24" curve radius capabilities

Discussion in 'FAQs' started by Bob Collins, Feb 2, 2001.

  1. Bob Collins

    Bob Collins Active Member

    I am in the process of beginning to put together plans to build Plan #82 in the Kalmbach 101 Track Plans. I feel I have found the answers to most of the questions I have for now except for one very basic one that has me stumped. Kalmbach identifies the curve radius for the plan at a minimum of 24". I would like to be certain I can run the larger steam engines on this track plan before I get any farther. I am thinking specifically of engines like the 4-6-6-4 Challenger and who knows, maybe someday a Big-Boy. Will 24" curves support engines such as these? Thanks
  2. BobMcD

    BobMcD Member

    Well Bob, it depends on what versions of the locos you plan to run. I think the Rivarossi articulateds will all make a 24" turn, because they use some elegant "cheating" to pivot the rear drivers as well as the front ones.

    Some brass ones need up to 30", and in my opinion and experience, none of them look GOOD on less than 36" radius. Those are very big locos. Good luck.

  3. Bob Collins

    Bob Collins Active Member

    Thanks very much. I think your answer is something of a confirmation of what I expected. I like the plan very much, so believe I will stick with it. I suppose the most obvious question is just what can I expect to be able to run if I maintain using 24" curves? Do you think it possible to run something as large as a 4-8-4? Is that still too large? I had hoped to theme my layout toward the UP, but without something like the Challenger that seems pretty bogus. My thought now is basically to run whatever I want without a lot of regard for road name, or I'll go to something like the Milwaukee, which was another favorite of mine as I grew up in Council Bluffs, Iowa, a hub or division point for seven railroads at the time.
  4. BobMcD

    BobMcD Member


    Most HO equipment will make it around 24 inch curves, but for very big steam locos it's a good idea to check the manufacturer's specs. If you use "shorty" passenger cars (shortened from 80-85 feet to 60-70 feet by the manufacturer) which are widely available, they should all handle the curves and look better doing it. Some very long modern freight cars or diesel locos might have a problem, but since I model the early 50's I'm not familiar with which ones.

    As for 4-8-4 steam locos, most of the ones I've seen have "blind" drivers (without flanges) on the second and third driver axles, just to let them get around sharp curves smoothly (often even 18" curves). In general, 24" curves will handle the vast majority of rolling stock in HO, and should look good and work fine. Have fun.

    Bob McDowell
  5. George

    George Member

    Hello Bob C.!

    Bob McD is on the money. In other postings, particularly an article in The Academy, I've mentioned clearance, which is what you're talking about.

    With 24" radius, you should have all the bases covered. On my last layout, I had 24" and my 4-8-4's and my Rivarossi Challenger made the curves just fine, but let me ask you this....

    The plan you're proceeding with calls for 24" radius as a minimum. Great. Now, with the space you have, how large can you go? Can you go 30"? If you have the space, why not? Working with flex track, you can go as wide as space will permit. Can you increase the radius and adapt it to the plan? You will always be glad you did. What are you operating? Full sized passenger cars? 85' auto parts cars? If this is what you want, go for the maximum radius possible. Like a Lexus, once you've seen a train ease into a 54" radius curve, there'll be no going back!

    Finally, when you lay paralleling curves, make sure that your tracks are two inches apart from the center. This will assure you clearance of the longest equipment currently available on the market, provided you go no smaller than 24" on the curve.

  6. Bob Collins

    Bob Collins Active Member

    Thanks very much for your kind reply and the wealth of information. I went back and looked at the plan again with the idea in mind of expanding the curves to 30". I imagine it could probably be done. On one end it would be relatively easy, but the other end of the layout would be very difficult I think. The other problem for me is that I am already working with a 9' X 21'layout and I have a feeling that I will need to go to a garden railway if I wish to use any more space!!

    I think I can do it all quite nicely with the plan the way it is designed. It is good to know and I have stored away your information regarding such things as passenger car lengths and the like. I too am wanting to do something from the 40's or 50's so don't plan to get myself into those areas of more recent developments.

    Again, my sincere thanks for your wise counsel. About the time I get to wiring (or maybe DCC) I'm sure I'll be back here with lots of questions. One just came to mind, with all of the talk of DCC I have seen very little reference to it being used with steam engines. Is it readily available there as well as diesel?

