Compensating grade for curvature How to ?

[bfsfabs]

I've wondered about this for a long time. Never dug into it very deeply due to plain laziness. Betcha mudchicken knows this stuff . . .

Is there a formula, tabulated data or a process that determines the actual grade to be used while in the curve ? If so what is it in somewhat simple terms. If tangent track was X % and the curve was Y degrees the grade in the curve would be Z %. Or what ?

I'm an HO scale modeller along with being a railfan and wonder if it would be worth the effort. Or just make a good story . . . I like good stories.

Lowell Ryder

[michaelstevens]

Lowell,

Are you talking about super-elevation ? Also often called "camber" ?

i.e. the difference in elevation between the pair of rails ?

[mudchicken]

Corned-fusion????

bfsfabs: Compensation for curvature in profile grades is something of an art and an opinion, based on whose railroad and formulae you use. (Each railroad is different and explaining the physics of it results in major brain damage) Try this as a rule of thumb:

"If the usual curve resistance figure of 0.8 lb per ton per degree of curve is accepted, the recommended compensation for curvature will be 0.04% per degree of curvature" -AREMA 16-1.2.9a........In so many words, add 0.04% grade for every 1 degree of curvature (chd-def).....

michaelstevens: crosslevel (superelevation) affects curve speed along with degree of curve and unbalance. Grade/ gradient is NOT figured in...bfsfabs is trying to see how much power & braking effort (# of locomotives & train length) is required to climb a hill.

FRA (49CFR213.57)requires 3.0 inch unbalance until you get over 90 mph. Most freight railroads use 1.5 inch to 2.5 inches of unbalance in their designs to be safe due to freight trains having a less uniform center of gravity than passenger trains. Amtrak uses the 3.0 figure (or higher) and demands more frequent inspection and maintenance to get the higher speed...This is why you can have different speeds for freight trains vs. passenger trains....

SPEED (mph) = SQRT ( [CrossLevel (inches) x Unbalance (inches)]/ 0.0007 D (Degree of Curve))

Mookie will be administering the pop-quiz shortly. Class dismissed....[swg]


Mudchicken[banghead]

[bfsfabs]

QUOTE: Originally posted by mudchicken

Corned-fusion????

"If the usual curve resistance figure of 0.8 lb per ton per degree of curve is accepted, the recommended compensation for curvature will be 0.04% per degree of curvature" -AREMA 16-1.2.9a........In so many words, add 0.04% grade for every 1 degree of curvature (chd-def).....

mudchicken:

(chd-def) refers to number of degrees discribed by a 100 foot chord. Right ?

OK, I guess I didn't have even a clue, OR you mistyped, OR I missunderstand. I was expecting to see a reduction of grade through the curve. Without going through the major brain damage flavor of explanation, do you mean the grade should "stiffen" through the curve ? ?

DUUHHH !! I get it, maybe, ADD 0.04% to the actual physical grade to get the effective grade through the curve. Then to keep a constant equivalent grade, reduce a planned grade through the curve by the magical 0.04% per degree. This makes more sense, at least right this minute.

Yell at me if I am assuming incorrectly . . .

Thanks,

Lowell Ryder

[edblysard]

Ok, lets see if I get this...
If train A leaves the north station headed south at 100mph, and train B leaves station B headed north at 45mph, the the red chevy should meet the blue ford somewhere near Nebraska?
uhhhh......

[bfsfabs]

Ed,

You must have miscalculated. The meet, collision, will occur at Main Street and First Ave in Bismark, ND.

[mudchicken]

Brother bfsfabs has "seen da' light"![bow]

(1) The effect of grade increases in curves because of the friction of the against the rails! [Trucks on a railcar want to go straight ahead until the rail dictates otherwise]...

