- [Instructor] We can really see our bike frame
starting to come together now.
And in this video,
we're going to finish off the front triangle
by adding in the down tube.
We'll follow the same process
that we used for the top and the seat tube.
So, open the assembly that you've been working on.
And first let's insert a new plane for the down tube.
Go to the assembly tab and click on reference geometry
and choose plane.
For the first reference,
let's choose that down tube line.
And then for the second reference,
let's choose the front point of the line.
Press OK.
And let's call this new plane down tube plane.
Now let's insert a new part into the assembly.
So go to assembly,
click on the dropdown under insert components
and choose new part.
Similar to the previous parts, depending on your settings,
you might be prompted to enter a file name at this point.
And if so, call the new part down tube.
Then you should be back in the assembly
with this little green tick next to the cursor.
So let's select that new plane we just added,
the down tube plane.
And now we can sketch the tube profile on that plane.
Get the circle tool,
zoom in and let's draw two concentric circles
at the end point of that line.
The outer diameter is 25.4.
So it's one inch.
And then the wall thickness is 0.9 millimeters.
So grab this second circle.
Make sure it's inside the first one.
And then get smart dimension.
Just click on both circles and make it 0.9.
Then we've got a fully defined profile sketch.
And we can use this to extrude the tube.
Let's go to features, Extruded Boss Base.
And from the dropdown let's choose up to surface.
And for the surface,
let's choose the outside of this bottom bracket shell.
So we're extruding
all the way down to the bottom bracket shell there.
And then on this end, let's offset the start point.
Go to from here on the left,
click on the dropdown and choose offset.
And let's offset 40 millimeters.
And then flip the direction by clicking this box,
if you need to.
And then activate direction two and choose up to surface.
So let's choose this surface,
but don't press OK yet.
And let's have a closer look.
We're actually straddling two surfaces
because of that curve.
So if we go all the way up to this surface,
then we're going to be cutting into this bottom surface.
If we try to go up to this bottom surface,
then you see that doesn't really work correctly.
So instead of up to surface, let's use up to body,
which is this one.
It's pretty similar really.
But we can choose the entire body.
And now that looks correct.
Let's press OK to add that feature.
And then exit editing the part by clicking up here
in the top right.
Now at this stage we can rename the part if you need to.
So right click on the part, press rename.
And I'm going to call it down tube.
You can also save your assembly.
And if you're prompted to, just save that part externally.
Now let's have a look at the part and see how it looks.
So in the graphics area, it looks good at this end.
I'm just going to zoom in on this end.
It looks okay.
If we do an interference detection.
So go to evaluate interference detection and calculate that.
You can see we've got an interference down here
in this red area.
The problem is that we notched this end of the tube,
but only against the bottom bracket shell.
We didn't notch here against the seat post.
So there's actually an overlap here.
So we need to cut away
either some material from the down tube,
or from the seat tube,
or from both of them and meet in the middle.
As far as I know, there's no hard and fast rule for this.
But generally, I've seen the down tube
notched more than the seat tube.
So we'll go with that.
I'm going to exit this tool.
And there's a few different ways
we could do this in SolidWorks.
But probably the most foolproof
and the easiest way to avoid any errors with the angles
is to use the cavity feature.
So let's edit that down tube part.
Click on the part and press edit part.
And let's use the cavity feature.
This can be found in insert features cavity.
So any components or any parts
that we put in this design components box
will be cut away from the part that we're editing.
So I'm going to click in that box, keep the scale at zero.
And let's choose the seat tube there.
So now when we press OK,
every way that the seat tube overlaps with the down tube
will be cut away from the down tube.
So I'm going to press OK.
Now we've actually cut the down tube into two new bodies.
Because we've just cut away that overlapping section.
So we need to choose which bodies we want to keep.
Click on this option, selected bodies.
We can have a look at what the two bodies are.
So for the first one, it's this large down tube body.
And then for the second one,
it's just this small section here.
We actually want to keep that large one
and get rid of that small one.
So let's just put a check in that first option.
Your numbers might be the other way round.
But we want to keep this large section.
Press OK.
And now we've got that nice double notch there.
So we've cut away here and also here.
So now we can exit editing that part.
We can zoom out and try interference detection
one last time.
Go to evaluate, choose the tool, press calculate.
And now we've got no interferences.
So that looks great.
And at this point, you can save your assembly.