curves and articulated steam

Articulated engines look out of whack on O-72 in my opinion.  Full length passenger cars and modern 89 foot freight cars look out of place on O-72 also. 

 

My home layout is 8' X 20'.  I use as large as curves as I can.  My minimum is O-72 but many curves are larger.  I do run a scale Big Boy from time to time.  I need to make sure nothing is on adjacent tracks when I run the Big Boy around O-72.

 

 As a general rule, use as large curves as you have space for.  All rolling stock and engines look better on larger curves.  

Even doubling O-72 to 72" radius (O-144) still gives quite a bit of overhang (and is still smaller than typical prototype curve radius). I was tinkering around with some super-wide curve module designs and a 2-rail modeler sent me some clearance shots on 72"/76" (O-144/O-152) concentric curves with a Big Boy vs. Passenger Cars. The clearance is about 3/8". So even with broader curves you're still going to get boiler swing-out on articulated locomotives.

 

Overhang doesn't bug me, as long as nothing is hitting.  I'm happy to run my semi scale articulated on O-36, so yes, it is a matter of opinion.

The amount of overhang, and what is "acceptable" is strictly a personal preference.  Some will argue that if the user is going with smaller radii, that the user should go with smaller motive power, and no 85' cars.

I'm not one of those people.

I'm primarily an HO modeler, and in my HO world, my smallest mainline radius is 36", roughly equivalent to 72" in O scale.  Most of my curves are even broader than that.  Does it look good.  Sure do.    Well, there is not too many people that have the real estate for 72" or greater radius in O scale.   That is why I model in HO at home. 

However, when I started playing with three rail O scale (or hirail if you prefer), I designed a layout for my friend Hot Water.  Hot wanted to be able to run his fleet of articulated steam, and 85 ft. passenger cars, and we had to use radii that were a heck of a lot smaller than 72" radius (O-144).



Here is a track plan on Hot Water's railroad, and the curvature on the loop by the turntable is O-99, O-89, and O-79.  We determined that to run the largest articulated, with 85 ft. passenger equipment, we need 5" track centers.

Here is a photo on my Great Northern R-2 on the O-99 radius.



On the other portion by the yard, the curvature on the loop is O-82 on the outside, and O-72 on the inside.

Here is a video of Hot Water's AC-9 on the O-72 curve.



I believe that the layout height is at 45", and at that height, instead of "helicopter railfanning", the viewer looks more straight on the equipment.  I'm a big fan of building at 52", which for me, at 5' 11" is a VERY nice viewing height.

The higher the layout, the less visible the overhang becomes to me.

So, judge for yourself and decide if articulated locomotives don't look good on the smaller radii.  I'm quite OK with it, and I think that is one of the big advantages of three rail.

Regards,
GNNPNUT

Like you, the overhang bugs me.  My outer main is 0-72....for now....and my 2-6-6-2 really looks silly, IMHO, going around the corners.

 

From what I have watched online, stepping up to 0-96 doesn't really get it done either.  (Again, simply my opinion.)

 

For what it's worth, if you are running more than one main, Articulateds seem to force you to keep at least a 12" difference in diameter between your curves to maintain clearance.  In other words, if you had a double main, you'd have to go with 72/84" or 84/96" curved "sections".  (This is right in the neighborhood of 5" center delta mentioned by another poster.)

Those pictures really illustrate the point! 

 

I thought I would be good with O-110/O-120 but I see now that probably isn't going to be best for what I am after.  I simply don't have the room to go any bigger, so I guess I'll compromise.  I wanted to keep the boiler overhang minimal, like the real railroads did, but it just requires to much space.  

 

I love the articulated steam engines, and with so many nice ones available, I can't help but buy them!

On my oval I made the curve closest to the viewing area 0-96.  Over by the wall it is 0-72.  Really helps and does not take up so much real estate.

 I use O-148 for five axle locomotives, but the articulateds can negotiate O-140.  Biggest problem is the rear of the front drivers striking the rear cylinder block.  Second biggest problem is engine and trailing trucks striking things.  On Challengers it is not much of a problem, but a Big Boy can be problematic.  For me it is an operational problem more than an appearance item.

