Intro: SAE BAJA CHASSIS
So this professor of mine had a vision a few years ago to gather up a few Mechanical Engineering students and start a SAE Baja team. The first year was a bust, but this year is looking up. After having a first hand experience at the competition and Technical Inspection, all lot more thought and time has been invested into this new build. In this instructional guide, I'm going to give some pointers on how to build a SAE Baja chassis.
Step 1: Step 1: LEARN THE RULES!!!!!
The most important part of your Baja design and fabrication is to ensure the every member cut and attached to the chassis is within the specified rules and regulations. READ, READ, AND READ!!!!!
Step 2: Step 2: Be Creative and Design a Sweet Chassis Frame
Don't be afraid to think outside the box here. As long as you can stay within the bounds of the SAE rules, the sky is the limit for a design. REMEMBER THOUGH! Even though you can make some sweet designs with insanely slick bends, you will likely NOT be able to replicate it in the real world. Does someone smell marshmallows and a camp fire?
Step 3: Step 3: Test Your Design With a Little FEA. Don't Be Scared, Just Press the MAGIC BUTTON
This step is kind of important. Use your SOLIDWORKS Simulation to conduct FEA on your design. This will help you get an idea of the how well the chassis will hold up when it's taking a beating on the track or starts doing front flips after coming off a jump wrong.
Step 4: Step 4: Sanity Check!
Stop what you are doing, sit back, and run a quick sanity check. If you feel certain you want to continue after this, then proceed to the next step.
Step 5: Step 5: Find Some Extra Hands
At this point, you might want to find yourself a little help. This project can get deep quick.
Step 6: Step 6: Let the Fabrication Begin
The best method I have found for building the chassis is to start with the rear roll over hoop (RRH). This is pretty much the back bone of the chassis. Find yourself some plywood and make a jig/template to build around. Once you have your measurements laid out and the board cut, you can start sizing, cutting, and bending your tubing. I would recommend getting a good protractor, a tube notcher, and a really good bender.
Step 7: Step 7: Read the Rules
You will need to continue to return to the rule book to ensure you are staying within the SAE specifics.
Step 8: Step 8: Build Prototypes
Prototyping other components of the Baja is a great way to ensure the chassis has enough space and is oriented correctly.
Step 9: Step 9: Lets Get It Together
So now that you have your RRH completed, start building the rest of the chassis. The rear end is probably the best way to proceed here. It will likely be smaller than the front members, and it makes it easier to continue the flowing contour once it's in place. Here we boxed in the rear end with some sweet bends, but made sure that it attached to the RRH above the specified 8" minimum height. MIG welding was used for this build, because the shop TIG had a thumb control instead of a foot control. I attempted the TIG, but I am not coordinated enough to roll the thumb wheel while trying to keep a good arc distance. If you are able to do this or have a TIG with foot control, then I would recommend that method. NOTE: ALWAYS USE EYE PROTECTION!!! No one likes a squinting welder.
Step 10: Step 10: Moving Forward
Once you have completed the rear end, continue to move forward on the chassis. Here we proceeded from the bottom of the RRH to the nose, so the front suspension guy could start his stuff. Same techniques apply here. Measure, cut, bend (if required), and weld. Also, you have probably returned to the SAE rule book about a dozen times now. Remember, "Ok it is you do Young Padawan. #Yoda_is_the_man"
Step 11: Step 11: Move'n on Up
Next we moved to the upper members and side impact members. Measure, cut, bend, weld, and repeat! Oh, and check those calculations again!
Step 12: Step 12: Sanity Check!
Just to help you stay in good spirits. Just say'n
Step 13: Step 13: AW SEAT!
Here we received our new seat and are making sure are calculations and assumptions were correct. Good idea before getting too far into the project.
Step 14: Step 14: Add in Extra Support
Here we have added in a few upper gussets and lower side impact members. Not only should these keep us safe, but it'll help make the Tech Inspection run smoother by removing any "You Need to Have"situations.
Step 15: Step 15: V'ROOM
Testing out the seat vs. steering wheel heights and locations. Not a bad idea to check as you go.
Step 16: Step 16: Add in the Sheet Metal
Here we used cardboard to make a template for the firewall. After sizing and cutting the sheet metal, holes were drilled and rivets were installed so that sheet metal strips could be installed that would cover the joining sections. Weld bolts were installed to fasten the firewall sheet metal.
Step 17: Step 17: Chassis Complete
The image shown is of the completed chassis. Now the welds need to be cleaned and then comes a paint job. The only additions to the frame now are mounting brackets for the suspension guys.
Step 18: Step 18: DESTROY ME
This is one of the most important tasks you will need to complete with this project. Two samples will need to be made for Technical Inspection. The one shown above is a T shaped assembly. The sample was installed into a tensile test machine and pulled until failure. The SAE requires that the tube breaks near the weld, but not at the weld. This was a great test. As you can see, the tubing eventually failed at 26,800 lbf!!! That's awesome sauce!
The chassis is now complete and is ready to have the steering, suspension, drivetrain, and braking systems installed. I think this Baja will rock it out in Maryland this year. I hope this Instructable was useful and that you will enjoy building your own Baja.