Little Tikes Go-kart

August 24, 2023

Once I had the idea and looked for frames for a couple days, I found one in an autobody shop in northern Massachusetts and went on a roadtrip to get it and an electric motor from southern Vermont. It had smaller, and wider tires than many of the other ones I came across, and a frame that would be a good candidate for all the modification I was planning for it. 

August 24, 2023 Continued

Once I found a the shortest wheelbase I could have without modifying the steering column (which would take longer than the time I had) I cut 22" out of the frame and ground off the floor pan. 

Next, I tried to MIG weld the front and back half of the frame back together, but due to my minimal experience MIG welding, and the thin walled, partially rusted tubing, it was hard to get a clean bead and I kept blowing holes in the tubing, so I switched to TIG for more control.

August 26, 2023

After getting the correct length, I cut the frame 5" narrower, to be able to cleanly fit through doorways with a couple inches of clearance to allow for wider wheels to be added later as well.

Although this was one of my first times TIG welding, it went very well and was great to learn on such a fun project too. There were 9 points to weld the frame back together with a mix of round and square tubing, and by the end I could see how much I had improved.

August 27, 2023

Next I cut a keyway in the horizontal mill, cut threads onto the end in the lathe and cut it down to size. The frame is now 5" narrower, but I only cut the axle down enough for it to not stick out past the wheels, and cut much longer threads onto end for later adjustability.

Next I faced the rear wheel hub on the lathe and then marked and milled out the internal shape of the mountain bike brake rotor. Then I drilled and tapped two bolt holes to hold it on as well. 

August 27, 2023 Continued

I used mountain bike brake components as I already had spares and experience servicing them from previous projects, and it allowed for less project specific parts and maintenance.

I then designed in Fusion 360 and 3D printed in PETG a spacer for the sprocket. I also had to drill new holes in the sprocket for the wheel hub hole pattern.

August 27, 2023 Continued

Next, using some of the square tube I cut out of the frame earlier I mocked up and then welded on a caliper mount.

August 31, 2023

With one day left until I returned to college for the semester, I cut the Little Tikes body apart to fit it onto the frame and allow a person larger than a toddler to fit it in. This involved cutting the inside of the door out and zip tying just the outermost wall back on, cutting the out the plastic between the roof pillars and sides of the seat to bend the seat plastic to create a deeper seat. I then added back in the seat pad from the original go-kart frame.

September 3, 2023

After finishing the brakes and electronics and putting the go-kart back together, I took it for a first test drive.

The brakes needed to be upgraded, and the brake lever remounted, but even running off 3x 4s 5.5Ah LiPo batteries it worked very well. 

Even from the very first time taking it out, it started so many great conversations with people walking by, started friendships, and even inspired some of the people I met the very first time out to build one of their own.

I met, talked with, and let over 30 people drive it within the first 3 times I took it out to test, something that would become a common occurrence nearly every time I took it for a drive. 

Not only was it super fun but it actually became a very helpful vehicle to get groceries in, as I could fit a backpack and two bags of groceries on it.

October 6, 2023

I upgraded the brakes to 2 piston hydraulic mountain bike brakes, which gave it a much better braking feel, as well as much stronger braking. 

In the first month one of only things that didn't work was that the mounts for the caliper were bending from the braking force so that the rotor was actually grinding into the caliper. 

The plastic lid for the phase connections also melted due to the phase wires and connectors being too small and overheating in the 90+ degree weather.

October 7, 2023

I sketched various methods to mount the much larger 48v 24Ah Li-ion battery from my e-bike project for the ability to have much more range.

I ended up with the simpler, quicker, and more easily adjustable system using straps that used to hold the batteries onto my racing drones that I had from previous projects.

October 15-27, 2023

Since a portion of the time I was driving the car around was at night, I had been using the lights from my e-bike, but I wanted to add permanently mounted lights as well, so I sketched various ideas for headlights and tail lights. 

I not only ended up adding headlights, but also EL wire to outline the body, and addressable LEDs to the bottom to look like it had star power from Mario Kart.

October 27, 2023 Continued

To power all of these lights, as I didn't have a buck converter rated for enough power that could run off of the 48v battery, I used two smaller ones I had, and made a box that took 33.6v in from the same Li-Po batteries that used to power the whole car, and output 12v and 24v to run the lights. I also added a small fan to keep it cool just in case the converters heated up.

October 27, 2023 Continued

To control the front led strip for the headlight I took an inline PWM dimmer and added a different connector to allow it be able to fit on the steering wheel.

I also designed and 3D printed a mount for the original horn from the Little Tikes car to attach it to the go-kart steering wheel.

Additionally, I added a new thumb throttle which was more ergonomic and didn't stick up as far from the steering wheel.

November 3, 2023

The people who I met the very first day I drove the go-kart got their go-kart running and so we talked and rode our karts around, and invited many of the other people that I met along the way who had been interested to talk about how they could make their own too.

I also ended up towing their go-kart back when the chain broke. 

November 10, 2023

Due to both the frame and wheels being narrow, the go-kart could be unstable at speed and could get up on 2 wheels or flip if you weren't careful.

The solution to this was getting racing go-kart wheels, wheel hubs and adapters. I cut the previous drive hub in half to keep the sprocket and rotor mount as well. 

The wider tires helped immensely and even if you tried now, you couldn't get the go-kart onto two wheels, and it had a lot more lateral grip.

November 26, 2023

The wider tires were also heavier, and so I upgraded the controller for more power, now almost double what it started as. 

However, the battery and phase wires on the new controller were very thin so I took apart and soldered 12 AWG wires onto the controller instead, as well as adding three more power wires to simplify the wiring and remove the need for a separate battery system to power the lights. 

December 31, 2023

After a lot of CAD in Fusion 360 I started machining a new sprocket and brake rotor hub. This would use a brake rotor with a much larger internal diameter, allowing it to be positioned much closer to the frame, reducing the standoffs that used to hold the caliper out from the frame. 

Not only does this provide an increase in strength, but also with this new design allows for easily changing between sprocket sizes as it uses the original sprocket holes, not the ones I drilled.

January 5, 2024

The next step in going back through and upgrading the silly car was upgrading the motor. I removed the stock 14 AWG phase wires and soldered 50% larger 10 AWG wires on instead. I had to Dremel the access hole larger to fit the larger phase wires.

January 5, 2024 continued

I drilled the holes on the end plates out for more airflow, and cut down and glued screen into the holes to stop dirt from entering.

Then I designed and 3D printed a mount for an 80mm computer fan to mount to the rear of the motor to increase airflow, and mounted a screen to the outside of it too.