(2) chd-def is chord definition, the degree of curve is the deflection angle (in degrees-minutes-seconds) as measured at the radial point (center of a circle) for a 100 foot chord....This is what railroads use to describe curves with...(The delection angle for a 100' chord coming down the center of the track at the point where tangent (straight) goes to curve (radial) is exactly one-half of the degree of curvature at 100 ft.of chord) .....In the days before calculators, this allowed surveyors to lay out curves in a hurry and not worry about longhand division and multiplication. (makes life simple - army artillery surveyors figured this out long ago, they needed to work quick when the bullets and cannonballs started flying)[:D](most early railroad surveyors were trained in the army in the 1800's)...unfortunately, most local surveyors think in radius or "arc" definition and the fact that railroaders don't use arc definition screws them up when they encounter railroads - #1 Cardinal sin for most non-railroaders! I see lots of screwed-up plats, maps, plans and legal descriptions because of this. You caught-on right away! Chalk-up one atta-boy for your side...

Mudchicken[banghead]
"Radius?....Real railroaders don't need no stinkin' radius!"

[mudchicken]

QUOTE: Originally posted by edblysard

Ok, lets see if I get this...
If train A leaves the north station headed south at 100mph, and train B leaves station B headed north at 45mph, the the red chevy should meet the blue ford somewhere near Nebraska?
uhhhh......

They all met in farmer Jones' cornfield somewhere south of Omaha![swg]

Dirty Bird[banghead]

[edblysard]

Uh, yeah, what yous guys said...

QUOTE: Originally posted by mudchicken

Brother bfsfabs has "seen da' light"![bow]

(1) The effect of grade increases in curves because of the friction of the against the rails! [Trucks on a railcar want to go straight ahead until the rail dictates otherwise]...

(2) chd-def is chord definition, the degree of curve is the deflection angle (in degrees-minutes-seconds) as measured at the radial point (center of a circle) for a 100 foot chord....This is what railroads use to describe curves with...(The delection angle for a 100' chord coming down the center of the track at the point where tangent (straight) goes to curve (radial) is exactly one-half of the degree of curvature at 100 ft.of chord) .....In the days before calculators, this allowed surveyors to lay out curves in a hurry and not worry about longhand division and multiplication. (makes life simple - army artillery surveyors figured this out long ago, they needed to work quick when the bullets and cannonballs started flying)[:D](most early railroad surveyors were trained in the army in the 1800's)...unfortunately, most local surveyors think in radius or "arc" definition and the fact that railroaders don't use arc definition screws them up when they encounter railroads - #1 Cardinal sin for most non-railroaders! I see lots of screwed-up plats, maps, plans and legal descriptions because of this. You caught-on right away! Chalk-up one atta-boy for your side...

Mudchicken[banghead]
"Radius?....Real railroaders don't need no stinkin' radius!"

[Anonymous]

QUOTE: Originally posted by mudchicken


They all met in farmer Jones' cornfield somewhere south of Omaha![swg]

so that's what was in his yard. And he had me fooled when he told me a UFO made a crop circle around the tracks! I'm never list'nin to him 'gain!

[wabash1]

You are all wrong. The dispatcher will put train "A" in the siding 1 hr after he leaves to wait on train "B" who is hot and late . ( now remeber we are in abs territory) . After 3hrs of train "A" setting here waiting on train "B" the dispatcher sees that he can make a better meet 10 miles up the road and proceeds to take both trains to the next siding and put both in the hole. then send a relief crew for both as they dont have a chance at making it anyways.

[wabash1]

It should be noted at this time also that the conductor is 10lbs lighter from losing his money at the card game. and the several trips to the convienace store getting junk food to eat. when they was parked at the first siding.

[Big_Boy_4005]

I come from the school of mathmatical dropouts, [D)]where the formula is: if the train doesn't make it up the hill, either add another engine, or shorten the train.[:P][;)][:D]

Actually I have long been aware of this issue, but have never had enough curiosity to ask the question. I too, am more of a modeler, so the units would be expressed in inches and ounces, rather than feet and tons. Smaller trains, smaller problems, thank God.

Great question, great answer, thanks guys. [bow]

No wonder real railroads don't use helixes!

[tree68]

QUOTE: Originally posted by Big_Boy_4005
[
No wonder real railroads don't use helixes!

