# Curves and Easements



## McMatt

Hi there all,

I'm new to the hobby and I was wondering "Is there any set of rules for curves and easements?" I know that locomotives, carriages etc have minimum radii so that they can get around a curve but this doesn't make them look very realistic. I'm just wondering if anybody could please help me by letting me know if there is a rule of thumb or not when it comes to creating model railway turns?

I'm using the Anyrail to plan my layout and I've been using a rule of thumb that the two easements on either side should be 1/3 of the total turn. i.e. a 90º turn would be 30º of easement, 30º of curve and 30º of easement. 

What do people think? Thanks for your help in advance!


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## broox

Something like this, you mean?








I imagine the Black is how most people would go into the turn.
and Red to be how it should be done.

I have seen a diagram, of the 'correct' measurements. I'll see if I can find it...

EDIT:
I just can't think of the right words to search for. But it was usefull.


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## McMatt

Hi there Broox thanks for your reply! I know to add more realism there should be easements added onto either end of a curve and that's what you've shown with your diagram. I was just wondering if there was a set standard as to how much of a "turn" should be easement and how much should be curve. Thanks!


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## broox

hahaha, always the way. I trawled the MRH e-zine for half hour, punching various things into their search... and thought i'd just do a quick google before I gave up for the night (its 10:30 pm here atm)

I googled the term "track angle offset curve"
and the first result was a PDF file... just what I was looking for... haha

PFD Link here -> http://bellsandwhistles.us/modelrailroading/Clinic06_handout.pdf



> The bent-stick method is very simple, with the steps
> shown in Figure 2. Working with track centerlines, first offset
> the fixed-radius curve from the tangent and establish the
> transition length. Tack one end of the stick along the tangent
> and then bend the stick to match the fixed radius of the curve
> at the end of the transition length. The track centerline can
> then be drawn along the stick.
> Spiral Easement Dimensions in HO Scale
> 
> *Radius of*......*Transition*...........*Offset*
> *Curve*............*Length*........... *Distance*
> 18” ................12” ................3/8”
> 24” ................16”.................7/16”
> 32” ................20” ................1/2”



Excuse my lousy table, but check out the PDF, it is pretty usefull.

cheers and g'night!

Mod edit: language


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## McMatt

Thanks for that link Broox! The interesting thing is that I'm doing my layout with Flextrack and it's a little different I guess when planning using the Anyrail software. As you have to state the angle of your curves and easements. If I had set track curves etc. I would be able to use the above menthod allot easier from what I can see (Though I may be wrong). Obviously I would be able to easily make the distance of 20" but I'm working in angles. If somebody has any further help with my issue I look forward to hearing from you. Thanks all! 

P.s. Broox i'm to the east of you a little so I'm half an hour in front


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## sstlaure

The answer is there is no one answer. The bigger the better on curves. If you want flexibility to run any kind of stock, keep your minimum radii 24" or greater. You'll find that when you design you'll be able to do just about any radii you want, so design for bigger and the operations will look better.


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## broox

Also, in the first installment of the MRH online magazine, on page 45 (gotta download it, no online view for the first few magazine editions), they talk about minimum curve radius for rolling stock, what 'looks right', and what radius is good for reliable coupling on curves, etc.

They had a formula, it was something like, to make it a piece of rolling stock look good on a curve, make your curve radius 2x the length of the longest piece of rolling stock (coupler to coupler). But if you want reliable coupler operation on a curve, make the curve radius 2.5 to 3x the length of of the car you want to couple/uncouple.

I don't think I got that formula too wrong, but I'm on my phone atm, and the article is on my pc so i'll double check this arvo after work.


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## norgale

Broox that's a really great link to building specs for our railroads. very informative. Thanks for posting it. pete


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## broox

McMatt said:


> Thanks for that link Broox! The interesting thing is that I'm doing my layout with Flextrack and it's a little different I guess when planning using the Anyrail software. As you have to state the angle of your curves and easements. If I had set track curves etc. I would be able to use the above menthod allot easier from what I can see (Though I may be wrong). Obviously I would be able to easily make the distance of 20" but I'm working in angles. If somebody has any further help with my issue I look forward to hearing from you. Thanks all!
> 
> P.s. Broox i'm to the east of you a little so I'm half an hour in front


I'd use the anyrail as a good guide, but it might be hard to follow it 100% in the real world.
Are you laying your track on a solid board? It should be easy to sketch out the track plan on that before laying anything.
If you know it should work in Anyrail, then you can make it work in the real layout.

