How do I draw a propeller in 3D?

[visith]

How do I draw a propeller in 3D? I use Auto CAD 2002, Please help me. Thank you all who can help me :? :shock:

[fuccaro]

Usually the propeller blades are complicated 3D shapes. What are your inputs? Do you have a mathematical equation for the surface? Or maybe some cross sections?

[Jose]

For what I've seen, propellers, as stated by fuccaro, are complicated 3D shapes. This is due to the double curvature nature of its blades. You may achieve its complicated form by using the 3D surface drawing commands. I did an exercice inventing my own cortoon_like geometry just to give it a try. I used the "edgesurf" command. You'll need a bit of experience to get it right. After modeling the first half, I did a mirror3d to make it simetrical. After one blade was finaly done, I did a 360° polar array. Note that did not use the 3D array command. I did the array for 3 elements (blades). After doing so I changed my UCS so that X was now Z. This way I could rotate each blade 30° using its buttom as rotation point. I repeated this with the resting two blades. At the end I had a 360° array of three blades each rotated 30°. For uniting the three blades I drawed a curve and did the rev command to make a cone shape, and extruded a small circle for the axle.

For marine blades, things can get a little more complicated, but still doable with the surf commands. These type of models are better done using NURBS.

[Jose]

When drawing with 3dsurf take to account the isoplanes, surftab1 and surftab2 system variables. These will define how accurate the curved surfaces will be rendered.

[fuccaro]

Jose
SURFTAB1 and SURFTAB2 will give the precision of the construction. For better render try to modify the FACETRES system variable

[Jose]

sorry I meant isolines, and note isoplanes. Thank you fuccaro for that.

[jac]

Hello everyone and seasons greetings. I searched for this topic on the internet and wound up here.

I followed Jose's advice using edgesurf to create a propeller. You can see it here:

wwwdotlightmypumpdotcom/blade3dotdwg

I am using Acad 2007.

I used thin elliptical sections that were spaced upwards on the z-axis and individually rotated. I connected the edges with a 3dpoly and then egdesurfed the section between ellipses.

I used a cylinder solid as the hub. At this point I would like to trim the connection between the prop root and the cylinder but the union command will not work. Any suggestions?

I am also trying to do a model of a complicated chair.

wwwdotlightmypumpdotcom/my_chair2dotdwg

I created this by first making a polyline of the edge of the chair ( if you are sitting, the edge coresponding to your left side) and then extruding it. I then fiilleted (a fishy term) the edges. Now the problem is how to make the back of the seat narrower than the front. Here is a picture of the chair for more clarity:

wwwdotlightmypumpdotcom/my_chair-picdotjpg

Any suggestions? It's amazing how even a simple chair can be complicated to model correclty in 3D.

And finally, thanks for your patience, can you recommend a good book to help modelling these types of surfaces.

Cheers,

Jacques:D

[fuccaro]

Welcome in the forum, Jac!
I can't open the drawings because I use AutoCAD 2006. Probable I am not the only one, so I would suggest you to save back the files in 2k file format or so.
Without seing the models, I can just guess; you can not trimm a surface. Can you convert the blades to solids and perform boolean operations?

[jac]

Hi, I saved them as Acad 2004.

at

wwwdotlightmypumpdotcom/blade3-2004dotdwg

&

wwwdotlightmypumpdotcom/my_chair2-2004dotdwg

[fuccaro]

Now I see. Try to use the THICKEN command (newly introduced in 2007) to convert the surfaces to solids.
About the chair
In the top view add an axis line and two yellow lines to delimit the shape. Use the SLICE command to get rid of the margins. When AutoCAD prompts you for 3 points to define the slicing plane, pick the two ends of a yellow line and enter @0,0,1 for the third point. Repeat the slice for the other side
9168
You will have to remake the fillets

[JD Mather]

I am using Acad 2007.

...then egdesurfed the section between ellipses.


I would not use obsolete surface commands like edgesurf in r2007 and later. And Thicken will not work on edgesurf created surface.

[fuccaro]

Thicken will not work on edgesurf created surface.
I just learnt something new. Thank you!