A polarity reversing commutator-type switch is fitted and the interrupter adjustments for spacing and rate of spark can be easily adjusted. An internal 1uF Dubilier condenser is located inside the base-this serves to quench the primary contact-breaker spark to some degree and has been tested for no leakage, etc.
The coil secondary high voltage wires are brought out to two brass pointed rods mounted on insulated pillars, which form a spark gap. The spacing of this is adjustable by the thumb type nuts on each pillar. The coil has been tested with input DC voltages between 6 and 15 volt s and, using a nominal 12 volt DC input, a maximum spark length of just over 2 inches (5cm) was achieved, with an input current of 5-6 amperes. Due to the high primary current sparking at the interrupter contact points is normal and running time should be kept to a few seconds to prevent excessive erosion of the contacts.
These should be regularly cleaned to remove oxide deposits by using fine grade emery paper. All the ORIGINAL plating on the brass surfaces is in good condition, with minimal pitting, and the bakelite and the insulation on the outer coil is intact, with no cracks or splits. Similarly the mahogany base is free from splits or gouges. This is a nice authentic example of an early induction coil and one which looks very striking, either running or unpowered. A battery can be used as a power source as long as it can deliver 10 amps maximum.The item "ANTIQUE INDUCTION/RUHMKORFF COIL-GRIFFIN &GEORGE-1900's" is in sale since Monday, December 31, 2018. This item is in the category "Antiques\Science/Medicine\Scientific Instruments". The seller is "bown007" and is located in Middlesex. This item can be shipped worldwide.