    Rolla, MO
  7. George

    George Member

    Greetings Bob C.!

    Glad I could offer some help. Some final thoughts....If your ends are nine feet, you should not have any trouble implementing a wide radius curve. However, as I mentioned in an article you can see in The Academy, you might want to use a tunnel to hide a tight radius curve. Why would you want to even consider a tight radius curve anywhere? To give space elsewhere. Perhaps you want a yard on one end. Build it, then install a tight curve to the side for a return loop on the main, and hide it with a hill or a raised tier covered with buildings.

    Isn't imagineering fantastic? Endless possibilities! [​IMG]

    An 18" curve looks horrible to the eye, yet most conventional equipment will take it. Though toylike in appearance when doing so, AHM/IHC/Rivarossi full length passenger cars will take an 18" curve. If I'm not mistaken, the Rivarossi Berkshire and Hudson will negotiate such a curve also. The longer equipment needs a long drawbar attached to the coupler to achieve this feat, such as the IHC passenger cars come equipped with. 85 foot auto parts cars will derail, as their couplers do not have the same ability to swing radically enough to make the curve. Articulateds probably handle down to 18" as well, as the wheel sets are spaced on separate bogies. I have a Challenger which takes tight curves, but asthetically, I wouldn't want to see it on anything below 24".

    As for DCC, can't help you there. At this point in history, I'm a DCCophobe [​IMG] Primarily of the conversion cost for the fleet, topping a slew of other reasons. Perhaps I'll change my opinion in the future, or by force like when they switched from vinyl to CD's, leaving us no choice! [​IMG]

    Good Luck!

  8. Bill Stone

    Bill Stone Member

    I know this is an older thread, but I just ran across it and had to comment --- not on your curve radii, but on the plan itself. I have always thought this one of the better plans in the old "101 Track Plans..." book.

    I cannot recall where I saw it, and cannot locate it just now (it was probably in either the 2000 or 2001 Kalmbach "Model Railroad Planning") but there was an article on "updating" this very plan. The single most significant thing they did was spread it apart side-to-side. Super easy to do as there is no track connection between the two sides except at the top (as illustrated in the book.) What this does is give you a walk-in track plan. And THAT is really something you would never be sorry you did.

  9. Bob Collins

    Bob Collins Active Member

    Hi Bill;

    Thanks for the note. Always glad to know that folks are willing to step in and have a say.

    The article and plan modificatuion you are talking about was one done by Joe Taylor and appreared in the 2000 issue of Model Railroad Planning.

    I had already completed construction of all my benchwork when the article was brought to my attention. I gave some serious thought to making the necessary modifications to make in a walk through plan, but decided to keep it that way it was originally planned.

    I did add a foot the deminsions each way of the plan because of my original concern about curve radius. Joe's plan also gave me the idea to move the passenger depot area away from the lower right corner of the original plan. That "congestion" in that area bothered me. I will insert the passenger station in what is identified as the Manitou Beach area, coming in from above.

    I've also made some elevation changes to eliminate the slope in the elevation in the yards.

    I will be happy to keep you posted since you are interested in this particular plan. Again, thanks for the interest.

  10. shamus

    shamus Registered Member

    Hi Bob,
    That is going to be an interesting project building the "Toledo &Southern Michigan RR" I would like to see photo's of your construction as you go along, would make excellent reading. By the way, 4-6-6-4 Challenger WILL go around 24" without a problem.
    Have fun with this one, it's quite a project.
    I like the Turntable area on this plan.
  11. Bob Collins

    Bob Collins Active Member

    Well Shamus, you've sent me back to the drawing board! If a Challenger will negotiate the curves I will need to readdress the main turntable. I had planned on using a 16" one which will handle the 4-8-4 FEF. I'll have to get some measurements as I sure want to include the Challenger in my plans if possible.

    This has turned out to be quite a project, but even though I am rather impatient I find it quite refreshing to spend the time figuring out my next move.

    As I mentioned about the passenger yard which I have moved, there will be a few other changes, but nothing major that would cause you not to be able to recognize the plan. In widening the layout by a foot I was able to run the spur/branch on the outside of the mainline and to eliminate the grade up to 10". I am not just exactly sure what I am going to do there although I will plan to install a smaller turntable as called for in the plan.

