Modeling a precast concrete tank

[TKall]

Hello everyone. I have been following the questions and answers here for a few months and learned a great deal. Thank you all.

 

I never thought I would need to learn AutoCAD and still wish my draftsperson hadn't run off with that marauding outlaw motorcycle gang...but that's another story and I sincerely hope she, the baby and (I think his name is Blaze) are well.

 

I have been trying to draw a precast concrete tank and have run into a problem. The tank walls are not constant thickness. At the bottom they are 3.5" thick and taper to 3" thick at the top. Also, the top dimensions of the tank are longer and wider than the bottom dimensions of the tank. My solution has been to draw the outside bottom as a rectangle and offset the rectangle by 3.5". Then repeat this for the top dimensions, set the top two rectangles at the correct elevation and loft them. Then, I press-pull the center out of the tank. This results in a quasi-correct representation of the outside tank but the wall thickness does not taper correctly and the walls are hollow. I can post a link to the manufacturers drawing of the tank.

Thank you for your help I really appreciate it.

[MSasu]

So, the tank should look in transversal section like the sketch below, if I had read you correctly:

 

 

In this case you may draw the plan shapes marked 1 to 4, in their respective location (that it, on Z) and then apply the LOFT command on the pairs 1 and 2, respectively 3 and 4. You will get now two solids; use the SUBTRACT command to remove the small item from the outside one and this should give you the hollow tank you were looking for.

[TKall]

Thank you. That is what I was looking for. I knew I should have asked two days ago. Again, thank you.

Tom

[BIGAL]

Like msasu draw shape use rotate3d to stand up the draw a pline for the base use vpoint 1,1,1 to see whats happening extrude Path

 

 

Ps for a laugh this has no bottom !

 

added bottom re extruded the original pline then union

[JD Mather]

Face draft is another option.

Extrude with taper and the subtract might be another option.

Post a hand dimensioned hand sketch (or traditional 2d drawing) and someone here will do it for you and then explain how it was done.

[TKall]

I thought I had it by drawing the sections with plines and lofting them together. My walls are still hollow and now I am not sure how to finish the ends of the tank. I would uploaded the dwg file but was not sure how to do that. The manufacturers pdf is at this link:http://www.billingsprecast.com/Combo%20Tanks/SDCE15S%20-%20Eliminite%20120C%201000-500%20Gal%20Combo%20-%20SP%20-%20Copy.pdf I appreciate the help and advice.

Tom

[ReMark]

It looks as though you have created surfaces and not a solid. Not sure if that was your intent or not or if it even matters.

[Dadgad]

I thought I had it by drawing the sections with plines and lofting them together. My walls are still hollow and now I am not sure how to finish the ends of the tank. I would uploaded the dwg file but was not sure how to do that. The manufacturers pdf is at this link:http://www.billingsprecast.com/Combo%20Tanks/SDCE15S%20-%20Eliminite%20120C%201000-500%20Gal%20Combo%20-%20SP%20-%20Copy.pdf I appreciate the help and advice.Tom[ATTACH=CONFIG]39664[/ATTACH]

 

Were the PLINES which you lofted CLOSED or OPEN?

Mid command one of the commandline options is MODE,

you may want to specify SO for solid.

If your PLINES were closed, it should have defaulted to SOLID,

so I would guess that your PLINES were OPEN.

In a linear situation like this you could have used EXTRUDE, instead of LOFT, (or SWEEP or PRESSPULL)

although either could work.

I suggest you try BIGAL's suggestion in post # 4.

[TKall]

ReMark: I want a solid tank wall. The surfaces would not matter that much, but if I am going to take the time, I want to get it right. And considering that incredible guitar of yours, I think I should be able to figure out a concrete tank....even if it takes me a month!

 

Dadgad: I drew plines, snapping to the appropriate location. When I was done I used the join command to create one object. I then selected the outside sections and used the Loft command. I wondered why I got surfaces instead of a two solids form which I could subtract one. I am confused by the fact that the tank walls are not at right angles but rather, "splay" out along the length and width.

[the downing effect]

The pdf is missing quite a few dimensions, but there are a couple of ways to get a solid instead of surfaces. One is to use the pedit>m>yes>join>0 to create a closed polyline out of your sketch then extrude one sketch or use loft between two, you could also create a region and extrude it, or use press pull to extend the sketch to the proper length.

