3D CAD Software Comparison Blog Series: Starting the Motorcycle Frame Design in Solidworks™ 

Welcome back to our 3D CAD software comparison blog series. Recall that in last week’s discussion, as Mechanical Engineering Consultants we introduced our plan to to model a motorcycle frame in three different 3D CAD software packages.  We gave a brief history of the three CAD software packages that Glew Engineering employs: Solidworks™, Creo™, and Inventor™.

In this week’s blog, as Mechanical Engineering Consultants we use Solidworks™ CAD software to model a portion of the motorcycle frame, a simple tube, while comparing three modeling techniques:

  • Extruding
  • Sweeping
  • Weldment

Motorcycle Frames

We designed a simple bobber inspired motorcycle frame, this is conceptual, yet realistic enough to illustrate our points. See Fig. 1.

Solidworks CAD Motorcycle Frame Components

Fig. 1 – Rigid Bobber Frame Components[1]

3D CAD Software Sketching and Feature Generation

For comparison, as Mechanical Engineer Consultants we modeled the bottom rail portion of the motorcycle frame via three different techniques: (1) an extrusion, (2) a sweep, and (3) a weldment.  Each modeling technique has advantages in certain design scenarios. In other design scenarios, any modeling method may do.  As is the case in most 3D CAD programs as well as Soldiworks™, one first creates a 2D sketch of a profile, then converts it into a 3D feature.

Solidworks™ Extrude Command

First,  we created the motorcycle frame bottom rail from a 2D sketch of two concentric circles (to simulate the tube profile and wall thickness).  We extruded it to a specified length of 20 inches. Solidworks™ represents the length with the parameter D11, visible in the figure. See Fig. 2.  This parameter can be changed, hence the term "parametric design." As Mechanical Engineering Consultants we have many tools available to perform the most intricate of designs. 

Motorcycle Frame Bottom Rail Solidworks Extrude

Fig. 2 – Motorcycle Frame Bottom Rail via Extrude Command

Solidworks™ Sweep Command

Secondly, we created the motorcycle frame bottom rail with the Solidworks™ Sweep command. It requires a 2D sketch of the geometric profile, in this case the concentric circles, as well as a 2D sketch “path” to sweep the profile over, creating the 3D part. See Fig. 3.  This is analogous to gouging out a groove using a chisel to follow a penciled line drawn on a piece of wood.  The shape of the chisel is the profile and the penciled line in the wood is the path. 

Motorcycle Frame Bottom Rail Solidworks Sweep

Fig. 3 – Motorcycle Frame Bottom Rail via Sweep Command

Solidworks™ Weldment Command

Thirdly, we created the motorcycle frame bottom rail using the Solidworks™ Weldment command.  See Fig. 4. It creates information in a Solidworks™’ database to recognize the feature as a welded or weldable part for manufacture. Soldworks™ contains a list of weldment profiles from which to choose, including both ANSI and ISO metal pipes and beams. 

Motorcycle Frame Bottom Rail Solidworks Weldment

Fig. 4 - Motorcycle Frame Bottom Rail via Weldment Command

Solidworks™ Feature Comparison: Extrude vs Sweep vs Weldment

There are advantages to each technique: (1) extrusion, (2) sweep and (3) weldment.

  • The Extrude command is simple to use, but requires one to piece together individual parts to form an assembly. This procedure may be tedious for large welded structures, such as motorcycle frames.
  • The Sweep command in Solidworks™ may fail due to geometric interference when sweeping a large 2D sketch profile over sharp transitions along paths, and should be considered carefully.
  • Because Solidworks™ treats weldments differently, observe care when drawing the 2D sketch path the weldment will follow.


As Mechanical Engineering Consultants we designed a custom bobber motorcycle frame.  Next, we modeled (designed) a portion of tubing in the motorcycle frame with Solidworks™ by three different methods.  We showed that Solidworks converts 2D sketches into 3D parts in multiple ways. We discussed some of the issues faced with each of the three techniques we showcased.  As of yet, we have not determined which of the three is the best method.  However, as we progress through the design, there may suggest one method as the best choice for patrons of the frame.

[1] http://www.custom-choppers-guide.com/how-to-build-a-chopper-frame.html