Weeden Caloric or Hot Air Engines
Weeden Manufacturing produced three "Caloric" or "Hot Air" engines, the No. 22 and two different models of a No. 23. Introduced in mid 1890's and produced to 1916.
These are not steam engines, no water is heated, in fact it is not even used for cooling as is the case in many other hot air engines.
In a typical implementation, air is repeatedly heated and cooled in a cylinder and the resulting expansion and contraction is used to move a piston and produce useful mechanical work.
The No.22 Caloric engine was introduced in the mid 1890's and produced until 1916. It stands 9" high and has a 4 1/2" diameter base. Early flywheel supports are cast lead, later models have pressed steel.
Ebay sales of No. 22's
July /09 - Missing parts - 5 bids - 142.50 USD
May /17 - One flywheel not original. - 19 bids - 170.50 USD
October /15 - Good condition - 13 bids - 340.00 USD
The No.23 Caloric engine was introduced in the mid 1890's and produced until 1916. It stands 7 1/2 " high and has a 4" X 8" base. A limited number of reproductions are on the market.
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Early No. 23
The expansive property of heated air was known to the ancients and Hero of Alexandria's Pneumatica contains descriptions of devices which might be used to automatically open temple doors when a fire was lit on a sacrificial altar.