1 in 26, but the brain went wrong at what that meant! Definitely something to avoid, although plenty of question get asked here about 'What is the steepest grade' etc.

Sorry Mark, a6et and others.
Kevin Martin

Juniors moment Kevin!
  SAR523 Assistant Commissioner

Location: Chicago, IL
As others have said, a 78mm rise over 2035mm is 3.83%.

In general, this would be considered too high unless you are modelling something that requires that sort of grade, like a logging railway or possibly a streetcar layout or you are running very short or under-weighted trains.

While this is a bit of a 'how long is a piece of string', 2% grades are generally considered high but do-able, even for steam locos.  There are a few things to keep in mind:

1. Diesel locos can certainly handle steeper grades than steam locos.

3. Consisting locos is always an option but requires that they be well speed matched otherwise you get other problems from having one engine surging against the other which acts a brake.

3. Things go wrong on even the best laid track.  If a coupler breaks or disconnects, the steeper the grade, the faster everything hits the curve at the bottom if you don't catch it in time.

4. You will read about people having 4% helixes.  I have never met anyone who was happy with grades anywhere near this (there are a lot of helixes in the US).  It's normally more like 2-2.5% and there's normally a lot of time taken to improve the entry and exit vertical curves and the general alignment.

5. What are you building your subroadbed out of and how much does the humidity change over the year where you live?  Basically, while your test train works now, what will happen in 6 months when the subroadbed has changed?  Will you suddenly have a very sharp vertical curve somewhere?

6. Are there any curves in this elevation change?  If yes, you are actually increasing the effective grade and increasing the liklihood of operational problems.


Assuming you don't have the space for a normal helix and depending on your layout and operational desires, you might want a vertical transfer table.  This is basically shelf of track mounted on high quality drawer sliders that you can use to move from one level to another.  It's certainly less than ideal but gets rid of the very high grades.  

Alternatively, the prototype also built too-large grades around the place requiring the train to be broken into two (or more!) pieces and taken up the hill over multiple trips.  This certainly increases the operating interest but is very annoying if you're more a run-the-trains sort of person.
  DF4D-0130 Junior Train Controller

G'day all,

From what has been said here, looks like I am in the doggy-doo well and truly!  My layout that has been under construction for the last 5 years was worked on a 4% gradient!  

The 4D laughs at the incline, but the 7G, well, it stops at the bottom and looks at me as much to say:  "You want me to pull this lot up there???  What are you on?  Snappy Tom???"  

It raises an interesting point:  When the QJ is purchased, how is that going to cope with the long and steep gradient?  

Ding.
  a6et Minister for Railways

G'day all,

From what has been said here, looks like I am in the doggy-doo well and truly! My layout that has been under construction for the last 5 years was worked on a 4% gradient!

The 4D laughs at the incline, but the 7G, well, it stops at the bottom and looks at me as much to say: "You want me to pull this lot up there??? What are you on? Snappy Tom???"

It raises an interesting point: When the QJ is purchased, how is that going to cope with the long and steep gradient?

Ding.
DF4D-0130

Well if its a Bachmann QJ forget it, especially the middle flangless tyred versions, sadly looking to sell my CNR collection bar one modded with HD deflectors.
  petan Chief Commissioner

Location: Waiting to see a zebra using a zebra crossing!
Just trying to plan out my layout. If I take the track to a height 78mm over a distance of 2035mm
whiskymac

You have noted the change in height of 78 mm over a distance of 2 meters 35 mm which is a pretty long distance to build a perfectly consistent climb on a model track . Problem is possible fluctuations over that 2 meters which would mean some parts are steeper than other parts of the climb. All it would take is one support to be slightly out in measurement or positioning.

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