I recently read the obituary for Bruce [Blackwell]. Here is a bit more on his regulator. It was an amazing piece of mechanics rather than electronics. At the time I asked him why he did not opt for an electronic solution and he replied that he understood mechanics better. In any event his solution could keep the frequency of the Base mains accurate enough to ensure the Met charts would not be more than six seconds out in 24 hrs.Briefly, he took a 50 Hz signal from Andy's Rubidium clock, passed it through an amplifier (provided by John (Iono)) and then used the resulting 'mains' voltage to run a synchronous clock motor. Bruce then ran a second clock motor using the mains from the 'in service' generator. One of the clock motor drives was then reversed by a gear train, made by Bruce. The two motors were then mounted face to face (so both spindles rotated in the same direction). Each had a disc mounted on its spindle. On one there was a metal track, in two segments with a space between them, and on the other two brushes. There were also two concentric tracks on the back of each discs to bring the electrical connections to the discs.
So long as the frequency of both supplies was 50 Hz the brushes stayed in the gap between the tracks but if, say, the generator ran too fast the brushes would make contact with the tracks on the facing disc and current would flow to a motor coupled to the engine regulator, turning the motor in the direction required to slow the engine down. If the engine ran slow the current would flow in the opposite direction so speeding the engine up.
The machining of the parts that Bruce made were of a good enough quality to last a very long time; so I wonder how long the Blackwell Regulator was in service.
[7 November 2006]
Further comments by Andy Smith:
[24 February 2007]
- The regulator was described in a paper published in The Electrical Review:
Synchronisation in the Antarctic by B. Blackwell, J.E.I. Nockels and A.J. Smith, Electrical Review, vol. 192, p. 204 (9 February 1973).- Although the rubidium clock was a local time standard, the ultimate accuracy of the resulting 50 Hz mains was set by the 16 kHz signal received at Halley Bay from the Rugby transmitter. This was synchronised to "atomic time" from the National Physical Laboratory at Teddington.
- In 1972, Bruce upgraded to a Mk-II system in which the flimsy sonde motors were replaced by a heavy duty system involving massive solenoids.
- I don't think the regulator survived for long after Bruce's departure in early 1973. It was ripped out by an incoming genny mech as being non-standard, in spite of the protests of the scientists, who had to go back to doing frequent timing adjustments on their paper charts.
24 February 2007