Running on less than recommended track radius

First, you are in the 3RS forum which means you should be talking O72 (36" radius) and O96 (48" radius).  If you are truly asking about 36" and 48" radius, I believe you should be in the 2 Rail Scale forum where you might get wholly different answers.  The main reason I say this is because I'm not personally aware of any 3RS equipment that requires anything larger than O72 curves.  Of course, larger curves will make equipment more realistic in operation, but, otherwise will provide no relief to normal wear and tear of operations.

The biggest risks for anyone using smaller than expected curves are derailments and equipment damage.  Much equipment will work at slow speeds on somewhat smaller curves than recommended, but you will only find out what "somewhat smaller" means through trial and error.  Success may also depend on how well the track is laid and on what grade the track is running.  Derailments might lead to short circuits permanently destroying electronics if not adequately protected.  Other damage might occur to passing trains on the curve due to too much inside or outside overhang or to scenery and buildings just a little too close to the curve.

Hope this helps some.

Chuck

Some wheels make contact with stirrup ladders on tight curves, brass models have many more details which may be ruined.  Scott Mann has mentioned this in a couple of his posts.  If you're running scale size large steam engines, in addition to the overhangs Chuck mentioned the trucks of the tender may jam in a curve.  Some engines have some blind drivers (no flanges) but most tender trucks have flanges on every wheel.  Why would you disregard the manufacturer's recommendations?  John in Lansing, ILL

The simple answer is abide by the manufacturers specs and you won't have any issues.  

Beyond that, to see if a particular combination works, you need to test it.  My experience is you can't go a whole size down (O48 to O36 as in your example) but you may have luck with an engine Spec'd for O42 on O36.

At slow speeds they will stall and at higher speeds they will de-rail.

I have an early '90 Lionel Chessie Steam Special T1.  It is spec'd for O42 curves.  I have a loop of Fastrack the uses O72 easements into O36.  The T1 runs fine on that combination.  However, another gentleman on this forum has the same model from MTH and it will not navigate 036.  

You will need to test every combination.

Tony

Question #4 - Yes, a steamer with pilot and training trucks may derail

said steamer may just run off of the track 

It will definitely slow down

6 wheel truck diesel - may work ok

Note that in many cases, it's not the locomotive that's the issue, it's the cars it's pulling.  Case in point is the Lionel Three-Truck Shay.  It's rated for O54 track, but it'll happily go around O36 curves all day.  However, the car that is next in line will derail due to the coupler design.

Issues, derail and or extra wear and tear on the locomotive.  Or they simply won't go as they'll get stuck, and you could burn out motors or drive boards as it's trying to push the train around.  another issue would be with pickup rollers.  If you go on tighter curve track than it's speced for, the rollers could fall off of the center rail.  This can cause power shorts, derails, or damage to the pickup rollers.

Now, having said that, I run my trains under the speced min curve all the time.  One of the 1st things I do with a new rolling stock is find out just how tight it can go.  I go slow and watch it to make sure I don't damage it.  Most freight and passenger cars can do O36, unless they are coupled to another car.  Then some of them long ones will hit, or clothesline on a curve.  Most locomotives can go down one sized curve, sometimes more like John pointed out, you just can't pull anything behind it.  On steamers sometimes the locomotive can go tight, but the tender can't.  Here's a list of some of my locomotives:

K-Line Big Boy - spec O31, does O27 just fine.

Lionel Visionline Big Boy - spec O72, locomotive does O54, tender will do O63, but doesn't really like it.

Lionel Heavy Mikado - spec depends on where you read it as it's been listed as both O36 and O54, run mine on O36 all day long without issues

MTH Protosound equipped PRR T-1 Duplex - spec O72, just barley got it to do O48 but the motor was trying too hard (Pulling too much current.), so O54.

Just keep track geometry in mind.  Like my Mikado.  Sure it can do O36 curves, and switches, but I have to be really careful on O36 S-curves.  When backing the tender has come off the track.  The VL BB, sure it could do O63 curve and switch, but any S-curve smaller than O72 will stop you in your tracks (Yup, I went there with a pun.).  So best thing is if you really need to go smaller, lay some track out and slowly and carefully push/run it through the track and see how comfortable you are with it.  If you have a LHS that you are a regular at, they may even help you try it in the store before you buy (Did that with Lionel and MTH auto racks on O31.  They do it, but not coupled, and will hit switch stands.).

Considering the context of the OP's post, it is reasonable that he is referring to diameters and not radii. 

