Reverse Engineering a Motorcycle Foot Peg

Part 1: Planning Out A Project

Any bike lovers? I have a 2003 BMW F650CS. A while back, a friend of mine was transporting it for me and he accidentally sheared off one of the foot pedals. I can’t get too mad at someone doing me a favor so when he offered to get it fixed, I said, “Nah I’ll take care of it.” Later I saw a set of the foot pegs on eBay but didn’t pull the trigger on purchasing them. I decided to replace them with generic ones, though I wasn’t satisfied. Like a true engineer, I realized this was a perfect chance to do some reverse engineering. Follow along to see how I leveraged the capabilities of SOLIDWORKS and Markforged for my DIY project.

This series will go over the steps that I went through and some of the essential detours on my road to success. Hopefully, I’ll even have a finished product on my motorcycle when everything is said and done, to show off when I go for rides. I will be highlighting some of the built-in features of SOLIDWORKS and some of the training that is available here at DesignPoint. For anyone who has a project where they need to resurrect a legacy part or make something new from concept sketches, this series should give you some good pointers.

Measure and Take Pictures

I’m sure you have all started out with the best of intentions and then hit an immediate roadblock. My first challenge was: How am I ever going to create something so complex in SOLIDWORKS from scratch, especially when I have to measure curves?

Motorcyle Part

First of all, there are some straight sections where I can use good ol’ calipers and get some basic dimensions. For everything else we’re going to import pictures directly into SOLIDWORKS sketches. Then, we can use splines to capture the basic shape.

Plan Approach - Where is Accuracy Essential?

We should try to use SOLIDWORKS solid modeling techniques where we can, but, eventually, we’re going to have to transition to surfacing. Don’t worry too much about it, though, because we’ll show you, step by step, how to do that in our next post. For now, we can start with the back bracket where it would fit onto the motorcycle. These structures are linear and, honestly, they need to be in order to fit onto the pin. However, the rest of the foot peg is more aesthetic and contains more curvature. In order to design these parts we will use top down modeling and multi-body design to determine the shapes simultaneously.

plan approach 1

Initial Design – Solid Modeling

One of the most difficult aspects of this design project is the asymmetry. There are actually two ways of looking at aligning this object:

1) Relative to the footrest where the rider interacts with the peg
2) The back bracket where the peg interacts with the motorcycle

In both instances, each is offset by an angle and must be accounted for in the design approach, especially when considering improving the strength of the design. In fact, the part was sheared at this interface of the two alignments, so this is critical. In order to make the next portion of the design process easier I chose to keep the front, top, and right planes relative to the rider because that will help when we are doing the more difficult steps. Feel free to look over the included model to see the approach used and consider if I’m going to run into any problems later (pro tip, I am)!

What's Next?

So far we’ve done a pretty good job of planning our project.  By gathering information, measuring and taking pictures, planning our approach and mapping out the initial design via Solid Modeling, we’ve set the right foundation to (hopefully) move forward without any problems.  Check back next time when we will use Surfacing to keep the project running smoothly.