# Getting the radii correct with Flex Track



## tgoulart (Dec 16, 2015)

Getting back in the hobby and have decided to model HO scale using Atlas Flex Track and Peco turnouts. I will have a combination of diesel and steamers (2-8-0). 

When I moved into the current house last year, I inherited an enormous 3x18 workbench in the basement. I plan to convert half of this workbench into (the start of) my train table. The bench is against a wall, so 3x8 of the top will only be accessible from one side.

I know I will be expanding the table to add lobes on both ends to accommodate the curves for a continuous loop design. I would like 2 mainline tracks around the edges serving a small station and 2 industries. Likely one of the industries will be at the end of a spur.

The basic question I have is how do I know the radius of the track I am laying if I use Flex Track? Is there a curve template I can follow? Do I try to figure it out with a compass? I have spent about 30 with SCARM but it originally seems like more work than the output I got.

I've attached a very rough layout. Any comments welcome.


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## CTValleyRR (Jul 26, 2014)

Not sure what you mean by "spending 30 with SCARM". But laying curves with flextrack is fairly simple. You just need a few tools.

First of all, you can buy commercially made radius tools. I believe Ribbonrail, JMD Plastics, and Peco all make them in various radii.

The second way is to form it yourself. You may have a tool called a trammel if you do a lot of woodworking. Basically, this is a big compass -- mine is a set of two points that fasten to a yardstick or any 1x dimensional lumber. A pencil can be substituted for one of the points. You can also make your own simply by drilling holes in a yardstick or piece of lumber.

Remember that the curve radius is to the centerline of the curve. Use your trammel to draw a curve of the appropriate radius, incorporating easements (gradually increasing the radius at the ends of a curve) if needed / desired on your tabletop. Roadbed should be added, butting each piece up against the centerline you just drew. Then install your track, keeping the track center on the center of the roadbed (which will be the centerline you just drew). After a few tries, this process is pretty easy.

One thing that helps me is using MicroEngineering flextrack, which stays curved. I find that much easier to use than other brands, which want to spring back straight, making it harder to hold it's position on the layout.


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## tgoulart (Dec 16, 2015)

CTValleyRR said:


> Not sure what you mean by "spending 30 with SCARM". But laying curves with flextrack is fairly simple. You just need a few tools.
> 
> First of all, you can buy commercially made radius tools. I believe Ribbonrail, JMD Plastics, and Peco all make them in various radii.
> 
> ...


Apologies CTValleyRR. Meant that I spent 30 minutes with SCARM. Thanks for the info about MicroEngineering track. I will have a look. I was set on Atlas, but will do some more due diligence.


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## mesenteria (Oct 29, 2015)

Build a trammel and use it, but use some graph paper and a compass and draw out your plans in scale. 

As explained, an inexpensive trammel can be had with a four-foot length of cedar lathe, the thin stuff only an inch wide. You drill a small hole very close to one end, say within half an inch, and you insert a 3/4" wood screw so that its sharp tip can serve as a pivot point. Next, starting a foot or 18" away, you drill a series of 1/4" diameter holes, smooth all the way through. You first mark each inch point outward after the first 18" mark, and then drill them all to the end of the lathe strip. When you go to make your centerline curve, you simply pick your center of curve, press the screw into that location or somehow lock it from slipping, and then insert your pencil into the appropriate hole further up. Sweep your trammel and make sure the pencil tip draws you a curve of at least 5 degrees past your arc length.

Use only the middle third or so of the curve centerline to hold the flex track in place. Let the ends form a natural easement so that you don't have sectional track-type fixed radii. Flex forms its own easement if you let it. Micro Engineering flex, especially the weathered kind, needs a LOT of shaping...it will NOT form an eased curve on either end of it.


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## CTValleyRR (Jul 26, 2014)

MicroEngineering flextrack is kind of a love it or hate it kind of thing, as you may be able to tell from mesenteria's post. The weathered stuff is definitely tough to form, but for my money, I'd rather spend my time doing that than weathering it. Personally, I think it works out in favor of the pre-weathered flextrack.

It does not form natural easements, as in his description, but it CAN be formed into easements.

