Effect of radius on locomotive

@Denis H posted:

Running an engine that calls for 54”radius, my layout has only 45” radius,

1) Do you mean "054 curves"? Actually "54" radius" is really 0108, in O Gauge "Toy Train" terms.

2) Does the engine operate OK, i.e. no binding?

what effect if any on the locomotive or does it have to be changed out

Does WHAT "have to be changed out"?

Is this a steam or diesel locomotive?

Tom

While it probably will work, it most likely will look odd given the overhang on the curves.  You can always install wider radius curves or just stick with locos that are designed for the radius track you have.

Given the overhang you need to be more careful about placement of items near the curves so they do not obstruct your new loco.

Can you start with the make and model of the locomotive in question?

Are you sure it calls for 54" radius and not 054 track???

Agree with others that we need more info. Also bear in mind that just because it can run on the smaller radius track, doesn't mean it's a good idea - I recently picked up a 2-8-8-2 (rated for 072) and was curious if it could squeeze through 060 curves. I ran it at speed step 1 or 2, and it can indeed squeeze around the curve, but while watching it crawl I saw that portions of the driver rods on the front articulated drivers looked like they were bumping into (or very close to bumping into) some of the detail parts mounted on the boiler just above the drivers. Since these detail parts are attached to the boiler, they don't swivel with the articulated part, potentially causing problems. So the 2-8-8-2 will have to stay on the 072 curve, which tragically means I can't run my 2-10-4 and the 2-8-8-2's simultaneously  

@0-Gauge CJ posted:

Agree with others that we need more info. Also bear in mind that just because it can run on the smaller radius track, doesn't mean it's a good idea - I recently picked up a 2-8-8-2 (rated for 072) and was curious if it could squeeze through 060 curves. I ran it at speed step 1 or 2, and it can indeed squeeze around the curve, but while watching it crawl I saw that portions of the driver rods on the front articulated drivers looked like they were bumping into (or very close to bumping into) some of the detail parts mounted on the boiler just above the drivers. Since these detail parts are attached to the boiler, they don't swivel with the articulated part, potentially causing problems. So the 2-8-8-2 will have to stay on the 072 curve, which tragically means I can't run my 2-10-4 and the 2-8-8-2's simultaneously

Well, you have no choice but to double head them. Pat B.

Running on too tight a curve will introduce premature wear on the flanged wheels.

I don't understand why consumers don't generally trust the manufacturers minimum curve specification these days 

Even worse, when seeking an exception, they provide minimal information on the locomotive and track plan.

On infrequent occasions, a manufacturer will test on track curvature that they manufacture and no one else's. Until FasTrack came around, Lionel didn't make any curves between 054 and 072, but AtlasO made 063 curves. A Lionel locomotive that would not negotiate 054 was thus rated as 072, even though it would make it through an 063 curve, but Lionel doesn't make those and didn't test on them. From their perspective,  why would they? That would amount to recommending someone else's track system.

It's isolated reports of examples like this that give rise to wishful thinking that a desired locomotive might be able to cheat its way through that one place on your layout containing a curve just under it's rated minimum, at the cost of looking weird for the few seconds squeezing through.

---PCJ

That a loco can negotiate a curve does not necessarily mean that it can pull cars around it.  Teh coupler may pull a following car off the track.

I would follow the recommendations of the manufacturer re minimum radius of curves for a particular locomotive.

Here is an interesting example. What amazes me is how well my Lionel 773 Hudson (1964 version) runs on my Postwar tubular 031 curves and 022 switches. The locomotive is huge, I believe Lionel said 031 curves are OK for this locomotive, and it runs very well through those curves and switches notwithstanding its size. I believe Lionel brilliantly designed and manufactured it so it would do that.

Arnold

@Denis H posted:

Running an engine that calls for 54”radius, my layout has only 45” radius, what effect if any on the locomotive or does it have to be changed out

This minimum is not a recommendation - it is a geometrical physical limit.  A locomotive designed for 54" "radius" (actually diameter) will not physically go around a 45" curve. It will derail or bind.

That is the engineering and it is correct, but, manufacturers limits are typically conservative to prevent disappointment, and some locos will successfully negotiate under-sized curves relatively gracefully and smoothly. I wouldn't bet money on it as a policy, though. There are limits. Like with most things, it is better to follow the instructions.

The size of an engine is not the only factor limiting it to a certain diameter track (like others, I suspect the original poster meant diameter, people generally don't use radius in 3 rail O, keeping the tradition established by Lionel).  Limits to curves it can negotiate can be things like body mounted couplers, steps on the back of the engine or other details, on a steam engine if the drivers are all flanged it generally will not negotiate tighter curves. Arnold's 773 is a classic example of this, they used selective compression, blind drivers (I believe) and other tricks to make it run on a small diameter curve. My Williams brass Hudson is likely the same physical size of his engine, but because it is doesn't have all the compromises it runs on O72 (or was spec'ed at that).

Companies with their own track IME generally specify the smallest size of their track that it can run on, rather than some number representing an absolute minimum, so the listed minimum may not represent the true minimum. These days given how many diameter curves they make when it comes to Lionel or Atlas (or likely MTH, even if they are out of the track business), it likely is closer to the absolute.