 

I agree with GNNP– I will never again build lower than 52".  I prefer to see my trains from the same angle I saw the real ones.

I have 72-, 84- and some 96-inch curves on my main loop, but  only my too smallest scale articulated locos, the Legacy Mallet and Vision  PRR0-8-8-0  look even halfway reasonable on them.  The rest of my scale articulated locos, particularly the really big ones, look good only on straights or on the shelf, where, frankly, they spend all but maybe an hour a year (when I lube and run each for a few minutes to make sure it's still well maintained). 

Thanks for all of the excellent input so far.  Great information!  AGHRMatt and gnnpnut, thanks for sharing the pics and video.  Very helpful!

That's because your semi-scale articulated uses the two-point articulation method developed by Rivarrossi in the 1960's, where both engine sets pivot. The overhang is split between the front and back of the locomotive. 

The scale articulateds use the one-point articuation like the prototype and only the front engine pivots for the curves, and all of the overhang is experienced by the front of the locomotive.

 

Rusty

i've read a number of places that the minimum curve a Big Boy could negotiate was 20° which in O gauge is almost exactly O144 (72" radius).  of course mainline curves would be more in the range of 6-10° (~O480 - O290); that's between 12 and 20 foot radii.

 

the benefit prototype mainlines have over home layouts is little need to turn complete circles.  if i were to design a home layout for a road with articulated locomotives on the roster, i would definitely try to break up any long straight sections to include a few gentle curves.

i've read a number of places that the minimum curve a Big Boy could negotiate was 20° which in O gauge is almost exactly O144 (72" radius).  

 

Did not know that.  No wonder I have problems going tighter than that.  I use scale wheel spacing, cylinders, and tail beams, except that my tail beams taper to the rear to accommodate tighter trailing truck swing.  I also add about a 1/16" to the spacing of the front engine from the rear cylinders.  Some of my problems come from too much superelevation, which looks good but presents problems for large articulated locomotives.  Solving such problems is my hobby.

I know that the smaller ones have a dual pivot and the scale have a single pivot.  I've seen photos of scale (As I don't currently have the fortune to own a scale steamer, but I hope to remedy that next year with help from Lionel.) swinging and it still doesn't bug me.  I'm not one dead set on prototypical looks.  I just love trains!

We reached the same conclusion a few years back and re-did the track alignment between the Atlas and the concrete arch bridge. The curve at the bottom is approximately 72" radius on the inside main. At the depot it's above 200" and we couldn't get a clear estimate on the curve at the far end. The distance here is about 30 feet. Boilers on articulated locomotives are mostly over the track and you don't see rail showing underneath 89-foot flat cars and full-scale passenger cars. If you have the space, definitely go for it.

 

So I'm clear - My layout has sections of 072 curves, equal amount of 081 and some areas of 90, 99 and 108. And despite the manufacturer stating these large engines require 072, none of my curves are actually big enough to accommodate our first ever purchase of a large articulated - the Vision big boy I just pre-ordered?!!

No, you are a bit confused, probably by the statement made about the REAL UP 4000 class locomotives curve negotiation of REAL curves!

 

ANY of the large articulated steam locomotives currently available in 3-Rail scale size, will REQUIRE a minimum of 072 curves. Also, do to some of the greater overhang, you should also have track spacing of AT LEAST 5" center to center (even more may be a bit better).

 

Think I've got the curves covered in terms of clearance. Start at 4.5 inches center to center (Atlas O spacing) but quickly diverge and at apex are around 5.75-6 inches apart.  My question was really not about advice on curve spacing but a reaction to people saying they have 0100+ curves and still don't think articulateds look right. If so, I'm wondering how bad the Vision big boy is going to look on my 072s.

