Undulating track

[derekelse]

Can anyone tell me if they experience the same problem as I do in surveyor,I've laid miles of track ,smoothed the spline where needed but I allways end up with the same problem ,when moving into Driver I find that the rails in places have lifted causing a rollercoaster effect when the train passes over.is this a regular thing ? and more to the point is there a cure for it??
Comments most welcome :wave:

 

[martinvk]

Not sure what you mean. A screen shot perhaps? Are you saying the track between two spline points is not straight after you apply track straightening to it?

 

[Mikado]

Have a look here:

http://trains.0catch.com/Tut6-ConstructingRailroadBridges.htm

What you need to do is make sure the ‘fixed track vertex height’ option is checked. Othervise the track will move up and down with the terrain.

In Trainz 2010 you will find it in Surveyour settings under the options menu.

R/Tom

 

[psferg]

YES!

I have recently had the same issue. this is how i've figured to solve the problem:

first of all, when you're planning a route and you want to maintain a constant grade you have to notice that when you lay a section of track, one half of the section is shows a"+" sign and the other half shows a "-" sign. this does not mean that it's humping in the section, but that it's on one side or the other of the midpoint. Why? who knows.

lay the section of track.

secondly what you do is plug in the grade you want next to the get grade button (click to highlight the number). then click the "apply grade" button, and click the section of track. Then click the other adjustment button...the adjust spline(?) height button (or whatever it's called; i don't have it open at the moment).

this isn't a perfect way of doing it, there may still be some variation in the grade from section to section, but you should be able to get it pretty close. and you can check it by using the "get spline height" button, to verify that the far end is higher (or lower) than the originating end.

FYI: this is actually more realistic to prototype railroading. Railroads don't have constant grades for miles on end. it is typical for there to be variations in gradients, although on a hill the variations are generally in a positive (or negative) direction.

 

[martinvk]

..., one half of the section is shows a"+" sign and the other half shows a "-" sign. this does not mean that it's humping in the section, but that it's on one side or the other of the midpoint. Why? who knows.

...

Actual quite simple when you think about it.

Lay a section of track and place the first spline point at say elevation 18m and the next spline at elevation 19m with 100m between the two splines. Now if you select get gradient and click on the track near the first spline you will get a value of 1.00. If you click on the track near the second, higher spline you will get a value of -1.00. The first positive value mean the track is rising toward the second spline point. The second negative value means the track is lowering toward the first spline point. Where the values change is the mid point between the two spline points. The gradient is always calculated from the nearest spline point towards the furthest spline point.

 

[Xengeance]

The first positive value mean the track is rising toward the second spline point. The second negative value means the track is lowering toward the first spline point.

Indeed, the grade is always made to face the track direction. If you place a track direction marker (so you can see the default track direction) on a section of graded track, the steepness of the grade is always taken from the spline point behind the marker, and traveling forward in the direction the pointer is marking reading either downhill (a negative value) or uphill ( a positive value).

One thing to remember with straightened track is that much like the curvature of a spline track, if the change is too abrupt or the spline points are slightly askew to one another, there is usually a kink in the track that makes it want to go in the opposite direction (typically this occurs at the very end of the side of the spline vertex on the bottom of the slope.) You can add a few spline points on either side of the affected section of the spline and gradually adjust their height to sort of ease into the grade (much like a curve easement starts with a very broad curve radius and gradually becomes sharper toward the middle of the curve to compensate for spline kinks in curves). Very often pieces that have been straighted need things like this in order to prevent your track from looking like something out of that Thundermountain Mine train coaster in Disneyland.

You can also fiddle with the 'Smooth Spline' tool in the advanced tab on the Track Editing Tab. It attempts to vertically blend the vertex points to get rid of any jittery bumps in the spline, and also will adjust any underlying terrain to match the new height (this also makes it handy for quickly building end fills, embankments, and cuts).

