3D propeller blade problem

[VWX]

My friend has a problem:

quote:

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I?m working to make a 3D model of a propeller blade. I have an old 2D dxf file from the blade, where the cylindrical cross-sections with right scale and shape are on plane. Now my problem is how to exploit these cross-sections by bending individual section to equivalent radius.

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VectorWorks version is 11.5.1.

[ 11-07-2005, 11:49 AM: Message edited by: MS ]

[propstuff]

I don't understand the request.

Propellers don't generally have circular cross-sections, and a cylinder is not generally thought of a s a cross-section.

Can you explain more what you have and you're trying to do?

N.

[grant_PD]

I think I understand the problem. You'll want to make each of those cross sections into nurbs and them place them at the correct height and rotation at their cross section. You'll then want to loft curves to get them all to make the correct shape.

[islandmon]

Each of those cross sections should have exactly the same number of segments & vertices before you convert them to NURBS & Lofts... getting the correct dihedral-pitch is a bit tricky.

Also the stem will need to be modeled separately from the blades.

[VWX]

quote:

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Originally posted by propstuff:

I don't understand the request.

Propellers don't generally have circular cross-sections, and a cylinder is not generally thought of a s a cross-section.

Can you explain more what you have and you're trying to do?

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quote:

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I have cross sections of the profile of the propeller blade so that we think to cut the blade with radius R1 we get a cross section area on this radius. If the center line of the blade is situated on z-axis then the other edge will be on -40? and the other on +35?. I have now this section area on the flat plane so 5? is corresponding 2*π*R1*5?/360?[mm]. My problem is to bend the area once again back to radius R1.

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Hopefully this helps? It's quote from my friend.

[ 11-08-2005, 03:08 PM: Message edited by: MS ]

[VWX]

quote:

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Originally posted by grant_PD:

I think I understand the problem. You'll want to make each of those cross sections into nurbs and them place them at the correct height and rotation at their cross section. You'll then want to loft curves to get them all to make the correct shape.

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quote:

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You are right, that's my problem and how to place them at the right position without many calculations. It is not difficulty but how to avoid a huge number trivial calculations.

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Quote from my friend.

[VWX]

quote:

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Originally posted by islandmon:

Each of those cross sections should have exactly the same number of segments & vertices before you convert them to NURBS & Lofts... getting the correct dihedral-pitch is a bit tricky.

Also the stem will need to be modeled separately from the blades.

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quote:

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Thank you all these hints are with then most important how to prepare nurbs. And then the problem is like comments above.

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Quote from my friend.

[ 11-08-2005, 03:10 PM: Message edited by: MS ]

[islandmon]

With a little effort the precise functions can be modelled in Excel and exported via vectorscript text.

[islandmon]

Your Prop Problem inspired me to create one built from a single NURBS fractal and a single iterated Phi function. The result is a very sophisticated dihedral&pitch design with minimal cavitation:

[NickB]

That is amazing. How the did you do that, or would I need an Engineering qualification to understand? What's a NURBS fractal, and how can I get an introduction to using phi functions to create geometry? I see all these great shapes and possibilities, but have no idea how to get into it. Can you recommend a good book? Do you do it through a worksheet or is it VectorScript? Sorry, don't mean to hijack the post, but that's got me really excited.

[ 11-12-2005, 05:01 PM: Message edited by: NickB ]

[CipesDesign]

Hey EJ. That is truly amazing! Nice work! Just out of curiosity, is that "pool water" you've applied as a texture?

[islandmon]

NickB... after 30+ yrs , I've developed a fairly simple process of analysis and creation. Earlier on my mentor was RBuckminster Fuller and his 'Synergetic Geometry v1&2'. Over the years it seems my work is expanding on a few of those original concepts. The Prop was created exclusively with VW and took about 1 hour to work out the vertex placement details based on a logarithmic sphiral.

Cipes ...the FQR takes 10secs. using a modified water texture which provides excellent 'surface netting of contours'. Keep in mind that although the shape appears complicated it is really composed of a single simple surface created from one NURBS logarithmic curve created at low conversion. The curve can be compressed and/or extended harmonically to allow for various configurations.

Link to 4.5mb VRML Prop movie.

[NickB]

islandmon, I'm sitting here with my copy of "A Fuller Explanation" by Amy C. Edmondson right now and have many tensegrities lying around the house. I have also done projects on logarithmic spirals. What I am looking for is a way to put that geometry/equations into the computer. So I suppose the piece of your answer that I am interested in is where you "work out the vertex placement details".

Also is there software out there for computing tensegrities? At the moment all I have is sticks and string and a lot of trial and error.

regards, Nick

[islandmon]

Nick ... you sound like me ... I've been in that predicament as well.

So a few years ago I decided to just work it all out with the help of numerous references. The system I use is rather unique in that it only requires iterations of a fractal. Once you the hang of it ... it's all actually pretty simple... the way Nature intended it to be. But you need to think like Nature and not necessarily like Newton/Descarte.

As for software .. there are numerous different applications including javascripts to asist. I'll post some links tomorrow.

[islandmon]

Well .. it's tomorrow and I'm in a rush ...

Some thoughts :

The 90? XYZ coordinate system is far from ideal for programming geodesics & tensegritys. A superior option is the Isotropic Vector Matrix.

Intro to IVM & Synergetic Growth

Expansion of the IVM

Stereo movie of rotating Dodecahedra

Stereo movie of rotating Phi Crystals & Geodesic vectors

Stereo image of IVM & TetraSeeds

Stereo image of dual nested Tetra & 16frequency geodesic

Stereo IVM duo Tetra

Stereo image of IVM & Dymaxion with duo tetra & 16F geodesic

_____

Some apps..

Design your own Geodesics using Dome4.6 by Rick Bono, SIT file

Dome4.6 C++ code via pdf file not embedded in html

search web vZome by Scott Vorthmann

[NickB]

Thanks so much for putting that together, I'll tuck in and see how I get on. I've understood the IVM, I was looking for something that would let me deal with that. At some point though I'm really going to have to brush up on my maths.

Thanks again for the pointers, Nick.

[islandmon]

Let's take another look at that 'primitive' logarithmic Sphiral for a minute. I undercovered this artifact during last years dig:

VRML of Sphiral , 2.2mb QT

[VWX]

quote:

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My orignal problem was to create a 3D model from a propeller blade shown on a attached drawing. I know the cross sections along cylindrical cuttings and distances from center R2 ... R5. But these cuttings are drawn straightend on the plane.

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Quote from friend. Hopefully this helps and shows, what the problem is.

[islandmon]

MS, have you considered XPlane ... it's a Super Flight Sim and it includes AirFoil-Maker with instructions. Also, there's a Mac Classic app called PlotFoil32 it includes dozens of different airfoil sections and functions ... it's awesome...you can grab it off my server:

Right click > to download Plotfoil32.zip

[VWX]

quote:

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Originally posted by Chris Manus:

If you have mathematica 5 you can export your equations in 3D dxf or STL ?- then import and assemble in VW-

Upon trial,Forget 3D-Dxf importing..HTH

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My friend doesn't have Mathematica 5. There isn't mathematical equation for picture, because the shape of the propeller blade is acc. to practice and it has been drawn on 2D drawing.

[ 11-16-2005, 02:06 PM: Message edited by: MS ]

[VWX]

quote:

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Originally posted by islandmon:

With a little effort the precise functions can be modelled in Excel and exported via vectorscript text.

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quote:

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It will be possible to find out the function, but the blade has four quite different cylindrical cross sections. It will be supposed not to be easy to find out the functions.

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Quote from my friend.