Shot Towers

By Anupum Pant

The way of making lead musket balls before 1782 involved a lengthy process. And if you had a huge army, then you were in for a massive task. To make each ball:

  • A chunk of lead was melted in a crucible
  • Poured into a mould
  • It was let to stand to solidify
  • The mould was broken
  • Final finishing of each ball was done
  • and each ball was checked for roundness by rolling it on an inclined plane

Then everything changed in the year 1782, when a plumber from Bristol William Watts, got this seemingly simple idea – Drop molten lead from a long tower and let the surface tension do the work.

He got this idea by observing raindrops, which formed perfect spheres while they were free-falling. Before telling anyone about it, he tried implementing his idea. He dropped molten lead into a bath of water from the tower of his local church. It worked perfectly.

He did a couple of other experiments at home and finally patented his idea by the end of the same year. It wasn’t long until shot towers started sprouting all over the world. William made a good fortune out of this.

A shot tower is a long hollow building, like a light house, which has the machinery to melt lead at the top point. The molten lead is dropped into the long hollow shaft through sieves, and the bottom part of the building has a bath of water to catch lead balls. The free falling lead turns into a sphere due to surface tension and solidifies in air due to flowing air. After shots are made, they are lifted from the water and checked for roundness by making them roll on an inclined plane. Defective ones are sent back to the top.

The tallest shot tower ever built was 263 meters long and was constructed in the year 1882. It still stands in the Melbourne suburb of Clifton Hill in Australia. There are several others around the world which are still standing. While many others have either been destroyed by men or nature.

via [PSSA]

Disposable Paper Microscope Costs Just 50 Cents

By Anupum Pant


While doing my daily rounds on the internet today, I came across this awesome piece of modern engineering – An extremely durable and disposable microscope made out of paper and very tiny ball lenses. I saw it first on a Ted talk that I’ve attached below. Ingenious I say!

What’s new?

Microscopes are no longer those sensitive, bulky and costly instruments which were used to observe tiny life forms. These engineers have changed the age-old definition of the microscope. The fold-able paper microscope or foldscope is an origami microscope that weighs just 9 grams and is designed by a Manu Prakash, a Bioengineer professor and his team from Stanford. Instead of costing thousands of dollars, this ingenious origami microscope costs less than a dollar and is set to transform the way people use microscopes.

Besides being light, cheap and foldable, the microscope is water proof, durable to the extent that it can be dropped from the top of a building without getting damaged, does not require any external power, provides a 2000x magnification, can be assembled by a first grader in ten minutes, is easy to carry and is absolutely flat! What more can we ask for!

It can even project the image of bacteria on your wall. How cool is that! I bet your lab microscopes can’t do that.

It is set to transform the lives of those billions of people living in the developing countries. The piece of engineered paper will change the speed and accessibility of medical diagnosis in the poor nations.

Material and actual cost

Well, as the heading tells you it is a 50 cent microscope, not really. It costs only a little more than that. Still, it costs lesser than a dollar – about $0.97. Here is the material cost break-up:

  • Tiny Spherical lens: $0.56
  • 3V button battery: $0.06
  • LED light: $0.21
  • and a couple of other things like tape, paper and switch: $0.14
  • Total: $0.97

Beta testing: The team is currently looking for beta-testers for Foldscope. They’ll choose 10,000 people who would test it in a variety of settings and would help them generate an open source biology/microscopy field manual. See “Ten Thousand Microscopes signup” for details.

It reminds me of

The incredible cheap microscope discussed above is new and very precise. Until recently we didn’t have that. DIYs on the internet taught us to construct (not really) not-so-accurate microscope setups at home using a laser pointer.

All you were supposed to do is point the laser pointer through a suspended drop of bacteria infested water (or other clear liquids).This is how I toyed around (I still do) with a laser pointer to see hazy pictures of possible micro-organisms:

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A Flashlight That Uses Body Heat Instead of Batteries

By Anupum Pant

I talked about a light that utilizes the power of gravity to light up a few days back. This flashlight is a bit similar in a way that, it also doesn’t need any batteries. But the underlying mechanism it uses, is completely different.

The winner of this year’s Google Science Fair, in the age group of 15-16, was a 15-year-old girl from Canada, Ann Makosinski. In her project she created a flashlight that, instead of batteries, uses our body heat to light up. She calls it “Hollow Flashlight”

The flashlight uses 4 Peltier tiles to convert the temperature difference (between body and room temperatures) into energy. One side of the tiles is heated by our body heat and the other side is at room temperature. This temperature difference creates electricity using the Thermoelectric effect. The tiles used for this light need a minimum of 5 degree difference of temperature to work.

Peltier Tiles

Peltier tiles utilize thermoelectric effect to convert temperature difference into electricity. When there is a enough temperature difference, charge carriers move from hot area to the colder area. This separation of charges builds up a potential difference across the height of the tile. This potential difference can be used up for various things. In this case, it was used to light up LEDs.

Advantages: The amount of potential difference produced depends on the material. Peltier tiles are great because they are compact and they do not use any moving parts. Elimination of any moving parts eliminates wear and tear. They last long and do not need a lot of maintainance. However, their efficiency is not so great. So, they are used only where long life is essential.
The Voyager space probe and other deep space probes, where long life is of prime importance, use Thermoelectric generators (another image). The heat there is produced by a radioactive isotope. Implanted pacemakers which require long life also use it as a source of energy. All of them work utilizing the same effect – thermoelectric effect. The eco-fan, a wood stove fan, also uses the same effect in a very creative way.

Thermoelectric Generators have a very interesting history.