Rollercoaster Track

[Anonymous]

Hi,

I have ONE requirement that I'm unable to achieve using regular old AutoCAD and understand Inventor is capable of.

I'm trying to create a 3D spline or polyline of a rollercoaster track for a ride I'm working on. I've always been able to do a 2D layout with no problem in ACAD, but to achieve elevation changes MATHEMATICALLY seems impossible.

They way we normally do tracks is to both create a plan view and then an elevation view with coincident points marked on both drawings. I need to be able to describe EXACTLY the vertical radii into the ascents and descents, many of which are happening on a horizontally curved section of track.

I'd LIKE to be able to merge the horizontal view with the vertical view ideally, but have no clue how. Maybe the INCLUDE function?

Thanks

[Anonymous]

You could draw the plan view and extrude it as a surface

Then draw the side view and extrude it as a surface

Then use 3dsketch to work out the 3dintersection of the two.

See the attached file (Inventor 10)

Regards
Rory


wrote in message news:4898946@discussion.autodesk.com...
Hi,

I have ONE requirement that I'm unable to achieve using regular old AutoCAD
and understand Inventor is capable of.

I'm trying to create a 3D spline or polyline of a rollercoaster track for a
ride I'm working on. I've always been able to do a 2D layout with no problem
in ACAD, but to achieve elevation changes MATHEMATICALLY seems impossible.

They way we normally do tracks is to both create a plan view and then an
elevation view with coincident points marked on both drawings. I need to be
able to describe EXACTLY the vertical radii into the ascents and descents,
many of which are happening on a horizontally curved section of track.

I'd LIKE to be able to merge the horizontal view with the vertical view
ideally, but have no clue how. Maybe the INCLUDE function?

Thanks

[Anonymous]

Thanks for the quick response, but that doesn't quite work for most of the layout.

You have to project the elevation view perpendicular to the plan view, so with this method when you have a curve ascent/descent it distorts.

In other words, if you project an 15° descent (for example) onto the side of the plan curved surface (unless you are able to make it perpendicular to every point) you aren't going to end up with a 15° descent all the way through.


Once the 3D drawing is created, however, how do you get that exported to something ACAD recognizes?

[Josh_Petitt]

Yes, this is possible (although tedious). If you have a set of 3D points approximating the track path, you can create a 3D sketch in Inventor, then sweep a profile along this path. You can then create an idw with plan and elevations shown. There is an option to include the work points (RMB on assembly in view browser and select "Get Work Features") on the drawing so they are visible in both plan and elevation.

btw, I think Inventor would be MUCH more suitable for designing roller coasters than AutoCAD. Also with Studio (IV10) you could create a realistic "ride" animation for demonstrating your design.

[Josh_Petitt]

>Once the 3D drawing is created, however, how do you get that exported to something ACAD recognizes?

Create the .idw (Inventor drawing), and "Save As" a .dwg.

[Anonymous]

If I use the 3D points do I have control over the transition radii? Does it turn into a bezier where I have to fool around with handles? This is no good as I need it to be precise.

The vehicles are capable of 20' vertical turn radii, so I need to be able to spell this out.

In ACAD, I create the plan view and can easily spell out radii horizontally. I can also do the same thing with vertical turn radii and piece the whole thing together. I just cannot have a turn and ascent/descent at the same time (without using a lisp for a spiral, and that's no good).

I take the track and all the building infrastructure into 3D studio for visualization, so I have that covered. It works really well with our graphics and proper lighting as most of our attractions use artificial lighting.

[Josh_Petitt]

>If I use the 3D points do I have control over the transition radii?

yes. the arc lies in the plane defined by the two lines it connects.

> Does it turn into a bezier where I have to fool around with handles?

no

>The vehicles are capable of 20' vertical turn radii, so I need to be able to spell this out.

If you always use a 20' radii, this should be really easy cause IV has an "auto-bend" function when creating 3D sketches. Tell it the radius you want to use, and everytime you create a new line segment, an arc will be created as a transition.

[Anonymous]

I think the problem to define BOTH tracks at the same time. A path is no
problem... but how do you control the roll/yaw of both rails as a unit and
maintain consistent spacing and radii??