But that said, the OP should clarify. As we all know 3-rail track curves are noted by diameter, as in O36, O72, etc. (not by radius)

My VL-BB will not do an O60 curve, the tender derails right off the bat.  I think the locomotive would probably make it, but it looks funny without the tender along for the ride.

gunrunnerjohn posted:

My VL-BB will not do an O60 curve, the tender derails right off the bat.  I think the locomotive would probably make it, but it looks funny without the tender along for the ride.

It's your railroad, use a tender that will. 

I agree with all of the above. To me it just looks plain stupid running locomotives/trains not intended for their radius.

Thanks for the replies, I am new to the hobby, I should have been more specific in my original post, I was referring to diameter.  O gage fastrack 036 curves vs 048 curves.

It is helpful to know that negotiating O36 curves is less troublesome than O36 switches, and so on with larger diameters.

A good rule is to use the largest curves and switches that space permits.

I am extremely space limited. I use O36 curves and O48 switches. I only run B-B wheel arrangement diesels, and as short as I can find that I like (GP7's, F3's, and ALCO S2's). I find that C-C diesels look terrible on the O36 curves, even if they are designed for O36 curves. I have small steam locomotives like Yard Goats (0-8-0) and Mikados. I have no passenger cars and only freight cars not more than 12" long. These are only my personal preferences.

sinclair posted:

Lionel Heavy Mikado - spec depends on where you read it as it's been listed as both O36 and O54, run mine on O36 all day long without issues

Glad to hear this. I've had my eye on the cataloged B&O Light Mikado but am not going to make a $1K gamble to see if it can/can't run on my layout. I have 0-42, 0-31, and 0-27 curves. If it can run on 0-42, I'm OK but I've seen 0-36 and 0-54 listed. Not risking it. If the Heavy Mikado can do it, I assume the light can. I would imagine the powertrain/chassis is the same, only the shell is different.

FYI my MTH NJ Transit passenger cars listed as 042 min do not really like 042.  Apparently my loop was 041 7/8 or so resulting in a derailment every time.  These sit on a shelf until there comes a time when I can build a layout with larger curves.  On the other hand, my MTH spine set is also listed at 042 min and handles the curves quite fine.  My take away is bigger is better if you can swing it.

The best advice is to test equipment on your actual layout. You may be surprised to discover many trains will run perfectly on curves that are tighter than the specified minimum.

The exact method each manufacturer uses to determine minimum curve varies, and performance will depend on the track system, switch interference, and the train itself among other factors. There may also be some arbitrary assignment based on aesthetics.

For example, the Lionel genset switcher ambiguously states, “Min curve: O-42 / O-54 recommended”.  So, one might conclude the absolute minimum is O-42. However, this engine runs perfectly on my Super O layout with 36” curves! This being the case, what is the “O-54 recommended” really intended to represent? Are they recommending O-54 because it looks better on a larger curve? Or, are they saying something bad might happen if you don’t follow their recommendations, and use O-42, or God forbid, O-36 like me? 

Then there are also a few engines  where the manufacturer appears scattered and can’t make up their minds about minimum curve. For example, the Lionel Legacy 10-wheelers from 2014 state, “Min Curve: O-42 / O-54 recommended”, but a previous run of this identical engine from the 2010 catalog states “Min curve O-31”.

Again, the best option is to test where possible. But don't expect a VL Big Boy to run on your postwar O-27 layout.

The A Train posted:

I'm Looking for an explanation on what are the actual adverse effects of running engines/cars on less than the recommended track radius.  

Lets say I want to run 48" engine/car on some 36" track curved sections.

1.  If the recommended radius is 48", can I substitute 36" curved sections with straight sections interposed to come close to a 48" curve  radius or must I use all 48" curved sections?

2. Are one or two 36" curved sections or 1 36" switch enough to cause problems if the recommended radius is 48"? Or is it more of a problem with consecutive curved sections forming 180 degree curves?

3.  What are the actual adverse effects on the engines/ cars?  Does it hurt the engines, wheels, or frames?

4. How do you know if there is a problem? Derailments? Or just extra wear and tear.

5 is there a rule of thumb for the length in inches of a engine/car that would run on 36" curves safely?

Thank you

Radius vs. Diameter aside (36" radius=O-72/48" Radius = O96), the recommendations of the manufacturers SEEM to focus on a few things:

• Can the equipment out of the box make it around?
• Can the equipment make it around with a similar piece of equipment coupled to it?
• In the case of locomotives, can the drive mechanism handle the curve?
• Is there the risk of "string Lining" (the equipment hangs so far inside the curve that it gets snatched off the track).

