Trains.com

Subscriber & Member Login

Login, or register today to interact in our online community, comment on articles, receive our newsletter, manage your account online and more!

15 and 18 inch radius curves

36974 views
48 replies
1 rating 2 rating 3 rating 4 rating 5 rating
RA1
  • Member since
    August 2009
  • 3 posts
15 and 18 inch radius curves
Posted by RA1 on Monday, August 10, 2009 10:21 PM

I only have a small corner of the basement to devote to my model of the Western Maryland, circa 1965.  I know that larger curves, like 22 or 24 inch radius, are best, but in my limited space, that isn't always practical. Assuming that I intend to run locomotives like the F7 and 50 foot boxcars and coal hoppers, can I get away with 15 and 18 inch radius curves on some of my tracks off the mainline?  Will it help if I ease into the curve with 18 inch radius track on each end and only use 15 inch radius in the middle of the curve. 

  • Member since
    April 2003
  • 305,205 posts
Posted by Anonymous on Monday, August 10, 2009 11:17 PM

 Try to avoid 15" radius curves in any case - 18" is fine and should work with 50" cars. Aside from looking really toy-like, 15" curves are a likely source of derailments.

If you have the option, go for N scale. 15" curves in N scale equal 27.3" in HO scale!

  • Member since
    February 2005
  • From: Vancouver Island, BC
  • 23,326 posts
Posted by selector on Tuesday, August 11, 2009 12:40 AM

Sir Madog
If you have the option, go for N scale. 15" curves in N scale equal 27.3" in HO scale!

Yes, I would agree.  You can get away with 15" radii in industrial tracks and small switcher motors when you are pushing a single 40' boxcar in HO, but any passenger cars, with the possible exception of Overtons/Shorties, are not going to work well at all.  You could use a Life Like Heritage 0-6-0 steamer on 15" curves, I am pretty sure, but anything bigger would be an exercise in frustration.

The fact is that the standard smallest curve in HO is the 18" curve.  If you are really pressed, why not give N scale a good look and enjoy better operations and visuals?

-Crandell

  • Member since
    February 2005
  • From: Southwest US
  • 12,914 posts
Posted by tomikawaTT on Tuesday, August 11, 2009 12:44 AM

Caveat:  I run very short 1:80 scale equipment on my 350mm (<14 inch) radius route - tank locomotives and cars about the size of a Minnesota ore car.  Anything longer is embargoed - which isn't a problem, since the mainline curves are 610mm (24 inch) and up.  I don't have to run container cars and such up to the coal mines.

Contrary to popular belief, one length of 18" radius sectional track doesn't do much toward easing the entrance to a 15" radius curve.  Using a 'fixed radius segments pretending to be a proper spiral easement,' the late Ed Ravenscroft came up with a radius ratio set of X / 1.5X / 3X / tangent.  Substituting 15" for X, you would need one carlength of 22.5" radiius and one carlength of 45" radius.  Personally, I find it easier to use flex track and lay an honest spiral easement.

If you had said 40 foot cars, I'd say you can snake them around a 15 inch radius.  50 footers would be pushing your luck.  The best way to find out would be to assemble a test curve with 15 inch radius sectional track and one length of flex at each end, put your train on the flex and run it onto the curve.  If it can make the curve, both pulled and pushed, you're good to go.  If cars bump corners or leap sideways off the rails, well, back to the drawing board (or CAD program, if you're using one.)

Chuck (Modeling Central Japan in September, 1964 - with short cars on tight curves)

  • Member since
    November 2006
  • From: huizen, 15 miles from Amsterdam
  • 1,484 posts
Posted by Paulus Jas on Tuesday, August 11, 2009 2:20 AM

Rai

I did it (14"), John Allan did it (13", on his oldest layout), Marklin is doing it all the time.

John Armstrong found a 1:2 ratio between the longest car and the min. radius just acceptable.

But all depends, I used short trains( 5 foot max) powered by geeps or switchers only. Test running over a short 4,5% grade and the small radii with 20 cars ( 80% 40-footers) in tow was no problem at all.  Pushing with low speed neither; the boy's tried pushing at full speed; with predictable results. I just had to make sure only "cheap" Athearn's with a few cars in tow were on the pike before I let the monsters in. I must have been a lucky man; never had one of my brass engines  on the floor.

