Virtual Study Group

[alexgoei]

Hello PJW,

I have a question please.

Where the question paper states that the permitted speed for all running line turnouts is 40 km/h, is this speed only applicable for a train performing either a diverging and converging movement. In other words, if the movement is none of these ie. straight, then the permitted speed of the line applies.

Thanks

[PJW]

Hello PJW,

I have a question please.

Where the question paper states that the permitted speed for all running line turnouts is 40 km/h, is this speed only applicable for a train performing either a diverging and converging movement. In other words, if the movement is none of these ie. straight, then the permitted speed of the line applies.

Thanks

Yes it only applies to the divergence from the straight for facing points / convergence for trailing points. The straight path is unrestricted

[alexgoei]

Thanks

Hello PJW,

I have a question please.

Where the question paper states that the permitted speed for all running line turnouts is 40 km/h, is this speed only applicable for a train performing either a diverging and converging movement. In other words, if the movement is none of these ie. straight, then the permitted speed of the line applies.

Thanks

Yes it only applies to the divergence from the straight for facing points / convergence for trailing points. The straight path is unrestricted

[KonduriRaghavakumar]

In this year i want to write the module 1 and module 2 examinations. Hence I want to join the virtual group.

[PJW]

In this year i want to write the module 1 and module 2 examinations. Hence I want to join the virtual group.

Ok; it has been quiet recently due to the Signet event at the begiing of the month. I am on holiday this coming week but we do then need to make progress.

So look at the question A1 in Study Pack Appdx W as per
http://www.irseexam.co.uk/showthread.php?tid=367.
Some answers to most have been posted but get yourself familair and perhaps attempt those that have yet to be done.

Also we are supposed to be doing the 2004 mainline layout and the first stage of that is the calculations.

Post your attempts by 01/06/10 and we will take it from there.

[KonduriRaghavakumar]

Actually i did not have any idea about the braking distance and time calculations I recieved the study pack from IRSE and I gone through it upto now and just attempting this appendix left over question. please tell me is the method what I adopted is correct or not?

[PJW]

Actually i did not have any idea about the braking distance and time calculations I recieved the study pack from IRSE and I gone through it upto now and just attempting this appendix left over question. please tell me is the method what I adopted is correct or not?

Broadly but not exactly.
Q8 was in fact a hard one to do as your first- the others had left it as being "too difficult" I expect!
It is actually a "double" one because there is a requirement to satisfy for passenger trains by day and a DIFFERENT one by freight trains at night and the signalling designed needs to respect the requirements for BOTH. So there are two braking distance constraints that define possible minimum spacings (and when considering degree of over braking the associated maximum), two headway constraints that define possible maximum spacings. Your task is to see what the smallest minimum and the largest maximum is, in order to determine the acceptable range of spacings for your signals.

I don't think you "saw through" the question to appreciate that and hence the figures you used in your calculation mixed some things from the two scenarios.

Otherwise in outline you were putting numbers into sensible formulae; not quite sure where the 155sec required headway figure was derived from even using 25% contingency. You generally seem to have used figures relating to the passenger train so the stated requirement was 120s; if you wanted some contingency then you'd need to be designing signalling to do BETTER than that, say 110s or 100s. If you design for 155s then you will fail to deliver the train service even if it is otherwise running 100% to time at the commencement of the area of your signalling.

Suggest you rework your answer to Q8 in the light of the above whilst I take a look at the remainder of the questions (but the stopping looks pretty good at first sight and you made a good job of the drawing!)

[KonduriRaghavakumar]

Thank you, sir, I again reattempted this question no.8 please check it sir. I am gaining knowledge about these calculations from the study pack only. It is some what feeling difficult to me but i am trying sir.

[PJW]

Thank you, sir, I again reattempted this question no.8 please check it sir. I am gaining knowledge about these calculations from the study pack only. It is some what feeling difficult to me but i am trying sir.

I think the Study Pack should be enough, but also look on this website; in particular there are more example attemts of stopping headway here.

You need to be careful to distinguish between max permissible speed used for braking and timetabled running speed used for headway. When you modified the sheet I think you rather confused yourself re whether 44.7m/s equated to 100mph or 80mph so it was difficult to see what you were doing.

The braking rate for freight in this example was not the same for passenger trains, so its braking distance is 1440m. However I agree that the braking distance for passengers is 200m, so that is the dominant factor rethe minimum spacing.

You should have done two calculations for the headway requirement to ensure that with a signal spacing as above that you could deliver the passenger (by day) and the freight headways (by night) demanded. You should use the 100m length for the former and the 400m for the latter. have a go at this bit and determine which is the more onerous.

Then you will be able to tell what is the maximum signal spacing you can permit. i suggest for tis question you are best off not trying to use the "DGR" method as you are likely to confuse yourself.

One other issue- be careful not to get confused between "baraking distance" and "signal spacing"; they are relaed but not the same. In 3 aspect signalling the spacing cannot be less than the braking; in 4-aspect signalling, the distance between alternate signals cannot be less than the braking. Go back and read what you wrote........

As I said before, you started with a hard one; noone else has had the guts to have an attempt at it and it is designed to ensure that you are clear re what figure you are using where.
Keep plugging away at it, re-read the Study Pack section in the light of what you have learned. You are on the right lines, but not quite there yet

[KonduriRaghavakumar]

Thank you, Sir. I think I need to say need to say sorry. I am in a hurry mood to solve a difficult problem without actually seeing what values I am using. I will improve this and will come back with a good attempt sir.