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Brake and stop markers in Train Controller....the basics - RR & Co - Getting You Started. - Your Model Railway Club
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 Posted: Tue Jan 5th, 2016 08:31 am
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John Dew
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These notes are primarily intended as an add on to Charleybishop's query.

 http://yourmodelrailway.net/view_topic.php?id=14068&forum_id=151&jump_to=255047#p255047

Lets imagine a block that is 36" long and you want to stop all trains at the end of the block.

Set up a stop marker and, to be on the safe side, enter the distance at 34"  

If a train has to stop in the block for any reason (destination block, intermediate stop, next block occupied etc) the stop marker will be activated the moment the blocks contact indicator turns on......ie the moment the occupancy indicator detects current drawn by the leading wheels of the train.

TC does a time and distance calculation and, assuming the loco has been correctly profiled, the train will stop with its front wheels 34" from the front of the block.......albeit very abruptly.:shock:

However setting up a brake marker and associating it with the stop marker will ensure a smoother more prototypical halt.

There are two measurements to enter for the Brake Marker......distance and ramp.

 Distance is the measurement between the entrance to the block and the point where the train starts to slow. Ramp is the distance the train travels while slowing down.

So in this case if we enter! a distance of 22" and a ramp of 12". TC calculates when the the train has travelled 22'' and then progressively slows the the train to crawl speed over a distance of 12" ........by which time it has travelled 34" so the stop marker stops the train
 
It is important to recognise that although a stop marker is associated with a brake marker they act independently. The stop marker will stop the train after TC calculates the stop distance has elapsed, regardless of the distance and ramp measurements for the brake marker.

To take an extreme example, if a brake distance of zero is entered with a ramp of 6" then the train will start to slow the moment the train enters the block.......it will slow to crawl speed over 6"........and then travel at crawl speed for a further 28'' until the stop marker kicks in!

Generally speaking, at entry level, it is best if Brake Distance+ Ramp = Stop Distance.

TC relies on the the data it has acquired when profiling each loco in order to accurately make the time and distance calculations involved with these brake and stop markers.   Profiling is essential

These notes assume the use of only one occupancy indicator per block. Most people I know operate this way and Mr Freiwald argues the case very well in the handbook. Nevertheless two occupancy indicators*, provided they are electrically isolated, can be allocated to a block to provide greater precision in stopping (over an uncoupling magnet for instance). In our example above ......one detected section could be 24" long and the second 12". The brake and stop markers would be assigned to the second indicator. The shorter distance TC has to calculate then the more accurate the calculation.

Clearly it is essential that both brake and stop markers are assigned to the same indicator





*These are entry level notes and do not touch on the use of Flagman Indicators or any of the various conditions that can be attached to brake and stop markers.


Hope these notes are of use to you Charlie and anyone else starting with RR&Co







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 Posted: Tue Jan 5th, 2016 12:53 pm
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charliebishop
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Thanks John, that all makes perfect sense and I'll sort out my parameters over the next few days.
However, how does TC know the length of each block?
I don't recall inputting those lengths or indeed any layout sizes.


Regards Charlie

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 Posted: Tue Jan 5th, 2016 01:19 pm
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RFS
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TC doesn't need to know the length of the block - the stop marker you have set defines it. In John's example above that's set at 34".  However, I would normally leave a greater margin for a stop marker, so for a 36" block I would set a stop marker at 26-28".  This does allow for a slight variation in stopping accuracy, plus a margin of that size is essential if there are turnouts at the end of the block.



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 Posted: Wed Jan 6th, 2016 12:54 am
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gdaysydney
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Just a quick comment on block size and "margins" 
As John mentioned in the other thread the profiling of locos is an important step that should be undertaken sooner rather than later.
A correctly profiled loco will stop consistently within 2-3 cm  of a stop marker ( even better with good decoders)  thus allowing for less of difference between the length of a block and the distance to the stop marker. 
Basic profiling is relatively straightforward if not time consuming,  brake and acceleration adjustments and brake compensation can take longer and are more subjective ( trial and error).








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 Posted: Wed Jan 6th, 2016 03:15 am
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MaxSouthOz
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I've been able to get stopping consistency of a couple of millimetres by using Atlas locos with Loksound decoders - but like they say; spending time getting the profiling right - particularly the Brake Compensation, is key.

I found that the quality of the locos is probably of the most importance.



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 Posted: Wed Jan 6th, 2016 03:27 am
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John Dew
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charliebishop wrote: Thanks John, that all makes perfect sense and I'll sort out my parameters over the next few days.
However, how does TC know the length of each block?
I don't recall inputting those lengths or indeed any layout sizes.

Regards Charlie

Glad you found it helpful Charlie.

Robert has answered your question about block lengths........I guess you can give TC a hint by entering the maximum permitted length of train in the block properties. I used to do this but dont bother now.

TC does everything based on the moment the occupancy detector senses a train entering the block

Its actually quite handy that TC doesnt know (or care) about block length. I stupidly laid my track too short between the xover points on one of my platform faces.......so the end of block stop marker distance is actually 3" longer than the actual block:roll: The loco stops over the end turnout......not a problem even though it isnt part of the schedule.....I just set it so the loco doesnt foul as a schedule start operation

Cheers

John



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