Cycloidal Backgear B2 only

The Pittler B2 differs once again from the normal type of backgear, it is not actually backgear in the recognised sense but performs the same function,  it is actually rather cleverly hidden inside the drum next to the pulley shaft. Although von Pittler patented the idea of epicyclic back gear, which in later years was adopted by a number of other manufacturers worldwide inc the Swiss Micron and American Craftsman lathes, it didn't stand the test of time and was eventually discontinued in favour of the more conventional back gearing we still see today.

The drum contains a Sun & Planet system via a fixed annular gear of 66 teeth, two planet wheels and a centre gear of 22 teeth each. Normally the entire drum turns with the cone pulley, by raising a lever on the head-stock it pushes in a catch which locates in the drum which then releases the cone pulley and locks the rim of the drum from turning. The side plate will continue to turn at a slower speed than the cone pulley, the Sun gear being driven by the pulley cone, this revolves the two planet gears around the annular gear on the rim. For one complete turn of the cone pulley the planet teeth will walk round the 66 teeth of the fixed ring, this give it three revolutions on it's axle. In doing so it makes itself a fourth revolution in relation to the centre (sun) gear and therefore giving a total reduction of 4 to 1

The cone pulley is not permanently fixed to the mandrel but is attached only to the centre (sun) pinion of 22 teeth, this therefore powers the two 22 teeth planet gears which revolve on axles fixed to the side plate  of the drum , the latter of which is permanently locked on to the mandrel via a lug located in a keyway.