# 20 FT "S" CURVE



## John J (Dec 29, 2007)

I am putting in a S curve using 20 ft diamater track. Do I need a "Transistion" track? A straight piece between the two curves. Does Body Mount couplers as compaired to Truck Mount couplers have any effect on if I use a Trasistion Track? Such as with Body mounts you don't need a trasistion track and with Truck mounts you do.


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## steam5 (Jun 22, 2008)

*RE: 20 FT "S" CURVE*

I think they generally recommend a straight section as long as your longest car, usually a passenger car. 

As you’re using a broad cure, it may not be necessary; I’d suggest laying it out and giving it a shot.


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## Dave F (Jan 2, 2008)

*RE: 20 FT "S" CURVE*

I have a couple on my layout. I have a quick "S" behind my shed that is a 6' diamater that's just not workable, causes no end of headaches. I'll be replacing that in the spring. 

BUT.. (a big but).. I have a 12' diameter "S" on the mainline that works just fine. Seems like the larger curves are gradual enough to be workable.


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## blueregal (Jan 3, 2008)

Posted By John J on 12/30/2008 5:19 PM
I am putting in a S curve using 20 ft diamater track. Do I need a "Transistion" track? A straight piece between the two curves. Does Body Mount couplers as compaired to Truck Mount couplers have any effect on if I use a Trasistion Track? Such as with Body mounts you don't need a trasistion track and with Truck mounts you do. 

jj save yourself alot of grief and do it right the first time and put a straight track in there. The Regal


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## Marauderer (Jan 5, 2008)

*RE: 20 FT "S" CURVE*

with 20ft dia. I wouldn't worry about it and if you are pulling a long consist body mount couplers are better as they let the trucks float and not tend to derail


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## Semper Vaporo (Jan 2, 2008)

Posted By John J on 12/30/2008 5:19 PM
I am putting in a S curve using 20 ft diamater track. Do I need a "Transistion" track? A straight piece between the two curves. Does Body Mount couplers as compaired to Truck Mount couplers have any effect on if I use a Trasistion Track? Such as with Body mounts you don't need a trasistion track and with Truck mounts you do. 






I have a big "S" curves with 8.5 ft radius and no intentional straight section in the middle and have had no problem with truck or body mounted couplers. It will depend somewhat on how much side play is in the coupler mounts and between couplers and how close the cars get coupled (length of coupler shank). But, 10 ft radius is a pretty big radius and I doubt you will have a problem without a straight section.


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## John J (Dec 29, 2007)

I am correcting a mistake I have been ingorning for about 5 years. The container train has brought it to a head. 

This is a picture of what did earlier. Since this pic was taken The rock mountians have been installed. But now I still got something to fix.

I am taking pictures as I go but it will be a while before I post them. 











The New Grade and S curve wtill take me out to where that creosote bush is by the car.


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## aceinspp (Jan 2, 2008)

It's best to use a transitional piece of tangent track much like the real RR do. It's almost a requirement to prevent even the the slightest possibility of a derailment. I have 8 ft diameter S curve with a two ft straight between them. It's needed to operate the USAT pass cars. Better to do the track work right instead of pulling out what hair you may have and haveing to redo your track work. If room is availble do it. Later RJD


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## Paul Burch (Jan 2, 2008)

JJ,
If you have the track why not just find a level place and do a test setup? Then you will know for sure what will work or not. I would probably use some straight in there anyway just because it will look better to the eye.


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## jimtyp (Jan 2, 2008)

*RE: 20 FT "S" CURVE*

I have a couple of S curves. All the ones less than the 20' diameter caused me problems. The 20' I've never had an issue.


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## Dean Whipple (Jan 2, 2008)

Posted By John J on 12/30/2008 5:19 PM
I am putting in a S curve using 20 ft diamater track. Do I need a "Transistion" track? A straight piece between the two curves. Does Body Mount couplers as compaired to Truck Mount couplers have any effect on if I use a Trasistion Track? *Such as with Body mounts you don't need a trasistion track and with Truck mounts you do*. 




JJ,
It's just the opposite....truck mounted couplers will be more forgiving in a 'S' curve, however with 20 foot 'S' either type of coupler mounting should work just fine however a straight section will look better and will for sure eliminate the possibility of any problems in the future....


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## fildowns (May 17, 2008)

I have an S made from 12.5ft dia curves without transitional straight. I can pull and push my Aristo heavyweights through it with no problems at all. They are fitted with body-mounted KD 789.










The join between the two curves is just a tie-space off the piture to the right.


