# 18" radius curves, locomotives, and decoding what fits.



## Treozen (Jan 22, 2019)

hello all - 

I got my hands on a track layout program and starting playing around with fitting routes to my space / table design. I started with 22" radius curves and #6 turnouts (as recommended) but in the space I have, its gets tight. Obviously I'm still learning about layout, but it doesn't take layout genius to figure tighter curves will free up real estate. Enter the 18" radius.....

I haven't actually put anything together, but in just a quick comparison, the 18" curves should really open things up in terms of how and where I can route things, but at a cost - limits locomotive choices. I am not sure this is an issue though, because in my ideal layout, I'm not looking to run "big honking locomotives" - frankly I think they'd be out of place in a mining / lumber town. 

The problem I have though, is that I can't quite figure which engines will work well on 18", and which wont. Sometimes websites tell you, other times, they don't. On forums I see people quoting 4-6-4, 2-4-2, 2-8-4 (or variations there of) as either working, or not - what what is a 4-6-4? Just the number of axles? Does a 2-4-2 work on 18", but a 6-8-6 won't? Is there a standard engine length that typically works, but a threshold beyond which they don't? Here are some of the locomotives I like and would probably want to run - style at least, regardless of brand....


http://www.katousa.com/Zcart/index.php?main_page=product_info&cPath=65_78_171&products_id=1782

https://www.trainworld.com/manufact...615-usra-0-6-0-w-smoke-slope-tender-prr-3234/

https://hobbyking.com/en_us/roco-fl...egmawLXtu-hz7wcwuiMaAlXsEALw_wcB&gclsrc=aw.ds

https://www.trainworld.com/manufact...52202-b-o-baldwin-4-6-0-locomotive-dcc-ready/

https://www.trainworld.com/manufact...eam-loco-dcc-and-sound-equipped-nickel-plate/

https://trainlife.com/products/ho-s...khAvzEbN5EjnIg2HCh04IkrVSnxismbEaAuf7EALw_wcB

Thanks, 
Allan


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## wvgca (Jan 21, 2013)

usually on an eighteen inch radius, steam locos OVER six drivers don't work [or look] very good ...
same goes for diesels OVER four wheels on each truck [two axles]


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## DonR (Oct 18, 2012)

If it is at all possible to add a foot to the table width you
can achieve 22" radius. It is highly recommended.

Tight radius affects not just locos but also
long cars such as passenger equipment.
Their ends stick out beyond the rails, and their bodies
overhand inside rails. They just don't look right are
likely to give problems when backing.

Don


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## Dennis461 (Jan 5, 2018)

Could you maybe post the make model of loco you are looking at rather than links?

Some of us older folks forget why we clicked on a link after the new web page opens
The first link is an N scale locomotive.


Go as big as you can on the track.
Atlas #6 or PECO large radius to eliminate some problems.

I have a shelf layout with 18" reversing loop and S-curve and can run;

Varney 4-6-0
Mantua 4-6-2
Rivarossi 4-6-4, 2-8-4
Rivarossi articulated Cab forward (looks kinda silly on the curve)
Athearn SW7, F7


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## mesenteria (Oct 29, 2015)

But WAIT!!! There's more! If you call in the next ten min..

...er...sorry, wrong script.

Our scale trains have to have engineered slop. Not slope...slop. They'll take a fairly wide range of tolerance to the conditions a wide range of skill-sets and experience will put them to. Across a broad range of users, the buyers out there, these toys have to work about 90% of the time or people will stop buying them.


Eighteen inch curves used to be the standard about 30 years ago and earlier. That radius has begun to creep upward, and upward, to the point where many locomotives and long cars just won't work on them any more. Walther's heavyweight passenger cars simply won't stay coupled, or they'll derail, on curves less than about 26". Sure, they claim they're good down to 24", but so many of my forumites across forums have called BS to that claim that I go along with it...adding in my own call of BS learned the hard way....by trials.


Again, if ya gotta, then 18" is what you'll make and use. But if you can eke out another two or four inches, you'll have a much better tracking experience AND be able to select from a broader range of rolling stock.


But wait!!! There is even more! Our trains may stay coupled trailing around short radius curves and through short frog turnouts of #4.5. Some may actually go through a true-blue #4. The trouble, though, comes when you decide to back them out and take a different route. You'll find that most rolling stock bunches the slack when you reverse the locomotive, and you'll find some items snagging, bucking, and derailing. Happened to me. With those purdy Walther's heavyweights. On true 26" curves.


