06 August 2010

Wooden air engine - 3

This is a third post in a series exploring wooden air engines possibilities, all this inspired by Matthias Wandel models.  This time I go for higher complexity.

When searching details about  the oscillating cylinder steam engine I came along a Chebyshev steam engine concept to transform a linear movement in a circular movement in a compact way.  It is tempting to include it to make a more attractive systems in a model, but I am not sure about the quality of the movement and have no view of the geometry of his implementation.

Looking into Mechanical Movements Powers and Devices by Gardner Hiscox I found many systems converting linear to circular and stopped at 'a curiosity of old-time engineering'.  Searching further I found more information like a date and a name 1666, De La Hire and even a working model of: "Murray's 1802 Hypocycloidal Steam Engine"

Thanks to Matthias Wandel it is even possible to easily implement a plywood air engine using this mechanism as he has two template generators for wooden gears. Although cutting convex forms from the inside is probably not that easy  It is probably a good idea to follow Cotswold Heritage design by making the tooth containing the shaft hole oversized by grouping for example two teeth,  certainly because this tooth is at the end of the stroke and does not take up much force. The template here has 20 (for the generator it is -20) and 10 teeth.  It could be less as Matthias experimented with sparse toothed gears and says that even then the movement stays very smooth.
gears for a hypocycloidal movement


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