2.007 Grand Prix

The end of a long semester with 2.007 is finally here! We will have our final race this Sunday at the Albany St. parking garage and we will also be having a drag race in the nearby area. This also marks the end of phase 1 in the development of MelonKart. The project has come a long way from a concept in early February to a fully-realized, functional vehicle ready to race. Here is a general wrapup and assessment of the project in my own opinion, and a list of improvements that I would like to make or things that I wish we would have done differently.

Acceleration and Speed: Exceeds Expectations
MelonKart was much lighter than planned, so the acceleration is significantly more punchy than predicted. I am still amazed with the how fast it feels to drive the go-kart, since it is only using one model airplane motor.

Handling: Acceptable BAD
I would like to accurately model the steering geometry in the future with MATLAB or SolidWorks and refine it to make it more linear in nature. I also would like to add a steering ratio similar to a real car into MelonKart. There was also some manufacturing error in the uprights that severely increased the camber of the front wheels, and I believe that the handling would have a substantial improvement if this was corrected. I flipped MelonKart twice in the competition; steering needs improvement.

Robustness: To be determined, but so far so good
We have accidentally blow several of the fuses in the batteries by accelerating too hard and having the software limit in the motor controller set too high and have suffered no ill effects in the electrical components of the vehicle. We have also hauled the Go-Kart around campus to be filmed for 2.007 and for the DeFlorez Competition (We won a hundred bucks!!), as well as demonstrated it at the MAES extravaganza and MelonKart has held together (even with Radu and Actanner taking it for test rides) so the mechanical components seem to have a certain amount of durability to them. It also did not suffer damage from a few crashes.

The final race video

MelonKart at the DeFlorez Design Competition

Future Improvements

Add a second MelonMotor (if they ever come back in stock on HobbyKing)
Switch to a belt drive that has an auto-tension, or redesign the tensioning system for the chain
Add more structural rigidity to the motor mount and support the motor on both sides
Consider a roll bar?
Weatherproof the system
Increase the ground clearance to not drag on a speed bump

Takeaways

I think I took a lot away from this class. First, I now possess half of a functional MelonKart and an extremely messy design notebook covered in chips and cutting fluid. Beyond these physical takeaways, I really feel more confident as a mechanical engineer. I got to collaborate on a project, go through an entire design process, create a working CAD model, source parts for our design, create a manufacturing plan, build it, troubleshoot, and finally walk away with a working thing. I think that out of everything that an engineer does, the design process is what really stands out to me as a quintessential engineering trait. This project made me feel more like an actual engineer than any pset or test ever has. I really enjoyed the team aspect as well, and feel that the sum of our two ideas on the Go-Kart made it a much better project than either of us would. This project gave me more confidence in working with a higher voltage and a much more powerful system than I have ever worked with before. This class also renewed an interest in building things and applying the knowledge taught in my classes, hopefully resulting in many more successful projects!

So this will be my first post. My name is David Wise and I am currently a sophomore in Mechanical and Ocean Engineering at Massachusetts Institute of Technology. I started this blog to document the various projects and other cool stuff I do while I am here at MIT. I have tried to update the pages on the sides with projects that I have already made substantial progress on. But now that is enough about me. Let's talk about something substantially more interesting...

This is the name of the Electric Go-Kart that Jackie and I have been building as part of 2.007: Design and Manufacturing 1. We will eventually compete with a handful of other kids that have been building electric scooters, roller blades, skateboards, and tricycles under the tutelage of Charles in a race in May. We are pretty far along with the project at the moment (just putting on some finishing touches) but I will try and go through the construction from the beginning

MelonKart after its first official Garage Run (1:35, 23.5 W-H)

Some of the preliminary Solidworks Models of MelonKart

Measure Twice, Cut Once...

Here is the start of our construction. We bought the red plastic seat form Summit G racing and about 35 ft of 1" x1" 16 Ga square steel tubing from Ebay. We cut the frame tubes to the correct length and then we cleaned the ends with a grinder and a wire wheel to prep them for welding. We were planning on using the TIG welder in the metal shop in N52 to do the welding. The only problem being that neither Jackie or I had ever used the TIG welder before... 

Which is where Dario came in. He is on the Formula SAE team here and one of my suitemates in Burton-Conner. He offered to teach us how to use the TIG welder and helped us tack the frame together.

Me welding a practice piece of tubing before working on the actual frame.

Now that the frame had enough welds on it to be load-bearing, we began to attach our snazzy red seat.

Drilling holes for the mounting brackets

The seat is mounted!

I spent a good chunk of my time designing an fabricating the uprights and the steering linkage. This is the front left upright after I had welded it.

Sizing the bolt that would act as a kingpin

I did some FEA analysis on the axles that came with the wheels from Monster Scooter Parts that we were planning on using and decide that we were pushing the limits with a 10 mm diameter axle if it was cantilevered. I designed a set of aluminum step shafts that would work with 6903 bearing to replace the stock ones. I got to learn to use the CNC lathe at the Edgerton Student shop to manufacture them, which definitely saved some time!

Here we are sizing the length of the steering column. We decided to use an old endcap from an underwater vehicle that we found in the MRT lab as a steering wheel, for nostalgia.

Skipping ahead a little bit

We have finished the front steering linkage, mounted all the wheels and the questionable quality brake (we salvaged the brake cable and handle from a dumpster) and mounted the namesake of our project: MelonMotor.

Rolling Chassis: COMPLETE!

After an all-night marathon, the entire electronic system is in place. The orange batteries were donated by A123 and are Li-Ion Phosphate and we are currently using one of the KBS motor controllers from Kelley. The powertrain is a 4.5:1 ratio with #25 chain.

Charles programming the controller.

IT'S ALIVE!!!!!!!!!!

MelonKart works! We even got to debut it to an audience of about 200 middle schoolers. Ed Moriarty of the Edgerton Center was asked to give a keynote speech about engineering and asked me if I had been working on anything cool recently. I thought MelonKart fit the bill, so in the middle of his introduction I got to drive in to Johnson rink honking the horn and do a loop of the building before parking in the front while Ed finished his speech. It was a ton of fun!

Adrian testing MelonKart later that day

and to culminate this exceptionally long post: the video of the parking garage run #1

 

Youtube links: here and here

so this is the current state of our project. I will try my best to update as much as possible and Thank you for reading!