Minimum radius for 2 rail Yellowstone

the 3 rail version says 072 curves. Look under features near the bottom:

20-3378-1 | MTH ELECTRIC TRAINS (mthtrains.com)

I would think the 2 rail is near the same. I would recommend large curves for the beast to run smoothly and look the part.

I'm dying to ask what size curves are you trying to run it on?

My MTH 2 rail Bigboy goes around my layout very well. I know you don't want to discuss it. It's all I have to compare with that type of axle arrangement (big).

The Challengers and Alleghenies seem to go around tighter curves better.

Sometimes it's the tender that becomes the "tight curves" issue.

Maybe someone here has this engine in 2 rail? I just don't remember. There was a 2 rail club that maybe has it?

Checking against the product number, it doesn't give the information. Typically, MTH lists the RADIUS as twice the O-## recommendation for the 3-rail product. However, that isn't always the case as the 2-rail version of the locomotives are essentially 3-rail framework with 2-rail wheels and a full set of flanges. That "other" big articulated we won't talk about will negotiate as sharp as 36" center line radius (confirmed), but it's driver size and spacing are pretty similar to that of a Mikado.

If I were to guess, you might be able to squeeze it through something as sharp as 42" radius (O-84), but you'd have to test it to confirm. DO NOT USE LIONEL FASTRACK for the testing as it's sharper than the "O" number actually indicates.

I'm going through  design dilemma right now between 42" and 54" center line radius.

Hope this helps.

72 INCH radius is the old answer to what most ANYTHING 2R can negotiate. When you are building your layout, take some flex track and lay out some temporary curves of different radii and test the thing! If you already have a track plan, test the smallest radius.

That will tell you two things: will it get around that radius and does it look really STUPID doing so?

Simon

What Simon says.  There is simply no correlation between 3-rail radius (diameter/2 ?) and 2-rail radius.  It might squeak around less than 72, but I doubt it.

Who is the importer of this locomotive?  Unless I missed something it seems as though MTH is assumed.   I believe that Sunset also imported that locomotive model not too long ago.

General reccomendation is to choose your minimum mainline radius very carefully.  Your plans today may not reflect where your interest might lie in five plus years.  Maybe consider  leaving the option open to run whatever you may have,  whenever that may be.

When building an 0 scale two rail layout within the size you mention you may wish to consider making 72" radius with spiral easements as your minimum curve.  There are a variety of track plan concepts that will fit 72" radius inside of your confines.

Most folks on board would jump at the opportunity to build within the size you have available.  Best wishes in all you do.

If your thoughts run to anything like Yelowstones, IMO, please  dismiss any 3 rail based 072 diameter curve thoughts, there is absolutely no comparison.  36" radius / 072 diameter is  just way too restrictive. and the overhang really plows back the scenery.

@bob2 posted:

There is simply no correlation between 3-rail radius (diameter/2 ?) and 2-rail radius.

"Radius" is the same measure, regardless of the number of rails, yet this should be the main header across the top of this website. 😁

Mark in Oregon

Well, "0-36" is a diameter.  That confuses some folks when they move into 2-rail, where we always specify radius.  A 72" radius is 0-144, in Lionel-speak.

@Simon Winter posted:

72 INCH radius is the old answer to what most ANYTHING 2R can negotiate. When you are building your layout, take some flex track and lay out some temporary curves of different radii and test the thing! If you already have a track plan, test the smallest radius.

When in doubt, yes, test things empirically.  Doing so rarely fails.

That will tell you two things: will it get around that radius and does it look really STUPID doing so?

The level of acceptability on STUPID is also something to determine empirically as it varies widely across the spectrum.

Well? if we're going to discuss it......

It always amazes me that some posters who have the smallest curves, want to run the biggest engines. They knew that they were limited. Yet force the manufacturers to comply with their wants. So the engines get modified to please the masses.  I'm always reminded of the elephant on roller skates picture.

After awhile, we will see the usual post about the lead car in the consist keeps derailing or complaints of derailing on switches forming s curves.

I still don't know what the OP expects this massive engine to turn on?

I always believe we should look up what the real engines ran on and what the RRs went thru. I believe some got scrapped early for these exact reasons. I prefer modern diesels for so many of these reasons.

Running locomotives on tight curves is usually a 3-rail issue. Most 2-railers, like myself, seem to know what a locomotive can handle by simply referring to the manufacturer's recommendations and/or personal experience, I prefer the latter as it leaves no doubt.

Once my layout eventually becomes a reality I already know that I'll operate on 49.5" & 54" curves with #5 turnouts. I rolled my longest car ('89 flat car) thru the curves and turnouts coupled to other cars to make sure everything is copacetic. Same goes for my biggest locomotive, an ES44DC. It seems like 48" is the minimum to run any diesel.

@Engineer-Joe posted:

It always amazes me that some posters who have the smallest curves, want to run the biggest engines. They knew that they were limited.

Limits can be good.  In part just one of the reasons I have very tight radius curves - to impose limits both of size of engines and era modeled.  Nothing larger than a relatively early 2-8-0 and in places only the 0-4-0 can access some sidings.

As for diesels, on anachronism days the RS3 and NW2 work just fine,

@bob2 posted:

1.Well, "0-36" is a diameter.  

2.That confuses some folks when they move into 2-rail, where we always specify radius.

