What Curves Will Scale Equipment Actually Run on

That's such an arbitrary question. A scale 40' reefer can run on O-36 curves, but a scale autorack needs at least O-54, and a scale passenger car needs O-72. Same goes for locomotives. A switcher can run on tight curves, but a large diesel or steam locomotive will need much larger.

Will Ebbert posted:

That's such an arbitrary question. A scale 40' reefer can run on O-36 curves, but a scale autorack needs at least O-54, and a scale passenger car needs O-72. Same goes for locomotives. A switcher can run on tight curves, but a large diesel or steam locomotive will need much larger.

Another point to consider would be the couplers, i.e. SCALE vs. lobster claws. Body mounted SCALE couplers (such as Kadee 805 or 740 style), will produce nice close coupling of cars, and thus will require much larger diameter curves, while the truck mounted lobster claws, will negotiate 027. 

This is why I asked the question. In order for a beginner to gather as much info as I can.

Generally speaking, universally all 3 Rail Scale equipment is designed to run on 072 or greater curves. Anything smaller, as stated above, depends on the length of the car and/or the swing of the couplers.

If you aren't interested in running the biggest of the big, and especially with the kinematic coupler Lionel has been using, most scale cars can be run on a layout with O-54. O-48 will still get you quite a bit, but O-60 would be better, or if you have the room, just go O-72 and you'll never have any issues.

There's what equipment will "operate" on; then there's what it will "look better" on. To date, every three-rail item produced will negotiate O-72 (36" radius) curves, but some of it would look better on something larger (think of a Big Boy). Real railroad mainline curves are extremely broad (relatively speaking) when compared to model railroads (and they do have equipment curve restrictions as well), but in industrial areas they can be surprisingly sharp. If you want an idea of what might be "best practice", measure the distance between the truck mounting screws (bolster-to-bolster distance), then multiply that by three and that will give you the minimum curve that car could generally handle with body-mounted couplers. Multiply it by four and you get what it operates better on; by more than four you get into appearance. With 3-rail equipment, since truck-mounted couplers are used, the equipment can typically handle sharper curves. On the club layout, we run O-96 (48" radius) or larger, but we do have a sharp O-72 (36" Radius) curve hidden in a tunnel. Even my scale-wheeled, Kadee-equipped locomotives go through just fine, but the six-axle locomotives are all listed as requiring 42" radius (O-84).

All of that said, with any given piece of 3-rail equipment, if you go up from the "minimum curve" requirement it's going to yield better results.

Matt's advice is as sound as it gets.

All I would add is, go as big as you can and everything (short cars and long ones) will look and operate much better. I would challenge you to push past what you think you can have and make them as wide as possible wherever you can.

Enjoy!

richtrow posted:

Matt's advice is as sound as it gets.

All I would add is, go as big as you can and everything (short cars and long ones) will look and operate much better. I would challenge you to push past what you think you can have and make them as wide as possible wherever you can.

Enjoy!

Thanks Rich.

If you decide to build outside, you can really "go for it" on curves if you have a big yard (curves also absorb thermal expansion/contraction well). I had designed a backyard layout with a 120" radius (O-240) to basically support anything I could throw at it, including the possibility of a kid operator going maximum throttle. That's still sitting in the back of my mind for when I bail out of California at retirement.

when it comes to the long O Atlas cars... I would not use anything less than 0100!

My previous layout had loops of 036 and 045 Atlas track. I have a mix of NY Central and modern scale locomotives from Lionel and MTH. My running experience was as follows:

036 - Scale four axle diesels - GP7/9, S-2, GP30/35, RS11, Alco C420, SW1500, F3's,

          Scale steam - Mogul, Ten Wheeler, 0-8-0 & 0-6-0 Switchers, Mikado

045 - Scale six axle diesels - SD40-2, SD60e, SD70ACE, ES44, Dash 9

         Scale steam - Berkshire, Hudson, Mohawk

I'm sure some of the six axle diesels would run on the 036, but that was not my preference. Rolling stock is all over the place. I have quite a few passenger sets where the locomotive can handle tighter curves than the cars.

I disagree somewhat with Matt's philosophy.  On real railroads mainline curves are used to avoid terrain features, or approach rivers or to get into and out of yards.  While curves on mainlines in excess of 90 degrees exist, they are relatively rare, and most curves are only of a few degrees.  On the typical model railroad the most common use for a curve is to fold the mainline back on itself to increase running distance.  The wider the curves used for this purpose the less space there is available on the layout for other features that may be desired, and the more wasted space there is on the corners and the wider the layout has to be.   I realize when comparing O-72 and O-42 we are only talking about an extra 15 inches to turn the mainline 180 degrees, and bench work that only has to be 30 inches wider, but many of us are fighting to gain as many feet and inches as possible for other uses.

Certainly you want to have curves wide enough to accommodate the needs of everything you run or plan on running.  Beyond that look at the reason for the curve in determining whether to go wider.   Physics permits our scaled down equipment to operate on curves considerably tighter than the prototypes, and at higher speeds, so we don't NEED curves as broad as the prototypes do.  When deciding how broad to make a curve (beyond the minimum your equipment requires) ask yourself whether the visual benefit of the more gradual curves justifies the increased space they require.

There are tricks that can be used to get the visual benefit of wide curves without paying the full price in terms of space.  These include using broader curves on the middle of the layout and tighter ones on the fold backs, and using easements.

This assumes that you like many of us don't have unlimited space available.

And, once again, if you have had any HO experience before leaving that Dark Side, think of it this way...

An O3R curve designation of O36 is a 9" radius in HO.  Not much made in that scale will operate on such a sharp radius...even if it were pre-fabricated. 

An O3R curve designation of O72 is an 18" radius in HO.  O88 would be an HO 22" radius, the maximum doable for a typical 4'x8' HO layout.

Many of HO's manufacturers of scale equipment...say, full 85-foot passenger cars...recommend use on a radius no less than 24", a limit of functionality.  In O3R parlance  that would be an O96 curve.  

In some respects it boils down to a balance of available space, functionality, and appearance in the world of O3R track curvatures.  How much space for a layout do you have?  What equipment do you have....or do you dream of having someday?  What appearance would you prefer as the train negotiates the curve....at speed?

Oh and BTW...Do you plan on backing up a train of scale equipment through the curves?  If so, a word of advice from the school-of-hard-knocks: There are different rules of derailment physics that kick in for running/pushing an O3R train in reverse through curves than for forward/pulling operation.

I would say, summing it up for operating scale equipment on an O3R layout:

     A minimum of O72 curves......but bigger is always better, real estate permitting.

You know....there's often more than one vote/opinion in the matter, anyway!...