Kepler 16 Orrery
Built by Chris Fry in April 2014
Designed by Michael Whiting, this orrery is based on an extra-solar double star system — the two stars rotating about a common centre of gravity — the barycenter — about which a single planet has also been detected by the Kepler Space Telescope by inference from periodic changes in brightness.
Rather than operate the model by a motor or turning a handle I thought it would be a good challenge to drive the orrery by spinning up a flywheel. Pulling sharply on the lever causes flyweights to engage the ratchet pawls, then a steady pull spins up the flywheel through three 5:1 gear trains. The pawls disengage automatically allowing the model to free-wheel.
A low friction bearing beneath the flywheel is simply a 3mm steel ball set in a rod socket, with the Stuart Borrill flywheel being carried on a carefully selected rod. The other bearings are 1½” plastic strips bolted over holes in flat plates from which the paint was carefully removed with a de-burring tool.
Selecting gears carefully and lubricating well resulted in a smooth running mechanism which will drive the orrery for up to a minute or so after a couple of actuations.