topic Re: How to draw a Pipe in 3D in AutoCAD Forum

How to draw a Pipe in 3D

Drewpan — Wed, 10 Feb 2021 23:31:59 GMT

Hi People,

Yes this is my homework. No it isn't the task, it is an element of the task.

Ok - so my Project is to draw a Bicycle. Everything good so far until I get to the

Handlebars. Just a simple bent tube right? Uh-Oh!

So I know how to do this, I just cannot get it to work. The method I am doing is

to draw the handlebars then draw a circle of the correct diameter, rotate it to 90

degrees to my line and extrude it along the path. This method works when I do it

to a line in 2 Planes, but when I add the 3rd dimension, my lines rotate and no longer

join so the path is broken.

How do I draw a 3D line that connects up?

The handlebars are simple - 300mm wide with 300mm "wings" at 60 degrees

(like a U with a flat bottom and angled arms). I then put 2 more 300mm "arms"

at a 60 degree angle in the XY plane and a 90 degree angle in the Z plane.

If you remember what a Dragster Bicycle looks like or a Chopper Motorbike

then that is what I am looking for.

The middle part is easy and is curved, but the arms are not working.

I start by drawing lines in a roughly M shape then filleting the 60 degree angles

in the middle. The arms are now at the correct XY angle but I need to sweep them

back at 90 degrees in the Z plane. This works but the lines are now no longer joined.

I cannot get them to join using PEDIT or JOIN. Once they are joined I want to fillet

in the curve of the correct radius, make sure everything is joined up then do the

extrude.

So basically what I want is a 25mm tube with nice curves to bolt onto the Frame and

mount the Hardware.

Thanks in advance.

Andrew

PS See my failed attempts in Files area.

Re: How to draw a Pipe in 3D

Patchy — Thu, 11 Feb 2021 00:09:57 GMT

Can you save as 2007 version?

How to draw a Pipe in 3D

BeKirra — Thu, 11 Feb 2021 00:40:29 GMT

IMO you are on the right track except for setting up UCS properly...

"sweep" is the command to use for your task.

All you need to do is drawing the path (for sweep) properly.

By doing this you may use "3dpoly" command to drawing the path. The tricky thing may be creating pipe profile (circle) on different UCS you defined.

Here is an example for your reference.

HTH

Re: How to draw a Pipe in 3D

GrantsPirate — Thu, 11 Feb 2021 01:36:50 GMT

Here you go Patchy.

Re: How to draw a Pipe in 3D

GrantsPirate — Thu, 11 Feb 2021 01:53:40 GMT

I would first set THICKNESS to zero, not sure why it is set to something other than zero. You have two intersections so I used UCS, 3 to set a UCS, picking the intersection of two lines then the endpoints of the two lines. Start PLINE command and snap to the endpoints from the outer part of the handle bar to the intersection to the mid point of the next section. Fillet that pline. Set UCS with the above method for the other intersection and the outer endpoints of the two lines forming the intersection. Use PLINE again, snap to the endp of the first pline, to the intersection to the middle of the center section of the handlebar. Fillet that pline. Draw two circles of the correct diameter, doesn't matter the orientation of them. Use sweep for one circle and the first pline, repeat. Now mirror the two pieces and join if desired.

Re: How to draw a Pipe in 3D

leeminardi — Thu, 11 Feb 2021 02:06:15 GMT

First, select all your lines and change the thickness to 0.0. The lines will display better and I see no reason for the thickness.

There's no need to create any UCS's. Just create two 3dpoly's with 3 vertices (the cyan segments in the image below) and a polyline for the red segment ( I exploded your lines and joined the 2 arcs and straight line). Create one circle with a diameter equal to the diameter of the tubing. Give the sweep command 3 times picking first the circle then one of the 3 segments.

Re: How to draw a Pipe in 3D

BeKirra — Thu, 11 Feb 2021 02:37:37 GMT

Nice one. 👍

And yes, it is not too complicate with OP's case.

But it would be another story if the red segments in your copy were not on a horizontal plane.

Re: How to draw a Pipe in 3D

Patchy — Thu, 11 Feb 2021 02:40:42 GMT

Thank you.

Re: How to draw a Pipe in 3D

leeminardi — Thu, 11 Feb 2021 02:45:38 GMT

@BeKirra wrote:
Nice one. 👍
And yes, it is not too complicate with OP's case.
But it would be another story if the red segments in your copy were not on a horizontal plane.