So what's the deal? Only believe the importers' claims when you have nothing else to use for information. And then, be prepared to be disappointed and to have to ship back items for a refund. You may be pleasantly surprised, but the general rule is this, for all engineering purposes:


The closer you run to design tolerances, the higher the probability of failure, damage, or injury.


So, most of us know that before we affix our track with glues or spikes, we run trials. Or, we mock up the track arrangements we're interested in and run trials. Trailing, shoving, forward and reverse, everywhere, through all trackage.


It's the only way you'll have proof of concept for the track geometry you want, and for the rolling stock you envision running reliably on it. Sorry, no shortcuts.


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## Treozen (Jan 22, 2019)

Dennis461 said:


> Could you maybe post the make model of loco you are looking at rather than links?


I'd love to, but the forum wont let me until I prove that I'm a real human boy, rather than an evil spam bot. 



Dennis461 said:


> The first link is an N scale locomotive.


Yes, yes it is...Why? Because I'm an idiot.


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## cale10 (Jun 15, 2013)

I can tell you for sure that my Bachmann Niagara is hit or miss with 18" radius curves. sometimes it goes through fine, but others it would jump the rails, but it would derail more often than not so i dont run it anymore. However, I can say that the older Bachmann SP 4-8-4 Daylight will run through my layouts 18" curves all day long. It might look a little goofy, but it works. If you like steam though, you could get some (smaller) late steam locos, and some early F units and have a mixed era layout. Those F units are great because they will go through the tightest curves it seems.


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## CTValleyRR (Jul 26, 2014)

Be patient. You only need something like 10 posts before you can freely post images.

I see that no one really answered your question about the numbering. It is called Whyte Notation (after its inventor) and is a shorthand to describe steam locomotive wheel configurations. The first number refers to leading, non-driven wheels which help guide the locomotive, and the last number refers to trailing, non-driven wheels supporting the firebox. The number(s) in the middle refer to the number of drivers. Thus, a 4-6-4 has 4 leading (or pilot) wheels, 6 drivers, and 4 trailing wheels; a 4-8-8-4 has 4 pilot wheels, two sets of eight drivers each, and 4 trailing wheels.

Each wheel configuration has a more or less standard name. The 4-6-4 was commonly referred to as a Hudson; a 2-8-2 was a Mikado, 4-4-2 was an Atlantic, and a 4-6-2 was a Pacific.


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## MichaelE (Mar 7, 2018)

Foot long cars just don't look good on an 18" radius even if they can negotiate the curve while still staying on the rails. As was mentioned, backing is going to give problems that leads to avoidable frustration.

I would do anything short of knocking a wall out to get 22"-24" radius curves on any layout.

If you are going to stay with 40' box cars, gondolas, and flat cars, I say go for it. If not, I would reconsider your curve radius.


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## Treozen (Jan 22, 2019)

Hmm, well, I guess I'll keep at it with the 22" radii. The one design element in my favor is that I'm picturing a fictional small town / village in the Pacific NorthWest, with some sort of mining and or lumber operation as the theme of my layout. It seems to me that smaller locomotives, carriages, etc would be at home in that theme, rather than bigger long-distance interstate-type routes. Course, I know nothing of rail yards really, but here are two that actually ran on the local line:

I believe the two below were 2-8-0 Freight service. The line also ran 4-4-0 passenger service and 0-6-0 yard service.


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## traction fan (Oct 5, 2014)

Treozen said:


> I'd love to, but the forum wont let me until I prove that I'm a real human boy, rather than an evil spam bot.
> 
> Five posts should work for posting photos I think.
> 
> Yes, yes it is...Why? Because I'm an idiot.


Maybe not. If you could possibly go to N-scale that 18" radius curve can handle just about any locomotive or car you want. I agree with the advice not to trust manufactures claims about minimum radius. I model in N-scale and found by real world testing that a Kato N-scale 2-8-2 mikado was much more reliable on 16" radius curves than the 11" recommended or even on the 12" radius I had originally adopted.

Traction Fan :smilie_daumenpos:


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## lajrmdlr (Apr 25, 2014)

Allan
How big is your layout space? If it's a room have you thought about going around the walls? Do a Google search using the layout parameters you've mentioned here. There's a gazillion layout plans already on the internet.


