I know from reading walthers curved turnouts are a bit of a lie just wondering if the same is also true, they are listed as 30" and 22"
This discussion was open on an another forum.
It seems they are not, the real radius are somewhat smaller because the method to calculate the arc seems somewhat obscure; the diverging arc is not a composite of the first arc but an arc used to be compatible with the rest of the geometry Atlas use.
Same remark can be done with Peco track and finaly all the brand of track which are offered on the market.
The best to do is draw them and see what is really the arc, to estimate and draw the needed radius.
But anyway you must live with these radius and all the geometry of the Atlas track system is done to work with these radius.
This is important if you desire to use the full Atlas geometry, but you can go out with ease and have a natural flowing track using these turnouts but going out of the Atlas geometry
If you are asking to have flowing track, may be make a try to the yardstick method.
In fact each group of turnouts or a lone turnout is connected by a piece of track; this connection is straight or curved following your desire and your plan.
The yard stick is a thin piece of wood with a lot of flexibility.
You attach one end at the edge of the ouside track of the turnout with some nuts and slowly you flex the yardstick slowly to reach the next turnout or group of them and you drawn a line along the yardstick.
You have now an extremly flowing track between the turnouts with natural easement and with no care of inside and outside radius from the coming turnout
Just check if the radius is not under the minimum radius you ask to use and you can lay the flextrack to join everything together.
The yardstick work for opening a radius or close it further in the curve
thats know where near what they say why caint any of these manufactures label things the right way.
RR_Mel I took a picture off Google Images of an Atlas 595 and did an insert into my CAD. I sized the picture using the length of a tie and came out with inside curve 24” and the outside curve 36”. Mel My Model Railroad http://melvineperry.blogspot.com/ Bakersfield, California I'm beginning to realize that aging is not for wimps.
Mel,
Wouldn't the actual radius be measured at the centerline of the curves?
Research; it's not just for geeks.
Don Z Mel, Wouldn't the actual radius be measured at the centerline of the curves?
RR_Mel Don Z Mel, Wouldn't the actual radius be measured at the centerline of the curves? Yes but you are talking about less than a ½” and my drawings are only close to accurate not knowing the length of the turnout. Using the width of a tie for reference only gets the radius in the ballpark, if the published Atlas pictures are accurate my dimensions should be within a ½”. EDIT: I used the same process on Peco curved turnouts before I bought a pair to see if they would work for my needs and when the turnouts arrived my drawings were within a 1/16”. The 24” & 36” are only close, the radius to center track measurements are actually 25.6467” & 37.1892” Mel My Model Railroad http://melvineperry.blogspot.com/ Bakersfield, California I'm beginning to realize that aging is not for wimps.
yes a sketche explain more than any discussions, and yes the radius is smaller than the one announced by Atlas.
And this is right for Peco and all the other brands of ready to run track, the annouced radius are not the real ones for the most.
This was also concluded on a similar thread on a another forum.
Seems the answer is because the manufacturer need to use a radius which is able to be used in a universal geometry arrangement of their track system.
But, many seems killed by this news and this seems sometimes to be an insurmountable step to drawn a plan and use these turnouts.
This seems crazy when I explain my method, but I never have take care of these nominal radius of any ready to run turnouts.
Like everybody, I start from a plan, draw the radius I use and make connection between turnouts; the turnouts are placed on the plan and their place is precisely mesured.
This way I have an idea of the space of the arrangements of track.
But when building the track, I put first the turnouts precisely in place as designed on the plan.
Like I mentionned before, I draw my track with a yardstick, this method don't need to take care of the nominal radius, the yardstick connect the turnouts or groups of turnouts together
The only needs is to not go with a radius which is smaller than the minimum you ask to use, but you ended with a track design which is flowing and yes it's not really like the track plan but all together you obtain an excellent trackwork with a ultimate flowing track
More over this method give natural easement and she's easy to use.
This way even if the radius is smaller or bigger than the one announced, all the tracks flow together extremly well; this allow also to mix different brands of turnout with ease and no need of pervers calculations to see if it's work because of different geometry.
Cheers
Marc
when i studied curved turnout geometry for building my own turnout, i couldn't understand how the frog of commercial turnouts were so close to the points. What I found was that this is the result if the curves actually start of different locations
so when looking at commercial curved turnouts, you may need to account for this when measuring the curve radii.
greg - Philadelphia & Reading / Reading
OK, a few facts, a few thoughts.
