Volute Design

[graphicmetals]

Does anybody have a formula or procedure for designing volutes?

Regards,
Kevin

[gerald_d]

What type of volutes are you talking about - surely not for pumps and impellers (http://www.fluent.com/solutions/turbomachinery/turb2.htm)?

[graphicmetals]

Hi Gerald, I mean decorative wood volutes, i.e. volute shapes in wood.

-Kevin

[alano]

Kevin, a while back Bill Young made available a program called "ShopBot O Graph" or something similar to that. It will produce a .dxf file and based on input will yield some pretty interesting shapes (including a volute). If you e-mail me back I can send you the .zip file.
Regards,
Alan

[rgbrown@itexas.net]

Kevin,

If you are talking about stair parts, a stair building text will have more information. The geometry may be "Spiral". If I remember correctly stair part coordinates can be calculated. On complex stairs, such as a true spiral, and not a "circular", the points must be calculated to layout the stairs properly.

[gerald_d]

Kevin, would this pass as a volute?:


2728

Well, it isn't really a volute, it is just a bunch of half-circles - much easier to do!


2729

[rgbrown@itexas.net]

2730

[graphicmetals]

To qualify as a volute, the space between the curves has to increase as you go outward. Somebody sent me a nice tutorial for Rhino that I am trying to get permission to post here.

-Kevin

[graphicmetals]

OK, I have the permission of the author, Mr. Bill Tromans, to post his volute tutorial for Rhino. I have never attached a file before, so I hope this works.




-Kevin

[kfitzgerald@graphicmetalsinc.com]

OK, I have the permission of the author, Mr. Bill Tromans, to post his volute tutorial for Rhino. I have never attached a file before, so I hope this works...

...bother, the file size is too big; 291k (zipped). If anyone would like this tutorial, I would be happy to email it to you. Just send me an email at kfitzgerald@graphicmetalsinc.com (mailto:kfitzgerald@graphicmetalsinc.com).

-Kevin

[gerald_d]

Kevin, your question is starting to take shape at last!


"Does anybody have a formula or procedure for designing volutes?"
"I mean decorative wood volutes, i.e. volute shapes in wood."
"To qualify as a volute, the space between the curves has to increase as you go outward."

Bearing in mind that a SB can only cut semicircles, you have to find a design method that uses semi-circles. Here (http://perso.wanadoo.fr/rocbo/graph/geom_peintres/phi/) is a French site (don't know if you Americans are still allowed to borrow from the French
) This drawing (http://perso.wanadoo.fr/math.lemur/archi/volutor.gif) shows the diagonals that are used for constructing the points.

[rgbrown@itexas.net]

Gerald,

The tutorial is on stair Volutes. Your French site shows construction of a "Draftsman's" spiral as does the drawing - which is a series of arcs (semi-circles to those in Africa). Good site...

BTW - I believe thre is a "One time exemption" for borrowing from the French for Americans. However, if one simply steals it, they are pardoned.

[papadaveinwy]

My french is a little rusty, But if I translated right that sight is for the United Nations on how to skirt around the issues, and trying to still come out on top. David in Wyoming Yep I'm still here gerald.

[mrdovey@iedu.com]

Kevin...

The formula for a linear spiral (in polar coordinates) is:

r = a * t / c; where:

r is the distance from the origin
a is the angle
c is the number of angular units in a circle:
360 if a is in degrees
2 * pi if a is in radians
t is a constant that determines the 'tightness' of the spiral.

To convert the computed polar coordinates to the cartesian coordinate system used by the ShopBot, use these formulas:

x = r * cos(a)
y = r * sin(a)

I used this approach to write my own 'drill' function so that I could 'pocket' from the inside out.

[rgbrown@itexas.net]

http://www.talkshopbot.com/forum/

2731

[Ron Brown]

OH, ~13" X 8" Cutting time ~1.5 Minutes not including bit changes.....