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## Treozen (Jan 22, 2019)

lajrmdlr said:


> Allan
> How big is your layout space? If it's a room have you thought about going around the walls? Do a Google search using the layout parameters you've mentioned here. There's a gazillion layout plans already on the internet.


Going around the walls isn't option - the space I have is actually a portion of an 1,100sqft basement, with other rooms, doors, closets, necessary storage, etc. The space I can reserve is 14' X 8' - to be used however is best - giant walk-around table, duck under (eek), dog bone, 5' table with a 3' walk behind, 8' table with a 3' squared control area...and so on. 

I'm sure it very possible to get something interesting and retain the larger radii curves - part of the issue is just me learning how to put together a rail layout - I look at some of the designs on google, and frankly get confused about how they are supposed to work - plate of spaghetti comes to mind. I'll get there.


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## MichaelE (Mar 7, 2018)

Would it ba possible for you to add a foot in width for a 3'-4' length at each end of the table to accomodate the curve radii at each end? Like this:


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## Treozen (Jan 22, 2019)

MichaelE said:


> Would it ba possible for you to add a foot in width for a 3'-4' length at each end of the table to accomodate the curve radii at each end? Like this:


At one end, yes, the other, no - would interfere with double french doors.


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## mesenteria (Oct 29, 2015)

Could you fashion a hinged section that could be up when you want to run trains, and then leave it suspended vertically when you need to use the doors? Many solve their space problems this way. Have sliding arms that will support the raised/hinged length, and make their top surfaces angled to provide a wedge or cam effect to keep things aligned.


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## ebtnut (Mar 9, 2017)

Just curious if you know the railroad those locos belonged to. Can't quite make out the lettering on the posted pics. Both are typical early 1900's light/medium Consolidations. Roundhouse once made a kit that builds up very similar to No. 16. They show up occasionally on e-bay and at train shows. The model will easily navigate 18" curves.


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## Treozen (Jan 22, 2019)

mesenteria said:


> Could you fashion a hinged section that could be up when you want to run trains, and then leave it suspended vertically when you need to use the doors? Many solve their space problems this way. Have sliding arms that will support the raised/hinged length, and make their top surfaces angled to provide a wedge or cam effect to keep things aligned.


I thought about that, but I'm not sure how to make the track and scenery "fold" reliably if its a sectional hinge, and if hinging the entire apparatus, I'd be looking at some weight. This is also a daylight basement and anything folding vertically against the wall would block the windows. Its a good space in many ways, but also has its challenges.


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## Treozen (Jan 22, 2019)

ebtnut said:


> Just curious if you know the railroad those locos belonged to. Can't quite make out the lettering on the posted pics. Both are typical early 1900's light/medium Consolidations. Roundhouse once made a kit that builds up very similar to No. 16. They show up occasionally on e-bay and at train shows. The model will easily navigate 18" curves.


Yes - The three locomotives were ordered from the American Locomotive Company by the Columbia & Puget Sound Railroad. The C&PS railroad changed its name to the Pacific Coast Railroad in 1916. This name persisted until 1951 when due to financial difficulties, The Pacific Coast Railroad was sold to the Great Northern Railway. So, depending on where you are between 1910 and 1951, the locomotives could have been Columbia & Puget Sound, Pacific Coast Railroad or Great Northern Railway, although the railroad itself remained "The Pacific Coast Railroad" and the steam engines were all scrapped in 1953. Regardless of the name, the railroad served coal mines, clay mines, logging operations, general produce and passenger services for local communities. Note that this is the Washington State PCR. 

In my layout reality, its the mid to late 50's and the steam locomotives are still running strong.

Here are some other pictures: Engine #16 (2-8-0), traveling eastbound out of Renton, 1951. Engine #17 (0-6-0) and Engine #18 (4-4-0)


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## J.Albert1949 (Feb 3, 2018)

*OP:*

For smaller steam engines like those in your pics above, 18" radius should do well enough.

4-4-0, 2-6-0, 2-6-2, 4-6-0, 2-8-0, even small 2-8-2 -- should do fine.

Also, geared locomotives.

Why only 18" and 22"?
Have you considered 20"?

I believe Kato Unitrack has 19.5" radius (approximately).


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## ebtnut (Mar 9, 2017)

Thanks for the info on the PCR. I would note that the Bachmann Richmond early 4-4-0 would be a decent stand-in for No. 18. The aforementioned MDC/Roundhouse made a kit for an 0-6-0 that would serve well for No. 17. They too show up on e-bay and at train shows. The kit is based on an SP prototype. All will do 18" curves.


