Minimum Radius for coupling

[Loco722]

Hello there,


I need to know what is the minimum radius curve, HO scale, on which 50' cars would couple without intervention.

The 50' cars I have, have body mounted couplers, no talgo trucks, and all my locomotives also have body mounted couplers.

I have being running on 18" radius curves from when I started model railroading, and I'm thinking of upgrading to 22" radius curves and switches. I will be considering 24" curves also.

Thanks in advance,


Loco722



 

[ACY]

If you can fit 24" radius, use 24" radius it allows you to safely run most locomotives and rolling stock with the exception of some brass locomotives and some cars 89' or longer.

[Doneldon]

722-

The radius at which couplers will connect is mostly a matter of trial and error due to the large number of factors which influence minimal coupler operation curvature, and the interactions between those factors. To mention just a few examples: coupler brand and whether both cars have the same brand of coupler, coupler shank length, car length, how far from the ends of the cars the truck bolsters are mounted, whether the cars are on level or graded track, and whether the couplers are maintained at NMRA and manufacturer specifications.

It is safe to say that coupling on curves is less reliable than coupling on straight, level track. The same can be said of uncoupling. You'll have the best luck if all of your couplers are the same brand and if they are maintained within specifications. IMHO, Kadee Couplers are the best and they certainly have the most shapes to make it a little easier to find one which will work on a given model. Kadee also offers the choice of scale size or oversize knuckles. Most are metal but you can also find plastic. That can be important with cars with metal bodies or lights because the couplers can cause a short circuit.
                                                                                                                                                                                      -- D

[Loco722]

Hello there,


Thanks for the advice guys. I was in the opinion that the couplers, irrespective of brand were generally more or less the same.

I did come across a site saying that to get good automatic coupling with 50' cars on curves the minimum radius should be around 20-21". So I just wanted a second opinion.

Anyway, maybe I should take ACY's advice and try to see if I could fit 24" radius curves on my new layout. But I think it's gona be a tight fit as I have limited space. Also, if I do use 24" curves, what are the equal switches for it? #6 or #8?

Thanks in advance again!


Loco722   

[ACY]

Either #6's or #8's would work with 24" radius, sometimes people use #6's because they take up less space, but if you can fit #8's then use those.

[jward]

peco's small radius switch, sometimes referred to as a #4, has a 24" radius curved route.

there is no reason if you don't have room that you couldn't use a #4 or #5 switch.

[ACY]

Jeff according to the NMRA: "In sectional track, you could consider the No. 4 to be like an 18" radius curve, the No. 6 a 22" radius and the No. 8 a 24" radius."

[Len]

To answer the original question, for 'hands off' coupling on curves with HO 50' cars requires a 39in, or greater, radius.

There was an article in 1st Quarter 2009 Model Railroad Hobbiest Magazine had a good article on figuring curve requirements for different length cars, regardless of scale. It's available on-line as a free downloadable .pdf file at: http://model-railroad-hobbyist.com/taxonomy/term/23

Len   

[jward]

acy,
the effective radius of an atlas #4 is greater than 22" radius. operationally, i can tell you they work well with 50' cars. i should know, i've built enough layouts using them, because they work. and later, when i started to lay my own track, i built my own copies of that proven geometry.

what the nmra is talking about is for cosmetic purposes. operationally, the curved route in a #4 or larger switch is large enough to operate reliably, even when backing trains through them. while i do respect the nmra, you must distinguish between "standards" and "recommended practices"....... the nmra page you refer to is for recommended practices, not standards.

i am sure, given the room we'd all love to have 48"r curves and #12 switches, but when space is critical you have to go with what works. #4s and #5s work.

[Loco722]

I agree withe jward, if I had a room that was 20'x20', I would have 48" radius curves and #12 switches. But I'm not fortunate to have that kind of space to dedicate for a HO scale model railroad, as I'm very sure most of you do not too.

At the moment I'm having about 4.5'x7' of space to work with!

[ACY]

i can tell you they work well with 50' cars. i should know, i've built enough layouts using them, because they work. and later, when i started to lay my own track, i built my own copies of that proven geometry.

I am not disputing whether they will work with 40' cars, but as an aside, 89' cars, especially some passenger cars are a different story.

[jward]

the original post referred to 50' cars, which work quite well with 18r and #4 switches.

4.5 x 4 is the main part of my layout, with a 2x6 yard externsion along one wall. i grew up trying to make a 4x6 work while my dad took the rest of the cellar for his railroad (luckily i got trackage rights in exchange for handlaying alot of the track.)

in your space you probably have more options than you think. some possible configurations are a doubel track main with 22r and 24r. an over and under twice around (i did this in 4x4.5, and kept the grade to 4%. you should do alot better)

you could put a small yard down the centre, maybe some industries in the corners.

above all, avoid the use of the 18r switches for yard trackage. the added problems are not worth the minimal amount of space you'd save.

[Loco722]

Hello there!

Thanks guys for Your input it's very helpful. By the looks of it, I may have to stick to 22r curves and switches, but still have a itch for 24r curves and #8 switches, only time will tell.

I have one more question, I'm trying to build an oval layout, single track representing a generic branch line which runs thru a forest-like area with a single spur line.

I'm going to be using code 83 nickel-silver tack. I want to know, assuming this oval is around 45"x75", how many points or at how many feet/inches of track should I supply power to maintain smooth operation?

The trains I'm running are short (around 5 box cars) with a single locomotive running on standard DC.


Thanks once again in advance!   


Loco722.

[ACY]

I'm going to be using code 83 nickel-silver tack. I want to know, assuming this oval is around 45"x75", how many points or at how many feet/inches of track should I supply power to maintain smooth operation?

I would just put 2 feeders, and you could just use 1 if you wanted to.

[Doneldon]

722-

Variables like what kind of track and rail joiners you are using and whether you have all sectional track or some longer pieces like flex track can influence the answer to your question. I would use at least three feeders if you have both sectional track and flex track, and good tight rail joiners. I would put one feeder on the middle of the spur and the other two on the oval, equidistant from one another. If you have all sectional track I'd suggest four feeders around the oval rather than two. In either case, I'd put a dab of conductive lube inside of all rail joiners. This can either be conductive oil or the petroleum jelly-like stuff you put on light bulb bases to make them easier to remove. The purpose of this material is delaying how fast the metal in the joints oxidizes and becomes less reliable at conducting electricity from one rail to the next. I'm assuming you are using nickel-silver rail. All bets are off with brass rail as brass oxidizes very fast and brass oxidation really interferes with electrical conductivity at joints. That's at least as big of a problem between rails as it is between rails and loco wheels. Oh. And be sure that any lube you use on rail joints is plastic compatible.

Either way, good luck.
                                           -- D