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Although there is now a mobile lifting beam and a walkway around the walls at the level of the upper windows, prior to augmentation the 10m of space between bells and roof was inacessible, as this photograph shows. Somehow a digital camera and an array of flash guns had to be suspended in the middle of this space, to be operated from the ringing room.
[click on most of the images on this page to view larger versions] |
| The uppermost windows of the tower are open to the elements. Because of this, photography could not be done on windy days (gusts would shake the camera), cold days (the camera was unreliable below about 4 degrees celsius) or during the day (use of flash required darkness). |
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The photography for a single bell took around 3 hours to complete, and to ensure a fixed perspective it had to be done in a single session (it was not possible to guarantee exactly the same perspective every time when hoisting the camera into its position high above the bells). This plus the requirement for darkness meant that the photography had to be done during the winter months when there was sufficient time to complete the photography for a bell between the onset of darkness and a reasonable curfew of 9pm.
The photography was completed during the winter of 2003 (i.e. from June through to September). However, technical problems with the trigger mechanism caused some unacceptable gaps in the animation and to fix this the photography for four of the bells was repeated the following year, six months before the bells were removed for augmentation: there could be no third attempt.
| The belfry, frame and bells were not very easy on the eye at the start of work. This photograph is one of the early experimental shots and shows the rather grubby state of the frame. A clean-up was required, along with a coat of paint for the frame. |
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Painting the frame proceeded pit by pit. This photograph is one of the tenor's series. Clearly it was one of the first bells to be photographed (most of the other pits have yet to be painted). Because the frame was destined to be removed within a year or two, cheating was acceptable. Strict attention to line of sight was observed: what the camera couldn't see wasn't painted! |
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With the space above the bells being an empty void, something had to be built to hold a camera and flash guns some 7 metres above the bells, suspended in the centre of the tower and held firmly enough to remain steady in the same place for several hours while all the shots were taken.
This gadget had to be supplied with power for the camera and flashes, a control cable to open and shut the camera's shutter, another cable for triggering the array of four flashes, and a video cable to allow the pictures to be seen downstairs as they were taken. Plus it had to be easy to hoist it into position and to lower it afterwards to retrieve the camera. |
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This is the contraption that did the job. Nicknamed Sputnik, it was hauled into the air by nylon cord and pulleys and held in place by guy ropes to all corners of the tower. Apart from a tendency to wobble in the wind and shut down in cold weather it worked perfectly. |
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The triggering of the flashes was achieved using string and a microswitch. This photograph shows the switch mechanism. The procedure involved slotting the string into a notch at the correct position for the next photograph; opening the camera shutter; then ringing the bell. As the bell swung around, the string would be pulled out of the notch, triggering a flash. After the bell had been stood, the camera's shutter closed and the resulting image inspected as it appeared briefly on a TV screen, the whole procedure would be repeated for the next image.
Bells move slowly near the balance and very quickly at the bottom of their swing. To keep the number of images to a minimum this difference was exploited by spacing the images out much more widely at the bottom than at the top. An approximate frame rate of twenty per second was chosen as a compromise between a perfectly smooth animation and the need to keep the total memory consumption within reasonable bounds. |
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To control a bell properly, ringers need to think two blows ahead (if you have just struck in 5th place and you are hunting down, your handling to strike your next blow properly (in 4th place) will depend on what happens after that - whether you continue hunting down to 3rd place, make a place in 4ths, or dodge back into 5ths). Assembling all the possibilities, there are nine different two-blow "manoeuvres" that can be rung, as shown on the left. These nine must be doubled to eighteen if there is a handstroke gap (the handling to ring a certain manoeuvre starting with a handstroke will be different when ringing the same manoeuvre starting with a backstroke). |
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While not intending to go into the details of the algorithm used to calculate the forces for each manoeuvre, it is interesting to reveal a little blue line that was used for the purpose. This short stretch of ringing contains all eighteen manoeuvres with no repeats. A combination of forces that would get a bell successfully through this line, striking on time all the way and ending up travelling at the same speed as it started, would allow that bell to ring any method at all (jump changes excepted).
The calculations had to be repeated for every bell, for all numbers of bells being rung (from 3 to 8), and for every different peal speed setting that the program supports (2h30 up to 4 hours in 1 minute increments). The program to calculate these forces took a while to design, several weeks to write and test, and 16 hours to do its job. |
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