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## Treozen (Jan 22, 2019)

J.Albert1949 said:


> *OP:*
> 
> For smaller steam engines like those in your pics above, 18" radius should do well enough.
> 
> ...


Two reasons really 1) 22" was basically universally recommended, and 2) 18" seemed to be the most popular (only, actually) acceptable alternative I could find. I figured you could make any radius you wanted with flex-track, so something between 18" and 22" would be achievable, but despite my earlier thought about using flex track, I'm wondering If I shouldn't use some good sectional track, if only to take some complexity out of my first build.


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## Treozen (Jan 22, 2019)

ebtnut said:


> Thanks for the info on the PCR. I would note that the Bachmann Richmond early 4-4-0 would be a decent stand-in for No. 18. The aforementioned MDC/Roundhouse made a kit for an 0-6-0 that would serve well for No. 17. They too show up on e-bay and at train shows. The kit is based on an SP prototype. All will do 18" curves.


I'll keep an eye out for them. There is a nice Broadway engine I like for Engine #16, 2-8-0. Spendy thing though.


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## traction fan (Oct 5, 2014)

*Spaghetti plates indeed*



Treozen said:


> Going around the walls isn't option - the space I have is actually a portion of an 1,100sqft basement, with other rooms, doors, closets, necessary storage, etc. The space I can reserve is 14' X 8' - to be used however is best - giant walk-around table, duck under (eek), dog bone, 5' table with a 3' walk behind, 8' table with a 3' squared control area...and so on.
> 
> I'm sure it very possible to get something interesting and retain the larger radii curves - part of the issue is just me learning how to put together a rail layout - I look at some of the designs on google, and frankly get confused about how they are supposed to work - plate of spaghetti comes to mind. I'll get there.


Treozen;

I hear you about those "plate of spaghetti" track plans. They're OK if your goals are to cram as much track into a given space as possible, and then watch trains cycle through the complexity. From your posts and photos though, I get the impression that you may be more interested in building something that resembles the "track plan" of a real railroad. Is that correct? If so, since you have obviously done some homework, you likely realize that the ratio of track to scenery/structures etc., is way less in the real world, than it is on many model railroads. 

So, could you, or would you want to, use larger curves on a simpler track plan? Both the simple track layout and broad curves would be more prototypical. 

If you ever do get to the point where you want to build a hinged section, have it hinge downward, rather than upward. That way you not only won't block the window, but the track and scenic joints at the hinge point will work, and look better. That's not to say I recommend hinged sections in general, but sometimes they're useful, and they're always better than duck-unders!  It's also possible to build a hinged section that is very light weight using extruded foam insulation board & minimal wood.

If you can post a scale drawing of your available space, some of us could perhaps advise you better.

Thanks for the photos of the Pacific Coast Railroad. I model some of the same area of Washington state.

good luck with what ever you choose;

Traction Fan :smilie_daumenpos: Sorry about double posting the files. I went into another thread and saw that I had already sent them to you. I tried to delete them from this thread, but I wasn't able to make them go away.


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## Treozen (Jan 22, 2019)

traction fan said:


> Treozen;
> 
> I get the impression that you may be more interested in building something that resembles the "track plan" of a real railroad. Is that correct?


Essentially, yes, but with some caveats. Basically I want to build something "in the spirit of" a real railroad - something that has drawn its influence from the real thing, but has made accommodations for size, complexity and fun - an example is that I do want some sort of continuous loop - not something you see much in a real railroad. 

When I started down this path, I just wanted a layout that was "northwest" in theme, but as I gather information, I'm thinking more and more about drawing on the local PCR through Black Diamond as inspiration. 





traction fan said:


> If you can post a scale drawing of your available space, some of us could perhaps advise you better.


See attached image "railroad size"



traction fan said:


> Thanks for the photos of the Pacific Coast Railroad. I model some of the same area of Washington state.


I've attached a few other things you may find interesting. 

1) Black Diamond area of the PCR, around 1926. Yellow highlight is the railroad

2) Black Diamond as it is today - found as much of the railroad as I could

3) A hand drawn map of the entire PCR, circa 1958. The red circle is the part I'm looking at as a guide, although I would like to include the bridge by Dowlings Cut.

4) Black Diamond train depot / passenger platform - 1910

Allan


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