This experimental unit demonstrates theconversion of smooth rotary motion into reciprocating motion. The inputangle is set on a ball bearing mounted crank disc made of anodised aluminiumand read off on an angle measuring scale integrated into the base plate. Amillimetre scale is fitted for the outlet stroke. The crank radius can beadjusted in three positions. The simple insertion of a bolt enables theswivelling cylinder to be locked, thus a crank drive with either a fixed oroscillating cylinder can be demonstrated. The components are attached to asolid, painted base plate. Two handles make the unit easier to carry.