The classical trade off you'r in. The heigth of your layout is also important; the ravine will be deeper,  when your pike is build high enough ( 4' 8" ), you won't notice the small radii that much. A birds-eye view can be unpleasant indeed.

What are you up too?  A switching pike in an urban area  or the last miles up to the mine (small radii and engines, low speeds) or a branch in a rural area (moderate 24" radii and larger engines, medium speeds)? The WM had it all.

Have fun taking the decission

Paul 

 

   

  • Member since
    April 2003
  • 305,205 posts
Posted by Anonymous on Tuesday, August 11, 2009 5:50 AM

Paulus Jas

I did it (14"), John Allan did it (13", on his oldest layout), Marklin is doing it all the time.

 

I have to add another My 2 cents to the issue. Small radii curves are quite common in Europe, but so are short wheelbased cars. Bigger cars with trucks have truck-mounted couplers, allowing them to negotiate the Marklin standard radius of 14.2 ". They even built the "Big Boy" to be able to negotiate that curve! I dare to say that it looks stupid, although the operation is safe - no derailments.

US outline cars usually have body mounted couplers which require a bigger radius - 18" should remain the minimum!

  • Member since
    June 2003
  • From: Culpeper, Va
  • 8,202 posts
Posted by IRONROOSTER on Tuesday, August 11, 2009 7:05 AM

 If you have room to use 18" radius for "easements" then you could use flextrack for a curve a little larger than 15", say 16".  I would do that. 

While 15" is usable be prepared to use short locomotives and cars, tinker with locomotive and cars, have near perfect trackwork thru the curve, and run at very slow speeds.

But hey, if that's all the room you have, then go for it.

Enjoy

Paul

If you're having fun, you're doing it the right way.
  • Member since
    January 2006
  • 621 posts
Posted by dsmith on Tuesday, August 11, 2009 10:57 AM

I used flex track on my 4' x 6' layout and have curves that are 11" - 15" radii and includes steep inclines and declines.  I even run short passenger cars with no problem, although they look a little odd on the tight curves.  The only modification I've had to make is filing out the engine trucks a little so the trucks will turn tighter and occasionally filing coupler holders so they rotate farther.  The short engines and cars work great.  Here is a video showing the layout in action.

http://www.youtube.com/watch?v=xkArgyfouo4

  David from Dearborn  

  • Member since
    October 2007
  • From: Wisconsin
  • 378 posts
Posted by Wikious on Tuesday, August 11, 2009 11:31 AM

 It's been mentioned before, but I felt the need to weigh in, too. Geeps and 50' cars work just fine on 18" radius curves. (Fortunately, my prototype uses many of these). You can push it with 6-axle locos like an SD40 and up to 60' cars, but they start to look a bit funny and may derail/uncouple.

  • Member since
    February 2008
  • From: Sunny SoCal
  • 423 posts
Posted by Margaritaman on Tuesday, August 11, 2009 11:54 AM

Click on the link to my layout.  All 15" and 18" curves except for one long spur that is about 22".  No freight over 40'.  It's all how you lay the track down and scenic it.

  • Member since
    April 2003
  • 305,205 posts
Posted by Anonymous on Tuesday, August 11, 2009 12:06 PM

 Very nice layout, Margaritaman! I really like it - and agree, that 15" can be ok for layouts with a logging theme and the use of geared locos!

  • Member since
    December 2008
  • From: Heart of Georgia
  • 5,406 posts
Posted by Doughless on Tuesday, August 11, 2009 8:09 PM

RA1

I only have a small corner of the basement to devote to my model of the Western Maryland, circa 1965.  I know that larger curves, like 22 or 24 inch radius, are best, but in my limited space, that isn't always practical. Assuming that I intend to run locomotives like the F7 and 50 foot boxcars and coal hoppers, can I get away with 15 and 18 inch radius curves on some of my tracks off the mainline?  Will it help if I ease into the curve with 18 inch radius track on each end and only use 15 inch radius in the middle of the curve. 