Again, this is a very personal thing. I recommend you buy a couple of pieces and try it out, before making a commitment one way or the other.


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## DonR (Oct 18, 2012)

A 2-8-0 is going to be picky about curve radius. 
There has been no mention of your plans along
those lines. For best effect you would want more
than 22" radius.

Have you seen this thread, how to make a beam compass?

http://www.modeltrainforum.com/showthread.php?t=58537

Any thought of DCC? That's the new way to enjoy
your trains. It also makes layout planning easier. You
can have reverse loops, wyes and turntables without
complex wiring, automatically. Another DCC layout
possiblility, single track main line with passing sidings.
You can run 2 trains at the same time, one clockwise,
the other counter clockwise. Impossible with DC.

Don


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## CTValleyRR (Jul 26, 2014)

DonR said:


> A 2-8-0 is going to be picky about curve radius.
> There has been no mention of your plans along
> those lines. For best effect you would want more
> than 22" radius.
> ...


Depends a lot on the manufacturer. I have an IHC Command XXV Consolidation (manufactured by Mehano) that does pretty well on 18" curves, and takes 22" like a figure skater. Overhangs a little, but not badly so.


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## tiger (Dec 16, 2015)

Fascinating topic -- new here, learning a few things.

I had no idea track radius was measured at the centerline.

Interesting talk on the various brands of flex track. I think this product is in my future.

Haven't used my trammel bar for years ("_Nobody knows the trammel I've seen..._"); good to have a use for it.

I've been told there's no lexicon for the forum, but what is an easement?


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## tgoulart (Dec 16, 2015)

Thanks for all of the feedback. I think I am settling on an L shaped 8x8 layout. I decided to chop the current workbench (3x16) in half, add a foot and then add another 3x6 "L" for a pretty nice siding area. I think I will also add casters to the legs so I can pull it away from the basement wall to work on it and then push it back. I will have at least 22" radius curves on the out loop for my steamers and approx 18" on the inner loop for my diesels.

It will be a DCC design using Atlas Flextrack and Peco turnouts (mix or 4 and 6). I'm still in the midst of DCC research but think I will use insulfrog turnouts and power the track(s) at several points along the way.


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## flyboy2610 (Jan 20, 2010)

tiger said:


> I've been told there's no lexicon for the forum, but what is an easement?


An easement is a short stretch of broader radius curved track leading into a tighter radius curve. As an example, say your final curve is 18" radius. With an easement you may have a short piece of 24"radius followed by a short piece of 22" radius followed by your 18" radius curve. This enables the locomotives and cars to 'ease' into the final tighter radius curve as opposed to suddenly being hit with it from a section of straight track. It looks better and helps prevent swaying and derailments.
For a much broader curve of say 48" radius they aren't so important.


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## bluenavigator (Aug 30, 2015)

I get it for easement. Train going into 24" curve then 22" curve then 18" curve, rather than going 18" curve all of the sudden. 

Thank for the clarification and will take that in advisement as I am still working on the layout design.


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## tiger (Dec 16, 2015)

Thanks for the response. So, a turn on a railroad track has an "apex" like a corner on a racetrack? I never knew that, presumed it was constant-radius. 



flyboy2610 said:


> An easement is a short stretch of broader radius curved track leading into a tighter radius curve. As an example, say your final curve is 18" radius. With an easement you may have a short piece of 24"radius followed by a short piece of 22" radius followed by your 18" radius curve. This enables the locomotives and cars to 'ease' into the final tighter radius curve as opposed to suddenly being hit with it from a section of straight track. It looks better and helps prevent swaying and derailments.
> For a much broader curve of say 48" radius they aren't so important.


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## CTValleyRR (Jul 26, 2014)

tiger said:


> Thanks for the response. So, a turn on a railroad track has an "apex" like a corner on a racetrack? I never knew that, presumed it was constant-radius.


Yes and no. Real (prototype) railroads use curves that are much, much greater in radius (proportionally) than our little models. So real railroads don't have to use easements, although they do superelevate them sometimes.