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## Nicholas Savatgy (Dec 17, 2008)

Posted By Dean Whipple on 12/31/2008 10:58 AM
Posted By John J on 12/30/2008 5:19 PM
I am putting in a S curve using 20 ft diamater track. Do I need a "Transistion" track? A straight piece between the two curves. Does Body Mount couplers as compaired to Truck Mount couplers have any effect on if I use a Trasistion Track? *Such as with Body mounts you don't need a trasistion track and with Truck mounts you do*. 




JJ,
It's just the opposite....truck mounted couplers will be more forgiving in a 'S' curve, however with 20 foot 'S' either type of coupler mounting should work just fine however a straight section will look better and will for sure eliminate the possibility of any problems in the future....




I would agree, put a piece of straight track in for piece of mind..
Nick


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## fildowns (May 17, 2008)

Posted By John J on 12/30/2008 5:19 PM
I am putting in a S curve using 20 ft diamater track. Do I need a "Transistion" track? 





No, you don't need one. Don't sacrifice your 20ft curves and put tighter radius with a transition straight. There are no cars known to man that will not navigate an S made from 20ft curves even with body mount couplers. 20ft curves make a graceful S whereas 10 or 12ft with a straight in between looks clunky in comparison. Don't be put off by the scare stories it may have been true in Radius 1 and 2 days but everyone is putting in wider curves now and the fact is these longer cars and 6-axle diesels have no problems with S made from them.


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## NTCGRR (Jan 2, 2008)

*RE: 20 FT "S" CURVE*

JJ you have the room, make it so it will be the safest way possible.


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## Greg Elmassian (Jan 3, 2008)

*RE: 20 FT "S" CURVE*

Another opinion: 

If you were running a loco and cars that required 20 foot curves, then I would think you would not want an S curve. I would guess things like Aster 1:32 locos, a big boy, etc. 

But as fildowns says, you (probably) do not need to worry because almost everything else would shrug off an S curve of 20' radius. 

Now, I have been talking operation only. 

Appearance wise, I think back to back curves look toylike no matter what the radius. Also, if you are considering having your layout look prototype, I believe (R.J. ?) that prototype railroads ALWAYS had tangent track between curves of opposite direction. 

So, if it was me, I would find a way to put a short amount of straight/tangent between the curves. 

Regards, Greg


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## fildowns (May 17, 2008)

Yes you may need one on aesthetic or prototypical grounds, just not for physically reliable operation. As to whether you think '10ft left+straight+10ft right' looks less toylike than '20ft left+20ft right' that is, as is a lot of things, a matter of opinion and personal preference. 

I once saw someone's careful trackplan of 16.5ft curves with a short 1ft straight between them changed because he was bombarded with comments about "Ess bends with a straight shorter than the longest car possible are the spawn of Satan" (something along those lines...I'm probably exaggerating there...) His alteration to 8ft curves with a much longer straight was in my opinion a much more toylike substitute. From a graceful sweep that should have been a major photogeniic location on his railway now looked like a straight with horrible right-angles at each end, like it was taken straight off the living room carpet. And why? Well even though he was NG he "might want to run standard gauge with big pass cars one day..."

If we all had to go prototypical we certainly wouldn't be using 'toy-like' 20ft curves on the main!


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## docwatsonva (Jan 2, 2008)

John,

Perhaps you could clamp the 2 pieces of curved track together and run a Train-li railbender over the junction to create a smoother transition between them. You'd have to reverse the railbender on each side and only run it to the join and stop. You might only have to slightly straighten each curve about 6".

Just a thought.

Doc


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## Randy Stone (Jan 2, 2008)

*RE: 20 FT "S" CURVE*

Happy New Year all 

I just got my main line up and running today. 

It has all 8 foot diameter curves with an s curve and my little 2-4-0 Steamer pulling 14 MDC empty hoppers and an Aristo Craft bobber caboose are doing fine through it.


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## John J (Dec 29, 2007)

*RE: 20 FT "S" CURVE*

I went out this moning fired up the back hoe. Used the loader to scrape off a bunch of creosote bushes and I am working on the 20 FT cuves again. 
Will post pics at a later date. Mabye in another thread.


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## Paul Burch (Jan 2, 2008)

You have a backhoe? The world won't be safe!


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## John J (Dec 29, 2007)

Hey Paul 
Marty's got a chain saw. He is working on the Nebraska Desert. Me I am all ready in the desert so I am wroking on my Layout.

So far all I have done is rip out the pipe that runs from the Well to the house.







Heck I couldnt see it because of all the dirt that was in the way.