When experimenting with a tight industrial area, I used two sections of 18 inch radius with a section of 15 inch radius in the middle (standard Atlas code 83 sectional track).  I found that a cut of 50 ft cars pushed slowly took the one section of 15 inch just fine, but Athearn BB 54 and 55 footers rubbed on the inside.  I filed some of the center ridge material along the bottom of the others to allow the truck to swing farther, and that cured the rubbing.  I didn't want to do that to all of my rolling stock so I decided not to go with the 15 inch section.  Didn't notice a problem with the Athearn BB gp38. 

I'm sure negotiation of radius has to do with how far the trucks can rotate.  Probably differs slightly from product to product. You probably won't know which car will work on the 15 incher and which one won't until you run it.

18 inch radius should not cause problems with F7's and 50 footers. 

- Douglas

  • Member since
    February 2002
  • From: Mpls/St.Paul
  • 13,840 posts
Posted by wjstix on Wednesday, August 12, 2009 12:52 PM

RA1

I only have a small corner of the basement to devote to my model of the Western Maryland, circa 1965.  I know that larger curves, like 22 or 24 inch radius, are best, but in my limited space, that isn't always practical. Assuming that I intend to run locomotives like the F7 and 50 foot boxcars and coal hoppers, can I get away with 15 and 18 inch radius curves on some of my tracks off the mainline?  Will it help if I ease into the curve with 18 inch radius track on each end and only use 15 inch radius in the middle of the curve. 

One thing to keep in mind is that even 22"-24"R curves are fairly sharp in HO...18" is sharp and 15" is VERY sharp. Unless you use truck-mounted couplers you may not be able to run a train thru 15"R curves, at least you may find only some of your equipment will work. In HO "conventional" curves are 24"R, "broad" curves are 30+"R

I assume you're talking about a layout with a "continous run" loop?? If you get away from that, you can run very broad curves. My layout right now is an L-shaped switching layout in the corner of my basement, built on 16" wide shelfs. I am using Kato Unitrack, 31" min. radius curves and no.6 turnouts, so I can run anything on it. Eventually this will be part of a larger layout, but it's quite fun to operate as it is now.

Stix
  • Member since
    August 2008
  • 357 posts
Posted by EM-1 on Sunday, August 16, 2009 7:42 PM

I remember an article by one of MR's editors from sometime in the early 60s.  He got an invite for a 4'X6' layout operating session.  He started the report stating what his initial oppinion was, especially when he found out the layout had 15", 18", and 22" loops.

He reported that after several hours, he had totaly forgotten the small radius curves, 5 or 6 car trains pulled by an Akane Yellowstone among other road engines, and an almost total lack of scenery.  It was an operational joy.

I have to admit my Ambroid 95' Tobaco car does look a bit silly on a 22" curve.  But it sure is something different.  And it goes through Snap switches. Of course, the center frame is trimmed to give the widest possible swing, and the coupler draft gear boxes are similarly modified.

First rule is to thine own self be true.  Most 40 and 50 foot cars, most 8 drivered and even some 10 drivered steam locos will go down to at least 18" radius, my old Mantua 2-8-2 and 4-6-2 locos will operate down to 15" radius,  So will most of the shorty passenger cars, including probably the old Athearn Blue Box 72' passenger cars.

Build the layout to fit the space you have available, select rolling stock that operates reliably on that layout to fit your operating vision, and if somebody objects, give them the old "Corborundum non illegitimi est", loosely translated as "Don't let the B******* wear you down!"  It's your world, run it the way you want.

  • Member since
    April 2003
  • From: Martinez, CA
  • 5,440 posts
Posted by markpierce on Sunday, August 16, 2009 9:19 PM

EM-1

I remember an article by one of MR's editors from sometime in the early 60s.  He got an invite for a 4'X6' layout operating session.  He started the report stating what his initial oppinion was, especially when he found out the layout had 15", 18", and 22" loops.

He reported that after several hours, he had totaly forgotten the small radius curves, 5 or 6 car trains pulled by an Akane Yellowstone among other road engines, and an almost total lack of scenery.  It was an operational joy.

Until you can identify the specific month/year/magazine, I'll continue to believe your memory came from a dream.

