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15" radius

Started by mf5117, October 02, 2009, 01:46:05 PM

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Are 15" radius curves , rescipe for disaster . I was wanting to add on to the layout again . And wanted to add an L to the 5x9 ft layout . 18" is to large , due to space . I could make it . But would have to put a fold up with 18" radius on the L part . I could do what "I would like todo" with 15" radius . But I'm not sure if 50ft stock could handle the curve's and my sd40-2's .         What are the smallest rolling stock ft wise and engine that can handle a 15" radius                AS you know , I have gp 40's , ft-a , gp-35 and sd40-2's not worried about the switchers .  also pulling a 6 or 7 car string would it get pulled off around and threw the curve . "derails"    thanks    Mark f


I have a 15" radius loop on my layout.  I use it for small equipment (ore cars and the like).  However, I have discovered that all my GPs will negotiate the curves, even when double-headed.  My baby trainmasters go around fine as well.  My smaller SD's (7 thru 38) will negotiate the turn alone, but cannot pull any cars (too much coupler swing).

All rolling stock 40' and less will go around fine, even in long cuts of cars.  While the 50' stock will go around, I can only pull a couple at a time (they start to pull each other off the track.

I also use a 1/3 piece of 18" radius track to start the turns--an easement of sorts...




If we are talking about HO I think the SD40-2's will likely not work well, if at all, on 15". Going around the 18" curves on my layout have the couplers basically as far as they will go for my SD's. As for 50' stock I could see them working as long as the coupler shank isn't too short. It probably wouldn't be a high speed section of track though.
-Matthew Newman
My Layout Blog


if you want an extension why not build a yard or industrial facility. 15" radius is not going to work with 5 axle power and 50' cars. it is best restricted to small yard switchers, and cars 40' and under.

i know the temptation is there to use ultra small radius curves, i've had it myself. but you are better off staying away from the 15s if possible. the main area of my current railroad is only 54" x48", and i kept the minimum radius to 18' and was able to get a twice around over and under in that space.
Jeffery S Ward Sr
Pittsburgh, PA


I think J Ward hit the wrong key.  5 axle power?  I am sure is not talking about  2-10-0 or 2-10-2.  15" radius is bad news for 3 axle power. 


5 axle
an emd fl9 or perhaps one of the c liners new haven had?

i meant to type a 6.

Jeffery S Ward Sr
Pittsburgh, PA

Jim Banner

Weren't some of the Amtrak C-C SDP40F locomotives modified to A1A-C in an effort to keep them on the track?  Wouldn't that make them 5 axle power?  I suspect there are other examples as well.

But I have to agree with Jeffery.  The lone SD40 (6 axle)on my H0 layout can barely handle 18" radius while the GP40's (4 axle) handle 15" radius with ease.  However, thirty foot switchers look better.  Forty foot cars with body mounted Kadees are fine on 15" radius, at least in limited numbers.  The small branch line that uses 15" curves also has 6% grades and two switch backs which limit the numbers of cars.

Growing older is mandatory but growing up is optional.


HO TRACK     I didn't think it would be a good idea . I was surfing the net and saw a layout I liked for expantion . I'd like to put some sort of grade in . I was thinking the radius in the L part was 18" but after some calculations turned out to be 15" . So I still sit here scratching my head going what can I do . I thank you for the input . I kinda figured that would be the answer . But I thought I would ask .

My room that the trains are in is 9-6 x 12 ft  . I like being able to get in and around to the otherside of the bench and work on it when I need . When my son finishes collage I'll move the trains into that room . It's 11x15 . Thanks again Mark F


to answer your question, no matter the modifications made the sdp40f was a 6 axle locomotive. to a railroad this is an important distinction as it determines where a locomotive can go. on many lines 6 axle locomotives were restricted from certain branch lines because of curvature or track conditions.
Jeffery S Ward Sr
Pittsburgh, PA

Jim Banner

I agree, the sdp40f is a 6 axle locomotive.  But when only five of the axles are powered, it becomes 5 axle power.  Similarly, a C-C locomotive is a 6 axle locomotive and so is a A1A-A1A locomotive.  But one is 6 axle power and the other is 4 axle power.  At least that is the way they seem to use the term up here.  It becomes important when there is a limit on the number of powered axles allowed on particular trains or tracks.

Growing older is mandatory but growing up is optional.


15" radius is not a recipe for disaster.
However it does place some limitations on what you can do as far as train size and type goes.
Small locomotives and rolling stock are a must.
Also track work must be done to perfect+ standards to make sure you don't have problems.
That slight defect that is not a problem on a six foot radius curve will most certainly be a problem on a 15 inch curve.
Trains will be short or you will end up with the bow string effect.
Tight radius curves on a layout need carefull scenic work one to show why the curve is so tight and also so you don't end up wiping out telegraph poles etc on the line side.
The extra work involved with tighter curves is worth it if that's what you want just be AWARE of the limitations it imposes.
regards John
A model railway can be completed but its never finished



This is a penalty of using a tabletop layout. Can't you go around the walls-- longer run,larger curves and easy access to all parts. Can use a waterwings type layout to avoid a duckunder at doorway.
Or change to On30.LOL
I am in On30 and on my previous layout had one (hidden) end of the loop laid with Peco Setrack No.1 radius (14 5/8"). Regularly ran a BLI C-16  2-8-0 pulling 3 Bachmann passenger cars with no trouble.

Eric UK