In the end unless a dealer is willing to try the engine on smaller diameter curves, you may be better off following the minimum as specified. Among other things, as others point out, an engine might be able to make it around the curve without derailing but it might look pretty funky. I have seen engines rated at O72 that running on that track still looked pretty awkward, I wouldn't buy that engine since I have max O72 on my mainline. Not to mention with the overhang of an engine running on tighter than expected diameters you might end up with a situation where you have to have to pull any kind of wayside structures away from the tracks, plus also might be hard with some curved switches and the like, too. And as someone else said, you may find you can run on tighter diameter curves but the cars pulled behind it derail, even if it is truck mounted couplers because they swing so far out.

There are many reasons why someone may not want to stick with the manufacturer's recommended minimum curves.

First, they are not always accurate, especially taking into account variances between different track manufacturers. This Forum is littered with posts about how someone was able to run a particular engine on a track with curves less that the manufacturer's recommended minimum.

Second, if an operator has a favorite or desired livery or road number and it is only made in recommended curve diameters that are greater than what they have, they may do what ever they can to try and see if it will work on their layout.

Third, I suspect that many operators want to try and run big iron on their layout and will do just about anything to try and get them to work.

Fourth, many operators simply don't care what an engine may look like while going around a particular curve. Just because it's important to you, doesn't mean it's important to them.  Take someone who has two 25' long straights and O-36 curves - they may not care about what the engine looks like for the few seconds it's in the curves - they just want to see it slowly going back and forth on those long straights. 

I'm not saying anyone should do it, but I certainly understand why someone would want to and, thus, post a topic to try and see if anyone else has had success doing it with a particular model.

Just a thought,,,,,,,,,,why hasn't the original poster returned to offer additional comments/information????

I try to go with the catalogs advertised minimum radius, or diameter. Post War O gauge trains were able to run comfortably on 031 circles, and the smaller 0 gauge 027, on  27 inch circles, (utilizing magne-traction) however, that was mostly tubular steel trackage. That being said, these newer scale sized locomotives, with strong can motors, traction tires, should be operated on (no less than the advertised diameter) for reliable operation. Many locomotives will negotiate smaller diameter curves, however, wear and tear on the wheels, traction tires is devastating. If it says 054, Ok, then not 045, if it says 072, don’t try 063 or for certain 054. So, if one has small curves, buy rolling stock for that particular curve. I have sold off many locomotives that are rated 072, but had lots of overhang and didn’t really look appropriate on my layout. The 21 inch newer plastic passenger cars have a lot of overhang on 072 curves, although they are rated for 072. Actually Lionels aluminum 18 inch cars look great on 072 circles.  O gauge trains really run better on 081, 090, 099, 0108, 0120. Also, just for your knowledge, running long heavyweight passenger car trains on tubular trackage is more stressful on the locomotives than flat rail such as gargraves, Ross Custom, and Atlas O rails.  I’ve learned this from experience. So, in conclusion, go by the book, if it says an engine will operate on 054, then that’s the correct way to run your equipment. Happy Railroading Everyone

My apology for not responding sooner, had a family emergency and left town shortly after making my post. Just returned this evening and was checking my emails, I didn’t have anytime while away.

I need to clarify several things, I haven’t used my trains for several years and the layout I have has 045 track. I decided I needed some personal time and went to check out the layout, cleaned the track and took out a steam engine to test, that worked fine. The next engine I looked at was the Birch Valley shay, the manufacturer called for 054 track, since I haven’t used the layout for some time, I was trying to find out if that might run on the 045 or do I have to replace the 045 with the 054.

I feel like I’m starting this process all over and want to get started on the right foot, I haven’t run trains for approximately 6 years.

Sorry for the delay, thanks

The 6-11141 Shay has a very intricate drive system and a wide wheel base. That does not bode well for fudging the manufacturers recommendation, especially since they rated it O54 when they have an O48 curve available. Unless someone chimes in with firsthand experience with the particular locomotive design and O45, or you want to be a very daring guinea pig, I would look into larger curves, especially since you seem to indicate that being an option. Very rarely do those with the space allotment regret larger curves. If you can somehow manage at least a circuit of O72, you can pretty much run anything 3 rail on it.

apparently you have a layout and the engine. Try it out. Just be in a position to catch the engine if it derails. You do not want it to fall on the floor. Be sure to test the turnouts also.

Thanks for all the response, based on your information I’ve decided to change the track to 054 since I hope to have some time. My initial concern was running the shay on 045 track when the manufacturer calls for 054, better safe than sorry. All my other trains will not have any issues with this change.

So, if the manufacturer of this Shay says it can negotiate an O54 curve, does that not mean that it can negotiate an S curve made with O54 track? Because of the drive mechanism of a Shay I would imagine that an S curve would be difficult! And, if the shay can negotiate an O54 S curve, would it not be reasonable to assume that it might negotiate O45 track without any S curves? I use O48 as a minimum track diameter but all S curves are minimum O72. My guess is that the Shay would do fine on my track.

I’ve used 063 track on some curves but the original layout was done with 045 and I didn’t want any issues using the shay on that size curve. It has not been used in several years and that was on a larger layout and that was my concern if it could negotiate the 045 curves

I think you will be happier if you stick to 054 min.  I have attempted to run my shay (from 1992 catalog looks like basically the same locomotive) on 048 curves with limited success.  If the running gear is inside the curve it will not turn tight enough and will derail, if the running gear is on the outside of the curve the running connecting the third truck will pull out and flop around.  I now have a layout with 054 min curves and it runs fine.

Thanks Steve, I make the change t o 054 curves, haven’t had the chance to run it, hopefully that will happen soon. Most of the responses said to follow the manufacturer’s recommendation