Mark (not from Missouri, but might as well have))

  • Member since
    February 2009
  • From: The banks of the St. Lawrence
  • 208 posts
Posted by RailfanS on Monday, August 17, 2009 9:33 AM

myself, I wouldn't go less than 18" unless you're building a logging layout that uses geared locomotives for power or a compact industrial layout that uses 2 axle switchers. I have 1 curve on my L-Shaped layout and it is 18" radius. You shouldn't have any problems running an F7 over 18", I run all my modern mainline locomotives over it without any problems (SD40-2, SD70MAC, Dash 8 40-b, SD90/43MAC, ect). I can even run my GS-4 over 18" although it does look funny. On my off layout mainline (the loop of EZ-track I have on the floor) I use 22" radius because it preforms better with a long string of cars and the engines look better.

It's all up to you. I know how limiting space can be. Just recently I switched from having finances being my main limitation to space being my main limitation (myself I think it's easier to say "I cant afford that" than it is to say "I don't have the space to put that anywhere").

Personally I don't care how the train looks on the curves, as long as the train dosn't fall off the curvesBig Smile.

Good Luck,

Jamie 

Cape Vincent Southern Railroad

HO scale Horseshoe Curve in 5’x10’

My YouTube

  • Member since
    February 2005
  • From: Southwest US
  • 12,914 posts
Posted by tomikawaTT on Monday, August 17, 2009 9:57 AM

markpierce

EM-1

I remember an article by one of MR's editors from sometime in the early 60s.  He got an invite for a 4'X6' layout operating session.  He started the report stating what his initial oppinion was, especially when he found out the layout had 15", 18", and 22" loops.

He reported that after several hours, he had totaly forgotten the small radius curves, 5 or 6 car trains pulled by an Akane Yellowstone among other road engines, and an almost total lack of scenery.  It was an operational joy.

Until you can identify the specific month/year/magazine, I'll continue to believe your memory came from a dream.

Mark (not from Missouri, but might as well have))

Mark, I must have had the same dream.Smile,Wink, & Grin

I vaguely recall that the layout owner had a 'thing' for huge articulateds, and a layout more suited to traction.  In order to change engines, the 0-5-0 shop switcher had to move the line-haul loco to some totally disconnected tracks inside the loops - there was no room for any kind of turnouts to reach them.Whistling

I know from personal experience that running TTTO on a small layout can get so intense that the physical size becomes totally irrelevant.Approve

I also know that an Akane 2-6-6-2 will take a 300mm radius curve.Cool

Chuck (Modeling Central Japan in September, 1964)

  • Member since
    February 2005
  • From: Vancouver Island, BC
  • 23,326 posts
Posted by selector on Monday, August 17, 2009 10:01 AM

But....but.....but a Yellowstone has 16 drivers split between two engines.  15" curves?  

-Crandell

  • Member since
    June 2003
  • From: Culpeper, Va
  • 8,202 posts
Posted by IRONROOSTER on Monday, August 17, 2009 10:31 AM

tomikawaTT

markpierce

EM-1

I remember an article by one of MR's editors from sometime in the early 60s.  He got an invite for a 4'X6' layout operating session.  He started the report stating what his initial oppinion was, especially when he found out the layout had 15", 18", and 22" loops.

He reported that after several hours, he had totaly forgotten the small radius curves, 5 or 6 car trains pulled by an Akane Yellowstone among other road engines, and an almost total lack of scenery.  It was an operational joy.

Until you can identify the specific month/year/magazine, I'll continue to believe your memory came from a dream.

Mark (not from Missouri, but might as well have))

Mark, I must have had the same dream.Smile,Wink, & Grin

I vaguely recall that the layout owner had a 'thing' for huge articulateds, and a layout more suited to traction.  In order to change engines, the 0-5-0 shop switcher had to move the line-haul loco to some totally disconnected tracks inside the loops - there was no room for any kind of turnouts to reach them.Whistling

I know from personal experience that running TTTO on a small layout can get so intense that the physical size becomes totally irrelevant.Approve

I also know that an Akane 2-6-6-2 will take a 300mm radius curve.Cool

Chuck (Modeling Central Japan in September, 1964)

 

I had that same dream also.  I'm thinking it was in the old Bull Session column.

Enjoy

Paul

If you're having fun, you're doing it the right way.
  • Member since
    August 2008
  • 357 posts
Posted by EM-1 on Monday, August 17, 2009 11:14 AM

I can't look the date up right now, I have a 50+ year collection of MR and RMC in boxes in the attic, but I remember the issue was probably between 1961 and 1965.  It was several pages long, with a number of pictures, so it probably was not in the Bull Session, which usually was a single page column.

