Parabola in Sketch Mode

[Anonymous]

I am trying to create a parabola crosssection in sketch mode to revolve around a cylinder solid.

I used 3 point arc but with volume calculations is obviously not a parabola.

I need it to be 16 ft Base and 7 feet height. Is there an easy way? It shouldn't be hard I would think.
But I am googling and it seems that it actual is a difficult feat.

Any tutorials/instructions would be helpful.

Thanks,
Sean

[JDMather]

Can you attach what you have so far?
I'm thinking a spline with as few as three points.
What is the manufacturing tolerance?

[Anonymous]

Sean,

Sketch points using the procedure I've attached and connect the points using spline line.

Regards,
Gilbert

[Anonymous]

Great this looks like it will help.

I am not at the computer right now with the design on it.

I started by construction a 2 point rectangle height 16ft. Then drew an offset line 7 feet from the edge of the rectangle.
Then did a three point arc using the top and bottom corner of the rectangle and the midpoint of the line. This created an arc not the parabola.. (which I should have realized).

I will use your method here.

Thanks,
Sean

[Anonymous]

Attached is the solid part by revolving the parabola 16 x 7 ft.

Regards,
Gilbert

[Anonymous]

see attached. No need for splines or approximations, just draw a parabola...

[Scott_Parker]

To create a parabola you can create an intersection curve between a plane and a cone as Josh did, but to be a parabola, the plane needs to be parallel to the side of the cone. Josh's example would actually be a hyperbola.

[Anonymous]

right you are! Thanks for the correction 🙂

[Anonymous]

Thanks so much to all who have helped with this in this thread!

What I would like to know is how I can now revolve that parabola to make a paraboloid of revolution. Any ideas?

[JDMather]

See attached (delete after examining technique).

[cadman777]

Guys,

Thanx for the math tutorial!

The challenge I had w/the plane parallel to a plant tangent to the side is controlling the depth and width of the parabola.

JD, your ipt file is in a version newer than I have.

Can you send it to me in 2010?

I wanna see how you did it.

Thanx!

[cadman777]

gh,

I found your bmp in my Sheet Metal Pattern Drafting book.

Should've know it was a basic shape, and should'a resorted to fundamentals.

Thanx for the reminder!

[dowens2J2YQ]

That's not "drawing a parabola." That is creating a cone and line to intersect. 
I believe the OP, and I would like to know how to graph something like y = 3x^2 +2x - 4 Or y = 3(x-3)^2 +6. 

[SBix26 · Accepted solution]

Like this?  Inventor has had Equation Curve for ten years, at least... what version of Inventor are you using?

---

Sam B

Inventor Pro 2023.2.1 | Windows 10 Home 22H2