[MOC] Gravity-powered Hot Rod

[apachaihapachai]

This model was created to compete in the Downhill Race event. The goal of the event was to build a gravity-powered vehicle with working brakes and complete the course on inclined park walks.
 

Functions:
- 4-wheel transmission brake;
- Steering.

Free Stud.io model at Rebrickable

 

[gyenesvi]

I like the concept of this race, and it’s a nice looking build! So if I get it right, it’s still an RC car, but without drive, just steering and brakes. I have never build a brake system, but this looks like a meaningful application of it, wonder how it works. What does transmission brake mean? There is a drivetrain that’s not driven but free spinning, and braked at some point using a sevo motor for example?

[Davidz90]

Interesting idea. I guess the main design goal would be reduction of rolling resistance, e.g. large, bicycle-like wheels? 

[Daniel-99]

Cool! Though I would change the transmission. I would connect the front and rear wheels with double friction gear and connect brakes to the rear axe! It would prevent the car from making 180 degree turn while the emergency breaking

[apachaihapachai]

11 hours ago, gyenesvi said:

There is a drivetrain that’s not driven but free spinning, and braked at some point using a sevo motor for example?

Yes. The 4x4 drivetrain is free spinning. At the rear the drivetrain is connected to the improvised disk brake made out of the 30mm wheel and the actuator.

 

11 hours ago, Davidz90 said:

I guess the main design goal would be reduction of rolling resistance, e.g. large, bicycle-like wheels? 

Lateral grip is very important too. That's why I used wide slick wheels.

5 hours ago, Daniel-99 said:

connect brakes to the rear axle!

Rear brakes only are very bad idea. Everyone with the rear brakes only spun out during the race. 

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Video from the event:

 

Edited May 16, 2022 by apachaihapachai

[Nuts4Lego]

Always wanted to try a soapbox racer, never thought to do it in lego though. Looks fun :)