mechanical design engineer
overview
To create a modular upright vehicle rack for sprinter-type vans.
From surfing to skiing, camping to biking, there is a constant need to swap out various racks from their sprinter van because conventional equipment racks in todays market cannot accommodate to housing different equipment, limiting the types of activities that can be done. This process of mounting and dismounting equipment and their racks can be very time-consuming and labor-intensive.
approach
The primary objective of the project is to produce an upright vehicle rack for a Mercedes sprinter van than can universally mount surfboards, bicycles, snowboards, etc. User requirements highlighted by the team and the sponsor include:
Provide rear door access while equipments are mounted onto the rack
Support an array of modular attachments that securely fasten onto the base and withstand normal driving conditions
Maintain its structural integrity when loaded with the maximum tongue weight capacity of 341 lbs during normal driving conditions
Prevent theft of modular equipment racks with a user-friendly locking mechanism
base design
The base is designed to stay on the hitch of the van, with four slots for different mount options. Since the majority of the load
lock mechanism design
Each rack is built using standard aluminum extrusions. By integrating a slot into these extrusions, we enabled a locking mechanism to slide securely into place, preventing it from being pulled out by thieves or dislodged by roadside turbulence.
Externally, the locking mechanism features a handle with a hole designed for a padlock. This ensures the mechanism remains securely locked, preventing it from sliding into the unlocked position and adding an extra layer of security.
rack design
By designing our racks around standard vertical aluminum extrusions, we were able to maximize the equipment capacity on the base. The square shape of the extrusion insert prevents rotation, reducing the risk of damage to equipment or the vehicle.
FEA analysis revealed that each aluminum extrusion could support up to 100 lbs of horizontal moment at a vertical height of 6 feet. This made it ideal for securely holding standard equipment like bicycles, snowboards, or surfboards. Additionally, we incorporated a storage locker as an alternative solution for camping gear, providing greater versatility to the design.
bike rack
surfboard rack
storage locker rack
rejected designs
Initially, we considered using pegboards for modularity, but we soon realized they weren't a reliable solution for heavy sporting equipment due to their reliance on hooks and limited thickness. Additionally, a vertically tall base attached to the hitch of a van created another issue—it obstructed the van doors from opening.
An alternative design, featuring slots extruding from the base instead of holes, also presented challenges. It proved more difficult to manufacture, less structurally robust, and uncomfortable for users to sit on. These insights guided us toward a more practical and functional approach.
manufacturing
During the COVID lockdowns, workshop access was unavailable, and many third-party manufacturers were closed, requiring extensive emails and special arrangements to process requests. These challenges delayed our prototyping, pushing us to improvise by using hand tools and plenty of elbow grease in our apartment living room to complete the project.
Buying Materials
San Diego is blessed with many manufacturing friendly stores. From acrylic plastic, hardwoods, to metal, all can be found in the Kearny Mesa area. One of the biggest takeaway from this job that helped me in my future projects is knowing all the available resources in my local area.
Water Jet Cutting
Due to COVID, our workshop was closed and only took tasks on reservation basis. After waiting for our turn, we were able to cut our sheet metal into the dimensions we wanted. We had one shot, no room for mistakes and re-cuts.
Sheet Metal Bending
After inquiring many many metal workshops in the San Diego local area, we were able to find one place that agreed to work on our non-bulk order.
Welding
We then found a different workshop that allowed us to use their welding set up. Since it was my first time welding, I let the expert do most of the work as I learned from the side.
Rapid Prototyping Racks
The equipment racks were made in my apartment using 3D printers for mounts/joints/brackets. Aluminum bars were bent literally using our body weight against the sidewalk curb. Without any machines, we used hand tools that we borrowed or bought to quickly prototype our racks.
Finishing
After being sanded, coated with primer, then spray painted, our base looked polished and close to a shippable product.
final thoughts
The primary objective was to transform our client's concept into a highly functional prototype. Once attached to the hitch, the base was designed to withstand up to 1,200 lbs of force, as verified through FEA analysis. As a proof of concept, our prototype successfully demonstrated modularity, the ability to accommodate multiple types of sporting equipment, and user-friendly convenience.
However, it was far from a finalized product. The prototype had sharp sheet metal edges, was costly to replicate with its current materials, and lacked additional rack design variations. With the proof of concept complete, the next steps were left to the client to decide whether to pursue further development.