If the 36" curves you're referring to are Lionel FasTrack, then you're talking about 18" radius (O-36) and you want small diesels and extra small three-rail steam. You don't want body-mounted couplers. You're probably limited to Rail King and Lion Chief locomotives.

Running equipment on curves that are too sharp can grind on the flanges and the rail itself causing wear in both. In some situations it's hard on the mechanism. In other situations, it's just a matter of what's coupled to it.

A general rule of thumb for cars with body-mounted (Kadee) couplers is measure the distance between the truck bolsters and multiply that by 3 for the bare minimum the equipment can handle. 3.5 is better; 4 and above is best. This assumes the bolster for the truck is in the center of the truck and you may need a bit more for three-axle trucks. Cars with more overhang past the trucks (Auto Racks, passenger cars and 89-foot trailer flats) need a bit more.

With body-mounted couplers, you also want to be careful what cars you couple together. Don't couple long cars next to short ones. You want to keep the cars relatively close in length. Also watch for the risk of string lining.

With the 3-rail trucks/couplers, you can get away with more because the couplers are truck-mounted and swivel in the curve. They allow a car that might otherwise require 48" radius (O-96) to negotiate 27" radius (O-54). K-Line 21" passenger cars could pull this off but didn't look good.

I run scale-wheeled MTH engines and 2-rail cars now and everything I've bought so far has been able to handle 36" radius (O-72), but my 6-axle locomotives were all rated for 42" radius (O-84) primarily (it appears) due to coupler considerations. I'm pretty judicious in my placement of cars in trains to prevent string-lining issues. However, I've been bitten on the caboose by uneven track (my Big Boy video illustrates that well) because the engines ride up on the center rail pickup rollers and the flanges can walk out of the track. For that reason, I only run 4-axle diesels with scale wheels at the club now and will be switching some of my 6-axle diesels over to hi-rail wheels or restrict their use to 2-rail operation.

In the end, it comes down to experimenting, extensive testing, good track work (even without twists) and stable bench work (the moisture at the club is what caught up with me).

Hope this helps.

When it comes to some engines it depends if they are built like the originals that were rated for a smaller curve. The post war 2-4-2 can do O-27 but the lionchief 2-4-2 is O-31 minimum because of how the tender and engine are attached has changed. Tried spaced O-27 still no luck in getting it to work it would always derail. The Lionchief Plus NW2 and Hudson do O-27 because they are very close to the post war originals even if they are rated O-31. Though the Hudson ,4-6-4, looks odd, and the rear truck and wires make me worried looking at it.

SJC posted:

sinclair posted:

Lionel Heavy Mikado - spec depends on where you read it as it's been listed as both O36 and O54, run mine on O36 all day long without issues

Glad to hear this. I've had my eye on the cataloged B&O Light Mikado but am not going to make a $1K gamble to see if it can/can't run on my layout. I have 0-42, 0-31, and 0-27 curves. If it can run on 0-42, I'm OK but I've seen 0-36 and 0-54 listed. Not risking it. If the Heavy Mikado can do it, I assume the light can. I would imagine the powertrain/chassis is the same, only the shell is different.

Before I bought the heavy Mikado, I had asked about this, and someone with one of each emailed me with photos.  Yes, the two have the same drive train, just different shells.  So you'll be good on O42 curves.  I really need to hunt down one of them D&RGW locomotives.

GregR posted:

Then there are also a few engines  where the manufacturer appears scattered and can’t make up their minds about minimum curve. For example, the Lionel Legacy 10-wheelers from 2014 state, “Min Curve: O-42 / O-54 recommended”, but a previous run of this identical engine from the 2010 catalog states “Min curve O-31”.

I had forgotten about this one as my ten wheeler flies through O36 without any issues at all.  It's a great little engine.  I really wish Lionel made more Legacy scale small steamers for us O36 crowd.

To further clarify, my Lionel Legacy Heavy Mikado nicely negotiates my O36 loop. Visually, it nearly passes the eye test for appropriateness. But I should say that the speed that I run on my small layout (76" by 48") is slow for all locomotives. It is mainly an operating industrial complex, where switchers move cars to and from a specific (industry) spur to the mainline (loop). I have four industry spurs. GP7's are the primary mainline locomotives. The Mikado typically sits on its spur. My switchers are an ALCO S-2 and soon (hopefully) an Atlas VO 1000. Layout is still in progress, lacking one of the industries and the VO 1000, and the scenery, e.g., roads, turf, trees, etc.

