1:1 Scale BuWizz powered Motorized Go-kart

[Zerobricks]

 

The go-kart is one my most ambitious projects. To build it, it took over 7000 Lego pieces, 32 L motors, 8 BuWizz bricks, one BuWizz app update and hundreds of man-hours.

The final build, can easily drive a 60+kg person with the top speed of 4km/h.

The story of the go-kart starts right after finishing the video shoot of pulling the train card with the heavy transporter. The heavy transporter showed me that Lego pieces have the needed strength to carry and transport the weight of a person, albeit in that case quite slowly.

So I got an idea to create a carrier which would use a higher amount of motors than the heavy transporter and have a higher speed.

Unlike the 24 small wheels the transporter used, the new model would only use 4 wheels based on the Technic Gear rack 11 x 11 Curved.

 

 

Work first began on the wheels. They had to be capable of carrying a total weight of around 60 kilograms. When dealing with such heavy weights and forces, the only way to succeed is to distribute the load over a high amount of bricks.

In this case the wheels were designed with multiple parallel rings, each carrying part of the weight:

The rings would be stacked onto each other to form the finished wheel:

 

Each wheel is powered by a total of 8 L motors through a gearbox. The original idea was to gear the 8 L motors up 3x times using a combination of 24 and 8 tooth gears. But after testing the wheels I soon realized that we will need a lower gear ratio, so a combination of 20 and 12 tooth gears was used to gear up the motors by a factor of 1,67. The resulting gearing gave each wheel a top speed of around 4 km/h

 

 

The wheels were further optimized during testing to use clutch 20 tooth gears as the main weight-bearing wheels instead of the original 12 tooth gears.

This change helped the wheels to spin more even and it allowed the load-carrying axle to be stationary, reducing wear and tear. Since each wheel used a total of 8 L motors, a total of two BuWizz bricks were needed to power each wheel.

With the wheels finished, it was time to build the frame of the go-kart. The frame is based on two main pieces, a 1x15 Technic beam and 7x5 Technic frame.

The 7x5 frames are crucial to the rigidity of the frame, while the beams connect them all together. Of course there were also thousands of pins used to attach everything together. With the help of Lego Digital Designer I created the first sketch of the go-kart's frame:

With the virtual model created, I now had an estimate of the needed parts. With that information, I started looking for the cheapest deals on Bricklink, updating the digital model was I got along. Red beams turned out to be the cheapest solution, and we ended up ordering around 850 of them. Total number of parts ended up at around 7000-8000 with over half of them being pins.

 

Once the ordered parts were received, it was time to build the massive model, which took several days:

 

During the assembly process, the frame and model have been further improved and reinforced in order to carry my own weight without excessive bending. The wheel rims were covered with adhesive window rubber insulation to add grip:

 

The rear axle was flipped 90 degrees in order to increase its rigidity and the whole kart was split into several modules for easy assembly and maintenance. In fact the whole cart can be taken apart to a couple of modules and assembled in less than 10 minutes.

A couple of custom stickers and the Go-Cart was finished:

With all the mechanical problems solved, it was time to turn attention to the control of the model. Since each wheel uses a total of 2 BuWizz bricks, the whole model used a total of 8 BuWizz bricks. This resulted in a problem with control, since Android based phones can connect to a maximum of 7 Bluetooth devices at once.

We decided to try to use an Apple based device to see if we can connect to 8 BuWizz bricks at once. There were no issues, so a simple Iphone 5 was chosen for main controller. The phone was integrated into the steering wheel:

 

The control device also had to compensate for the difference of motor speeds when taking a corner. Due to the load on the wheels, a simple sharp turn could cause them to fail if we would not slow the inner wheels down when turning.

We needed a way for the BuWizz app to know that the wheels are being turned. This is where I came up with the idea to use the phone's own internal accelometer to detect the steering position. Since the phone turns along with the steering wheel, it always knows in which position of the steering wheel. We asked our app developer to add a simple gyroscopic command to the app, which we then used as an input for our tracked steer mixer. I experimented with different mixer steering ratios and in the end settling with the factor 0,1.

