55mm Heinrici hot air Engine

55mm Heinrici hot air Engine

Type: Closed (Stirling) cycle unpressurised hot air engine.

Piston dia.: 55mm.  Stroke 55mm.  Swept volume: 131cc.  Flywheels diameter: 204mm.

Layout: Inverted vertical, concentric piston and displacer (beta configuration).

Power: Fractional; a few watts at 500rpm.

History: Used for pumping carbide gas to a farmhouse believed to have been in the lower North Island.

 Unfortunately it was thrown down from the top floor of a barn during retrieval.  The engine itself has only minor damage, but its base is broken and mainly missing- it would have been similar in appearance to the one on the 65mm Heinrici in this collection.  The burner and gas valve were recovered undamaged (displayed).  The cooling system is missing and of unknown layout. The original gasometer (said to be copper) was not recovered.  A gas pump (Roots type) was recovered but appears to be far too large for this engine and is currently displayed with the 80mm Heinrici in this collection that was thought to have been used for pumping town gas in Temuka (no pump was recovered with that engine).

Louis Heinrici began manufactured hot air engines in Zwickau, Saxony (Germany) in 1876.  He died in 1930, but the business continued until 1940.  In total, 12 sizes were made, ranging from 26mm to 190mm bore (1.5 to 370watts).  Heinricis were made to a high standard with precision fits and interchangeable parts.

Their design (beta layout) shows a good understanding of Stirling engine principles.  Heinricis are prone to over-revving, which can cause their crankshafts to fail, and their displacer gudgeons are undersize and prone to wear (get noisy), but there is no doubting their reliability and popularity.  Lubrication (grease and oil caps) has to be attended to frequently.  They were sold in their thousands- being by far the most common European hot air engine of their era.  More than 20 of different sizes, have survived in Canterbury (New Zealand), most being of the 65mm (bore) size.

Its year of manufacture is unknown, but most Heinricis came into New Zealand between 1910 and 1930.  Heinricis were usually sold in New Zealand under the name Bradley, a Gloucester St, Christchurch company of glaziers who imported and re-badged them. 

Their most common use was for pumping water, but they were also used to run jewellers’ lathes and dentist’s drills (and to pump gas)- basically any low power application when electricity wasn’t available.  In smaller sizes they were most likely to have been used as toys or novelties, not being powerful enough for most applications (just a few watts for this 55mm size). 

Heinricis are heated by burning wood, coal, town gas or carbide gas (this one).

This engine was purchased from John Stewart, St Heliers, Auckland in 2000.

 Peter Lynn for the Mahan Heritage Centre, March 2024