Many model railroads don't use them either -- a starter set, for example, comes with an 18" oval and no easements. I myself am using 24" curves with no easements. However, the tighter the curve, the more likely that your models will jerk into it, at best looking very unrealistic and at worst jumping the track. Using an easement prevents this, or at least minimizes it, and so their use is a recommended practice with tighter radii.


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## mesenteria (Oct 29, 2015)

Some trains had to move their cargo quickly. Priority in times past was meat and silk followed by passengers. Some items were delicate and had to be transported carefully...but still quickly. When the train was going to be doing track limited speeds, say above 65 mph, and the right of way had to wind along a river valley, the curves it encountered would have imparted too much 'lurch', particularly to passengers on their feet, or crew, say in the galley swinging a heavy pot filled with hot oil for fries. So, the curves were eased. The curve is best described as a cubic spiral, and what it does is it allows both the train, and its contents, to accelerate into the path described by the arc in the middle portion, the uneased portion, of the curve. Think about it: the train is doing 79 mph, the maximum permitted in many places for given track conditions when passengers are aboard. It enters a fairly tight curve of maybe 8 degrees, and many passengers are forced into the laps of people sitting near the windows because the curve onset is instantaneous and constant, just like a curve element of sectional track. Now back up and ease that curve from tangent track all the way down to a tight 1000' radius at the central portion, and most people will have lots of time to both steady themselves and to adapt to the curved path when the train repeats its rush around the curve.


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## ED-RRR (Jun 4, 2015)

*Warning --> "Curved" Flex Track..*

Procedure:
When connecting tracks together, a metal track rail connector is required for each track rail..
The correct [Gauge] rail connectors "Must' be also used.. 







Caution:
When using metal track rail connectors on a "Curve", this will happen..
It is fundemental physics that the "weakest" connections will fail..
Notice the (x2) gaps in the picture..
-OR-
The misalingment in the other picture














What I Did - Procedure: (#1)
- Connect (x2) track ends together with (x2) rail connectors
- The (x2) track ends must be straight and parallel 
- Using a [HO] #MLR-5005 Soldering Tool to insure correct alingment (Highly Recommended To Have)
- "Only" soldering the (x2) "Outside" track faces














What I Did - Procedure: (#2)
- After the curved flex track has been permanently mounted
- The (x2) "soldered" locations are still the "weakest" connections 
- Solder is not know for it's strength
- Add (x2) small track nails to each "End" of the connecting track 







.............


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## ED-RRR (Jun 4, 2015)

*"Curved" Flex Tracks (x2 +) --> Parallel..*

Procedure: (#1)
- When using (x2 +) flex tracks in the "Same" curve
- Mark out "All" required "Center Lines" of the track onto the layout table
- Permanently mount "Only" (x1) flex track curve = "Master"








Procedure: (#2)
- Bend the adjasent track to the required track "Center Line"
- Using a [HO-N] #MLR-5002 Parallel Tool. (Highly Recommended To Have)
- Start at the "Beginning" of the "Curve" and permanently mount the track
- Slowly work around the "Curve" using the parallel tool and permanently mount the track







.............


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## Peter Herron (Jun 30, 2015)

*I have had good luck using these guys in O scale........*

......and even though I am hand laying my track, I can see where they would come in very handy for smooth curves in Flex Track in any Gauge. 

http://www.handlaidtrack.com/Fast-Tracks-SweepSticks-Laser-Cut-Track-Form-s/2196.htm

To do an easement for a 22" radius start with a 28" or 30" sweepstick for the first 3 or 4 inches then a 24" for the next 3 or 4 inches then your 22" for the rest of the curve. When ending the curve, go 24, then 28 or 30 (opposite of entry). See the little spaces in the center of the sweepsticks? They are for marking the centerline.

Peter


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## ED-RRR (Jun 4, 2015)

*Warning --> Flex Track To "Switch Tracks"..*

Procedure:
When connecting flex track to a switch track, it is "More" difficult..
The track "Must" be 100% in alingment to prevent any derailments in this small section..
This procedure is "Required" if the switch track "Frog" must be electrically isolated..
The correct [Gauge] --> "PLASTIC" rail connectors "Must' used.. 