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## Dr Rivet (Jan 5, 2008)

*RE: 20 FT "S" CURVE*

John J 

Go back and read the VERY FIRST RESPONSE from "steam5". It is absolutley correct. With ANY s curve, you should, if at all possible, put in a straight that is long as the longest piece of equipment you expect to operate. This is a "tried and true" rule of thumb used by everyone from N scale to 1.5 in/ft "ride on" trains. I will even risk mentioning that is has been in the NMRA track standards for the smaller scales for at least 60 years. There must be a reason. 

Do not confuse this sort of tangent track between reverse curves with a "transition spiral", often shortened to "transition". This is a gradual indecrease in overall radius when going from straight (tangent) track to a fairly tight radius. You don't really need this if your radius (not diaameter) is more than about 15 feet, or you do not operate at high speed. Even then, It is mostly a visual asthetic issue untill you get down to about 10 feet. At that point, operational issues intrude, and you do risk a high speed derailment. At "normal" speed, the engine will just lurch into the curve, reminding you that you are running toy trains.


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## Dr Rivet (Jan 5, 2008)

*RE: 20 FT "S" CURVE*

OOPS! 

I just reread your post. You say 20 foot DIAMETER, or 10 foot RADIUS. NOW the answer is absolutely YES, if you have any rolling stock that has body mounted couplers. The longest car "rule" is more important in this case too. 

As others have said, if you run short trains, slow trains, and have all truck mounted couplers, this is less important. BUT, if you have lots of visitors, consider the type of equipment that they may want to run on your layout. 

Happy New Year


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## steam5 (Jun 22, 2008)

*RE: 20 FT "S" CURVE*

Jim, Thanks for the support. It appears where on the same train of thought. 

A reliable running layout in all gauges starts with track work; the extra time an effort spent on the track work will pay off in the long run,


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## chaingun (Jan 4, 2008)

*RE: 20 FT "S" CURVE*

Hey JJ, 
You've seen my layout and over by the pond I have a series of S curves with no straight section and I have no idea what the radius is on them except I know they are way less than 10 ' - around 8 I think. I run body mounted couplers and 4 & 6 axel locos. The only problem I have is I am limited to 3 sets of Intermodel & 2 singles (double stacked) cars. I can run 5 sets empty no problem. If you go 20' radius I think (scary huh?) you will be fine. 
FYI : As an X - heavy equipment operator I believe if you aren’t tearing something up you are just not tiring hard enough. 
Best, Ted


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## livesteam53 (Jan 4, 2008)

JJ,

Here's my 2 cents...
I have had a S curve on my layout for a few years until last year. After starting to run larger and longer trains I took it out and added a 3' straight. Now I never have a problem and feel that it is better not to have a true S curve on any layout.


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## railgeek (Jan 15, 2008)

*Hi, 
Rule of thumb on S-curves is the striaght section between the curves should be at least as long as the longest loco or piece of rolling stock/pasenger car that will be running through the curve. As an example, the 3 foot long USA streamliners, straight section should be as long as the overall lenght of the car including couplers. Also, transition curves help. 
Thx, 
Marc


*


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## John J (Dec 29, 2007)

Well Yesterday I removed all the forms. I put track guides on the bridge to keep the track centered.

Today  I hope to do some cleanup, lay track and later on this after noon take a over head shot from a tall ladder.

I will also try and draw a track plan to post.

I always lay track first and then draw a tack plan that way the plan turns out exactly the way I vinsioned it.


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## Randy Stone (Jan 2, 2008)

*RE: 20 FT "S" CURVE*

While I've had little problems with my 8 ft dia s curve where my mainline travels around the hot tub, today my bobber caboose took a dive to the bottom of the hot tub. Why, well being on the tail end of a 15 car train, the caboose is getting whipped around like the last car of a roller coaster. The caboose is leaning to the left as the train travelsd through the right hand curve. But as the caboose travels through the transition from right hand curve to left hand curve, the caboose goes from leaning to the left to leaning to the right in an abrupt motion. The accelerated motion caused the caboose to raise up off the rail and take a dive. Being the caboose only was coupled to the car ahead by it;s loop, there was no hook to try and keep the car from raising up enough to derail. I tried turning the caboose around so there would be a hook and loop coupler to connect both cars, but the caboose still derailed although it didn't take another dip in the hot tub. Will additional weight help? Who knows, but obviously a pc of straight track between the two curves would help this issue.


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## Greg Elmassian (Jan 3, 2008)

*RE: 20 FT "S" CURVE*

Randy, how light is your caboose? Bobbers can be pretty light. Try for 3 pounds or so, also see if you are having some problem with the hook and loop sliding... 