Sure they do. They just stop after one turn! (think Tehachapi)

[Big_Boy_4005]

QUOTE: Originally posted by tree68

QUOTE: Originally posted by Big_Boy_4005

No wonder real railroads don't use helixes!

Sure they do. They just stop after one turn! (think Tehachapi)

And the Georgetown loop and and all over the mountains of Europe, one slight difference, they aren't uniform 360 degree curves.[8D]

P.S. I'm in the process of building a 10' diameter, 3 rail "O" helix, 6 turns ~2%. The first 2 turns are double track, then 4 turns single, to connect 3 levels.

[kenneo]

Don't forget Canada. CP has stacked helix tunnels -- I can't remember the pass name - I want to say Rogers, but that doesn't seem right. I don't think the tunnels are directly above each other, but rather, they are off set.

[Mookie]

Well......the Mookie is curved, helixed, looped, confounded and got exactly nothing out of that except what Wabash said.

But then Mookie's train always runs on a straight track.....

I have now confirmed that chickens talk funny!

Moo

[wabash1]

Mookie

All i can tell you is remeber this the wheels on the train go round and round.........

[Mookie]

QUOTE: Originally posted by wabash1

Mookie

All i can tell you is remeber this the wheels on the train go round and round.........

[;)] kinda like Mook's eyes!

[mudchicken]

QUOTE: Originally posted by Big_Boy_4005



No wonder real railroads don't use helixes!

BB4005: Real railroaders don't need helixes because we still think cubic parabolas (spirals) are kinda neat! (And if you read Ed's ode to Hemphill's paragraph, their are not many of us left who can figure the rascals out!)

Mookie: Your eyes apparently indicate that the unlimited supply of eggnog has had the desired effect. Her most feline furryness' noggin is fogged-in!

Wabash: You just figured out that dispatchers are out of touch and clueless?

Kenneo: Yes, it's CP's Rogers Pass line, 9th wonder of the world...


Mudchicken[banghead]

[mudchicken]

Well, the US Mule has failed to deliver Trains Mag here in Denver as well...

mc

[Mookie]

Here in the wild Middle West - the mail arrived just fine. Now if they would just deliver some spare time to read it!

Hey MC - I have a question for you - will post it on a new thread!

Mookie - (I like my "egg" nogg right next to my Fried Chicken!)

[Anonymous]

I have a question,

Thuis may be off topic, but i don't care.

What is the maximum garde a Train can travel, I know up here we got a 3.2 somewhere, like what would be unheard of?

4.0%?

[Big_Boy_4005]

Depends on the type of train, I think 4% is close to the max for non cog aided rails. US mainlines should all be under 2% these days. Unfortunatly, Columbus was right, and the Earth is not flat. More trouble for the railroads.[:P]

[Big_Boy_4005]

So MC, I get the impression that you aren't a big fan of the Post Hold service. (Or is it Holed?) I guess that's why they call it snail mail.[:D] We deliver for you. (eventually)

[PNWRMNM]

Dear Kenno and Mudchicken

The Spiral Tunnels are on West slope of Kicking Horse Pass, not Rogers Pass. Rogers Pass has the longish summit tunnels.

Mac

[kenneo]

Thank you, Mac.

Rogers just didn't seem right for the spirals.

Actually, they are not true helix tunnels because they have short "straight" (not so curved) sections so that when the tunnel comes around on top of itself it won't colapse. That makes them a spiral.

Also, the Siskiyou also has a tunnel situation like that. ( Was SP, now CORP) Tunnels 14 and 15 between the upper and middle Hall Creek crossings where Tunnel 15 was built to support Tunnel 14 which is just above it. 14 is on the uphill end of a (about) 200 degree (compas) reverse curve and is on an S curve. 15 is on the downhill end of that reverse curve.

And the POTB at Wolf Creek has a tunnel (Tunnel 27) with an S curve in it that leaps right out onto a trestle on a reverse curve. Ends up making a reverse of 180 degrees.