how to model continuous belt path

[potrero]

I am attempting to create a model of a simple "racetrack" oval belt path (two straight lines, two equivalent arc sections).

Is it possible to create a continuous curve, which can then be used to constrain to?

For instance, if I then made another sketch, and constrained a point to the path, I could drag it all the way around the path.

I've tried using the "use edge" command to copy a loop into a second sketch, after first creating the path out of straight lines and arcs, but it doesn't result in a continuous loop.

If someone has an idea of how to accomplish this, I'd appreciate it. Thanks.

 

[mjcole]

Yeah I've wished for this to be possible without the method I'm about to describe but it's only 1 extra feature and will give you what you want.

Using Geometry Select tool select all the racetrack curves and do a Copy Paster CTRL+C CTRL+V and choose Approximate as the composite curve type. If you use this as your sketch reference it should display as a single entity and you can drag a point around it but not in an endless loop. You can drag between the start point and the end point but not past it.

To get what you desire it would be easier to create a point on curve and do a pattern. Sketcher is very finickey about references for instance try sketching a circle a point and a centerline that goes both through the point and tangent to the circle. This should be possible but I have never seen it happen and the Sketcher Conflicting constraints dialog won't allow it.

Michael

 

[cadcamguy]

I'm missing what you are trying to do here.

 

[mjcole]

UPDATE,

With the method I described to you it is possible to drag the point all the way around the path as long as you don't use the Use Edge icon just select the copy curve as one of your references and you'll be all set.

I just tested it out and it works perfectly.

Michael

 

[mjcole]

I think I get what he's going for. Lets say you are modeling something and would like to reference another sketch with both splines and straight or arc sections and you want to be able to pattern a series of ribs or other features that reference various entities.

If you select the Sketch you will get entities with end points that you can apply a point on curve constraint to. However you cannot keep that point on curve costraint and drag it into the next part of the referenced sketch curve because it will stop at the end point vertex of each entity.

If you use exact as the composite curve type you are not able to do this, which is why I suggested using Approximate for the composite curve type.

Michael

 

[cadcamguy]

point on sketch <racetrack> ratio...
datum through point, normal curve..
then 2nd sketch...ref plane ...last dat

in sketch ref to point...fully placed


.. then you can change ratio and 2nd sketch stays oriented and walks around the racetrack

 

[potrero]

michael, I'm having difficulty doing the CTRL+C, CTRL+V. Instead of the expected "Copy Curve" dialogue, ProE interprets that I have copied the entire sketch, and then asks for me to place the copied sketch.

Is there a method to only select the curve, that I'm not using correctly?

Perhaps backing up slightly, the set of curves I want to "join" was created inside of a sketched datum; and all this is occuring in a motion skeleton.


cadcamguy,
i am sorry but I cannot quite understand your recommendation. would it be possible to give the verbose version?

Thanks all.

 

[cadcamguy]

when you are making the selection... is the whole curve "bright" red or just red?

 

[potrero]

aha, I simply hadn't been using the "Geometry" selection filter, so I was selecting the entire sketch feature, not the curves.

michael's method seems to work, mostly. Dragging around the resulting copied curve is possible, but not entirely smooth. It seems to "hang" near the points where arcs meet straight lines.

 

[cadcamguy]

aha, I simply hadn't been using the "Geometry" selection filter

..I thought that might be what it was... I don't think you will actually need to copy and paste.. provide all of your racetrack is the sketch

if the whole loop is bright red then the ratioed point should move along the entire track.

hth