    One thing I need to discover is where I can find a catalogue or website that has a selection of bridges I can use. Both spans are about 16" Yes, I know, I've looked at your site and I see where you have details for trestles, but I think what fits the plan better are a couple of the kind of bridges that have the raised sides that would be 3-4' in the real world, and are curved on the ends. Don't know the name of them.

    I have been taking pictures. When I finished installing the sub terrain risers, etc. I'll get some more and send them along to you. As you well know it is difficult to see the variances in something like this. With the camera too high you lose the elevations, with the camera too low you lose the distances. I'll see what I can come up with.

    Oh, by the way, it will not be called the Toledo,...... I haven't come up with a name yet, but I want to run a lot of UP and/or western US equipment and so that will have some bearing on my decision.

  12. shamus

    shamus Registered Member

    Hi Bob,
    Seeing as you are going to widen the plan by 1', you could increase the 24" to 25" for better running.
    Faller, Kibri & Pola make the kind of bridges you are looking for. checl out Walthers website for information on these.

  13. Bob Collins

    Bob Collins Active Member


    The curve radii now are from 27" to 301/2"

    That ought to handle things nicely.

    Thanks for the info on the bridges. I'll have a look right now.

  14. George

    George Member


    Now your trains will "flow" and glide instead of jerking into turns. You're going to love the result. [​IMG] Just remember to keep the track centres at least two inches apart. Nothing should "DING" then.

  15. Bob Collins

    Bob Collins Active Member

    I guess I'm to a point where I need some basic math help. In looking in the Walthers catalog(ue) I have I see a couple of bridges that might serve my purpose, but I don't know how to convert the 65' that they represent in real life into what I need in the way of inches. Am I on the right track (no pun intended) by multiplying the # of feet by 12" and then dividing by 87? (HO scale?)
  16. George

    George Member

    65' in "HO"?? Well, it's going to be almost two inches shorter than a Rivarossi passenger car. [​IMG]

    I have a friend I'll write and ask for the calculation if Shamus doesn't have it here first. I think it would be multiplying by 1/87, but don't hold me to that. Math was a weak spot, why I probably ended up in the field I'm in.

  17. George

    George Member


    I sure like people getting back to me in a hurry. This from the master architect/engineer/N-Scaler/Garden Railroader;

    Divide actual number by 87.1 to get physical length of HO model in 12"=1'-0"

    Freg Zam Pull:

    60 foot boxcar / 87.1 = .68886 feet x 12 (inches per foot) = 8.2664 inches
    long for the model.

    or converting to inches first:
    60ft x 12 in/ft = 720in
    720in / 87.1 = 8.2664 in.

    By the way, HO is 3.5mm = 12" (How's that for a mixed metaphor?)"
    I'd wager he didn't have this at his desk at work, but in his head!

    Thanks, David!!!!!

  18. Bob Collins

    Bob Collins Active Member


    Thank you very much. As you can tell math wasn't my stellar subject either, but I thought I saw the logic in the way I was trying to figure it out.

    The mm calculation will also come in handy as several of the bridges I am looking at are measured in mm.

  19. George

    George Member


    Bridges. My peeve is that it's hard to find any selection of double track bridges, and when you do, they cost a small fortune.

    Life-Like makes an interesting steel deck bridge with an arch underneath. What's fantastic with this kit is it's versatility. The span can be made as long as desired, and spliced together to make a double track span. What's fantastic with this bridge is that each span, consisting of two pieces, costs between US$12-US$16! That's a lot better than small bridges that start at US$26!

    A name? How about the Ozark and Seattle, "Scenic Route of The Lewis and Clark", whatever that is! [​IMG]

    All The Best,


    [This message has been edited by George (edited 05-04-2001).]
  20. Bob Collins

    Bob Collins Active Member


    My concern about a bridge with an arch underneath is that I am crossing over other tracks in both situations and I wonder about a clearance problem?

    Ozark and Seattle? Maybe. I like the Ozark, but Seattle is a long way from here!! I have also thought about calling it the Silver City and Western. My wife grew up in a wide spot in the road in southwest Iowa called Silver City. I grew up in Council Bluffs, Iowa which was a big railroad town with seven railroads there at one time. I'm still thinking about it.


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