First I cannot speake regarding PECO, but Atlas Custom Line Turnouts, including the new curved turnouts, are not designed to fit into any sectional track track system of curves. Atlas has no sectional track curves that large.
Side note, yes the straight Atlas Custom Line turnouts do have a geometry that makes crossovers and yard ladders without cutting, but they are straight frog North American geometry and the diverging routes do not match any sectional track curves.
Now that we have that cleared up, the radii chosen for most model curved turnouts is based on a few simple facts.
The main two reasons are simple:
First both radii need to be in a range useful to a large number of modelers......
AND, the two radii need to be different enough to create a frog angle that is sharp enough (low number) to be reliable under NMRA track standards.
Is anyone selling #20 HO turnouts? No, the frog would be too long and would require an operating closing frog in HO.
So the inner route of a curved turnout must diverge fast enough to create something in the range of a #6 (9.5 degrees) or #8 frog (7 degrees), and surely no more than a #12 at just under 5 degrees.
Turnout frogs above #12 can be problematic with regualar NMRA standard wheels/clearances.
You think you have some wheel drop now with semi scale wheels - that's why I don't use them......
So there you have it, the inner radius has to be enought smaller to give a sharp enough frog angle - period.
And yes, the inner curve need not begin on the same radius line as the outside curve, remember, on a prototype turnout, the points and the frog are both straight, points don't curve away, they change direction at a straight but shallow angle.
I have made very large outside radius curved turnouts by simply cutting the tie webs of regular turnouts and bending them.
Sizes like 36" radius and 60" radius.
I have little use for any radius below 36", except as industrial trackage.
Sheldon
gregc when i studied curved turnout geometry for building my own turnout, i couldn't understand how the frog of commercial turnouts were so close to the points. What I found was that this is the result if the curves actually start of different locations so when looking at commercial curved turnouts, you may need to account for this when measuring the curve radii.
coreyhkhthey are listed as 30" and 22"
mel
could you overlay 30 and 22" radii curve onto the image?
instead of using the tie length for reference, could you use the distance between the rails? the spec is between 0.649 and 0.672", 0.660"
ATLANTIC CENTRALAtlas Custom Line Turnouts, including the new curved turnouts, are not designed to fit into any sectional track track system of curves.
i don't believe modelers are trying to replace sectional track with curved turnouts, but they do need to know the radius and where the center is
ATLANTIC CENTRALAND, the two radii need to be different enough to create a frog angle that is sharp enough (low number) to be reliable under NMRA track standards.
without offsetting where the curve starts, the frog ends up being a long distance from the points making the turnout pretty long. Even then, the frog # isn't too large. (i figured out the offset thing after i built the turnout)
gregc coreyhkh they are listed as 30" and 22" mel could you overlay 30 and 22" radii curve onto the image? instead of using the tie length for reference, could you use the distance between the rails? the spec is between 0.649 and 0.672", 0.660" ATLANTIC CENTRAL Atlas Custom Line Turnouts, including the new curved turnouts, are not designed to fit into any sectional track track system of curves. i don't believe modelers are trying to replace sectional track with curved turnouts, but they do need to know the radius and where the center is ATLANTIC CENTRAL AND, the two radii need to be different enough to create a frog angle that is sharp enough (low number) to be reliable under NMRA track standards. without offsetting where the curve starts, the frog ends up being a long distance from the points making the turnout pretty long. Even then, the frog # isn't too large. (i figured out the offset thing after i built the turnout)
coreyhkh they are listed as 30" and 22"
ATLANTIC CENTRAL Atlas Custom Line Turnouts, including the new curved turnouts, are not designed to fit into any sectional track track system of curves.
ATLANTIC CENTRAL AND, the two radii need to be different enough to create a frog angle that is sharp enough (low number) to be reliable under NMRA track standards.
Marc suggested the sizes were selected to fit into brand specific track system geometries, not so in the case of Atlas, very true in the case of other/older European track systems.
Can't say one way or the other about PECO.
Regarding offseting the curve starts, I agree.
My minimum mainline radius is 36, so for me, a curved turnout is most often a function of a track that diverges off to the outside of a 36" or larger base curve.
