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Date: |
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Description: | Experimental Aperiodic Compass CAMPBELL 1918
Aperiodic compass attached to a wooden stand
Bowl: Brass, painted black. Filler plug at side, expansion chamber at base of bowl. Mounted on three legs fitted with pin and helical spring suspension. Inside of bowl painted white. Fixed arrow line mounted inside bowl below verge glass, this line is fitted with a cup to prevent card ( spider) coming off pivot. A rotatable verge ring, graduated to 1/2 points, carries six parallel wires (for grid steering).
Card: Spider of eight elements, marked at N, S, E & W.
Needle: Has two magnetic needles slung under the card.
Pivot: Unsighted, but presumed to be of bare needle type attached to base of bowl.
On ACO wooden stand 7" x 7" x 6.75" ( 17.8 x 17.8 x 6.75cm)
Inscription.
From the ACO catalogue 'The first working model of teh Type 6/18 aperiodic compass. This marks an advance over the preceding exhibit, the rotating ring - styled the grid ring - carrying the graduation which are clockwise, and being set by means of a fixed arrow head inside the bowl; the bar which carries the arrow also carrying a cup for preventing the system from coming off the pivot.
Six parallel wires are fitted across the grid ring instead of the two adjustable wires as shown in the previous exhibit and the ring can be locked in any requried position by means of two fly nuts on opposite sides.
The magnet system is sorted? with two needles and , besides the four pointers for No 321 it has four extra radial wires to give a greater degree of damping. These are bent downwards so that they will pass through a different part of the liquid.
The bowl is mounted on three feet fitted with the pin and helical spring suspension in vogue at the time on the 5/17 type of compass.
caption: Record Shot - Do not reproduce. | Publisher: | "http://collections.rmg.co.uk/" | Rights holder: | "Royal Museums Greenwich" | Subjects: | aperiodic compasses | Source: | Royal Museums Greenwich | Identifier: | http://collections.rmg.co.uk/collections... | Go to resource |
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