Maximum Track Circuit Length

[dorothy.pipet]

Assuming I'm signalling a layout with Track Circuit Block working and Track Circuits (not Axle Counters), what would be a reasonable maximum TC length to assume in the exam (for plain line sections, long signal spacing).
I'm thinking somewhere between 600m and 1000m - any advice please?

[PJW]

A conservative choice is 600m; a 867/939 dc track is ac immune over that length. Can get certain tracks up to 1000m- from memory a TI21 (now evolved into Ebitrack 200) is useable up to that if have good track and can use the highest gain setting. The Western Region Quick Release I think could be around 1400m in good conditions (but only where no electric traction).
For the exam then I think no eyebrows would be raised at 800m

Assuming I'm signalling a layout with Track Circuit Block working and Track Circuits (not Axle Counters), what would be a reasonable maximum TC length to assume in the exam (for plain line sections, long signal spacing).
I'm thinking somewhere between 600m and 1000m - any advice please?

[Peter]

Assuming I'm signalling a layout with Track Circuit Block working and Track Circuits (not Axle Counters), what would be a reasonable maximum TC length to assume in the exam (for plain line sections, long signal spacing).
I'm thinking somewhere between 600m and 1000m - any advice please?

Not sure why you would be worrying about the physical length of the electrical sections of the individual track circuits for module 2. What PJW writes is all true for the physical constraints (any a typical thing to consider in detail for mod 5), but for the detail shown in module two, you are showing the length of the functional section. Yes, on a real scheme plan, you would show xx/1, xx/2 etc, but for the module 2 paper, I am not sure that anything other than a note saying that "long" sections may be made up of multi section tracks will gain you much credit. To be hones, I have never asked that question of anyone involved. Does anyone have direct experience of that point?

Peter

[PJW]

Assuming I'm signalling a layout with Track Circuit Block working and Track Circuits (not Axle Counters), what would be a reasonable maximum TC length to assume in the exam (for plain line sections, long signal spacing).
I'm thinking somewhere between 600m and 1000m - any advice please?

Not sure why you would be worrying about the physical length of the electrical sections of the individual track circuits for module 2. What PJW writes is all true for the physical constraints (any a typical thing to consider in detail for mod 5), but for the detail shown in module two, you are showing the length of the functional section. Yes, on a real scheme plan, you would show xx/1, xx/2 etc, but for the module 2 paper, I am not sure that anything other than a note saying that "long" sections may be made up of multi section tracks will gain you much credit. To be hones, I have never asked that question of anyone involved. Does anyone have direct experience of that point?

Peter

Who knows how the examiners score the layout?
I agree that getting sensible track layouts is not the most crucial element of the paper, but we do know that they do award marks for SAFETY, OPERABILITY and ECONOMY and I believe in that order. If the layout is not basically safely signalled (i.e. an individual error won't be fatal but too many certainly will be) then it will not pass, if the layout can't achieve the operational moves and train frequencies etc. then it it may not pass, if far too much signalling is provided then it won't score a Credit.
Track circuit lengths most distinctly are the "icing on the cake" but elements like this could well be the difference between Credit and Distinction. Dorothy achieved a Credit last year in mod 3 and has thus set herself a standard to achieve in mod 2 this year!

[Peter]

Who knows how the examiners score the layout?
I agree that getting sensible track layouts is not the most crucial element of the paper, but we do know that they do award marks for SAFETY, OPERABILITY and ECONOMY and I believe in that order. If the layout is not basically safely signalled (i.e. an individual error won't be fatal but too many certainly will be) then it will not pass, if the layout can't achieve the operational moves and train frequencies etc. then it it may not pass, if far too much signalling is provided then it won't score a Credit.
Track circuit lengths most distinctly are the "icing on the cake" but elements like this could well be the difference between Credit and Distinction. Dorothy achieved a Credit last year in mod 3 and has thus set herself a standard to achieve in mod 2 this year!

True indeed. The more there is to give you marks for the better, but as you say, icing on the cake, probably not to panic about! I cannot remember what I did for my layout, and I cannot recall noticing on recent student papers. I'll pay more attention at this year's exam centre.

[YENDRI]

Assuming I'm signalling a layout with Track Circuit Block working and Track Circuits (not Axle Counters), what would be a reasonable maximum TC length to assume in the exam (for plain line sections, long signal spacing).
I'm thinking somewhere between 600m and 1000m - any advice please?

Hi..
Tryin to share some experience on the DC Track Circuits One.
And the good one in my opinion, what dorothy asked is the main thing that I need to count and calculate into a proposal once received a tender requirement for a TC.

For the DC TC length will be depend on value of ballast resistance, which the resistance it self will be depend on the sleepers type and ballast condition.

Normally in a new project to achieve value of relay drop away and pick up current (configure at varistor), I will put 850m length for the good ballast condition.

By assuming we design with the poor ballast condition (re-signalling) then I would like to present 500m length.

Please be free to correct me if I'm wrong


Yendri

[PJW]

Considerations such as ballast resistance is really for TC calc in mod 5. As ever read the specific question. However you are definitely correct that one of the factors to consider is the quality of the track; continouos welded rail with concrete sleepers and insulations means that ballast resistance is far less of an issue than for traditional jointed track on wood sleepers and thus- from that perspective- a longer track is practicable. However there are also other considerations, such as the ac immunity of dc tracks used within electrified areas which still need to be respected. Having said that, if question asks you to make assumptions re TC lengths without giving too much info that constrains, your statements are perfectly sensible

Hi..
Tryin to share some experience on the DC Track Circuits One.
And the good one in my opinion, what dorothy asked is the main thing that I need to count and calculate into a proposal once received a tender requirement for a TC.

For the DC TC length will be depend on value of ballast resistance, which the resistance it self will be depend on the sleepers type and ballast condition.

Normally in a new project to achieve value of relay drop away and pick up current (configure at varistor), I will put 850m length for the good ballast condition.

By assuming we design with the poor ballast condition (re-signalling) then I would like to present 500m length.

Please be free to correct me if I'm wrong


Yendri