Ive just moved to just outside of Gawler, Adelaide from New Zealand and am fascinated by the older looking trains they have in the stables....
ive never seen so many trains sleeping in a yard thats so far away from the city before... why is that?
I live in the opposite direction from the city, so I don't know which trains are in the Gawler yard. However, it's not hard to work out:
If, as I suspect, some of the "old trains" you refer to are these 2000/2100 class DMUs, they are life expired units which are simply stored there until they get scrapped because it's a good place to get them out of the way. These DMUs are nearly 40 years old, are now life expired, were never the right choice in the first place and have since been replaced by new Bombardier EMUs operating on the Seaford/Tonsley lines.
If some of them are these more modern 3000/3100 class DEMUs, they are stabled there because their final duty of the day will be an evening peak (i.e. outbound, carrying city workers home after work) commuter service to Gawler or Gawler Central and their first duty of the following day will be a morning peak (inbound) commuter service. Why add in a 60km round trip of non-revenue running to the Dry Creek depot 30km away when you could do a quick shunt instead?
If you went looking for them in the right places, you would also find stabling yards near the end of every other Australian city's commuter lines. For example, there are sidings for stabling next to Mount Victoria station, 126 kilometres away from Sydney (three times as far away as Gawler) in the Blue Mountains.
and why have they not any electrics is this because adelaide is so far behind?
If you go to the Seaford line (including Tonsley spur) in the south, you will find it has been electrified.
Adelaide is a bit behind many larger cities on electrification, but it must also be pointed out that passenger usage has only recently increased to the point that electrification is viable. Despite the project running late due to poor project management, Adelaide's first electric line (to Seaford, south of the city) still managed to enter service a few months before the backward sheep shaggers in Auckland got their first electric trains running.
There will no doubt be further electrification to come on the other lines (including to Gawler) at some point, but only as the existing 3000/3100 class DEMUs start to approach life expiry. They are excellent units which will continue to benefit from world-class build quality for many years to come so we may as well use them.
im actually blown away by the fact that the rail yard has such old trains but security system so advanced?
is this from delinquent children throwing rocks at rail cars? blood kids!
If the only trains stored there are the life expired 2000 class then the security systems will have been from when it was previously used as an operational depot and will be needed there again when it next returns to operational use.
Graffiti is more the issue than rock throwing. Certain preventative measures are cheaper than just accepting the issue and cleaning the trains each time. I'm sure that operational train depots in NZ have security fencing and CCTV too.