Minimum Radius

[jward]

!?

[Woody Elmore]

I hope that my post wasn't considered as "pompous." My point was that not all tinplate trains are operated at high speed around insanely sharp curves.

As for scale model trains, larger radius looks better and the trains will offer fewer problems. There are many people restricted to 18" radius track. They need to keep in mind that their UP Big Boy or Erie triplex might look a bit silly crawling around an 18" radius curve. Obviously, some people have no problem with that.

I think it's very sad that some readers read posts offering comments and suggestions and interpret them as preaching.

[ebtbob]

Don,

       As the one who started this thread,   I cannot figure out what has been said that is offensive.   It was certainly NOT me intention to do so to anyone here.   I just felt I wanted to share both personal experience and of others when buying large wheel based engines.
        There is obviously nothing wrong with running any engine that will perform on 18in radius,   but when major manufacturers go to the trouble to try to warn people about potential problems relating to equipment and radii,  I tend to listen.
          This subject comes up quite often here and there are always conflicting ideas,   many based on personal experiences.     If someone does not like the way a long car or engine appears on an 18in r curve,  that is an opinion not being a rivot counter.   I for one do not like the looks of the large equipment on small radii,   but anyone of truely knows me and has seen my railroad can attest to the fact that I far from being a rivot counter.

Respectfully,

Bob Rule, Jr.

[rogertra]

I draw everyone's attention to the August MR in the article about a 9 x 11 foot bedroom layout, see bottom right of page 62.

"The second concession is minimum radius.  Normally, at least a 30" radius is desired for appearance.  The absolute minimum for running six-axle locomotives is 24".  For this layout, I used a 28" minimum as an acceptable compromise."

Now tell me that the author of this article is a "pompus rivet counter."

[jward]

off hand i'd say you can get away with 22" for a 6 axle locomotive without affecting operation. i've run them on 18, but had alot of problems with the overhang pulling adjacent cars off the track on turns. when i was in n scale i had similar problems with 9 3/4 and 11" curves, when i rebuilt the layout using 14" curves, equivalent to 24 in HO, i had no problems.

[pdlethbridge]

    I have never had a problem with trains on curves ever, when I had built my first layout. I was using an assortment of athearn diesels and was using a 22" radius then and I'm still using that as my minimum radius in planning a layout. That does limit you in some ways, but a good plan will compensate for it and you'll be happier running your trains. My biggest loco is a spectrum SD45 which rarely gets run as it looks out of place on the 22" radius curves I use. All of my locos are small, 4-4-0, 0-6-0t, 2-8-0, 2-10-0, h16-44, GE 44 tonner, and 2 GP35's. These run well on the layout and have had no problem with my code 83 custom line turnouts from Atlas.
  If your happy with your curves, great! After all, it's about having fun. I don't hear people complain about some layouts with 9" radius turns in HO. Trolleys always were on tight turns.

[Yampa Bob]

Here's the problem; the author of the MR article has stated his "preference" as if it was a de facto standard: "The absolute minimum for six axle locomotives is 24"..  And this one: "...."a 30" radius is desired for appearance".  Whose desire? For what length cars?

Those are opinions, not facts . I run 6 axle AC4400 on my 18" layout with no problem whatsoever. Very little overhang, and NO, they don't require longer couplers, and the loco doesn't pull cars off the tracks. The actual rear and front  leverage arms of a diesel are actually less than a Spectrum 2-8-0.

If some modelers prefer a minimum of 22", or even 30" on their layout, that's fine, it's their railroad. However, they shouldn't confuse preferences with standards. There is no standard. 

[rogertra]

Many times, both MR and RMC will say something like, ".....the locomotive can take 18" curves but looks better or 30" or greater..."

That's probably a better way of putting it.

Personally, I much prefer the wider radius curves for visible trackage.

Unfortunately, the current GER's minimum visible main track and or siding curve is around 28" radius with the tightest visible curve around 22" radius on the east and west legs of the wye in Berger Yard.  As only 2-8-2s, used on the line to the D&H and CV, 4-6-2s on the local passenger, 2-8-0s and sometimes the light 2-10-0s on the Berger Yard to Granville freights need to use the wye, and the wye is partially obscured by the water tank and the m.o.w. shed, it doesn't look that bad.