I seem to recall the Akane Yellowstones were rated, at least in their ads, for 18" radius minimum. I have never had problems running my AHM 2-8-8-2 on 18" radius or through snap switches.  I am curious about the Rivarossi 2-6-6-6 that I bought earlier this year, but haven't had a chance to run yet.

Interestingly, a Trains mag around the same time had a few pictures showing the full sized railroads had problems with curves and tight switches.  The UP was moving one of the last 4-12-2s from a rebuild shop to a museum.  They had to have track walkers watching for derailments at some curves and switches on a main line.

  • Member since
    February 2002
  • From: Mpls/St.Paul
  • 13,840 posts
Posted by wjstix on Monday, August 17, 2009 11:25 AM

selector

But....but.....but a Yellowstone has 16 drivers split between two engines.  15" curves?  

-Crandell

One of the more interesting presentations I ever attended was given by a university professor maybe 20+ years ago at a regional NMRA convention. One of the things he talked about was how people forget that Mallets were designed as a way to get big engines around curves. He had grown up in the coal country in West Virginia and said it was amazing how tight a curve some of those big engines could go around, with a lot of overhang. I think 15"R for an HO Yellowstone might be too much, but still....

Stix
  • Member since
    February 2005
  • From: Vancouver Island, BC
  • 23,326 posts
Posted by selector on Monday, August 17, 2009 6:49 PM

Yes, Stix, and isn't an Akane a brass engine?  It just seems unlikely to me, but I don't have any experience whatsoever with brass engines....nada.

-Crandell

  • Member since
    August 2008
  • 357 posts
Posted by EM-1 on Monday, August 17, 2009 10:04 PM

Akanes are most definitely brass.

I used to drool over their EM-1 at a local hobby shop when they first came out.  $99.98, and I was working an average 20 hours per week at $1.37/hr while going full time to college.  Never could find the money when I could have bought one, and could never find one when I had the money.

The hinging of the two engines on the models nomally lets the model go through much tighter curves than the prototype could.  The front engine rarely has to cary any significant portion of the boiler weight.  And I have often watched DVDs of the Big Boy going through yard trackage and curves, and it seemed to me that the offset on the front engine occasionally swings almost as much as my Y-6 does on 18" curves.  The mechanical limitation is the rigid wheelbase of any of the individual engines.  Some (a lot) years ago, the father of a friend scratchbuilt a PRR 0-8-8-0 from an RMC article in RMC by Bill Schop.  Used the 51" Mantua drivers.  It was capable of 12" curves.  Each engine had one set of blind drivers.

It would be interesting if someboy with a few of the larger, especially brass, would build a small test track with say, 14". 15", 18", 22", and 24" curve segments and run some locos on them as a test.  In this months MR, they list a fairly large 8 drivered locomotive, the MTH J-1 4-8-4 as having an 18" minimum.

I'd say that you have to build a layout to fit the space you have, then select the motive power to fit the curves.  For turn-of-the-Century steam, 4, 6, and 8 driver locos.  For later steam, smaller drivered 6 and 8 drivered locos.  Diesel era, 4 wheeled Geeps, Alcos,things like the GE 44, 45, and 70 ton switchers, EMD SW series.  The old Model Trains magazine even had an article about a shortline that used a small 4 wheeled diesel that looked very close toan old diesel that used to be advertised by the old Penn Line company that was shown off running around a loop of track that used a Silver Dollar for the inner rail.

Just do what makes it fun and enjoyable for you.  If space is limited, don't start taking prototypical appearance too seriously.  You'll never have much satisfation or  fun.

  • Member since
    February 2015
  • 20 posts
Posted by BobVegas on Friday, April 29, 2016 1:56 PM

Hello,

Ok so I also have limited space and just went from Lionel to HO scale, space issues, the wife wanted the garage back! And I have a 4X8 table and want to replicate the layout I had with Lionel to this HO, it will work but only with 15 inch curves. Any suggestions, I really want this to work but I don't and cant get any more room.

