Vindaloo 42
Member
Do lines relaid with Continuous Welded Rail (CWR) still require flexity strips between the track circuit gaps?
I spent 40 years as an S&T Engineer but have been out of it a few years now. I haven't a clue either Must be some new fangled thing, or.......?For the uninitiated, could you describe what they are and what they do?
Examples of S&C bonding from the IRSE document I linked to earlier. The coiled bonds shown in the first example are the 'pigtails' referred to.As Jim says other than the temporary pre weld situation there are no bonds across welds in S&C. There are 'pigtails' between the switch and stock and sometimes at the crossings if fab'd crossings.
42 years and counting here, and it’s not a term I’ve ever heard. Suspect it’s some sort of bond.I spent 40 years as an S&T Engineer but have been out of it a few years now. I haven't a clue either Must be some new fangled thing, or.......?
Could it be a symptom of autocorrect putting flexity when Vindall 42 actually typed flexible? In typing this, I was corrected to flexitime!42 years and counting here, and it’s not a term I’ve ever heard. Suspect it’s some sort of bond.
No, they use audio frequency track circuits instead, most commonly now EBItrack200 (formerly known as TI21). In these the rail is continuous and voltages of different frequencies are used to divide it into sections. The separation is done entirely electronically.To turn the initial question around, how are track circuits separated in Continuous Welded Rail areas? Does the rail have to be cut and an insulating piece put in?
Not something I've come across with Asters either. I'm also of the opinion it's probably a typo/autocorrect error.Is it something to do with the old ASTER Track circuits?
20 years on Track Renewals and never heard of Flexity strips either.
I was trying to work out if Bombardier had announced a new "Strip" version of their Flexity tramsI'm also of the opinion it's probably a typo/autocorrect error.
Depends on if conventional track circuits are used, in which case insulated rail joints (IRJ or IBJ) are used. Or instead as said above, audio frequency track circuits are used. These use filter units and different frequencies to separate the different track circuit sections. No need for a IRJ or a break in the rail. Hence the railway preference for this type of track circuit on long sections of CWR.To turn the initial question around, how are track circuits separated in Continuous Welded Rail areas? Does the rail have to be cut and an insulating piece put in?
Indeed, jointless track circuits have been available since the 1960s, when continuously welded rail really started to become popular worldwide. The Aster 'U type' (universal) and the earlier '1 watt' (self-explanatory!) were early types employed in UK. ISTR the Aster TC was a French product originally. By the 1980s when I started on BR, Aster had given way to the more sophisticated TI21 (EBItrack200) as the standard jointless TC product for new schemes. That had the advantage of being compatible with DC and AC electrification, subject to certain configuration constraints. Of course there were still plenty of Asters out there in existing installations for decades to follow. I suspect Asters have become rather thin on the ground out in the field by now though if any still survive.Depends on if conventional track circuits are used, in which case insulated rail joints (IRJ or IBJ) are used. Or instead as said above, audio frequency track circuits are used. These use filter units and different frequencies to separate the different track circuit sections. No need for a IRJ or a break in the rail. Hence the railway preference for this type of track circuit on long sections of CWR.
ML engineering (Plymouth) made the ASTER units under licence from the French company. But went on to develop their own version that was compatible. Hence some units had ASTER written on them, but later units did not mention that name...Indeed, jointless track circuits have been available since the 1960s, when continuously welded rail really started to become popular worldwide. The Aster 'U type' (universal) and the earlier '1 watt' (self-explanatory!) were early types employed in UK. ISTR the Aster TC was a French product originally. By the 1980s when I started on BR, Aster had given way to the more sophisticated TI21 (EBItrack200) as the standard jointless TC product for new schemes. That had the advantage of being compatible with DC and AC electrification, subject to certain configuration constraints. Of course there were still plenty of Asters out there in existing installations for decades to follow. I suspect Asters have become rather thin on the ground out in the field by now though if any still survive.
An interesting paper about the tech here: https://dickthesignals.co.uk/onewebmedia/aster book.pdf
Thanks. So it follows the TI21 has a direct lineage from the Aster products.ML engineering (Plymouth) made the ASTER units under licence from the French company. But went on to develop their own version that was compatible. Hence some units had ASTER written on them, but later units did not mention that name...
ASTER ‘U’ type were in use on Western up until about five years ago. The main reason that they were phased out was due to the lack of spare tuning units and ACT track side units. Most were converted to TI21/EBI types, which is a more modern equivalent.
The TI21 equipment had the same style of housings as the Aster gear. It was essentially an AC-immune version of the Aster.Thanks. So it follows the TI21 has a direct lineage from the Aster products.
Makes sense. The TI was simpler in application too, with only two trackside tuning units per TC boundary rather than requiring a third unit, known as the track transformer, between them for the Aster.The TI21 equipment had the same style of housings as the Aster gear. It was essentially an AC-immune version of the Aster.
There were still some in use on the western up until last year, and I’m almost certain that they’re still there now. The spares are indeed becoming hard to come by now though. Some have been turned into hybrids, with TI21 equipment one end and Aster U the other. The frequencies used as close enough that they work.ASTER ‘U’ type were in use on Western up until about five years ago. The main reason that they were phased out was due to the lack of spare tuning units and ACT track side units. Most were converted to TI21/EBI types, which is a more modern equivalent.
Do you have any idea where?There were still some in use on the western up until last year, and I’m almost certain that they’re still there now. The spares are indeed becoming hard to come by now though. Some have been turned into hybrids, with TI21 equipment one end and Aster U the other. The frequencies used as close enough that they work.
No. I don’t know what he means.So are we any clearer on what a “flexity strip”, (as the OP described it), actually is, because if not aren’t a few replies going off into unnecessary detail? Noting that the first two replies weren’t already aware of the terminology?
Berks and HantsDo you have any idea where?
Thank youBerks and Hants