From the course: Fusion 360 Modeling Techniques and Workflow

Sketch - Fusion 360 Tutorial

From the course: Fusion 360 Modeling Techniques and Workflow

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Sketch

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- [Instructor] In this chapter, we're going to be tackling the design of the head tube of the bicycle frame. The head tube of the bicycle frame is a little bit of a tricky tube. I say this because there is a bearing on both the bottom, and the top of the tube that are both different sizes. Now, when you're working with bearings, it gets tricky because you need to have a very precise internal geometry that correctly locates the bearing in the right space so that you have the right axis of motion. Also the correct tolerance for that bearing to fit inside so that you have a good fit. Now for a bicycle frame, the reason you have these two bearings is so that the steer tube of the bike fork can go through the bearings and be rotated to control the steering of the bicycle. The technique we're going to use to draw the head tube is a sketch that is the cross section of the bike tube. Just one side of that tube, that's then going to reference the head tube line that we made in our previous chapter, we're then going to use a tool called revolve to basically spin that sketch around that access, and create a 3-D part. So let's go ahead and get started with our sketch. Now we're going to go back to the same view we had before, which is the left side, and we're going to create a sketch. So menu bar, top left corner create sketch, and we're going to select the construction plan we did before, which is our origin. We're going to go ahead, and use the line tool, which is in the menu bar all the way on the top left. You can also use the L for the hot key, and we're going to select the end point of the head tube here. Let's zoom in a little bit. And you can see how it snaps perpendicular the 90 degree or perpendicular mark to that head tube line that we need. So we're going to let it go there, and we need to be 26.05 is the radius of the OD of the bearing. And now we see that the geometry, it is 90 degrees, but we didn't get the icon. So we're going to do is let's use the perpendicular constraint tool, and let's select that line and select that line. So that way we know that these two lines are perpendicular to each other, which is what we need. Let's go ahead, and hit L for the line tool. And let's create an extension to this. Let's make this 3.5 millimeters, and that's going to be the thickness of the head tube in this area. You can also see that we have these two parallel marks that popped up. Now, that means that is a constraint so that these two lines are parallel. So that's what we want because it's a continuation, hit enter. Now let's go up to the top of the tube, and create the same line set up, but for the new bearing size. So the bearing on the top, the radius of the OD is 20.55 millimeters. And we got that, so at this time it snap to perpendicular. So we don't need to do anything else. And then let's continue that line, and this top one, we'll do three millimeters. Now go ahead and zoom out, and let's go ahead, and use the spline tool to connect these two points. So you'll see here, what I'm doing is I'm creating a couple extra points at the ends of the two. Now, the reason I'm doing that is because we have the bearing races that are going to be done right there. So we might want to finesse that outside, and control it around the race of the bearing a little bit. So I'm just giving us a couple extra control points. And now let's go back in here, and we can edit this shape a little bit, cause we don't need it to bow out. Let me give it a little bit of an hour class feel. Now you can see how adjustable this is, and you can do this however you like. You can also adjust the radius of these arcs, and also the pivot of the arcs makes a very big difference. You get the feel of this. So I'm pretty happy with that for right now. That's the right look. Now that we have that, this is the outside of our head tube. So this is going to be the top of the head tube. This is the outside wall of the head tube, and then this is the bottom here of the head tube. Now that we have the outside of the head tube, all designed, we're ready in the next video to dive into the internal geometry.

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