# Thread: rotating a large arc or spline to tangent on 2 arcs

1. ## rotating a large arc or spline to tangent on 2 arcs

I have a large arc or spline 40 inches long. I have the spline setting tangent on the left dowel. I want to rotate the arc/spline keeping it tangent to the left to where it is touching the tangent of the right pin. Pins are app 25 inches apart. Pins have to stay stationary on the tool as there are 7 different parts with different radiuses being located on the dowels how is the best way to rotate the part to touch tangent on both dowels. Im using X5 is there an easier way to do this than drawing a line tangent to the arc/spline to center of right pin then trim to edge of pin snap to lines and rotate the angle of the 2 lines using the center of the left pin as the axis. doing this several times until you get it within .0005

2. - Just thinking out loud !! ( dangerous, I know )

- offset the spline/arc by the radius of the pins
- create a 25" circle to bisect the new geometry
- Xform 3D the "paired" geometry so the new geometry intersection points go thru the pin centers
- delete new geometry and 25" circle

3. here is an image of what I am wanting to do The left pin is tangent to the arc I want to rotate the large arc to tangent with right pin while maintaining tangent with left pin

4. to throw in a similar step

- offset the spline/arc by the radius of the pins
- create a 25" circle to bisect the new geometry
- translate your arc ( plus offset geometry ) from L/H instersection of 25" circle & offset geometry to L/H pin center
- analyse the angle "3 points" from R/H pin center, L/H pin center, R/H intersection of 25" circle & offset geometry
- take that 1st angle value and then Xform rotate ( around the L/H pin center ) the previous translated geometry - you may have to reverse the rotation direction --- you have just placed the offset geometry thru the pin centers, which makes the old geometry tangent
- delete new geometry and 25" circle

5. I don't know MC but I would draw two arcs with a radius of the spline radius less the pin radius using the pin centres.
Then draw another arc with the spline radius, using the intersect point.