I was lucky enough to visit the bascule chambers and engine rooms at Tower Bridge yesterday & grabbed a few snaps. In the bascule chamber, we could hear all the vehicles above as HUGE sporadic BOOMs. As the vehicles go over the deck joint in the middle, the vibration resonates through the structure, bounces around inside the 5.5m void of the deck and then ends up rumbling around inside the Bascule chamber (pictured). The rumble-fest is punctuated by sharp drips from rainwater escaping through the gaps in the structure, above. Seriously atmospheric & cinematic…
The (historic) machinery was pretty huge too (see accumulator, pictured) – sadly all now lying dormant as it’s recently been replaced by smaller, more modern machines.
I asked our guide (also the bridge driver) what the channels cut in the walls of the chamber were for… He doesn’t actually know, but has a theory that, the decks of the bridge were constructed in their open position (to keep the navigation channel of the river clear during construction) and when the bridge was lowered for the first time, it would have been too risky to have relied on the hydraulic system alone (as it may have contained airlocks which would cause the deck to drop, suddenly) – so the bridge may have been lowered manually (for the first time) using propping wedges which engaged somehow with the channels in the wall… But that’s just a theory, apparently no-one actually knows for sure..?