13th July, 2022

Mechanical Engineering

Product Design

The Rain Bag - An Industrial Design project

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A blog post by Pravasith Chinthoju

Illustration of school children wearing the Rain Bag and dancing in the rain

What's this?

An umbrella designed to fit inside your backpack that can be operated hands-free. The umbrella is removable and washable. This product was designed for Indian rural kids, a personal project I spent 3-4 months working on after college.

A video of the working prototype of the rain bag

Children dragging their backpacks on the road to school, the backpacks have wheels

LMAO why?

I was in that stage of my life after college where I had just realised I wasn't good at Architecture and wanted to become an Industrial Designer. So I took a short course on mechanical product design and decided to make the hands-free umbrella. Fun fact, it took me 4 months to build the prototype. I went to Backpack and Umbrella factories and the lovely and amazing workers helped me build this project.

Two main problems faced by an Indian student while commuting to school

  • 🔺 Heavy load with many books becomes a major issue when you have to walk to school every day
  • 🔺 Exposure to the hot sun and heavy rains

The design process


To understand the users' requirements and get an idea of the potential for adaptability, I performed a voice of customers survey by personally visiting the rural schools of Karnataka and taking valuable inputs from children. One would be awestruck by the ideas proposed by children.

Ideation, concept sketches

Concept sketches for the rain bag design.

Concept sketches for the rain bag design.

Building a prototype of the backpack

Prototype of the bag made with flex sheets, and glue.

Prototype of the bag made with flex sheets, and glue.

After I had built the mock backpack with flex sheet and glue, it was time to prototype it with real materials. So I approached a well-known backpack company in India, and requested the founder to let me spend two days with a few of the workers so that I could fabricate my design. I successfully do just that in their factory. The bag has a 3 cm wide opening for the umbrella assembly to slide in.

Prototype of the bag made with real fabric.

Now, the fun part. Designing and engineering the umbrella prototype

The umbrella has to open from the bag without harming the user, which was quite challenging to design. I pulled an all-nighter to design the perfect mechanism and tested it using actual umbrella parts, and some sticks made of straw.

Prototype of the bag made with flex sheets, and glue.

Figuring out the Math.

Then I spent the next week modelling, calculating, rigging parts and 3D printing.

Modelling in Rhino, and the mock prototype built using umbrella parts and a few sticks.

Modelling in Rhino, and the mock prototype built using umbrella parts and a few sticks.

Annotated skeleton and parts of the umbrella opening mechanism.

After I was confident with the math I did, I approached many big umbrella companies in India, but none of them believed that my mechanism would actually work. After a long stretch, one of the biggest umbrella companies in India replied saying that they wanted to explore this mechanism of mine. The founder of Sun Umbrellas generously let me use his R&D workshop, and with the help of the workers there, I finally built a fully functioning prototype of the umbrella. Here's what it looked like.

The above model is just a mock prototype to show how the mechanism works. For production, I intended to modify the parts to be much more sleek with aesthetics taken into consideration.

What happened then?

We then had to close the project because after calculating the manufacturing costs, it didn't quite work out. This projects remains a unique experience in my life and I am very proud of what I was able to achieve.

A school girl wearing the rain-bag and turned around.