 

[martinvk]

Indeed, the grade is always made to face the track direction. If you place a track direction marker (so you can see the default track direction) on a section of graded track, the steepness of the grade is always taken from the spline point behind the marker, and traveling forward in the direction the pointer is marking reading either downhill (a negative value) or uphill ( a positive value).

....

Are you sure? Had to do a quick test and in TS2010 at least, the gradient is measured from the nearest to the furthest spline point, irrespective of the track direction.

 

[derekelse]

Not sure what you mean. A screen shot perhaps? Are you saying the track between two spline points is not straight after you apply track straightening to it?

What occurs is that despite the track travelling over a level stretch of ground the rails rise and fall several times in places,its as if the height has altered ,I didnt mean to give the impression that whole lengths are affected
Another problem I have is on the approach to a tunnel no matter how I try I cant get the tunnel to the same height as the track,Ive tried raising/lowering fbe ground level also the tunnel to no avail

 

[martinvk]

What occurs is that despite the track travelling over a level stretch of ground the rails rise and fall several times in places,its as if the height has altered ,I didnt mean to give the impression that whole lengths are affected...

What colour are the spline points at each end of the undulating track? Is the track following the contour of the ground or is it undulating independently of the ground elevation? Would still like to see a screen shot of that track.

 

[BobCass]

Hi Guys: Try to remember to lay your track in one direction..Apply your gradient in one direction, same as the Direction of your track..O=spline..Example..Lay your track like this..=>.O=Click==========O..You have to click each Section of track regardless whether it is flat ground or not..If you add a spline,the section immediatly after the spline will not have gradient any more..If you click behind the spline consistantly you will maintain your grade..If you click in front of it you will get the Hump effect..O=============click=O

 

[nickq7]

Might be careless mouse moves...

Not being leary, bud... I've done this a lot of times. It happens when I'm on the other side of a hill, adjusting the height of something like the edge of a grove of trees, or whatever - and the circle of activity extends beyond the area I'm working on without me noticing it...
The cause of much frustration, and time wasted correcting track.
Hope this helps. Nickq7.

 

[BobCass]

Hi: Do not use the height tool when laying track..The reason is you cannot maintain a grade properly..Use the gradient tool..There is only two ways it can be 0.00 or Grade Percentage..

 

[RPearson]

I know your point Bob but you can actually get the grades right by using the height tool and setting the height of each spline point. It's not easy though as it requires the calculation of the height using the grade you want between spline points. To do that you need the projected arc length of the track in the xy horizontal plane - not the straight line length - between spline points. Height of 2nd spline point is equal to height of 1st point plus the track length times % grade. Getting the track length from Surveyor is a pain and doing all the calcs is another pain and setting the required height of each point is almost as much of a pain as setting the grade between them. So I do see your point.

Both methods suffer in that they assume the track height in Trainz will vary linearly along it's length. That is the grade remains constant between spline points. It won't in most cases because the Trainz track is a 3-D cubic spline and bends not only in the horizontal plane but also in the vertical plane. Real railroads use transition curves in the vertical plane when laying out track gradients. Extending something like 100m either side of the theoretical grade end point. These give a transition from one section of constant grade to another. The Trainz track spline will make its own transition. You don't have much control over it unless you add in some extra spline points setting the heights along the transition.

So both methods - the method of specifing the height at one point then setting the grade of each section and the other of setting the height manually for each spline point - will set the grade correctly considering only the heights of the spline end points. The actual grade measured on the track spline will differ somewhat from this value because the spline bends in the vertical plane. With small changes in the grade and spline points mostly equally spaced the variation is small but in some cases you can get much steeper grades over portions of the spline than you designed for.

For the route I'm working on - for too long to mention now - I add in the transition curves at the grade changes and calculate and set the height of each spline point. These are all based on the grade profile for the route. Interestingly transition curves for the grade changes in the vertical plane are specified on the survey plans of this route. No transition curves are shown for the horizontal plane making transitions between the tangent track and the circular curves though my guess is they were used.

Bob Pearson