I would think that regardless of the actual "path" (which should be able to
be defined with a surface intersection as Rory mentioned) the "track
sections" would need to be defined in 2D sketches oriented with workfeatures
along the "path" which may or may not be a spline.

QBZ


wrote in message news:4899172@discussion.autodesk.com...
>If I use the 3D points do I have control over the transition radii?

yes. the arc lies in the plane defined by the two lines it connects.

> Does it turn into a bezier where I have to fool around with handles?

no

>The vehicles are capable of 20' vertical turn radii, so I need to be able
>to spell this out.

If you always use a 20' radii, this should be really easy cause IV has an
"auto-bend" function when creating 3D sketches. Tell it the radius you want
to use, and everytime you create a new line segment, an arc will be created
as a transition.

[Anonymous]

Fortunately the track is level the whole time. I only need a centerline as I extrude the rails along this centerline in 3D Studio.


Isn't there a way to simply "wrap" the elevation around the plan view?

I have to say I don't know Inventor well enough to follow some of the advice I've received (thank you) and will take some time to sort through the actual steps.

[Anonymous]

>Fortunately the track is level the whole time. I only need a centerline as I extrude the rails along this centerline in 3D Studio.

By this I mean there is not roll/yaw.

[Anonymous]

Oh! you build these things for day-care centers then?

QBZ


wrote in message news:4899215@discussion.autodesk.com...
>Fortunately the track is level the whole time. I only need a centerline as
>I extrude the rails along this centerline in 3D Studio.

By this I mean there is not roll/yaw.

[Anonymous]

No, it's a hybrid dark ride. The restraint system doesn't permit too much jarring of the passengers or our height restriction has to go up.

[Josh_Petitt]

>I think the problem to define BOTH tracks at the same time. A path is no problem... but how do you control the roll/yaw of both rails as a unit and maintain consistent spacing and radii??

define a parametric equation for centerline path where z is forward, x is left, y is up:

T = f(t) where T is [4x4] tranformation matrix w.r.t world coordinate system.

define the left and right transforms w.r.t local coordinate system:

Tl = [ [ 1,0,0,0 ],[ d/2,1,0,0 ],[ 0,0,1,0 ],[ 0,0,0,1 ] ]
Tr = [ [ 1,0,0,0 ],[ -d/2,1,0,0 ],[ 0,0,1,0 ],[ 0,0,0,1 ] ]

compute transforms for left and right rails w.r.t. world:

Tleft = T*Tl
Tright = T*Tr

extract position vector(s) from Tleft and Tright, these are used as the 3D points to make the two track sweeps.

Matlab comes in real handy here, Excel can also do this, but it is more cumbersome. Since the parametric equation is defined by the user, steps can be taken in its construction to minimize the jerk.


Note to ADSK: Is there any plans to introduce a parametric sketch element?

[Anonymous]

Are your layout requirements related to acceleration and load calculations?
Inventor is oriented more toward assembling 3D building blocks than solving
3D geometry problems. The ability to flat wrap plane geometry will be
missed, as will sweep control when you get around to creating parts. Post
a layout and see if anyone is able to coach you through it to your
satisfaction.



wrote in message news:4898946@discussion.autodesk.com...
Hi,

I have ONE requirement that I'm unable to achieve using regular old AutoCAD
and understand Inventor is capable of.

I'm trying to create a 3D spline or polyline of a rollercoaster track for a
ride I'm working on. I've always been able to do a 2D layout with no
problem in ACAD, but to achieve elevation changes MATHEMATICALLY seems
impossible.

They way we normally do tracks is to both create a plan view and then an
elevation view with coincident points marked on both drawings. I need to be
able to describe EXACTLY the vertical radii into the ascents and descents,
many of which are happening on a horizontally curved section of track.

I'd LIKE to be able to merge the horizontal view with the vertical view
ideally, but have no clue how. Maybe the INCLUDE function?

Thanks

[Anonymous]

could you model the rise and fall as flat planes / curves etc as full
solids then place sketches on the solids to develop the curves you
need?  If so, after all the curve sketches are done, you could cover
the entire solid with a sketch, use an extrude cut and be left with all
of the 2D Sketches that form the rails.



beanboon wrote:

Fortunately the track is level the whole time. I only need a centerline as I extrude the rails along this centerline in 3D Studio.

    

By this I mean there is not roll/yaw.