Oh goody, my specialist subject was bound to come up on Mastermind sooner or later!
Anyone like to guess the maximum useable length of cable?
It may also be useful as a rescue technique for putting bolts in, or getting heating or lighting to a casulty. Do CRO lay cables ever at an incident? maybe a generator and cable should be part of CRO kit.
A trick I have used is to use four core 2.5mm cable and parallel the cores so you get effectively 5mm. You can run 800W on the end of 150m with no appreciable loss in performance if you do this. Most power drills are double insulated so the earth wire is redundant, and in any case even if the drill is earthed, I've yet to see someone connect an earth rod when using a small generator for digging.
CRO don't bother with cables, for lots of reasons. The cables are difficult to lay, there are much more efficient ways of getting heat and light to a casualty (think lots of volunteers with cap lamps, and the Little Dragon) and it's very unusual to need more bolt holes on a rescue than you can put in with a single clip-on Bosch battery. The only time they would need the sort of power we use for digging is if they got into an extended passage reorganisation exercise, in which case they'd call out the digging teams and their gear anyway.
All i can remember is that the volttage drop cannot be more than 4% of the original,
Not come across that rule before. Where does it come from?
Pelicase and Ammo Box no good as they will not take the pressure.
I am thinking of using a piece of soil pipe with caps welded on each end, the caps have seals and they look 'man-enough
Anything with square sides and/or flat ends will be crap at withstanding pressure unless seriously re-inforced. We had this conversation a week or two ago, Johnny! Test your tube before you put anything valuable in it. I speak as somone who had to explain to Bob Mackin why one of his Molephones wasn't working after a CDG/MRO rescue practice in Wookey
The GBH is a good drill - but we definatley need to sort out the battery situation.
Naah, the TE5A is the mutts nuts - nearly twice as powerful as a GBH24 and sensible battery voltage unlike the TE6A. Add an extra couple of cells to get the maximum oomph.
Unfortunately the transformer idea is not viable. The auto transformer that you would need at the far end only has an efficency of about 75%
Don't know where you are getting your transformers from, but I suggest you ask for a refund if that's the best efficiency they can offer
. And you should never use an auto-transformer for a 110V site supply since an auto-transformer provides no isolation between primary and secondary, and isolation is the whole reason for using a transformer in the first place in these situations. But you're right about it being a bad idea - the last thing you need in places where you want to drill is to be lugging a bloody great lump like that about, never mind all the problems of keeping the water out of it. Mind you, I saw a neat electronic transformer the other day though which showed some promise - but I haven't been able to find one to buy to further my research yet.
A zap from 110 volt makes you jump a bit, 240volts can be seriously dangerous
If correctly wired, the maximum shock voltage from a 110V site transformer is actually only 55V because the centre of the 110V winding should be earthed (which is why they are properly known as "110V CTE" where the "CTE" stands for "Centre Tapped to Earth). So, "240V" is actually a lot more bite than it appears by first comparison. Nevertheless, it's all about where the current goes, and you'd actually be pretty unlucky to get a full 240V belt across the heart muscle (which is what's going to kill you) when using a small generator because the windings of the alternator probably won't be directly connected to earth.
yup in durham edge - john was lay flat out in the steady trickle when his arm started juddering - so what did he do - passed the drill back to me - I stood there juddering whilst, instead of pulling the plug - Dave just stood there pissing himself.
You need an RCD on the end of the cable (and arguably another one, with a higher trip current, at the generator end). I have seen and used one fitted into a small 'dongle' on a drill lead, which was made out of the guts of one of those 13A plug type breakers (Powerbreaker is the brand, IIRC). They need to be kept dry because they are electronic, unlike the ones which go in your mains distribution board, but it certainly worked - we 'tested' it on several occasions. I remember one occasion when drilling in Low Douk when the water was actually going in one side of the drill housing and out the other - fine so long as everything was kept the right way up, and the RCD saved any unpleasant tingling when the water flowed where it shouldn't.
Happy hunting!
Nick[/quote]