Well, I hate to use the old cliché, but it will all come down to WHAY YOU LIKE!  Also remember, that the vast majority of EVERYONE on the OGR Forums have never had first hand experience with REAL articulated steam locomotives, and have no idea how much the boiler really does swing out and "overhang" the right of way on very sharp curves. Having worked with the UP Steam Crew for many, many years as Fireman on Northern 844 and Challenger 3985, I can tell you first hand, that 3985 swings out a LOT more than rail fans and model railroad folks really think.

 

 

I have most of the big UP steam engines and I run them on O72. I have no problems whatsoever do this and they look great. Yea it would be great for larger curves but that is not going to happen.

 

If you want the big engines and have O72, then go for it. The guys who have larger curves and don't buy them because they just don't look right are being silly. They all run on O72 so if you like them, buy them you will not be sorry.

 

 

Do some searching on the forums to get an idea.  Lee Willis has posted photos of his scale Big Boy on O72 curves of his layout.  And toward the top of this thread, AGHRMatt has also posted photos of a Big Boy on an O144 curve.  Both are excellent examples of how the Vision Big Boy will look in a turn.

i haven't run on anything even close to an O72 layout for quite a while, but what i recall as the least desirable aspect of a big articulated locomotive negotiating its minimum curve was the quickness of the boiler movement to the maximum displacement followed by the same fast movement when the engine returned to the straight.  if at all possible, work in an easement, ...even a short piece of O96 to make that transition to O72 a bit more gentle.

 

and whatever you do, avoid at all costs any back to back O72 S-curves.  also one of the best arguments for using numbered vs curved switches for sidings.

Why is that?  Is it because of how it'd look for the boiler to be "nodding" no, or is there some other problem?

Because, it one is operating scale equipment, i.e. scale length passenger cars (21" long) along with Kadee scale couplers, the longer cars will pull each other off the track trying to negotiate a tight S curve.

Thanks.  I have heard the call to avoid S curves for a while, and understood the reason on tight curves, <O36, but didn't know it was still a problem at the large curves.  Something to keep in mind.

Basically, everything is relative. For scale equipment, which in real life would be looking negotiating 0180+ curves, 072 is tight I suspect.

Question - I have a straight track leading into an Atlas O No.5 turnout and the diverging leg then straightens out via a half section of 072. So this is a shallow S curve. Pragmatically, will this be a problem?  Seems I recall reading somewhere that this type of shallow S isn't a problem as the train isn't fully committed to two widely angled extremes as it would be in a full S?

I just picked up my first big steam engine a tmcc challenger so of course first thing is to view videos of real ones I saw videos of the 3985 mine is a Rio grande so the plan is to reletter it in UP since most of my layout is UP and seeing the videos of the 3985 that's what I plan on doing .

 

The only time my Clinchfield Challenger looked really good on my curve arcs was a 0156 in one end of a curved room. I had pair of 096s on the other end and it was quite a contrast with the wide end. 

yea I don't have that problem it's going to look funny no matter where I run it on my layout my biggest curve is 072 but I am mainly 036 thank god for a lot of straights

the challenger I got is the lionmaster and it's able to run o31 from what it says.

 

I agree with that, but,...

quote:

 also one of the best arguments for using numbered vs curved switches for sidings.

...this statement reads a bit contrary, although maybe it wasn't meant to read that way.

 

Using a curved switch to enter a siding will alleviate the problem of the "S" curve created by the turnout used off of a straight line track to a parallel siding.

Note that the same effect can be achieved using a straight switch just by using a curve section of track on the straight line going the same direction as the turnout. The use of a curved switch would save some space over using a straight switch in this manner. 

 

Part of the reason a Railking (and Lionmaster) articulated looks better on sharper curves is both engine sets pivot, a method developed by Rivarrossi in the 1960's for their HO articulateds.  This redistributes the overhang over the length of the locomotive rather than just the front.

 

On Premier and Lionel Standard O articulateds, only the front (or rear in the case of a Cab-Forward) pivots, just like the prototype.

 

Rusty

Some G gauge trains do the same, even to the extent of having each driver articulate/pivot on its own C/L with wiggle rods.

 

It ain't right but it looks a heck of a sight better than a Tyrannosaurus Rex on a wild  12 ticket ride reconfiguring the topography.