Bottom line, get rid of the S curve, even 12" would help a bit. 

Regards, Greg


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## rayjturner (Feb 20, 2008)

*RE: 20 FT "S" CURVE*

Before adding weight I would suggest looking for some other source of trouble. A 20' S curve isn't much of an S curve considering these trains are designed to run on 2' radius curves. There may be too much play between the bolsters and trucks. There shouldn't be too much side-to-side movement. Try another similar type car. Try adding another car after the caboose. Check gauge of wheels and tracks. Experiment. Maybe you're going too fast.


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## Greg Elmassian (Jan 3, 2008)

*RE: 20 FT "S" CURVE*

Ray, the title of the thread refers to the S curve on JJ's layout, who started the thread. Randy, (rlvette) is the owner of the spa and the diving caboose. (His spa is not 20' in diameter). 

Regards, Greg


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## Randy Stone (Jan 2, 2008)

*RE: 20 FT "S" CURVE*

I added a 12 inch section of straight track between the two curve sections today. It only got up to 52 degrees out side today, so I didn't run the train to see if the pc of straight track helped or not. Only supposed to get to 54 degrees tomorrow, so I may not find out until this weekend when the temps get back up into the 70s.


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## SteveF (Jan 2, 2008)

Here is a pic of some S Curves on the BNSF just west of Quincy, WA. Note that these curves are much bigger than 20 ft diameter in even !:20.3 scale, and the length of the tangents between the curves.


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## Randy Stone (Jan 2, 2008)

*RE: 20 FT "S" CURVE*

Great picture Steve


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## Greg Elmassian (Jan 3, 2008)

*RE: 20 FT "S" CURVE*

Randy, I have to give you a public compliment. Not everyone would have the guts to show the picture you did! 

You have taken all the ribbing goodnaturedly! 

For april 1 you should put a switch there going off into the water, and put up a "derail" sign! 

Regards, Greg


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## Randy Stone (Jan 2, 2008)

*RE: 20 FT "S" CURVE*

Hey, it was all fun and games until the guy in the caboose drowned.


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## Greg Elmassian (Jan 3, 2008)

*RE: 20 FT "S" CURVE*

You'll have to be running Freds not cabooses, you're probably in trouble with the union! 

Greg


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## Randy Stone (Jan 2, 2008)

*RE: 20 FT "S" CURVE*

Well, if I wasn't in trouble with the union before, I will be now. 12 inch Straight added and still the caboose jumped into the pool taking a second crewman to the botom. This time it tried taking the coal hopper it was coupled to with it. I hooked the other Bachmann caboose up and it goes though the S curve fine at wide open throttle. Time to add some weight to the sinker.


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## Semper Vaporo (Jan 2, 2008)

Posted By rlvette on 02/07/2009 11:17 AM
...
Time to add some weight to the sinker.




Either that or Pontoons!


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## Greg Elmassian (Jan 3, 2008)

*RE: 20 FT "S" CURVE*

Randy, I have to admit that your aim is getting better! You look like you have moved on to shallower waters at least! 

Metal wheels? 

Regards, Greg


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## Randy Stone (Jan 2, 2008)

*RE: 20 FT "S" CURVE*

Yes, I was able to hand winch the caboose back up on the track this go round. Interesting that the only cars that I am having problems with are Bachmann. The caboose and a gondola. I've got a second caboose and gondola both made by Bachmann and they travel through the area just fine. The track is level to the eye and the joints are smooth. No metal wheels. Just cheap plastic. Tomorrow I will check the gauge of the wheels.


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## Randy Stone (Jan 2, 2008)

*RE: 20 FT "S" CURVE*

Well, ain't it funny how we ignore the obvious sometimes. I took the calipers out and started measuring the gauge of the wheels on the Caboose and Gon that kept jumping off the track. As it turned out, the wheel gauge was a good 1/8 inch to wide on both cars. Now, if only I had noticed that the two plastic haves of the wheels had an 1/8 inch gap between them while all the other cars had the haves butted up against each other, I just might have figured this out sooner.


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## work4fil (Jan 4, 2008)

*RE: 20 FT "S" CURVE*

I know this thread is not as fresh as some other topics and JJ is currently updating us with his progress, but I was looking at a picture book I got back in the mid 80's (1980's, not 1880's) and found two "S" curves with no transistion track. The first was at Cisco, British Columbia and the other one was dated 1859 from City Point, Virginia. I am sure argument can be made for the Virginia "S" curve, as rolling stock was shorter, but the Cisco "S" more modern or mid 20th century. Anyway, I was surprised there was no transition track.


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