I've run O42 steam engines on O36 without a problem, but the greater overhang is hard on nearby scenery

For anyone interested in running steam on smaller layouts, the as yet to be released Lionel BTO LEGACY 2-6-0 Mogul Steam Locomotive in various liveries (B&M, Rutland, Vermont, etc.) is advertised as running down to O-31.

Performance through curves and turnouts may differ.

I had a 3-rail Y6b from 3rd Rail that I could get through O54 curves, easily through O63. But, required the wider turnouts.

The A Train posted:

1.  If the recommended radius is 48", can I substitute 36" curved sections with straight sections interposed to come close to a 48" curve  radius or must I use all 48" curved sections?

Putting straight pieces between the curves does not change the radius.....it just puts straight pieces between the curves.

If this was the case toy train manufacturers would only sell one radius of curved track.

I don't understand where folks get this idea. You are not the first.

Two tips for happy railroading:

Don't go smaller than the recommended radius.

Use a modern transformer with modern trains.

Depending on the age of engine, the other thing to keep in mind is that the variety of track we have these days didn't always exist, so for example an engine might run well on 063, but when it was built 072 was the largest radius and for example, the next size down may have been 042 , so it it was too big for O42 they might spec it as O72, so that could play into this (the more modern the engine, the less likely this is true, for obvious reasons). 

Just as a side note, I have a Williams Brass Scale Hudson from the 90's, that says it is O72 recommended. Has anyone ever tried that on smaller diameter curves? I plan when I start designing my layout to try and use O72, but having the flexibility to go smaller would make the design easier

RickO posted:

The A Train posted:

1.  If the recommended radius is 48", can I substitute 36" curved sections with straight sections interposed to come close to a 48" curve  radius or must I use all 48" curved sections?

Putting straight pieces between the curves does not change the radius.....it just puts straight pieces between the curves.

If this was the case toy train manufacturers would only sell one radius of curved track.

I don't understand where folks get this idea. You are not the first.

Two tips for happy railroading:

Don't go smaller than the recommended radius.

Use a modern transformer with modern trains.

 

Excellent point. Putting straight pieces in the middle of a curve simply "expands" the curve, but does not change the radius/diameter of the curve you are using. The train still has to be able to negotiate that diameter curve.

Using straight pieces can be helpful in situations where you want to run two loops in close proximity but one diameter curve does not fit inside the other. For instance, a Fastrack O31 curve does not fit "inside" a Fastrack O36 curve, but you can insert straight pieces into the O36 curve to "widen" it enough to fit the O31 curve inside it.

When I talked to MTH designer during one of the OGR trips to MTH, he stated the min curve was tested for a complex turnout situation.  When turnouts are not included, the min curve is usually less than the one posted.

Not all of us have the luxury of 072 or greater diameters. I picked up a couple of 3RS engines that I just couldn't pass up. The latest one, a MTH PRR FF-2 electric, was just irresistable. I decided it was going to run on my layout do or die (I have about 60 inch min). Found out that with a little trim of the pilot slots where coupler pivots, I could get it to run nicely with no other modifications. If I ever sell, will make sure the next guy is aware;. It's almost imperceptable.  I have another electric (MTH NYC CUT electric) that I will likely do the same. 

All depends on how badly you want it!

Jim

I have asked several times if a Williams Niagara and a Lionel challenger can traverse O64. I finally decided I am just going to have to try it.

When thinking about curves one also needs to consider your rolling stock if you are running scale passenger cars.

I have a Ross dual curve switch on our pike, the tighter radius is 096. As is normal, the switch machine is on the inside. When Atlas and Third Rail (21 inch)coaches ride through the curve they hover over and span the switch machine. Most clear it, some scrape it.

Of course moving the machine to the other side is on my to-do list, I'm just pointing out that clearance issues are multi-dimensional.

Jan

 It isn't exactly the radius, it is the angle:  Using half or whole straights between half sections of curve(1/8, 1/12) can help for some trains.. There is less angle when one truck at a time is on a curve (each curve must be short as the open space /wheelbase between two coupled trucks) It creates a jerky look though.

A "straights between curves" "rule" is more for small scale and associated with backing, and "coupler tracking" /"coupler overhang" binding, etc. in S curves,. I can't say if that is an issue with 2rs 3rs O, but small scale flanges and couplers don't like S curves IME.

FWIW, the original Lionel scale Mikes--Southern, Frisco, and I think NYC--are all spec'd at 031.  The later derivatives I don't know about (these are NOT the K-Line derived engines).