This is an incredibly simple project. All that needs to be done is build a turntable to replace the Victoria Memorial outside Buckingham Palace. From that, a long (31km) arch-shaped hand runs out to the M25, where it is supported by several large lorries. Sadly, there is a minor problem – there are several bridges over the M25, so the supports on the lorries will need to be folding. I imagine the hand being held aloft by 3 supports, whilst the 4th lorry goes past a junction. It then lifts up its supporting arm, and the next one drives through the junction. Much the same procedure will happen at small tunnels
The lorries will have to average around 10mph. I think that a minute hand would be a little too difficult. The numbers will be Roman numerals, supported by 65 airships (Plan A was for helicopters, but this option seems greener.
After much careful consideration, I have decided that the hand will rotate anti-clockwise as seen from above. Not only will this make the clock easier to read for Londoners below, but it also increases its impracticality, as at around 8:45 the QE2 bridge across the Thames will sadly have to be closed to all traffic as the hand passes across it in a contra-flow (The northbound lanes pass through a tunnel which is too long to use the above method). I’m sure this will not cause too much inconvenience, certainly little more than closing Heathrow at 3:15 as the hand moves over it.
As for the construction of the hand itself, in a slight re-think from my original plan, I see no reason why it can't be a long, lightweight tube filled with helium and (nearly?) neutrally buoyant. I'd want to keep it rigid enough not to blow around, but hopefully it should still be light enough to be supported by a few large lorries at one end and Queen Victoria at the other. It also needs to be able to adjust its radius from 20.5 to 31 km, but this design should be able to do that with care. Darn, it's almost seeming practical now!-- MadnessInMyMethod, Oct 25 2008 The M25 http://en.wikipedia...on_Orbital_Motorway [MadnessInMyMethod, Oct 25 2008] A big lorry http://en.wikipedia...ki/Caterpillar_797BSomething like this but a bit flatter would be ideal [MadnessInMyMethod, Oct 25 2008] Lollipop Lady http://en.wikipedia.../wiki/Lollipop_lady [monojohnny, Oct 25 2008] Milk Float http://en.wikipedia.org/wiki/Milk_float [monojohnny, Oct 25 2008] 7-segment display http://en.wikipedia...i/7_segment_display [monojohnny, Oct 25 2008] I'd rather see the world's smallest and least practical clock.-- Spacecoyote, Oct 25 2008 An analogue clock ? Nah...much simpler to design a 4 x 7-Segment display using residential street and people really good at parking milk-floats to drive around arranging themselves into the appropriate pattern.
And then finally two lollipop-ladies holding up their sticks to simulate the flashing colon in the middle. (gosh, that whole sentence sounds very very rude and quite unpleasant: quite inadvertent I assure you)
[+]-- monojohnny, Oct 25 2008 random, halfbakery