real life curve radius

Discussion in 'Getting Started' started by nachoman, Jul 19, 2007.

  1. nachoman

    nachoman Guest

    While working a job today at an industrial plant in Gilbert, Arizona, I noticed they had a rail connection that had a track long enough for about 5 tank cars. The spur was on the inside of a curve of a longer branch line, much like a model railroad may have an industrial spur leading to the inside corner of a layout.

    I thought - sheesh, that curve looks tight! And when a train came by, it was obvious how much the train slowed to make it around. Later, I thought about the dimensions of the industrial plant, and that "sharp" curve was probably 500 feet in radius. 500 feet is about 5.75 feet in HO scale. In other words, that "sharp" prototype curve probably would scale out to about 70 inches!

  2. TruckLover

    TruckLover Mack CH613 & 53' Trailer

    That is very interesting to know, thanks for sharing

    Atlas does makes a 71" radius curve in N scale for C55 track.
  3. Biased turkey

    Biased turkey Active Member

    That's the reason why a real railroad never looks toyish, while an N scale Mikado on a 9 3/4" radius curve does. :)
    And real railroads don't have to lay tracks in a corner of their "layout".

    Too bad you don't have a picture

    By the way TruckLover, I was unaware that Atlas make N scale sectional tracks with such a big radius
  4. TruckLover

    TruckLover Mack CH613 & 53' Trailer

    Yup, they go from 21.25" to 30.609" and then to 71" which is the largest they make.

    here is the link to there C55 page: Atlas N Code 55 Track Products
  5. nkp174

    nkp174 Active Member

    A real NKP berkshire can negotiate a 20degree curve...which is 288' radius. In HO scale, that's 3.3'...but, they're equipped with lateral motion devices to increase their ability to go around right curves.

    I've personally seen the MLW 261 take an hour to get around a tight why which an NKP berk flew around...due to the wheel base and lateral motion devices. I've heard similar stories about the 611.

    To model the Woodstock loop of my beloved DSP&P in On3 would require a 10' diameter loop!

    Real railroads use the measurement degree of curvature because taking a radius is unwielding...the method of measurement is something to the effect of holding on end of the tape at one point and place the 100' mark at another point on the curve. Measure the deflection from the tape to the rail and multiply by 4 or something to get the deg of curvature.
  6. MasonJar

    MasonJar It's not rocket surgery

    The Credit Valley Railway in southern Ontario was originally built as a narrow gauge road with "tight" curves on the order of 800' radius - that's just over 9' in HO.

    I think it was Triplex who pointed out that streetcars/trolleys can negotiate curves of 12 to 20 foot radius - necessary of course because they run in the street with all the vehicluar traffic that is much more manoueverable than the average locomotive...! ;)

  7. Bones

    Bones Member

    The narrow guage Uintah Railway, on the Utah / Colorado border, had 2 extremely sharp curves. Track was initially laid with one each, 75 and 80 degree!! curve. (66' radius I believe) After even the Shays and 0-6-2T couldn't negotiate the radius, they were opened to 66 degrees each. In N scale, that's a 6.6" radius; 12.1" for HO; or 88' proto.

    Theses curves were so tight that Baldwin didn't believe the specifications ordered, when they built the famous Uintah 2-6-6-2 mallets. Baldwin's shops decided 66 degrees was tighter than anything in existance, and only built the loco for 45 degree curves. On top of that, they aligned the boiler's crown sheet for a 5% grade; where the Uintah had a long 7.5% climb to get over it's Baxter Pass. Luckily, the railroad machinists knew how to modify the beast to work the radius. Baldwin built the second workhorse properly after correspondence about the previous deviations.
  8. slekjr

    slekjr Member

    the method of measurement is something to the effect of holding on end of the tape at one point and place the 100' mark at another point on the curve. Measure the deflection from the tape to the rail and multiply by 4 or something to get the deg of curvature.[/quote]

    Actually it is way simpler then that. stretch a tape from 2 points 62 feet apart on the inside of the gague, and the distance in inches at the center point of the tape to the rail is equal to the degree of curvature.
    We have a S-1 alco that according to the manual will turn on a 50 foot radius. The s-2 requires 150 feet. This may be 100 percent accurate, but for some reason I just don't believe the s-1 figure.
  9. MCL_RDG

    MCL_RDG Member

    It is...

    ...interesting, isn't it? Yeah, running models at XXMPH into a curve that you might realize now that the train would spill over. Well I drive my trains regardless of the curves in order to facilitate the next view I see them in as they-, "Blow thru town &^#,.-" Kicking up dust as it does if it's supposed to be a "mover".

    Yeah- real radius is reality- 'magine. I'm a modeler. Much like selective compression- I couldn't even have a model RR. I'd have a little bitty space- the whole layout room and it would model just a bit of where all the locos park in reality. I mean- look at a arieal view of a yard, geesh it's pretty frickin' big- not to mention a tiny, 'lil parking area for cars- the whole yard. Just a few square miles- just.

    So, yeah- real RRs have really huge radius curves so they can move weight at speed- thousands and thousands of pounds of commodities and consumer goods over ribbons of steel (the heart of doing all this modelling, no?). It'd be better if they slow so as to not dump the load. It means getting paid for the work.

    I think it's called centrifugal force. Well, actually I know it's called that because I do.

    Perhaps you had an epiphany? I once had one- then I...

    Well, I won't go into that.

    Well, thanks for bringing the subject up, I think.



    PS-I suggest you never use Wickedpedia for anything. I included a few links here to aggravate myself on account I I didn't feel I get too abused on the 'Net tonight. That may change.
  10. Triplex

    Triplex Active Member

    I thought only the Shays were assigned to the steepest section?
  11. Bones

    Bones Member

    The mallets had varying duties during their time on the Uintah, but the pass was shared between all engines. The only exceptions were the consolidations, and mikados.
    In general...
    Shays or 0-6-2T's usually handled the single passenger car.
    Shays or mallets took Gilsonite ore over the hump.
    The consolidations and mikados stuck to flat(ter) ground during their service life. One mike on each side of the pass, and the same for the consolidations when they were running. The only time they ever went over the pass, they were dismantled or loaded on tender trucks.

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