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Author Topic: Grade calculator  (Read 5372 times)
jowalmer

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« on: February 16, 2009, 10:28:09 PM »

Has anyone found such a thing that calculates inches for the math inpaired?  I would like to determine rise for 2% and 3% grades over 100" of track.  Thanks.

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James in FL

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« Reply #1 on: February 16, 2009, 10:50:35 PM »

There are calculators available by using “Google”

 From your post I would assume you already have the basic understanding of the math.

Grade is "rise" (height change) divided by "run" (distance traveled) expressed as a percent (multiplied by 100).

Therefore if you have a 2” rise over 100” of track you have essentially a 2% “Grade”

A 3” rise over the same 100” inches of track would be a 3% grade.
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jowalmer

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« Reply #2 on: February 17, 2009, 12:00:00 AM »

the calculators I found on the net had to do with miles and feet.  I know math basics bout get lost trying to convert.  A calculator would still be helpful if anyone has a link.

Thanks for your figures, James.
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jowalmer

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« Reply #3 on: February 17, 2009, 12:11:22 AM »

Had the wording wrong in my google searches.  I did a 'rise and run calculator' search and found what I was looking for.  thanks again.
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Woody Elmore

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« Reply #4 on: February 17, 2009, 10:01:17 AM »

Very simple - a one unit rise in 100 units would be a one percent rise.  Since we use four letter words when we measure length (inch, foot, yard) you'd measure 100 inches from where you want the grade to begin at that point if the track is elevated one inch, you have a one percent rise.

If you use fifty inches, a rise of a half inch would also be a one percent grade.

Grades in model railroading are deceiving. People don't often have the room to put in gentle grades so they put in steep grades and then complain to the Bach Man that the engine they have will only pull a car or two.

Model the SPNG in the Owens Valley - mostly flat - no grades.
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ebtnut

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« Reply #5 on: February 17, 2009, 02:17:48 PM »

While not "correct" from an engineering standpoint, for model railroad purposes you can use this short-hand:  1" in 24" = 4%; 1" in 36" = 3%; 1" in 48" = 2%.  Our models are not quite as sensitive to fractions of a percent of grade.  This is and easy way to measure and build without a lot of futzing around.  Oh, and don't forget the old geometry formula C = pi x D for measuring the distance around a curve.
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jowalmer

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« Reply #6 on: February 19, 2009, 01:45:57 AM »

I was going to guess at the curves, not anymore.  thanks nut.
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normsuds

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« Reply #7 on: February 22, 2009, 10:29:20 AM »

Calculating 2% or 3% over a hundred inches is not correct. To be done correctly the grade has to be claculated according to the scale you are using. 100" of n scale track is not the same distance in scale as 100" of HO scale. You would have to calculate by simple multiplication and division the actual scales of 1:160 for N scale and 1:87 for HO Gauge then you can get a correct grade for your set.
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fieromike


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« Reply #8 on: February 22, 2009, 10:49:05 AM »

Calculating 2% or 3% over a hundred inches is not correct. To be done correctly the grade has to be claculated according to the scale you are using. 100" of n scale track is not the same distance in scale as 100" of HO scale. You would have to calculate by simple multiplication and division the actual scales of 1:160 for N scale and 1:87 for HO Gauge then you can get a correct grade for your set.
Error.
Percentage doesn't scale.  You are also calculating percentage of rise over an actual distance (100"), not a scaled distance.
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Joe Satnik


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« Reply #9 on: February 22, 2009, 11:00:06 AM »

Percent grade = 100% x rise/run.   

If the rise and run units are the same (e.g. both "inches"), the units "cancel" each other in the division operation, and you are left with just a "percent" figure.

This means the equation works for every scale, 1:1 prototypes down to "t" scale, as long as the measurement units match each other.

If they don't match, use a scale conversion (e.g. 12" = 1 foot) then calculate the grade.   

Hope this helps. 

