tangent lines in sketcher

[2ms1]

I would like to find out what theangle from horizontal a line running through a point (spline)on the curve and tangent to the curve shown below is.


I have tried creating centerlines (construction lines didn't work either)that run through each spline and then makingthem tangent to the curve, but whenever I apply the tangent constraint it says 'invalid selection'.


How can I find out what these angles are?


Below you can see a "centerline" that I attempted to make tangent, but it's not actually tangent because my approach of applying a constraint to it to make it so didn't work.


View attachment 3229
Edited by: 2ms1

 

[jeff4136]

If you want to indicate / measure the tangent direction,
create a new sketch and project the spline as a reference.
You'll be able to constrain perp and tan to the reference.


If you want to control the curve (define a specific tangent
direction at a specific point) I believe that point will
have to be an endpoint (constrain it to an existing curve
or use the control polygon).

 

[Guest]

I didn't see what you say!Can you explain exactly?


my MSN is [email protected]


I like proe very much,want to use it earn money

 

[vlad1979]

make a small line that goes from that point, doesn't matter the direction only to have a vertex there to select later.


Then in your model make a plane perpendicular to the spline and thru the vertex given by the end of that small line. (magenta plane)


Then make a plane perpendicular to the previous plane created, perpendicular to the sketched plane (the plane where you sketched the curve) and thru the vertex of that small line. Now the resultingplane (green one) should be tangent to the curve in that point.


see this picture:


View attachment 3235
Edited by: vlad1979

 

[Geneg]

do it in 2 steps.


create 2 sketches, first with a conic that you want and second make a point referenceing the conic and than you will be able to make line tangent to the conic at that point.
Edited by: Geneg

 

[trillicomm]

what's the radius of the curve that the point is located on?
and where's the center of that curve located?


Edited by: trillicomm

 

[2ms1]

Geneg please explain what you mean with this conic method.


Trillicomm the curve has no single radius, moreover its shape changes all the time through relationswhen other parts change.


vlad, I do not see how I would be able to measure the angles with this method please tell me how I would do that if it is possible.

 

[trillicomm]

I meant the arc. There is a center of that arc. Where is it, if you zoom out (screen shot), you will see it.

What I want to verify is by taking a derivative of the arc function and it will have the tangent line in terms of y=mx+b, where m is the slope (or angle).

 

[vlad1979]

View attachment 3238


So you have something like above.


I understand from you that you want to measure the angle between the TOP plane and DTM2 plane (a tangent plane to the spline)


I tried making this in sketch with centerlines but I can't make it perpendicular or tangent, so I went around.


You need that point to be visible in part mode so that you can select it. That's why I suggested to create a small line that goes from the point (like I said it doesn't matter the direction).


Now, exit the sketch and create a plane (DTM1)thru the vertex of that line where intersects the curve, and also perpendicular to the spline.


Then you make another plane (DTM2) thru the same vertex, perpendicular to the previous plane created (DTM1) and also perpendicular to the front plane (sketching plane for the spline).


The resulting plane DTM2 should be tangent to the spline.


And you can measure the angle between DTM2 and TOP plane.

 

[2ms1]

Thank youfor the detailed explanation. I didn't know you could measure in part mode though. I thought you can only see dimensions that have been made "strong" in sketcher and/or are driven by relations. Please tell me how I would do the measuring of angle between the tangent data plane and Top. After that I should be taken care of

 

[vlad1979]

This is a work around because you can't create a centerline tangent or perpendicular to the spline in sketch (as far as I know you can make a centerline tangent to a spline only to its ends and not to a point like yours). So I created some datum planes in part mode to be tangent and perpendicular to the spline.


Now the only thing is to measure the angle: Analysis / Measure and select Angle and for first and second choose plane.


You can also create a dimension in part mode to show the angle: go to edit / setup / dimension / create and choose the sketch plane for the dimension (the plane where you sketched the spline) and make a dimension between the planes.

 

[design-engine]

you can also try to use a separate feature say... curve thru points and project that down onto the plane. That is how you can get tangency and the best way to get G2 continuity in a sketch. my 2 cents without reading all those posts.

 

[vlad1979]

I just found out, this is actually pretty easy, no workarounds, no construction features


To put an angular dimension on one point of a spline you do:


1 click on the spline, 1 click on the feature to dimension from and 1 click on the point, then middle button to put the dimension.


View attachment 3282
Edited by: vlad1979