Northeastern Electric Racing: 2024 Chassis Manufacturing
Jig Design Concept Overview
Chassis Jig Design
The welding jig for the chassis needed to be easy to manufacture, fix all tubes in their desired positions, and remain structurally rigid during welding.
​
I chose and prototyped the final design concept for the jig, which started with welding key vertical planar faces along the chassis as mounting points for all other tubes. These planes were welded on pegboards, which are explained further below. Then primary jigs in the form of planar sheets would position all tubes. Then secondary jigs would be used to interlock with primary jigs, keeping them from deflecting. The result was a network of jigs runnign horizontally and vertically along the chassis, fixing all tubes in place. All jig pieces in this design are planar and could be lasercut or CNC cut.
​
As a note, I did not design all of the jigs shown to the left. However I researched and started this design concept, designing the first revision of all pegboards and primary/secondary jigs for the front section of the chassis.
Pegboards
Pegboards served to weld key vertical planar faces along the chassis. This design used steel dowel pins to precisesly position tubes. A planar jig was used to locate all of the dowel pins, and consisted of two layers made of sheet steel and MDF. Steel was used as the top layer for fire safety during welding, and formaldahyde-free MDF was used on the bottom to add more thickness to the sheet and minimize dowel pin misalignment.
​
I research and tested this design concept, and decided to make the pegboards two layer jigs. This decision ensured safety during welding and was significantly cheaper than using multiple layers of sheet metal.
Manufactured Pegboard
Primary/Secondary Jigs
Primary jigs were used to locate and fix all tubes in the chassis. Using large planar sheets minimizes the number of jig parts and allows for tubes to better locate relative to eachother. These jigs would be cut from sheet steel for rigidity and easy manufacturing.
I researched this jig concept and created the first revisions of the front section primary jigs. The remaining primray jigs were designed based off of my initial designs.
Primary Jig
Secondary jigs were used to eliminate bending/deflection in the primary jigs by interlocking with multiple primary jigs along the top edges of the jigs. These jigs were also cut out of sheet steel and two were used in parallel to keep primary jigs from twisting in the secondary jigs.
I researched this jig concept and created the first revisions of the front section secondary jigs. The remaining primray jigs were designed based off of my initial designs.
Secondary Jig
Material Selection/Sourcing Outcomes
When looking for jig materials, we were going to use MetalsDepot for all the sheet metal. I researched a couple of different vendors to compare prices. I found a local vendor that was about 25% cheaper than our original supplier, reducing jig cost.
​
Much of the team was opposed to using MDF because most MDF compounds contain lots of formaldahyde, wich releses as a toxic gas when burned. However, I researched and found that our school's makerspace sourced formadayde-free MDF, and sourced this material for all of our pegboards. This sourcing effort was critical to ensuring welder safety in the event of the jig catching fire (which never came close to happening). It also provided proper support for the dowel pins and was far cheaper than using multiple layers of sheet steel.
Tolerance Tests
Manufactured Jig Tolerance Test
To ensure minimal tolerances on tube placements, it was crucial for any interlockign features between jig parts to be tight, but still easy for assembly.
​
I created this tolerance test to determine what design dimensions were needed for all interlocking features in the jig. This sheet tested the proper fit for dowel pins on pegboards, the fit between primary/secondary jigs and the base pegboard, and interlocking features between primary and secondary jigs.
​
Dowel pins as well as a test handle could be inserted into the test sheet, allowing us to test different tolerances for the fit we wanted the best. This test sheet was cut out of both MDF and sheet steel, testing features dimensions for both materials.
​
This test was a simple yet critical step in the design process, and provided us with information that resulted in a welding jig with all pieces fitting tightly and positioned correctly.
Assembled Jig
The welding jig was a major success, resulting in a chassis accurate to the intended design. As we continue to evaluate the manyufactured chassis to our CAD, we took a simple tape measurement of the chassis length, and it was exact to the CAD at 92". The tolerance on our previous chassis was about 1-2", whereas the measured tolerance on this new chassis' length is the tolerance of a tape measure.
Fully Jigged Chassis
Me Celebrating a Fully Welded Chassis
Relevant Skills
SolidWorks Assemblies
Used to reference all jig features from the chassis design.
Lasercutting
I manufactured all MDF parts and contributed to file preparation for many sheet steel parts