spiral shape

[James__S]

I have come this far with a sketch...how do i get the sketch to have a spiral shape...This is a 2013 part sketch attached....i thought of the Coil tool but i had no success....can this be done

Thanks

James

[-niels-]

I don't really have enough experience with what i'm going to suggest, so i hope it is relevant.

Maybe you could use the "equation curve" function (if it's in 2013, think it was...)
There's a lot to find on spiral equations:
https://www.google.nl/search?q=equation+for+spiral&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:nl:officia...

Sorry for not providing a more meaningful solution, but i hope this helps.

[CCarreiras]

Hi!

In 3D sketch, you can use the helical tool.

There's a option for spiral, all you have to know is how many turns and the pitch you need.

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[-niels-]

Also found this:
http://www.cadlinecommunity.co.uk/Blogs/Blog.aspx?ScoId=59b66e99-d736-4823-88e3-116fe3eedd23

[James__S]

Thanks Niels....

Carlos.....how do you use the Spiral Tool.....i opened the Helixical Curve and selected Spiral but could not get the same effect as you did

Thanks

[CCarreiras]

HI!

Pay attention to the values in the chart...

The spiral always moves from the inside to the outside, so you need to calculate how many turns (this is easy) and also the correct pitch to connect the end of spiral to the arc geometry.

Make some calculations to have propper values, my values where aproximated.

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[WHolzwarth]

Proper values are:

232 --- 16.9099 (=14*360°/298.05°) --- 298.05/360

But the 120mm distance at 15° is not on the spiral.

Walter

[JDMather]

Do you have a picture of something similar that you are trying to model?

[James__S]

Please see attached

Thanks

[James__S]

Walter can you please explain the values you used....how did you get the values please?

Thanks

[WHolzwarth]

See picture, James.

Starting dia = 2 * 116 = 232

Winding = (270° + 28.05°)/360° = 0.828

Pitch = 130 - 116 for 0.828 turn (or 14*360/298.05) = 16.9099 for full turn

And take a look at the yellow circle for the different position of distance 120.

[CCarreiras]

Hi!

Usually, volutes are a combined 2 or 3 tangent arcs with different radius, not a spiral, maybe that's why WH's spiral doesnt connect in every points.

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[James__S]

Thanks

Cannot get a smooth shape with Loft.....would using a centre line work better...i tried with centreline but does not work

Thanks

[WHolzwarth]

Here's my attempt (2013 file)

[James__S]

thanks wh......

I am still playing around with my sketch.....i tried using centreline on Loft command but it says Not Smooth...how do i make it smooth...i am presuming the dimensions are not quite correct

Would also the Equation Curve work here?

Thanks for any further help

James

2013 part attached

[James__S]

any help on previous post please

[WHolzwarth]

IMO, your sketches are not optimal, James.

- Rail curve is not smooth, but has different segments. Only one curve for similar sections is best.

- Sections are not rectangular to rail curve

- Section size and angular distance between them must match better. Otherwise no smooth Loft is possible.

- Flat spots on sections can be troublesome.

- S-Shaped rail on the big end can't help without additional section in the middle at curvature change.

What would I do?

- Use two different lofts. One for the inner part, one for the outer S

- Use a real spiral instead of a number of circular rails for the inner loft

- Apply as few sections as possible for the spiral loft. Perhaps only start and end section and a rail curve does it.

- Apply the sections rectangular to the path. Take caution, that the center of the circles are meeting the path

- Use only circular sections. Aplly flat spots later.

- For the S-Shaped part, I'd suggest 3 sections (R=85,90,95). Perhaps it's better placing the biggest section rectangular to the path, and cutting it later. Another possibility could be a tangent constraint to vertical for the last arc.

Now up to No. 9 ..

[WHolzwarth]

Hmm. I just tried for myself, and have seen discouraging things.

IMO several tasks for Autodesk.

[WHolzwarth]

Well, lots of troubles with lofting.

I think, a sweep with draft would be the best way.

It's another sample for my testing, but could be transferred to your values, too.

[James__S]

Hi WH

Are you able to attach your sample from your last post  --- i use Inventor 2013

Cheers

James