science

Tjasker

Tjasker is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Tjasker rather than just read about it. In short: The tjasker (West Frisian: jasker, German: Fluttermühle) is a small type of windmill used solely for drainage purposes. It is distinctive for its simple construction, featuring only a single inclined shaft that carries the sails on one end and an Archimedes' screw on the other, in this way avoiding the need for any gearing.

Key takeaways

Tjasker belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Tjasker to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Tjasker from memory before moving on to harder problems.

Reference excerpt

The tjasker (West Frisian: jasker, German: Fluttermühle) is a small type of windmill used solely for drainage purposes. It is distinctive for its simple construction, featuring only a single inclined shaft that carries the sails on one end and an Archimedes' screw on the other, in this way avoiding the need for any gearing. The tjasker is commonly known as a typical Frisian windmill though it is also found in other Dutch provinces and in north Germany.

History The tjasker seems to have been developed somewhere towards the end of the 16th century, though there is no conclusive date for its invention. The total number of tjaskers at their peak is also unclear. The mills were used to drain small plots of land but also found their use at peat digging sites as they could be easily moved. Millwright Roelof Dijksma of Giethoorn was well known for his tjasker building. He constructed 400 to 500 tjaskers between 1910 and 1945, though these numbers include hand powered Archimedes' screws. In the first half of the 20th century tjaskers almost completely disappeared as they couldn't compete with the metal windpump which was more practical as it could turn itself to face the wind and didn't require any supervision. The last tjasker was erected in 1935 and by 1963 there were only three left in the Netherlands. In that year emerging views on nature preservation and cultural history resulted in the installation of a brand new tjasker in De Weerribben. Since then, several other new tjaskers have been built, to pump water into wetlands and as cultural monuments. Currently, there are 28 tjaskers in the Netherlands and six tjaskers in Germany.

Description

The tjasker has only one wooden millshaft on which all machinery is carried. This shaft is inclined at an angle of approximately 30° and supported in a wooden frame. On the lower end it carries the Archimedean screw which is partly submerged in water. The screw doesn't rotate in a pipe but has a fixed encasing which simplifies the design further. The top end of the shaft carries the Common sails with a span of approximately 5 to 6 meters. In some cases wooden slats are used instead of sail cloth. The mill can be stopped using a band brake on the brake disc which is fitted on the shaft behind the top bearing.

Paaltjasker and boktjasker The entire mill has to be rotated to face the wind. To accomplish this two types of tjasker have been developed. In the first type, known as paaltjasker (English: post tjasker), the mill is supported on and turned around a central post. The Archimedes' screw pumps water from the outer circular ditch to a central circular ditch or pool. The screw moves in a circle when the mill is turned so these circular ditches enable the mill to function in whatever direction it is pointing. Only the outlet from the central pool taking the raised water across the outer circular ditch prevents the use of the mill facing opposite that particular direction as the screw would collide with the water outlet. The second type of tjasker, the boktjasker (English: trestle tjasker), is not balanced on a central post but supported on a trestle. The lower submerged support is fixed, the mill is rotated around this point, while the other end is movable. Here the trestle is commonly equipped with rollers or wheels on a fixed ring to make winding easier. In this method of construction the Archimedes' screw takes water from a central pool and deposits it in a circular ditch that surrounds the central pool. Water can be taken to the central pool by a pipe or a gap in the circular ditch. Besides the structural differences, a typical paaltjasker is designed so it can relatively easily be dismantled to be moved to another location or stored indoors though nowadays this feature is rarely used. A boktjasker is more or less fixed to its location.

Staarttjasker A third type of tjasker has been rediscovered from old drawings. It has a tail keeping the mill facing in the wind and a scoop wheel instead of an Archimedes' screw. After having built a functional model the reconstruction of a full sized staarttjasker (English: tail tjasker) is now planned.

In popular culture A tjasker is seen in the Duran Duran 1984 music video for The Wild Boys, with the lead singer Simon Le Bon strapped to the blade dunked in the water with every rotation.

References

Illustrations

Worked examples

Example 1 — a first encounter with Tjasker

Start with the simplest possible case. Write down what Tjasker claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Tjasker before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Tjasker ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Tjasker

In research: Tjasker appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Tjasker in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Tjasker is common in secondary-school and first-year university syllabi. It links to neighbouring topics Windmills, so understanding it makes those chapters shorter.
In everyday life: Look for Tjasker outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Tjasker in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Tjasker means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Tjasker out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Tjasker in simple terms?

Why does Tjasker matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Tjasker?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Tjasker.