 

Rob

  • Member since
    April 2003
  • 305,205 posts
Posted by Anonymous on Friday, April 29, 2016 2:33 PM

15" curves are quite tight and you won´t be able to run anything larger than a 4-axle Diesel and 40 ft. cars, providing you change the couplers from body-mounted to truck-mounted.

Not really recommendable!

  • Member since
    May 2010
  • From: SE. WI.
  • 8,253 posts
Posted by mbinsewi on Friday, April 29, 2016 2:46 PM

Well, OK Bob, first, welcome to the forums, and, you probably could have started a new thread, but no problems, I don't know what your track plan is, but for a "main line" on a 4'x8', you could use 18" radius, which opens up a few more options, but if your plan needs to use 15", when I got back in the hobby, early 80's with my young son, I was able to "splurge" and by a new Athearn SW1200, and it would handle 15", but for cars, if one at a time, nothing longer than 50', but 40' was more the norm for any more cars, such as a train of 4 or 5.

The 15" radius track was short spurs off of a 18" radius oval, that took up the outside area of the 4'x8'.

Mike.

  • Member since
    December 2009
  • 94 posts
Posted by kh25 on Friday, April 29, 2016 3:38 PM

Hello I had been in the progress of building an ho scale 34"×80" layout all main line curves are a little less than 15 curves. I say less because I started with atlas 15R snap track and spread the tie spacing creating curves less than15R I ran 40' and 50' cars the athearn rtr 50' cars ran better than some of the early 50' kits. I used a Bachmann GP7 which ran great on the curves and did not look weird.now the layout is in storage.

  • Member since
    April 2005
  • From: West Australia
  • 2,217 posts
Posted by John Busby on Friday, April 29, 2016 8:39 PM

Always-always avoid R1 curves like the plague thats 14 5/8" for the UK and AU and 15" US.

They turn a model railway into a toy railway and place's far to many restrictions on what you can run.

And the manufacturers don't often put min radius information on the box so it gets very hit and miss when purchasing stock for the railway.

And technicaly a shop only has to acsept returns if something is not fit for purpose and buying something that wasn't designed to go round 15" radius isn't covered by that.

The caviat being in an industrial setting at ultra low speed they (R1 curves) can look right.

A lot of things will still get round 18" at normal track speed however at 15" radius that list gets very short  on what will get round at anything like normal track speed if it gets round at all.

Unless you are doing a very sleepy back water short line or purely industrial line with very small locomotives and cars 15' radius just won't cut it.

Try and get larger curves in visable areas if you can if you can't use the scenery to try and break up the view of the sharp 18" curves.

Thats my 50c + GST worth on the subject

regards John

  • Member since
    October 2001
  • From: OH
  • 17,574 posts
Posted by BRAKIE on Saturday, April 30, 2016 3:05 AM

BobVegas

Hello,

Ok so I also have limited space and just went from Lionel to HO scale, space issues, the wife wanted the garage back! And I have a 4X8 table and want to replicate the layout I had with Lionel to this HO, it will work but only with 15 inch curves. Any suggestions, I really want this to work but I don't and cant get any more room.

 

Rob

 

 

15" curves will work with 4 axle locomotives or a 2-6-0 or 2-6-2 steam engine and nothing longer then 40' cars.

However.

With that said why not use 18" curves which is far better then those 15" curves and will give you up to a small 6 axle locomotive like a SD35 or up to a 2-8-2 and 4-6-2 steam engines 50' freight cars and short passenger cars like ConCor or Athearn.

Larry

Conductor.

Summerset Ry.


"Stay Alert, Don't get hurt  Safety First!"

  • Member since
    February 2015
  • 20 posts
Posted by BobVegas on Saturday, April 30, 2016 2:05 PM

I want to take this 8X12 O gauge and make it a 4X8 or 5X8 HO scale, can it be done?

Here is the link;  http://ctt.trains.com/how-to/track-plan-database/2014/10/big-steam-in-the-coal-fields

 

Rob

Subscriber & Member Login

Login, or register today to interact in our online community, comment on articles, receive our newsletter, manage your account online and more!

Users Online

There are no community member online

Search the Community

ADVERTISEMENT
ADVERTISEMENT
ADVERTISEMENT
Model Railroader Newsletter See all
Sign up for our FREE e-newsletter and get model railroad news in your inbox!