The drinking bird is a fun desk toy that bobs up and down as if it’s “drinking” water. But why does it eventually stop moving? The short answer is that the bird stops once it becomes balanced and upright again. But let’s dive deeper into the science behind how the drinking bird works.
How the Drinking Bird Works
The drinking bird is an example of a heat engine, which is a system that converts heat energy into mechanical work. It uses the principles of evaporation, gravity, buoyancy and condensation to turn heat energy into kinetic energy to bob up and down continuously.
The main components of a drinking bird are:
- Glass bulbs at the bottom filled with a volatile liquid such as methylene chloride or dichloromethane.
- The upper glass bulb or reservoir which is empty.
- A tube connecting the two glass bulbs.
- The red colored head and body which acts as a counterweight.
Here is how it works step-by-step when placed on a table:
- Some of the volatile liquid from the bottom bulbs evaporates and transfers into the empty upper bulb due to the heat from the surroundings.
- This causes the center of mass of the bird to shift upwards allowing the bird to pivot forward due to gravity.
- The bird keeps tipping forward until the bottom glass bulbs are vertical and the upper bulb is horizontal.
- Now the evaporated liquid condenses and flows back down to the lower bulbs which shifts the center of mass back down.
- This allows the bird to pivot back to the upright position due to the counterweights, ready for the next cycle.
This cycle repeats continuously as long as there is heat energy to evaporate the liquid. The repetitive motion of tipping forward and pivoting back up gives the illusion of a drinking bird continuously dipping its beak into water.
Why Does it Eventually Stop?
While the drinking bird can theoretically operate indefinitely, it does require ideal conditions to keep the cycle going. There are a few main reasons why the drinking bird loses momentum and eventually stops:
1. The liquid evaporates away
The volatile liquid in the bottom bulbs will slowly evaporate away over time even when the bird is not operating. This means there is less liquid available to evaporate and condense during each cycle. Eventually so much liquid evaporates that the bird won’t have enough weight shift to pivot forward anymore.
2. The ambient temperature is too cold
The drinking bird relies on ambient heat to evaporate the liquid. In colder environments, the evaporation happens more slowly. This slows down the entire operation cycle and can eventually stop it if the temperature drops low enough. Ideally, the ambient temperature should be around 70°F or 21°C for the bird to function at its optimal rate.
3. Dust or dirt clogs the tubes
The thin tube connecting the two glass bulbs needs to stay clear for liquid to flow smoothly between the upper and lower chambers. If dust, dirt or debris makes its way into the tubes, it can impede the flow of liquid and operation of the bird. Proper cleaning and maintenance is required to prevent blockages.
4. The bird becomes perfectly balanced
When operating normally, the drinking bird is never perfectly straight or balanced. It’s designed to constantly pivot back and forth on its curved bottom. But if the bird ever becomes completely vertical and balanced, the cycle will stop because it loses the momentum to tip in either direction.
5. The ambient humidity is too low
Evaporation happens more slowly in dry air compared to humid air. So in environments with very low humidity, the liquid will evaporate too slowly which extends or stops the drinking bird’s cycles. Ideally, the humidity should be moderate around 40-60% relative humidity for optimal operation.
By understanding what conditions are ideal for the drinking bird to work, we can troubleshoot why it may have stopped moving. Simply adjusting the ambient temperature, humidity or providing fresh liquid can often get a drinking bird going again.
Interesting Facts About the Drinking Bird
While investigating why the drinking bird stops, we can also uncover some fascinating facts about this physics toy:
The liquid was once very hazardous
Original drinking birds from the 1940s-70s used methyl chloride or chloroform as the volatile liquid. However, these were found to be toxic and hazardous. Safer distilled water or glycol-based liquids are used today.
It was invented by accident
The drinking bird was invented accidentally by Miles V. Sullivan in 1945. He was an inventor at the Midland Ross Corporation and created it while experimenting with heat transfer systems.
NASA used it in space
NASA took drinking birds on space shuttles during the 1960s-70s to visually demonstrate the near weightless environment of space to the public back on Earth.
It is also called a dippy bird or dunking bird
The drinking bird has several informal names like dippy bird, dunking bird, sippy bird or drunk bird. These names refer to how it seems to drink or dip its beak endlessly like a bird sipping water.
The world record is over 14 hours continually
The official world record for longest continual operation of a drinking bird is 14 hours and 5 minutes achieved in 2015 by Flippy, built by Strikepoint Trade Toys & Games.
Name | Liquid Type | Year Invented | Aliases |
---|---|---|---|
Drinking Bird | Methylene Chloride | 1945 | Dippy Bird, Dunking Bird |
Conclusion
The drinking bird is a fascinating little gadget that demonstrates heat energy conversion. It operates on simple principles of evaporation, buoyancy and condensation but must have the right conditions to work properly. While it will eventually stop moving if left alone, we can troubleshoot issues by adjusting the temperature, humidity or cleaning the tubes. Understanding the science behind this classic physics toy helps us appreciate how heat and motion are connected in our everyday world.