Sincerely,

Joe Satnik 
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If your loco is too heavy to lift, you'd better be able to ride in, on or behind it.
BIG BEAR

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« Reply #10 on: February 22, 2009, 12:58:05 PM »


   Hey Jowalmer,
    The key to your question is in the question.
1"/100" = 1%, 2"/100" =2%, 4"/100" =4%, etc.
I think, and others will probably agree, the steepest grade you will want to make on your layout would be 4% other wise the engines will have problems making it up the hill, and will gain too much speed & derail coming down hill.

                 Enjoy,
                    Barry
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Barry,

...all the Live long day... If she'd let me.
jward


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« Reply #11 on: February 22, 2009, 04:15:02 PM »

I am going to take this discussion a step further. You didn't specify whether or not you were looking for a way to translate grade percentages to actual field conditions such as building your layout. On the assumption that you are, I am going to share a little secret for setting your grades.....

ebtnut mentioned that grades can be rounded so that a 1% grade is 1" in 96" (or 1/4" in 24") , 2% as 1" in 48" (1/2" in 24") and so on. Why am I rounding thes and converting them to rise in 24"? Simple, 24" just happens to be on of the standard lengths on a level, commonly available in any hardware store and one of the "must have" tools of the experienced layout builder. After all, if your table isn't level, all other grade calculations are moot.

1/4" moulding strip is also commonly available, and cheap too. we can build a simple grade calculator out of this strip. First, take the strip and cut it into 1" 2" 3" and 4" lengths, one of each length. Next, stack and glue them together in a stairstep configuration. they should all be flush on one end, and look like stairs on the other end.

Using this device is very simple. For a 1% grade, set the calculator on ryour track board. Set one end of your 24" level on the lowest step of the calculator, then raise the track board under the other end of the level. when the bubble reads level you will be within a gnat's eyelash of a 1% slope to your track board. You should already have riser blocks fastened to the underside of your track board where it crosses your table joists, simply clamp them in the new position and screw them securely into the joist. Move the whole works another 2 feet up the line and repeat the process.....

For 2% you'd use the second step, 3% the third, and so forth.

I purposely didn't add steps for 5% and above as 4% is about the practical limit for grades on model railroads. even 4% will drasticly affect the number of cars you can run in a train as a given locomotive will pull something like 1/6 of what it can pull on the level....

i have been using these devices for 30 years to set grades, and the only thing i have ever found easier to use are the woodland scenics foam risers, available in 2% 3% and 4% inclines....


Jeffery Ward Sr
Pittsburgh, PA
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Jeffery S Ward Sr
Pittsburgh, PA
BIG BEAR

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« Reply #12 on: February 22, 2009, 04:49:25 PM »


    Hi Jeff,
    I have been looking at the woodland scenic the past month or so, I think the ability to slightly curve your incline can make it look more natural than my straight wood board.
          Barry
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Barry,

...all the Live long day... If she'd let me.
jward


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« Reply #13 on: February 22, 2009, 07:07:43 PM »

I handlay my own track, so I can't use the Woodland Scenics inclines. I did use them in N scale, and i was impressed. But you can also curve your trackboards too with a jig saw. I currently lay all my track on 1x4 or wider pine board. It holds spikes better than anything else I've found, and can be cut to fit almost any situation.

Jeffery S Ward Sr
Pittsburgh, PA
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Jeffery S Ward Sr
Pittsburgh, PA
fieromike


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« Reply #14 on: February 22, 2009, 07:29:04 PM »


    Hi Jeff,
    I have been looking at the woodland scenic the past month or so, I think the ability to slightly curve your incline can make it look more natural than my straight wood board.
          Barry
Just to stir the pot a bit more, Using the Woodland Scenics incline sets won't give you a true 2,3,or 4 percent grade.  Their incline pieces are 24" long, giving you a 96" run instead of a 100" run.  The result is a slightly steeper grade than advertised.  In the big scheme of things, if you are aware of the 4" difference, it really doesn't amount to a hill of beans (like most of this discussion).
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