Loft and construction geometry

Tutorial series: Introducing Shapr3D basics


← Back: Bodies and patterns, part 2Next: Combine sketch tools and adjust with Design History →

What you'll learn

Create the framework for motorcycle handlebars working with the spline tool, construction planes, and a guide curve.



In this video, we are going to tackle the challenge of recreating the handlebars from this motorcycle model. This will involve a loft and quite a bit of construction geometry. So let's get started. I'll make a new project and open a new sketch on this top plane. From here, I'm going to make a rectangle starting from the origin and dragging it out. There are three types of rectangles.


Center point, three point or diagonal. You'll notice they all have the hotkey R. This just means that once you initiate the rectangle command, you'll have to switch to the specific type that you want using the drop down arrow next to the icon in the sketch toolbar. I'll select the whole thing and make it all into construction geometry. This is going to allow me to apply linear dimensions.


geometry that's not really straight. Now we have to get this rectangle squared up, clamp it down to the origin, and lock. Let's make it 12 inches wide and 8 inches deep.


Now I'm going to draw a spline. This one is only going to have three points. So I'll click at the origin, click in this area, and then click at the corner. And then hit escape or right click or however you get out of the spline. I also want to add a couple of lines. So I'll add a line horizontally here at the origin and then I'll add another line that's going to wind up tangent to the spline. But I'll just put it here.


both of these lines.


Both of these are going to be construction lines. Now I can tell that here I've made a mistake and I can grab this endpoint and drag it onto the origin. Now I want to make this spline tangent to the line so that when it's mirrored, it's a smooth curve right across. So I'll select the spline, Shift select the construction line and make the tangent constraint.


Now I can see that my rectangle is not where it's supposed to be, so I'll click on the line here in the rectangle, make that horizontal. Slowly getting everything in place.


I'll also click on the spline, shift select this angled line and make those tangent. And now I want to give an angle between the construction line and the rectangle. So shift select those two and key in 110. Now that's all we need to do in this sketch for now. So I'm going to exit this sketch. The next thing we're going to do is create three cross sections. This is a circular cross section.


but it decreases in size from one end to the other. So I'll use the orientation cube up here to reorient the view slightly and open a new sketch on this plane. I need a 3D view of the situation here. And so I'm going to use my space mouse to reorient the view slightly.


And here I am. I want to create a circular cross section for my loft, but there are a couple of secrets about lofts that the documentation doesn't tell you about. Or it does, but it's a little bit cryptic. If you're using a guide curve with a loft, your cross sections have to touch the guide curve precisely. We'll start out with an easy case, and then we'll get a more difficult case later on.


I've got my circle here and I want to start out with a two inch circle. So that's easy enough. I'm going to add a construction line and I'll make this right here and select that line and turn it into construction. And then I can drag that endpoint onto the origin and it snaps into place.


Okay, so that is set up properly. My guide curve intersects my cross section at a specific point. This would not work, for example, if the guide curve hit the circle at the center point, and that's the important distinction here. So next, I need to create another cross section, but I'm going to do it in the middle of the curve, and this is how to do that. Add,


construction plane, you can set the option to perpendicular to curve at point. So I'll select this curve and drag this point into the middle. If you needed this to be at a specific point on your curve, we could have added construction geometry in the previous sketch and then it would give this point something to snap to. But in this case, we just need it somewhere in the middle of the curve.


We're done with that. Now we need to open a new sketch on this plane. And again, the software has squared us up to the view. But it's easy enough to reorient the view so you can see it in 3D. You can see a very small point in the middle of this curve. It says plane intersection. That's where the sketch plane intersects that guide curve. And that point turns out to be very important to us.


So let's first draw a circle and then again draw our construction line from the center.


Select the line, make it into a construction line, change the diameter of the circle, and make sure you're getting the diameter instead of the radius. So here we'll change this to 1.8. And now I'm going to grab this endpoint of the construction line and drag it back onto that tiny point plane intersection. You'll see the tool tip pop up. Your guide curve always has to touch the shape.


Now you don't always have to use a guide curve, but in this case, we want to drive the shape of these handlebars with the guide curve. All right, so we've got two of these cross-sections set up properly. We'll exit this sketch and we'll do it again just for practice. Add, construction plane, perpendicular to curve at point. We're gonna pick this spline again.


and move the point to the end. Click Done.


add a sketch to this plane.


Reorient the view slightly.


Sketch a circle.


In this case, we'll type in 1.5.


going to add a construction line from the center to the radius.


Select the line, turn it into construction.


grab the end point of the line and pull it onto the plane intersection. Okay, so now we have three cross sections and we'll finish this in part two video.


Try it yourself

Motorcycle cover
Piston rod
Rod clamp
4 motorcycle wheel
Block casting


About the instructor


Matt Lombard is an independent product development professional, working in the field for 30 years. He has done a variety of work from plastics design and surfacing work to writing instructional and reference materials and writing about the engineering technology industry. Matt has also served as CAD Admin, PDM implementor, and engineering process consultant.

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