....Here's another one

[Anonymous]

Alright. I'm confroosed on this grade stuff. In HO scale, a percentage of grade is measured in 100 inches. I got that much. 1% grade means the track rises 1 inch in 100 inches....2% is 2 in 100 inches...and on and on. I got all that. Ok boys, here is where it gets for this old boy. The length of the Union Pacific Challenger is 106' 8". That's prototypical scale....real life, if you will. If the Challenger is supposed to be over 100 feet long, why do we use 100 inches in HO to equal 100 feet in prototypical scale? It just don't add up. Looks to me like we would need to use about the length of the Challenger. I mean prototypical 1% grade rises 1 foot in 100 feet, right? Then to be correct in HO, the track would need to rise 1 inch in about the length of the Challenger in HO. What am I missing?

[Anonymous]

Grade does not scale down. A 1% grade in HO, N or real life rises 1 inch over 100 inches. 1 mile over 100 miles.

If the UP Challenger in your example is sitting on a 1% grade it is 1 scale inch (OOPS 1 scale foot) higher at one end than the other.

[Anonymous]

You got the grade right. What you missed is that a 100" Challenger in HO just doesn't make sense; it shouldn't be over 2 feet. HO is 1/87 (i.e. 100 feet long in real scale is only 1.15 feet long, not 115 inches long. Hope this helps.
Just to let you know, not confuse you, grade is simply a fraction: rise/run (just take the distances ascended or descended and divide by the length. It doesn’t have to be measured in 100-foot sections although thinking of it that way makes it simpler.
James[C):-)]

[cacole]

A really easy to remember measurement is what all of this is based upon. Grade calculations came about long, long before a Challenger or Big Boy hit the rails.

Real railroads measure their grades in 100 foot increments; i.e., 1 foot rise in 100 linear feet of track is a 1% grade; so that's probably why HO and other modeling scales is based on 100 inches.

[gvdobler]

Everything is based on 100 because we're talking about a percentage of 100 percent.

If you have two dollars, you have 2% of a hundred dollar bill.
If a grade (hill) is 7,500 feet long (roughly a mile and a half) and it is 150 feet higher at one end than the other, divide 150 by 7500 and you get a 2% grade.
It can be a hundred inches, feet, meters, miles, yards, doesn't matter..

[selector]

Yes, we mustn't confuse size and scale with grade and percent. You can shrink a giant to any size (scale) you want, but he will still feel a 3% grade like a real loco will. That is because they are both climbing the same grade, but the smaller guy has shorter legs.

Another way to look at it is with the notion of 'proportion'. A scale model is proportionally the same as its big brother. They look the same and function the same visually. The same can be said for the grade, whether under your own two feet or under your model loco.

[loathar]

You can also just get one of those round adjustable bubble type angle finders that race car guys use to set up their chassis angles. Or I'm sure there's one made for the construction industry at Home Depot. 1% is 1% in any scale.

[Anonymous]

I have two. Been using them a long time. I just never thought of the connection. I got it now, though. Duhhhhh

QUOTE: Originally posted by loathar

You can also just get one of those round adjustable bubble type angle finders that race car guys use to set up their chassis angles. Or I'm sure there's one made for the construction industry at Home Depot. 1% is 1% in any scale.

[Anonymous]

Grade is always expressed in %, as the units for the rise and run are always the same. 1 inch rise over 100 inch run... 1 foot rise over 100 foot run... Most railroads in the past (when built) expressed grade as a rise in feet over one mile, not as a percentage.

Bob - where you went wrong was trying to use 1 real inch rise over 100 scale foot run (length of the loco). This works out to be more like 7.5%, since at 1:87 (HO scale), 1 real inch = approx 7.5 scale feet.

Andrew

[rrinker]

Grade and curvature are those things that have no scale. For a grade - 1 HO foot up in 100 HO feet long is exactly the same grade as 1 REAL foot up over 100 REAL feet long. Curvature is measured similarly - civil engineers don't make curves to XX radius, they are some number of degrees of curvature per a given run.

The key to such ratio measurements is that the units match - 1 HO foot rise over 100 REAL feet run is not a 1% grade - the units don't match! But 1 inch over 100 inches IS the same as 1 foot over 100 feet.

Look at it this way: 1 foot / 100 foot x 100%

Remove the numbers for a moment, you have: foot / foot x %

Through one of those math laws, since there is a FOOT on top and a FOOT on the bottom, you can cross them out, leaving you with: %

Stick the numbers back in: 1 FOOT / 100 FOOT x 100%
1 / 100 x 100%
1%

If the units are not the same (inches over feet, or something), they do not cross out and you are left with some nonsense like 4.253 in/foot % which makes no sense - an easy check to know you did things right. If you are left with more than just the %, you messed up.

--Randy