3. A 72" radius is 0-144, in Lionel-speak.

1. True. To think of "0-36" in another way, the standard radius for HO scale sets was ( and might still be) 18" radius...which is "0-36", right?

2. Also true...I still get confused!

3. True. George Orwell would have approved.

Mark in Oregon

I have a MTH 2 rail Yellowstone and run on 60  radies curve. I have no real problems with articks. The real test is if you cane have a Texes 2 10 4  with no bindig. I have a AT&S all flanged and have little problem. The articks can have a problem with over hang on the front engine bollar cleance.

An  all flanged PRR J or an  all flanged PRR T-1 will let you know how hospitable your curves are.

@Engineer-Joe posted:

It always amazes me that some posters who have the smallest curves, want to run the biggest engines. They knew that they were limited. Yet force the manufacturers to comply with their wants. So the engines get modified to please the masses.  I'm always reminded of the elephant on roller skates picture.

After awhile, we will see the usual post about the lead car in the consist keeps derailing or complaints of derailing on switches forming s curves.

I still don't know what the OP expects this massive engine to turn on?

I always believe we should look up what the real engines ran on and what the RRs went thru. I believe some got scrapped early for these exact reasons. I prefer modern diesels for so many of these reasons.

I actually have done a little research on this, and believe it or not, some of the largest engines in real life "should" be able to negotiate typical O-scale 2-rail radii of about 54".  This discussion linked below was limited to long modern diesels, but if the same specs could be found for steam locomotives, the calculations should still apply.

https://ogrforum.com/...radius-calculation-1

@Strummer posted:

1. True. To think of "0-36" in another way, the standard radius for HO scale sets was ( and might still be) 18" radius...which is "0-36", right?

The equivalent of 18" radius in O-scale is roughly 33", or O66 in 3-rail speak.  This is because HO is not quite "half O".  It's 1:87.5 vs 1:48.

@prrq2 posted:

I have a MTH 2 rail Yellowstone and run on 60  radies curve. I have no real problems with articks. The real test is if you cane have a Texes 2 10 4  with no bindig. I have a AT&S all flanged and have little problem. The articks can have a problem with over hang on the front engine bollar cleance.

Bingo! We have a winner.

I ground off the center main driver's flanges on my MTH Texas type to negotiate smaller radius curves on my inner mainline.

@Engineer-Joe posted:

I'm dying to ask what size curves are you trying to run it on?

I am interested in knowing your curve size as well. While I built a small amount of benchwork I am still in the planning stages of my layout. I don't think I can fit 72" R curves but I may be able to go a little larger than I originally thought. I am a steam guy but I plan to limit myself no X-10-X locomotives.

For decades a significant number of prototype oriented modelers in the mid Atlantic area built and operated O scale 2 rail model railroads with curves in the neighborhood of 54" minimum radius.  Our layout designs varied widely to suite available space and operating objectives.  A common thread was following design concepts put forth by the late John Armstrong in his book  Track Planning for Realistic Operation.  (John was a charter member of our DC area Friday night train group).   Where space permits for reason of appearance we used broad "scenic" curves, but in hidden areas (tunnels and out of sight staging trackage we used tight curves for additional track capacity, switching, branch lines, and length of runs.  On my prior layout (featured in March 2000 MR) I had a 50" radius yard lead and a triple track main with super-elevated 54", 58" ,62" radius curves in places).   With relatively minor modification to allow for lateral driver play and trailing truck swing fully flanged 2-10-4's,  4-4-4-4, and 4-4-6-4's negotiated the curves without issue.  Would they have looked better on wider radius curves - yes.  But by pushing the envelope the members of the group built good looking and interesting to run railroads in basements that some would have said were not sized for O scale 2 rail.

@catnap posted:

It seems like 48" is the minimum to run any diesel.

For Geeps and my Atlas SD40, 36" radius is the minimum.

https://youtu.be/YdhXghlga04

Thanks to all who responded, especially prrq2. Your Yellowstone is the same as mine. How much overhang do you see when rounding the 60 inch curves?

Pete

@SundayShunter posted:

For Geeps and my Atlas SD40, 36" radius is the minimum.

https://youtu.be/YdhXghlga04

FWIW: I may have mentioned this before (and not that it matters to the subject being discussed here), but the '70s vintage Atlas F9; the earlier, single motor Weavers and Red Caboose GP9 are all capable of operation on the original Atlas "train set" curves... which I think are 24"R. Just don't ask how they look! 😄

Mark in Oregon

Test it on several curves, and some reverse curves.

I seem to have three 2-8-2s that just about go around corners - they go around 30" radius curves, but look a bit silly doing it. It's quite possible the Yellowstone will happily sail around something sharp, but if you test it on something too sharp and it looks silly, you know to ease the curve.

Mick

@Grantham posted:

Test it on several curves, and some reverse curves.

I seem to have three 2-8-2s that just about go around corners - they go around 30" radius curves, but look a bit silly doing it. It's quite possible the Yellowstone will happily sail around something sharp, but if you test it on something too sharp and it looks silly, you know to ease the curve.

Mick

You can do a lot things, but it's not always wise to do so. A lot of friction and strain on those engines, that won't happen on proper radius curves.

Simon

Just a FYI: keep an eye on things close to your curves. A Yellowstone is going to have some decent overhang. On 3 rail 072 curves (36" radius) the overhang is over 2".