The finished model was also duplicated in LDD, where the final piece count is around 7500 bricks:

Now that our go-cart was fully functional, it was time to head outside to give it a final test run in the real world and the record the following video:

Few weeks later the Go-kart was also driven by kids on the Brick Planet exhibition:

All the long hours designing in LDD, building, rebuilding, fixing, optimizing, the blood, sweat and tears, they were all worth it when you see how happy kids are driving the Go-kart!

Edited January 21, 2020 by Zerobricks

[StudWorks]

Incredible! This surely must have been a challenging build, it just goes to show what BuWizz is capable of at a large scale! I'm happy I got one of their bricks and can't wait to use it in my future MOCs.

[Brickzone52]

MAN! This is amazing!!

 

[nerdsforprez]

Wow, surprized this hasnt got more attention.  Very large project.  Mechanically easy.  Structurally redundant, but looks like tons of fun and a lot of a shock factor b/c of size.  

[Zerobricks]

8 hours ago, nerdsforprez said:

Wow, surprized this hasnt got more attention.  Very large project.  Mechanically easy.  Structurally redundant, but looks like tons of fun and a lot of a shock factor b/c of size.  

Thank for the praise.

What do you mean with mechanically easy and structurally redundant?

Trust me, it's not easy to make a wheel out of Lego capable of holding 30 kilograms. Regarding redundacy, the model weighs 15 kilograms and can easily carry and drive 60 kg, even up a slope. How many models can do that? And when fully loaded the frame does visibly bend and there is a very large strain on the wheels - hence greased moving parts. And there are a lot of moving parts, each ring has at least 7 gear supporting them and there are 20 rings. That's 140 gears just to support the weight, not counting the gearing from the motors.

Edited January 23, 2020 by Zerobricks

[jorgeopesi]

Without words for this epic thing.

[1gor]

This is the most challenging Lego project that I ever saw. There is no word of praise that can keep up with your project. 

[Toastie]

All what others have already voiced plus: So much better - simply in another league - as compared to that stupid Chiron thing TLG folks built earlier. So much more fun and excitement here.

This is really extremely nice and truly outreaching to the kids as well as AFOLs!

All the very best
Thorsten 

[TeamThrifty]

Excellent.. love the solution for the wheels. And the result works perfectly. Brilliant work!

5 hours ago, nerdsforprez said:

Mechanically easy.  Structurally redundant,

What?!   Everyone's entitled to an opinion, but they should be backed up with logic. Throwing a couple negatives at something thats well conceived and implemented without an explanation is... easy and redundant?!

[Lakop]

Are there any studded bricks in the build ? I've not watched the video as yet.

H

[Zerobricks]

2 hours ago, Horace T said:

Are there any studded bricks in the build ? I've not watched the video as yet.

H

Only in the steering rack and to mark and hold BuWizz bricks together. Everything else is studless.

[nerdsforprez]

6 hours ago, Zerobricks said:

Thank for the praise.

What do you mean with mechanically easy and structurally redundant?

Trust me, it's not easy to make a wheel out of Lego capable of holding 30 kilograms. Regarding redundacy, the model weighs 15 kilograms and can easily carry and drive 60 kg, even up a slope. How many models can do that? And when fully loaded the frame does visibly bend and there is a very large strain on the wheels - hence greased moving parts. And there are a lot of moving parts, each ring has at least 7 gear supporting them and there are 20 rings. That's 140 gears just to support the weight, not counting the gearing from the motors.

 

3 hours ago, TeamThrifty said:

Excellent.. love the solution for the wheels. And the result works perfectly. Brilliant work!

What?!   Everyone's entitled to an opinion, but they should be backed up with logic. Throwing a couple negatives at something thats well conceived and implemented without an explanation is... easy and redundant?!

Jerry got it right.  My comments were meant in praise of this project.  Fun, huge, and certainly a feat.  I meant no disrespect by them.  I actually love this project!

But I do stand by them.  Redundancy is not a bad thing.  Modular cranes, with huge booms are redundant and mechanically simple as well. Yet, anyone who knows me knows my deep love for cranes and admiration I have for them.  Structurally, they are a marvel.  I see this project much the same.  A structural marvel.  Mechanically, simple.  Again, this is not a bad thing.  A ton of gearing calculation and experimentation to be sure, but just that.... experimentation to get the ratio right.  Not a bad thing, just a different type of thing

[kieran]

Nice job, it's amazing how capable Lego can be