Here's The Secret Sauce for Success in Spring Powered Cart Project

 

Video: https://www.youtube.com/watch?v=yp41kJOw2R0

 

The only cart that successfully travelled a distance of 2m while carried a 2kg load. 

During my first year studying Mechanical Engineering, there was a Design and Manufacturing compulsory class where we learn about 3D Computer-Aided Design software using CREO Parametric PTC. The important lesson is, during the design process with in mind that we will make the product made of steel material, which a lot of things need to take into consideration including ways to fabricate steel materials most efficiently. 

So, there is a group project that contributes quite a large part of the course merit. The project assignment is to build a Spring Powered Cart that can carry two-kilogram and travel a distance of two meters. Let me explain further on "What we plan in our mind will not be exactly executed". For 1 week consist of late nights, we finally completed the "Wonder" design. However, when we in the Mechanical Engineering Lab to use the Milling and Lathe machines etc. With limited allowed time to use the lab, we found that we can't fabricate the parts as we planned, therefore, we need to plan on our feet how to fabricate parts quickly and successfully to put all the parts together. Fortunately, we are at least able to build a rigid cart with a spring to power it, even though we don't know whether it can travel in 2 meters while carrying a *2-kilogram load*. 

On the testing day, after two attempts, all the groups including ourselves are unable to make our carts to complete a travel to the finish line at the 2 meters mark. At the last minute before the final attempt, after we tried to observe the weak point and hopefully able to counter the short distance travel, I realized that the wheel stops at a certain distance because the wheel moves close to the cart's body which makes friction. Fortunately, I found the small pipe lying on the floor which enlighten me to cut it as a spacer to put between the wheels and the cart body. In addition, I also added a lubricant inside the spacers with the idea that the spacers with lubricant will feed the shaft while travelling and make less friction with the chassis. This last-minute small modification, make it a winning formula as the cart moving frictionless between the components (shaft, wheels and body) and be the only cart that travelled a distance of 2 meters while carrying a 2-kilogram load. 

The modification of adding the spacers was inspired by the car toys TAMIYA (image below).