And in my experiance with hand layed track, that is the best way to build a curved turnout with the inner radius the constant one and the outer radius "diverging" away, just as your drawing shows.
But again, I have had great success simply "bending" regular turnouts for very large radius curved applications.
I have also dis-assembled Atlas #8 turnouts and used the frog and points to build curved trunouts.
here's a comparison of curved turnout geometry w/ and w/o a shift in the starting point of the curve. W/ the offset, a #7.7 frog is 10.1" from the points and w/o the offset, a #8.1 frog is 12.2" from the points. I wouldn't be surprised if the offset is greater. a 2" offset results in a #6.5 frog only 8.7" from the points
Again agreed, but that is also effected by radius, and radius differential.
And by which curve is considered primary and which one is considered diverging.
No doubt the study of a wide range of combinations my prove very interesting. But operationally I think it is always better to consider curved turnouts as diverging outside a minimum curve rather than diverging into a tighter curve.
ATLANTIC CENTRALBut operationally I think it is always better to consider curved turnouts as diverging outside a minimum curve rather than diverging into a tighter curve.
with a regular turnout, which path is considered diverging? which path applies greater force to the wheels.
gregc ATLANTIC CENTRAL But operationally I think it is always better to consider curved turnouts as diverging outside a minimum curve rather than diverging into a tighter curve. with a regular turnout, which path is considered diverging? which path applies greater force to the wheels.
ATLANTIC CENTRAL But operationally I think it is always better to consider curved turnouts as diverging outside a minimum curve rather than diverging into a tighter curve.
But we are not talking about a regular turnout.
If we first consider the wheel/rail relationship in a curve, where in theory we prefer the flange not touch the rail, but we understand it might, the wheel shifts to the outside, increasing the effective diameter on that wheel and steering the axle toward the inside of the curve.
Seems a lot more reliable to have the axle/truck/train in steering mode at a given radius and then relax it as if it is coming out of a curve on an easement rather than asking it to go into a sharper curve.
The likelyhood that possible flange contact would promote riding up at the points or the frog is thereby greatly reduced. Especially considering that no matter what we do, the points are also in theory a small but abrupt change in direction on the diverging route.
So, if we condsider the inner radius the constant radius, and use the curved turnout to diverge outside the given radius, all wheel relationships stay the same as inner curve or are reduced on the outer route, not increased.
With the turnout set to the inner route, wheel forces at the points do not change.
With the turnout set to the outer route, wheel forces move in the direction of less flange contact, not more flange contact.
isn't more force required to accelerate an object along a smaller radius path than a larger one?
gregc isn't more force required to accelerate an object along a smaller radius path than a larger one?
What does that have to do with this question?
The "given" is that we have a minimum desireable radius on the inner route to begin with.
On a regular turnout, thru the straight route, we are already at "best case", and the diverging route will always be less desirable.
But with a curved turnout, we should make the inner route our "best case in a curve" or "minimum acceptable best case in a curve" and make the outer route a move toward the best case of straight track.
You seem to be making assumptions not in evidence about available space and possible radius.
If I set 36" as my minimum radius, I am not going to diverge off the inside of that with a curved turnout.
So if a curved turnout will solve a space issue, I will first position the 36" curve to feed the inner route, than branch off the outside to feed the outer route.
I have been designing layouts for myself and others, and hand laying track, since about 1975.
If I decide that 36" radius is the minimum radius except for industrial trackage, that is the minimum. It is not the minimum "until I have a problem, or until I need to squeeze in that one more siding" and say, "well, 34" radius will be ok in this one spot".
If I set a multi tiered standard for radius, that's fine, but I would still design any curved turnouts the way I have explained.
ATLANTIC CENTRALBut with a curved turnout, we should make the inner route our "best case in a curve" or "minimum acceptable best case in a curve" and make the outer route a move toward the best case of straight track.
i think the diverging route is the one more mechanically stressful and requiring lower speed
gregc ATLANTIC CENTRAL But with a curved turnout, we should make the inner route our "best case in a curve" or "minimum acceptable best case in a curve" and make the outer route a move toward the best case of straight track. i think the diverging route is the one more mechanically stressful and requiring lower speed
ATLANTIC CENTRAL But with a curved turnout, we should make the inner route our "best case in a curve" or "minimum acceptable best case in a curve" and make the outer route a move toward the best case of straight track.
