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# Serie VIII, Nr 6a

## Right helicoid.

**Mathematical description**

A right helicoid is a surface generated by a straight line perpendicular to an axis which is rotated
uniformly about it and at the same time translated in the direction of the axis with constant velocity.
By a theorem of Catalan the helicoid is characterized as minimal surface.
This surface, together with the plane, is the only ruled surface which is a minimal surface.
A minimal surface is a surface with zero mean curvature.
One turn of the helicoid is described by:

**y**(*u,v*)=(*a*sinh(*v*)cos(*u*),*a*sinh(*v*),*au*),
when 0<*u*<2π.
**Title model and translation**

Windschiefe Schraubenfläche.

Right helicoid.

**Text on Sticker and translation**

Windschiefe Schraubenfläche.

Right helicoid.

**Designer**

G. Herting unter Leitung von Prof. Dr. Brill

München in 1882

**Company**

L. Brill in Darmstadt

**Original price**

Mark 19

**Dimension**

23-22 cm

**Material**

Plaster

**Literature**

Schilling, M., Catalog mathematischer Modelle für den höheren
mathematischen Unterricht, Leipzig: Verlag von Martin Schilling, 1911