The humble battery powered SDS drill is largely responsible for the modern exploration of Mendip caves, either through drilling holes for various rock splitting/ removal methods or for faster bolt/ aid climbing where the easy ‘just the follow the open passage’ phase of exploration has long passed. The ability to transport a drill through a sump opens up more opportunities where climbing or passage enlargement may not have been possible before.
A dry tube would be an obvious choice for some but to fit a powerful drill it would have to be big, and thus require a lot of weight to sink and this would complicate the transport element in the dry passage to the actual work site, dry tubes also tend to be quite expensive but on the plus side are usually capable of passing very deep sumps.
A previously well known/ used method is simply to get a large section of inner tube, put the drill inside and methodically roll and fold the ends over, this works in shallow sumps but for me posed too much risk of flooding and requires lots of faffing to seal properly.
I chose to create my own version of this, still using a section of inner tube but instead of relying on folding I made two sets of metal clamps which are used to seal each end. This has proved very reliable and is often bone dry inside even after passing multiple sumps up to 20 m depth. the metal clamps are 8mm thick stainless steel closed by M8 bolts and wingnuts, one end is clamped very tightly and never removed and the other end is used to open and close the inner tube, a spanner or bolting hammer is useful to help tighten and loosen the bolts. The drill is packaged in a sturdy drybag in case it does flood.
The packaged drill doesn’t require any additional lead to sink, if care is taken and all the air is removed from both the drybag and inner tube sleeve before sealing its about 2 kg negative near the surface but this increases slightly with depth due to further compression. I use this as part of my weighting system, combined with some climbing gear its more than enough to sink me in a wetsuit.
I use a very well worn tackle bag that has half the bottom missing, this makes for easy drainage when standing up to get out of the water fully kitted up, other gear goes in another bag without a massive hole in. The bag is side mounted over the top of diving gear, the drill bag on one side and climbing gear on the other balances out quite nicely underwater.
Using this method this drill was carried to Chamber 24 in Wookey Hole on numerous trips and was used to forge the dry link from Chamber 20 so that dry cavers can now visit without the need for diving. It occasionally gets a small pin hole sized leak, because of the inner dry bag this doesn’t really matter but its easy enough to patch them with bike repair kit bits. I’m not sure how deep this would work but it has been great in the UK for shallow sumps, it would probably be fine to 30 m, if I intended to take it deeper I would trial it with a block of wood inside to represent the shape of the drill as I did when originally testing it.