OK, but our models are already operating on the hairy edge of the engineering in question, why not given them a better chance in this already difficult situation?
Write whatever operating rules you think or prototypical, but make the trackwork work as well as possible.
What if the inner route is the mainline, or primary route?
ATLANTIC CENTRALOK, but our models are already operating on the hairy edge of the engineering in question, why not given them a better chance in this already difficult situation?
the name doesn't affect its performance
i believe straight turnouts on mainlines are aligned such that the mainline follows the straight path, the "normal" route and the "diverging" route take the path away from the mainline.
the divering route requires slow speeds because the turnout is forcing the wheels/cars to relatively abrupty change direction
i understand that using the normal path for the mainline is not often possible to do with model railroad.
gregc ATLANTIC CENTRAL OK, but our models are already operating on the hairy edge of the engineering in question, why not given them a better chance in this already difficult situation? the name doesn't affect its performance i believe straight turnouts on mainlines are aligned such that the mainline follows the straight path, the "normal" route and the "diverging" route take the path away from the mainline. the divering route requires slow speeds because the turnout is forcing the wheels/cars to relatively abrupty change direction i understand that using the normal path for the mainline is not often possible to do with model railroad.
ATLANTIC CENTRAL OK, but our models are already operating on the hairy edge of the engineering in question, why not given them a better chance in this already difficult situation?
Again, OK, I get that, it is the desired practice.
But the prototype breaks that rule all the time when they need to. They build high speed diverging route turnouts for junctions on high speed lines. They use closing frogs, and VERY high frog numbers when needed.
On my new layout I will have a number of double track junctions with equal priority traffic on each route, with diverging route "speeds" nearly as high and primary route speeds.
I run the mainline thru the diverging route of #6 and #8 turnouts without any thought, it is about smooth track flow, not rigid definitions of straight and diverging. After all, the substitution radius of a #6 is about 45", more gentle than my standard easement.
It is a model railroad, and even in my 1500 sq ft, with 36" minimum radius curves w/easements, and #6 and #8 turnouts everywhere but industrial areas, it is still selectively compressed.
I do avoid curved turnouts, and so far on the new layout plan I only see a few very large radius ones possibly in the yard ladders.
But my design method holds, design the inner radius as the constant radius.
gregci believe straight turnouts on mainlines are aligned such that the mainline follows the straight path, the "normal" route and the "diverging" route take the path away from the mainline.
If you are talking about real ralroads, I don't need to go 20 miles to find a dozen or more exceptions to that idea.
-Kevin
Living the dream.
ATLANTIC CENTRALBut my design method holds, design the inner radius as the constant radius.
i guess i missed this earlier. but aren't they both constant? mine is and my assumption is the turnout is coming off a straight piece of track.
gregc ATLANTIC CENTRAL But my design method holds, design the inner radius as the constant radius. i guess i missed this earlier. but aren't they both constant? mine is and my assumption is the turnout is coming off a straight piece of track.
ATLANTIC CENTRAL But my design method holds, design the inner radius as the constant radius.
Why would we assume that? Maybe the curved turnout is in the middle of the arc, or feeding out of the arc to make a siding longer.
No matter its position, imagine the point end track, and the inner track destination connected with a constant radius, then have the outer radius take off as a larger radius from whatever point is necessary for its destination.
I always thought the advertised radius was if you laid a circle of track in that radius, the turnout would fit in that circle pretty good.
Since a potion of the turnout leading into the points is shared by both routes, then it should be obvious that the published radius is just a "will work" for planning number.
Why do we need to over-think this.
The technical details offered in this thread are really interesting, but I think they might be missing the point, no disrespect intended.
The real question is whether or not a curved turnout will work in the desired location. My old club used several Peco Code 83 curved turnouts in order to make the track fit where it needed to go. Space was an issue. Our goal was to maintain a minimum radii of 32", and the Peco curved turnouts allowed us to maintain those radii quite nicely. IIRC, in all cases the through route was the inside curve.
However, one thing that we discovered as we were laying track is that in several cases we could make a regular Atlas Code 83 #6 turnout fit in just by moving the turnout location down the track towards the siding a few inches. The through route was still on the curve.
I have a feeling that the above my information serves only to muddle the conversation. Sorry!
Dave
I'm just a dude with a bad back having a lot of fun with model trains, and finally building a layout!