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Whippletree (mechanism)

technology Maturity 7-9 Next article →

A whippletree is a clever tool used to spread force evenly. It is also called an equalizer or a leader bar. This mechanism uses a bar that pivots near its center. One force hits the middle of the bar. Other forces hit the tips of the bar. This setup helps to distribute a single push or pull. It can work through tension, which is a pulling force. It can also work through compression, which is a pushing force.

Leader bars
Leader bars

When animals pull heavy loads, whippletrees make the work easier. A horse might pull a plow, a log, or a canal boat. The bar sits between the animal and the load. The center of the bar connects to the load. The traces, which are straps or chains, attach to the ends. This prevents the load from tugging on just one side of the animal. It also keeps the traces from pulling into the sides of the animal.

Leader bars
Leader bars

If many animals work together, they use more bars. Two animals might use a double-tree to balance their loads. For three or more animals, even more bars are needed. Some bars are made asymmetrical to balance odd numbers of animals. This ensures that every animal takes an equal share of the work. In modern farming, tractors use these tools too. They link several small tools, like mowers, into one single load.

Leader bars
Leader bars

We can see these tools in many other machines. A car windshield wiper uses whippletrees in compression. The bars spread the force of the wiper arm across the blade. This helps the blade clear the glass evenly. Large telescopes also use them to support glass mirrors. These designs are three-dimensional to support many points over an area. This helps prevent the mirrors from bending or warping.

Heckscheibenwischer kl
Heckscheibenwischer kl

In the past, people used whippletrees for math. Mechanical computers used them to add and subtract numbers. These machines used straight-line motions to do calculations. One famous example was the IBM Selectric typewriter. It used linkages to move a type ball. This same method was used for naval gunnery systems. Even artists like Alexander Calder used them in hanging mobiles.

Heckscheibenwischer kl
Heckscheibenwischer kl
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File:Leader bars.jpg
Leader bars.jpg
File:Heckscheibenwischer kl.jpg
Heckscheibenwischer kl.jpg
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