Storytelling Science

Play God -- make your own Ferocious Gecko!

Amitabha Mukerjee


My friend Tikku is in class five, and his mother is constantly complaining about how he drives her up the wall. So I told Tikku that instead of making his mother climb the wall, perhaps he should make a toy gecko which can do the climbing.

A few weeks back, we discussed in this space how Tikku is fond of geckos. But a gecko has bundles of fine hair (setae) for clinging onto a wall , and no one knows how to make this type of mechanism. If you can invent this (something like a nanoscale Velcro) your invention would find millions of applications and you would be rich and famous.

So, instead of the gecko’s setae. we decide to use simple stuff – straws, strings, scotchtape – which we found lying around.

The front and the back side of your card
We cut a card from a shoebox. Then Tikku drew a ferocious gecko on the white side, and painted it in ferocious colours. On the back side he scotchtaped two straw pieces (about 3 to 5 cm each) in a “vee” shape, and then he ran a long thread up one side and down the other. We hung this up from a tall nail, and by alternately pulling each thread, he soon had the gecko climbing the wall! By relaxing the thread, the gecko would climb down.

Soon enough, Tikku’s sister Chikku, who is in class nine, came in to watch the fun. But Tikku was too engrossed to let her share his toy, so in a few minutes, she made her own. Instead of a gecko, she drew a picture of Chikku and soon she had her brother climbing the wall!

Then they had a race to see whose toy could run up the wall quicker. Chikku realized that she needed to re-design her straws and made another one out of four pieces, two on each side, and now the paper-Tikku was going faster than earlier.

The physics: Why does it climb?

At this point, I asked them: Why is this gecko climbing up? This forced them to think about it from a different point of view. I could see them looking at the gecko when it was paused half way up. What they saw looked like this figure -- the thread is running through the straw. Soon enough, Chikku was talking about forces and Tikku was mentioning friction.

The string bends at the ends of the straw piece, rubbing the straw on the side. This makes friction, causing the side with the more zigzag string to rise with it.
The answer of course, involves frictional forces – and this is highest at the points where the thread bends at the end of the straw. If you play with this toy long enough, then this is the point on the straw which tends to get cut! Now, one string is being held with a higher force, and has a higher tension, causing high friction at the straw ends. So that side of the gecko moves with the string. At the same time, if the other side is being gently lowered, then the gecko will climb up. By talking about what was happening, Tikku and Chikku soon figured all this out!

That evening, I saw Tikku’s father playing with it, and it was Tikku who was telling him how it works! I love to see kids explaining things to adults – it gives them such a lot of confidence, raises their depth of understanding, and makes for great fun!!

So: don’t just sit there – find a bunch of kids near you, and sit with them and make this toy. Every time I play with children, I rediscover the child in me and this is what makes it so much fun. Unfortunately my mother thinks I take this childishness too far – but hey, why not give it a try?

Ten Little Fingers

This is one of hundreds of projects in the book “Ten Little Fingers” by Arvind Gupta, available from National Book Trust (Rs. 60/-). Arvind Gupta has devoted his life to hands-on learning, and has showed amazing toys to thousands of children in schools across the nation. He is a huge inspiration for us. If you are interested in changing the way our kids learn, why not donate some copies to a schoolteacher near you?