We carried on with the E2 module leg levelling today. This module still has the slippery blocks underneath the ski from a week or so ago, and the sun has warmed the black colour and sunk them down into the snow surface. The slushy surface snow from yesterday afternoon is now hard and icy. So when the dozer driver provides snow to pack beneath the ski it is much harder, has a poor size distribution and is difficult to handle. We ended up with the skis being slightly too high, which will prevent us from achieving our leg extensions, but BAS’s experienced engineer decides to leave it for a few days to see how the skis settle in. I will check the levels to the site Southern Gateway datum first thing Monday so we can see what adjustment will be required.
It is fairly easy to fill snow to raise a ski but reducing levels is really hard because under the metal ski pressure the snow turns to ice, and this takes a crowbar to break up. To get better predictability, it is worth scraping the top 400mm of snow from the surface to get to more consistent snow properties below (not affected by a warm days sun) and use this for filling.
I need to relate module soffit and ski edge to the HMI hydraulic system leg extensions. We need to get the leg extensions above the 1275mm target minimum to get the pins in, but also need a fairly level module which is checked initially via the soffit, and also the ski level to reflect the snow level. It is unlikely that leg extensions in one module to another will give the same height of the module above the snow. Therefore I will need to link these aspects together to achieve the best level alignment.
In terms of priority we need to achieve the leg extension range to get the pins safely in, the floor needs to be reasonably level and the loads on the legs should ideally be fairly equally balanced.
Another team cracked on and attached the second dropper to the bridge.
Some of the team played footy this afternoon. I was tired so took it a little easy and may sketch out an article for a local Wimborne magazine and Old Canfordian school magazine.