 

Basically you use closed profiles to create solids or open profiles to create surfaces. If applicable you can thicken surfaces to create solids but I don't think that will help in this case.

[TKall]

I started over and drew the sections with plines and lofted them. This gave me the everything minus the ends. For the ends I drew two new sections for each end and lofted them. then I used the union command to make one solid and deleted the plines. It looks good. Thanks everyone.

[Dadgad]

ReMark: I want a solid tank wall. The surfaces would not matter that much, but if I am going to take the time, I want to get it right. And considering that incredible guitar of yours, I think I should be able to figure out a concrete tank....even if it takes me a month!

 

Dadgad: I drew plines, snapping to the appropriate location. When I was done I used the join command to create one object. I then selected the outside sections and used the Loft command. I wondered why I got surfaces instead of a two solids form which I could subtract one. I am confused by the fact that the tank walls are not at right angles but rather, "splay" out along the length and width.

 

I believe the guitar to which you refer is Stykface's stratocaster model, and it really is nice, looking forward to seeing the final version.

I am unclear why you seem to be avoiding using BIGAL's very straight ahead technique.

It works, and is pretty simple, both of which are generally considered to be good things, eh?

 

You JOINED them, but did you CLOSE the resultant polyline?

You could have created the PLINE by snapping your way around the points, and for the last opening in the shape enter C for close.

Or you can CLOSE it in your PROPERTIES or QUICKPROPERTIES palette.

 

Glad you were able to do it. I'd still suggest you try BIGAL's technique as it is one you will use often, once you try it.

[TKall]

Sorry about my guitar comment. There is so much nice work in the gallery I got the names confused.

I took a closer look at BIGAL's technique and understand what he was saying now. I wasn't really avoiding it, I am just suffering a little bit of AutoCAD overload and waiting for the swelling in my brain to go down. What I lack in intelligence, I make up for in persistence.

You know our brains get wired to think a certain way, approach problems from a known perspective. What I have noticed about drawing with AutoCAD is that it demands flexible thinking and, for me anyway, a more deliberate consideration of the beginning point with an eye on the path toward the end. It is an interesting challenge.

And yes, I did close the plines. Thanks Dadgad.

[TKall]

I just tried the technique BIGAL described. wow. very cool. Thanks for the push.

Tom

[Dadgad]

When modeling you can either choose a 3D workspace, or you can just change to an isometric perspective of your regular 2D modelspace.

It makes everything much easier, as you are then able to read 3 axes, just like in real life.

From an orthographic perspective you can only view 2 axes, so it is easy to become confused when working in 3D.

The numerous other standard 3D modeling commands work in very similar ways to EXTRUDE, and most of them include

command modifier options, which are made available at the commandline, so take a few minutes and explore what they do.

SWEEP is essentially the same as what you just did, PRESSPULL is very easy, but unlike EXTRUDE does not generate

a PROPERTY (height) which can be changed in properties. REVOLVE is for making objects which are spun around an axis,

as if they might be made on a lathe.

In case you may not be familiar with them, the VIEWPORT CONTROLS which you will find in the upper left hand corner of

any viewport are probably the most convenient way to quickly access different perspectives, visual styles and viewport configurations.

I'm glad you checked that out, nothing to fear but fear itself.

Lots of good 3D tutorials available on the Tutorials tab.

 

http://www.cadtutor.net/tutorials/autocad/extrude-and-press-pull/

Edited January 18, 2013 by Dadgad

[BIGAL]

Once you get used to rotate3d it solves heaps of what appears simple like this tank.

 

Another example http://www.cadtutor.net/forum/showthread.php?76675-Help-to-rotate-Hand-Rail-in-3D

[Jimmy111]

The easiest way to do this is just make 2 cubes. One for the inside cutout and one for the outside. Taper the sides. Insert the smaller one into the larger one then subtract the interior one to form your walls and floor.

[TKall]

I have been playing with the method that BIGAL described. You can draw a lot of interesting shapes with that but it took me a little while to get my brain around it. I drew my submersible pumps, and I must say for my first 3d drawings, they look pretty good. I am kind of amazed to find a forum so packed with real experts. Do any of you write computer code, C#, VB.net, Java????

[ReMark]

Post an image of your submersible pump. We'd all like to share in your new found skills.

[TKall]

Two Hydromatic submersible effluent pumps, OSP 50 and SKHS 100.