Tuesday 2nd Dec
Several things happening today after a very useful morning briefing. A lot of stuff for us to focus on in the coming weeks.
Firstly Andy and Peter go to Winchcombe Box to resolve a problem with the Token Machine
Then John P and Peter W dismantle point rodding which impedes the replacement of sleepers, adjacent to Winchcombe box, by the Pway on Wednesday. We will re-connect on Thursday
The replacement of the cabling between Gotherington to CRC needs further investigation and planning. We want to have an understanding of the routing of the existing cable to avoid damaging it when we do the trenching for the new one. So off we go with some hi-tech Cable Tracing equipment that we have borrowed for a few days. This tells us the direction of the cable, it's depth and its alignment. So a bit of track walking between the CRC down distant signal and CRC - plus a visit to the Bishops Cleeve foot crossing.
We have marked the run with white spray paint which I think you can just make out on the following photos. Most of the way from the distant signal to the RDA crossing the cable is approx 1.5 metres from the adjacent rail and is at an average depth of 0.4m.
At the Bishop Cleeve foot crossing it is consistently about 18" from the rail. Here is Mike S with the detector
Curly
I wonder how the tracing equipment works - I mean, it must use the electromagnetic field, but how is that generated, etc: does one have to connect up signal generating gear to the line one is trying to trace (so that the line acts as an antenna), or is the unit entirely self-contained (like a metal detector)?
ReplyDeleteWe managed to borrow a CAT unit with all the accessories. It can trace alamost anything from a plastic pipe ( into which you insert an aerial) to a corroded steel pipe. The method we used was to place the transmitter close to the where you think the line might be and select from a wide range of frequencies and power. On telecom cable it worked well as far as we went , about 900yds. It gave indications of another cable on the other side of the trackbed about 1.5m down! We think that could be an old BR cable. A remarkable piece of kit- which we could never afford!
ReplyDeleteVery interesting explanation. I;ve often wondered how these things work. Thanks for making it clear.
ReplyDeleteRegards, Paul.
Colour light signaling was installed along the line by BR so these cable are still buried along the line. A few years ago when we trenched to install the treated water supply to Toddington yard we found them around Toddington signal box.
ReplyDeleteNeal
That might explain the cable(s) that we could detect on the Cotswold side whereas the transmitter was on the malvern side.
DeleteProbably we had set the output higher than we needed but it was a very steep learning curve and we were grateful to be able to detect and mark up as we did.
I gather the tech term for this is "bleed over" and that's why to avoid it the tx output is adjustable.
ReplyDelete