The "Green Arrow" = straight through (A.O.K.)
The "Red Arrow" = curved (Warning)
Notice the "Gap" at the curved section 
It is fundemental physics that the "weakest" connections will fail..
Notice the (x1) larger gap in the picture at the "Frog" connection.. (White Circle)..








Procedure: (#1)
- "Only" permanently mount the straight through "Tracks" and the straight through "Switch Track" connections
- Use the "Correct" required rail connectors (x4)
- The (x2) track ends "Must" be straight and parallel 
- Using a [HO] #MLR-5016 Flex Track Alignment Tool. (Highly Recommended To Have)















Procedure: (#2)
- Permanently mount (x1) end of the flex track to the "Curved" switch track
- Use the "Correct" required rail connectors (x2)
- Permanently "Connect" the flex track to the switch machine
- Do the same procedure I have posted in [Warning --> "Curved" Flex Track]
- Add (x2) small track nails to "End" of the connecting track 







.............


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## tooter (Feb 26, 2010)

I remove one rail of a flex track section and pre bend it by drawing it through three offset screws on a scrap of board, and then slip it back into the ties. Makes it possible to generate any radius right down to 6". 



















The track holds whatever curve you give it without any outside restraint. 




























Works slicker than snot. 


Greg


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## emmetd (Aug 1, 2012)

a quick trammel can be made with a cheap yard stick. just drill small holes at each inch mark.
put a nail at the 1" hole and use the hole that is 1" larger than the radii you want.


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## ED-RRR (Jun 4, 2015)

*Accurate Tangent Corners*



emmetd said:


> a quick trammel can be made with a cheap yard stick. just drill small holes at each inch mark.
> put a nail at the 1" hole and use the hole that is 1" larger than the radii you want.


I have a "Thread"..
Build a Beam Track Radius Compass.. 
http://www.modeltrainforum.com/showthread.php?t=58537
-- OR --
Use "Trammel" hardware.. 

Sample "A"..
A sharp pencil has an angled point, requiring "angled" drilled holes..

Sample "B"..
The pencil is "not" correctly secured 90' degree and can/will move during layout..








A cheap sloppy built compass will result with "faulty" markings..
Taking a yard/meter stick and drilling holes into it..
How accurate are the drilled hole locations ??
There is "no" fine accurate radius adjustments..

(#1)
It all depends on how "accurate" an individual wants to layout true 90' degree "tangent" intersection points..

(#2)
When there is an "error" of "only" 1/16" in a "set" radius, the mating radius will be "offset" by 1/8" 








......


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## thedoc (Oct 15, 2015)

flyboy2610 said:


> An easement is a short stretch of broader radius curved track leading into a tighter radius curve. As an example, say your final curve is 18" radius. With an easement you may have a short piece of 24"radius followed by a short piece of 22" radius followed by your 18" radius curve. This enables the locomotives and cars to 'ease' into the final tighter radius curve as opposed to suddenly being hit with it from a section of straight track. It looks better and helps prevent swaying and derailments.
> For a much broader curve of say 48" radius they aren't so important.


My tightest radius is 48" and I still use an easement.


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## thedoc (Oct 15, 2015)

CTValleyRR said:


> Yes and no. *Real (prototype) railroads use curves that are much, much greater in radius (proportionally) than our little models. So real railroads don't have to use easements, although they do superelevate them sometimes.*
> 
> Many model railroads don't use them either -- a starter set, for example, comes with an 18" oval and no easements. I myself am using 24" curves with no easements. However, the tighter the curve, the more likely that your models will jerk into it, at best looking very unrealistic and at worst jumping the track. Using an easement prevents this, or at least minimizes it, and so their use is a recommended practice with tighter radii.



I believe that real Railroads use an easement on curves as well as superelevating the curve.


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## CTValleyRR (Jul 26, 2014)

thedoc said:


> I believe that real Railroads use an easement on curves as well as superelevating the curve.


I didn't mean that in the sense that prototype railroads don't have curves that gradually increase or decrease in radius in a manner similar to that achieved by our easements. I meant that they don't use it so that they can use abnormally abrupt curves like those found on a model railroad. All of the prototype curves I see are so gradual that there is no apparent change in the arc throughout the curve's length.


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