The GER's largest steam power, the light 2-10-2s and the light and heavy 4-8-2s don't work beyond Granville Junction, "account tight curves and light bridges."  Through freights between Berger Yard and Adirondack Yard (Hidden main staging) change power at Granville Junction.  Eastward (By timetable), the larger power comes off and the Berger Yard section of the train is worked forward by a 2-8-0.  In the reverse (Westward by timetable) direction, a 2-8-0 takes the train to Granville Junction, where the 2-8-0 comes off, along with cars for the NYC and B&M, and the Adirondack Yard cars are added and the heavier power, a 4-8-2 or 2-10-2 are added for the run to Adirondack Yard.

In the reverse direction, the Adirondack Yard to Berger Yard daily through freight usually has about 16 cars, plus van, between Adirondack Yard and Granville Junction and about 10 cars plus van between Granville Junction and Berger yard, so the 2-8-0 can handle the train and the grades on the latter section.

I find that restricting the heavy power to work only west of Granville Junction and the light power to work eastward adds a realistic operational "headache" to the operation schedule.  Besides which, the 2-10-2s and 4-8-2s just don't look "right" to me going around the 28" visible curves.

[Yampa Bob]

Each modeler has to set his or her own "standard" for minimum radius. I think we all agree that appearance is an important factor, possibly more so than performance. You might say "if it looks right, it will probably perform well". Maybe, only actual track testing will tell. I am satisfied with my selection of locomotives for my 18" curves, in both appearance and performance.

While this topic is more specific to locomotives, let's consider the other aspect, freight and passenger cars. If someone asks (based on my perspective of proper appearance), what is the minimum radius for the following cars, I can answer with some degree of confidence.

85' Coach......38" radius
67' RPO.........30" radius
55' Boxcar.....24" radius
50' Overland...22" radius

1.  Consider the concept of "ratios" in a geometrical sense.
2.  You can develop a "standard" for what you don't have, based on what you do have.
3.  The correct constant (for me) can be applied to any car. Your constant will vary slightly depending on your preferences.

[Jake]

Well "proper" is relative. Technically, a 40' car running on 12.5" (90 scale feet) radius curves is indeed prototypical, and therefore "looks good." Has anyone here ever seen the Harlem River Transfers in NYC? If you have, you know what I'm talking about.

[pdlethbridge]

Those are some tight turns but are the exception rather than the rule.

[rogertra]

Those are some tight turns but are the exception rather than the rule.

Some people like to base their entire model railway on exceptions rather than the rule. 

[Yampa Bob]

Due to selective compression, aren't all model railroad layouts "exceptions"? My layout represents a 50 mile point to point between two yards. To model that "in scale" I would need over 3,000 feet of track.   

[pdlethbridge]

some model railroads are exceptions, I consider mine exceptional

[Atlantic Central]

Rather than consider anything a "standard", the NMRA term for such things is "Recommended Practice".

NMRA RP11 goes into great detail about "Recommended Practice" for curvature and rolling stock.

Grumpy, sorry you are offended, but while I would never "tell" you what to do with your trains, if you asked my opinion you would find it even more offensive than those posted here so far.

As for the the comment about a 40' box car going around 90' scale radius curves - true, but lets look at the other side of that. What is the minimum prototype radius for an F7 or a GP35? - 325' or about 45" radius in HO.

So even a 30" radius is signifcantly selectively compressed.

I CHOOSE to not run my trains around such tight curves. My minimum mainline radius is 36" and I still then avoid cars or locos over 75', locos with 5 coupled axles or rigid wheelbases over 20'. In his trackwork handbook Paul Mallery suggests that HO layouts of Class I railroads use nothing less than 48" radius. I might try to stay with that on my next layout.

I do this for both appearance and ultra reliable operations. I couple all my passenger cars at nearly scale seperation distances (literaly only a few scale inches more than the prototype) and have working diaphragms on them that touch and stay touching.

When I couple a passenger car to a pair of A units back to back, the diaphragm on the passenger car touches the locos buffer plate just the real thing.

As my trains go around curves the rails are never "uncovered" by the arc of the car. That is the mark of a realistic curve.

I understand that these personal "standards" do not interest everyone. And that many who would find them interesting do not have the space for such things. Understand that I could build an even more complex layout in my space if I compromised these standards, but I CHOOSE not to.

Whatever you choose is good for you, Bob was just trying help people avoid problems and Roger was just relating sound proven "Recommended Practice" for this hobby.

It is interesting these days how those with lower standards are "offended" by those of us with higher standards. Grumpy, I'm not ofended by what you choose. Do you have any locos with sound? I don't. Do you have DCC? I don't. And I'm not one bit offended if you think those things are "necessary" for the hobby. But for me big curves are necessary.

Sheldon