Choo Choo (member here) has a good guide of pre bending flex track. It still retains its flexibility, but its new 'natural' state is in a curve (of whatever angle you choose)
I'll see if I can track it down for you.
[edit] heres the link http://www.modeltrainforum.com/showthread.php?t=3931

Also,
Have you worked out your minimum radius yet?
The article I mentioned yesterday is in this issue link -> http://model-railroad-hobbyist.com/magazine/mrh-2009-Q1 (16mb download, but worth it)
The article, "Powerful new curve radius insights for any scale", starts on Page 45.

A couple of usefull excerpts. But theres plenty of pics in the article, it is worth checking out. 


> Ratio Guideline description
> 2.0 x Some equipment may track reliably, but 2x is generally considered pushing it.
> 2.5 x Most equipment will track reliably if everything is of similar length.
> 3.0 x All equipment should track reliably; coupler performance adequate if altered to allow 50% car width swing.
> 3.5 x Equipment will look less toy-like when viewed from inside the curve.
> 4.0 x Equipment will look less toy-like when viewed from outside the curve.
> 5.0 x Most reliable coupling on curves with body-mounted couplers and near-scale draft gear boxes.





> HO 43 foot cars
> 2.0x 12” radius
> 2.5x 15” radius
> 3.0x 17” radius
> 3.5x 21” radius
> 4.0x 24” radius
> 5.0x 30” radius


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## New Berlin RR

here is one rule of thumb so to say that I always run by, and thats "if you plan to upgrade your curves/layout to a larger size in the future plan for that upgrade from day one"

Meaning if I know one day I want to run engines that need 22" curves then from day one even tho I may have 18" curves now I have it planed out with the 22" (or 24") in mind so when that time comes I have to do minimum work when swapping out the 18" curves to the 22" (or 24"). it just makes it simpler in my honest opinion here...also make sure you plan for the largest loco you plan to get, same principal...if your planing to get a big boy one day then make sure your thinking has that big boy in mind at all times when designing your layout!!


anyways theres really no right or wrong way to do thing, there is only the fun way to do things...


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## broox

Hey man, just had an idea. You could do a little cheating with the Anyrail program (and save some maths in the process.)

When you lay the track in Anyrail, offset it by half a track width (or what you reckon is required) at the start of the curve, so you know that it works with the space you're allowed to use.

Like so. 








Just pretend for now that it joins with the appropriate easement (is that the right word? I dunno.)

Then when you're laying it on the table for realsies, get 2 pieces of flex. Lay them just like in the picture... All offset and stuff.
Pretend these _lousy_ pics are real life flex, I dont have any flex handy to demo my idea.










Then put a tack in each piece of flex track 8" (or what you reckon is required) each side of the offset, where they are supposed to meet. 










Smoosh them together so it forms the correct angle. Tack it. Mark it on the benchtop (tracing skills, yo). And replace with a complete section of flex so you dont have to deal with joining on a curve.










Take that, highschool maths teacher, who needs real world math skills now. :sly:


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## McMatt

Thanks for the feedback folks! I take a read through and get back to you all! I'm just on here now to have a quick browse and need to head off to bed.


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## McMatt

That magazine had some very good material in it. Thanks Broox! Thank you for your contribution too New Berlin!

I'm using a whole heap of Australian stuff to use on my layout. I'm currently planning everything as I'm not ready to build due to room constraints. My minium radius needs to be 24" (Recommended by the manufacturer of the product). Although I'm going to wait and see when I get it to measure from coupler to coupler and then use that magazine information to see how it would go on my layout with the current plans.

Thanks everybody for your help!


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## rrgrassi

IF the MFG recommends a 24" minimum, then that is what you should go with. I tried to get around a 22" minimum radius, and had nothing but problems with derailing.


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## McMatt

rrgrassi said:


> IF the MFG recommends a 24" minimum, then that is what you should go with. I tried to get around a 22" minimum radius, and had nothing but problems with derailing.


They recommend the 24" for the carriages to run on but I think I'm going to wait until I get the carriages to measure from coupler to coupler and use the maths provided in the linked magazine to determine the best radius for them.


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