Yes the red segments need to be on a plane but it need not be "horizontal". The circle and the polyline may each be at any 3D orientation for the sweep command to function.

Re: How to draw a Pipe in 3D

Drewpan — Thu, 11 Feb 2021 06:31:57 GMT

Hi,

Almost what I want except I want a nice curve on the "arms" instead of a join.

The original was just swept back because I didn't know how to fillet it into a

nice curve because the lines were not joined.

The chances of this actually being fabricated are low but the intention is to

simply fabricate the handlebars with Aluminium tube and a pipe bender. I agree

that the joined arms look cool but it would involve a weld which I want to avoid.

(Ahh vanity!)

Cheers

Andrew

Re: How to draw a Pipe in 3D

BeKirra — Thu, 11 Feb 2021 09:08:23 GMT

@Drewpan wrote:
Almost what I want except I want a nice curve on the "arms" instead of a join.
The original was just swept back because I didn't know how to fillet it into a
nice curve because the lines were not joined.
...

If you want to fillet the arms you may have to change UCS then you will be able to trim and draw arcs (fillets).

In this case please have a look step 2~4 on my screenshot in post #3 again.

HTH

Re: How to draw a Pipe in 3D

leeminardi — Thu, 11 Feb 2021 16:14:13 GMT

I recommend learning how to create and edit splines to model smooth bends in tubing.

In the screencast below I start with your line and arc 3D drawing of the handlebar centerline. Since the handlebars are symmetric only one half is splined with the intent of using 3dmirror to complete the model.

I start by setting osnap to end, nearest and node (for the point of symmetry). I typically like to start creating splines with the fit method knowing I will manipulate the CVs to get the final shape I want. Note that splinedit e (edit vertex) steps you through each "next" (n) CV or "previous" (p) CV at which point you can move (m) or add a CV (a).

When creating the spline you can specify the tangent vector. It is handy to have a line to reference when doing so. If you want to control the end tangency vector after you create the spline simply move the CV before the end CV to specify the direction of the tangent vector. At 2:10 in the screencast I create a construction line to reference when moving the nearby CV to make sure it is on the desired plane.

https://autode.sk/3a8HNLU

Re: How to draw a Pipe in 3D

R_Tweed — Thu, 11 Feb 2021 18:57:38 GMT

I created the the path for two pieces and then used union to join the bars. UCS allows you to align to the separate sections to create the bends. This would be similar to taking the bar, bending it and then rotating the assembly and bending it again. See (screencast)

Re: How to draw a Pipe in 3D

Kent1Cooper — Thu, 11 Feb 2021 20:11:04 GMT

Simplest way, I think: I broke the mid-cross-bar part at its midpoint to work with half of the thing [left] for the first few steps. I EXPLODEd the Polylines, so their line segments were just Lines. I set a UCS with its XY plane defined by the outer two Lines:

and FILLETed the corner [right above]. The reason for Exploding the Polylines and making the pieces just Lines -- you can't Fillet a Polyline with a Line that's not in the Polyline's plane, so for this Fillet, you don't want the midway piece and adjacent arc connected to the next one as a Polyline.

I returned to the WCS, MIRRORed the pieces across the midpoint, and JOINed them all together into one Spline [lower left below]:

Then I drew a CIRCLE [anywhere], and used SWEEP with it along the Spline path [upper right above, and below].

EDIT: In further experimentation, I find that you can FILLET two Lines if they share a common plane, any plane, and that doesn't even need to be the XY plane of the current UCS to do it, as I was assuming. So you can skip the changing-the-UCS-and-back parts of the above.

Re: How to draw a Pipe in 3D

Drewpan — Sun, 14 Feb 2021 00:59:20 GMT

Hi Guys,

Thanks all so much for your help.

Of the several varied techniques (There is more than one way to kill a cat than drowning it in butter!)

I actually discovered by accident the difference between 3DROTATE and ROTATE3D.

In this particular case it did what I wanted, which was rotate the section along a known axis.

The good news is I have learned a few more tricks from you wonderful people.

I did try the change the UCS method but couldn't quite get it where I wanted. I do know about

changing the UCS but haven't needed it before.

As for Splines, I am also familiar with the command and have used it a few times.

Basically I am learning how to use this stuff practically as it is very different from doing

a set Tutorial with relatively easy shapes to Design it Yourself and work it out as you go.

I am enjoying the experience and learning which is the point.

As I have said, I may never actually fabricate this bicycle, but it would be nice to know that I

COULD make it if I wanted to.

Cheers All.

Andrew