V3 · Sonnet

What has to turn into the wind?

The sails must always face the wind. The koźlak (post mill), paltrak and holender (Dutch tower mill) from Dziekanowice do this differently: what sets them apart is how much of the structure has to be turned. Move the wind and see.

  • black: stationary
  • red outline: turns
  • white disc: support point
  • axis of rotation
  • grey: wind (plan view)

Drawings: koźlak, paltrak and holender

All: black is stationary, the red outline turns, the white disc is the support point.

Koźlak (post mill), schematic cross-section A black trestle of beams and a vertical post stand on the ground. The whole body rests on the post: white, with a red outline, with a roof, a long tail pole reaching the ground, and sails. A dashed red axis runs along the post. Schematic, not to scale.
Conventional cross-section, not to scale. Sails facing right.

Type 1

Koźlak (post mill)

from Mierzewo · 1801 per V2

Koźlak from above, rotation model Plan view, north at the top. The black trestle with the post stays in place. The red outline of the body with the tail pole and sails turns around the post so that the sails face the grey wind arrow.
Plan view, north at the top. Model: sails set exactly into the wind.
Turns
the whole body with the tail pole — 0°
Stationary
trestle with post — 0°
Support point
the body rests on the tenon of the post (sztember)
Paltrak, schematic cross-section A black round foundation stands on the ground, with a white rail with rollers on top of it. Above the rail is the whole body with its storeys and roof, with a red outline, a short tail pole and sails. A dashed red axis runs through the centre. Schematic, not to scale.
Conventional cross-section, not to scale. Sails facing right.

Type 2

Paltrak

from Kędzierzyn · 1887 per V2

Paltrak from above, rotation model Plan view, north at the top. The black foundation ring with rollers stays in place. The red outline of the body with the short tail pole and sails turns along the ring so that the sails face the grey wind arrow.
Plan view, north at the top. Model: sails set exactly into the wind.
Turns
the whole body on rollers — 0°
Stationary
round foundation with a rail — 0°
Support point
the rollers run along a rail near the ground
Holender (Dutch tower mill), schematic cross-section A black tower, tapering towards the top, stands on the ground and is not turned. On its crown lies a white ring with rollers, and above it the red outline of the cap with sails and a long tail pole. A dashed red axis runs through the cap only. Schematic, not to scale.
Conventional cross-section, not to scale. The axis is shown at cap level only.

Type 3

Holender (Dutch tower mill)

from Trzuskołoń · c. 1810 per V2

Holender from above, rotation model Plan view, north at the top. The black circle of the tower stays in place. Only the red outline of the cap with the tail pole and sails turns above the tower so that the sails face the grey wind arrow.
Plan view, north at the top. Model: sails set exactly into the wind.
Turns
cap with sails and windshaft — 0°
Stationary
the whole masonry tower — 0°
Support point
rolling ring on the crown of the tower

The difference in five rows

Question Koźlak Paltrak Holender
What turns The whole timber body with the machinery and sails. The whole body on rollers. Only the cap with the sails and windshaft.
What stays still Trestle of beams and a vertical post (sztember). Round foundation with a rail; brick in the museum, originally stone (per V2). The whole tower, brick-built according to V2.
Support point The body rests on the tenon of the post. The rollers run along a rail near the ground. Rolling ring on the crown of the tower.
How it is turned back into the wind (per V2, to be checked) A long tail pole, with a winch braced against posts in the ground. A manoeuvring tail pole at the base. A wheel with a chain or a rope winch; the tower stays still.
What is easy to confuse A board skirt can hide the trestle and, from a distance, resemble the plinth of a paltrak. The walls and roof can look like those of a koźlak; you have to look for the rail under the body. From a distance the sails are visible, but the turning of the cap alone is hard to notice.

Explanation and limits

The koźlak and the paltrak respond to a changing wind direction in the same way: they turn the whole building. The koźlak does it on a post supported by a trestle, the paltrak on rollers along a rail near the ground. In the holender the building stays still and the cap turns. This allows the tower to be built of masonry.

Greater Poland is strongly associated with koźlaks; a regional tourism portal states that this type predominates among local windmills (to be checked in the source). The shared display in Dziekanowice makes comparison easier, but it does not recreate the former neighbourhood of these mills: the place names refer to where the structures came from.

What cannot be reconciled (rules of the schematic)

  • Only the cap turns, and the support is a trestle with a post. The post of a koźlak carries the whole turning body, so this arrangement describes none of the three types.
  • A rail with rollers near the ground, and only the cap turns. A rail at ground level serves to turn the whole body.
  • The whole body turns, and the support is a ring on the crown of the tower. A ring at the top allows the cap to turn, not the whole tower.
  • A masonry tower on a trestle or on a rail. In this schematic neither a trestle nor a roller rail would support a masonry tower being turned.

This is a comparison against the rules of the schematic, not an expert assessment of a historic monument. A real structure may have been rebuilt or reconstructed.

What is the model and what is not

  • The drawings are the author's own schematics, not to scale, not survey documentation. The proportions, the number of rollers and the shape of the sails are conventional.
  • The wind angle is set in steps of 5°. In the model the sails face exactly into the wind; a real miller set them approximately. When the direction changes, the model turns the shorter way, for example from 355° to 10° by 15° to the right.
  • The type of construction, museum reconstruction and ability to operate are three different things. The page describes only the type.
  • The dates, places of origin and relocations of the structures were taken from V2 and not checked again. For the koźlak V2 gave the provenance trail Gniezno, Mierzewo 1850, museum 1977; this needs confirmation in the source.
  • No photos: no photograph is embedded. Photo of the paltrak from Kędzierzyn in the open-air museum, as indicated in V2: Wikimedia Commons, photo: Łukasz Bakuła, CC BY-SA 4.0 (data from V2, not verified again).
  • We do not give the open-air museum's opening hours, ticket prices or dates of demonstrations. Observe from the paths open to visitors, without going under the structures or onto the protective embankments.

What changed compared with V2

  • The scored quiz removed. The rules of contradiction remain as the four sentences above, because the knowledge should be readable without guessing.
  • The field notebook, saving in the browser and printing removed. The topic does not need the reader's data, and the page saves nothing locally.
  • The 1:1 matching with two lists replaced by a simultaneous view of the three types. On a phone you choose a pair and read the differences in the table.
  • The continuous rotation animation and sails turned by double the azimuth angle removed. That movement of the sails did not follow from the model. Now the wind angle turns only the turning part, in a short movement that is switched off when reduced motion is set in the system.
  • The rows on stability and interior (for example “insensitive to gusts”) removed, because they went beyond the material provided.
  • Kept: the zones all, stationary, turns, support point; the wind angle 0–360°; the schematics of the three types; the description of differences and the source links.
  • The photo from Commons is no longer loaded, so that the page works offline. The link to the withdrawn “new attempts” has also been removed.

Sources

  • Muzeum Pierwszych Piastów na Lednicy: Wiatraki [Museum of the First Piasts at Lednica: Windmills]. Identification of the three structures, dates, construction and relocation of the koźlak. Link from V2; in this version it was not opened or confirmed.
  • Wielkopolski Szlak Wiatraczny [Greater Poland Windmill Trail]. Regional context and the principle by which the koźlak turns. Link from V2; to be checked.
  • NID: paltrak w Gumienicach [NID: paltrak in Gumienice]. A description of the rollers and rail as a comparative source for the paltrak principle, not a description of the structure from Dziekanowice. Link from V2; to be checked.

This page is an educational project about the kinematics of rotation. It is not a certificate of historical facts or an assessment of the condition of monuments.