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Slow down on power off


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I have a couple of areas on our 009 layout (isolations at platform ends, return loop isolations) where I would like the loco to slow down rather than coming to an instant and abrupt halt. I would prefer to add this to the locos rather than the track especially on my shuttle 'ends' as the same track is also used on regular DC control rather than the shuttle module (Block Signalling SSA2) and can be switched between the two. Interestingly one of our locos - a Roco HOe 009 1:87 baureihe BR99 does have this feature but I have not figured how - it is DCC ready but not chipped. Most of the other locos are too small to fit DCC chips.

Any ideas?

David

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9 hours ago, cliff park said:

Surely the easy answer is a flywheel. Electrically the other way is a great big capacitor, BUT it would always have to run one way.

 

If there's no room for a chip where do you suggest I put a flywheel?  These locos are tiny and the bodies are full up with motor & gears etc,

 

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Such slowing is pretty simple with DCC.   (How small are your locos really - its probably a matter of skill/ability, rather than impossibility to fit decoders to run them on DCC.  But it may not be the most time or cost effective way. ).

 

Flywheels to be effective have to be quite big, and also need to be very carefully balanced, or you end up with a loco which runs worse than when you started.   You'll be engineering new chassis to fit them. 

 

 

The simplest may be a more sophisticated tracks-side DC control system; which detects the train passing the "stop" detector, and then reduces power in a controlled way, rather than a "clunk switch off".    Can be done, not sure who makes anything "off the shelf" commercially, but the old MERG block system would probably do it (kit/DIY), and, using more modern options, its a fairly simple Arduino or PicAxe DIY programming DIY task.    An automated controller could be switched in/out of the sections to allow control with manual controllers if that was wanted at other times. 

 

 

 

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DCC is not an option with this layout, it's wired with a 4-CAB DC system. How small? Joueff P10 tank loco is one of the bigger ones ! Believe me I have looked at adding chips and/or capacitors; about the only way would be with a permanently attached coach or wagon and that is not operationally an option.

 

Trackside detectors and a control circuit is probably the way to go and something I will need to look into in detail. I'm familiar with Arduino programming as I use them for the semaphore signals and for point control on another layout. Integrating this into the existing controls for reverse loop polarity change might be interesting. There is another idea I'm playing with - a switchable series of resistors and diodes in the slow-down area which would gradually reduce the voltage over a few inches of track. This is the most attractive option as it is independent of rolling stock. Much research and thinking required :)

 

Cheers

 

David

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Diodes sounds like a good idea, but probably not for 009.  If you use several rail breaks and put diodes to bridge the insulated joiners on one rail with other diodes the other way round from the same track section straight to a bus connected to the full power section then the train should slow and stop, yet reverse out quite easily.  Trouble is diodes drop voltage somewhere round 0.7  volts per diode so you could need quite a few sections and the loco would not necessarily reach the dead section which could cook the armature.

Folk used to put a capacitor across an insulated rail joint and that slowed the train as it charged up. Not sure quite how it worked or how it was discharged for the next train, but I am sure someone has a 1960s Railway Modeller or similar where the principle was explained.

 

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You can install a DCC chip and if you choose the right one then you will get the acceleration and deceleration that you get on DCC with pure DC. If you are interested then come back and I will check but I think that the Zimo MX617 operates like this, probably all Zimo do but that is the one I use most :)

 

EDIT - the MX617 can operate as I suggest when running on DC. Change bit 6 of CV14 to a value of 0 (this is the default) and you will get the same behaviour as seen on DCC, though how the deceleration works when you cut the power I am not sure, the chip must have some capacitance to enable the slow down of the motor.

Edited by WIMorrison
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  • RMweb Gold

If the loco is always coupled to the same coach then one option is to put a motor, with flywheel, in the coach where there is plenty of room.  This can power the coach wheels with the loco running with no motor at all. A sort of "tender drive" with a coach instead of a tender.

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12 hours ago, Colin_McLeod said:

If the loco is always coupled to the same coach then one option is to put a motor, with flywheel, in the coach where there is plenty of room.  This can power the coach wheels with the loco running with no motor at all. A sort of "tender drive" with a coach instead of a tender.

Good idea but that doesn't fit the operational model - unless it was an Auto-train

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23 hours ago, rynd2it said:

DCC is not an option with this layout, it's wired with a 4-CAB DC system. How small? Joueff P10 tank loco is one of the bigger ones ! Believe me I have looked at adding chips and/or capacitors; about the only way would be with a permanently attached coach or wagon and that is not operationally an option.

 

I'm sure it can be done, but it requires some effort.  I have much smaller locos than a P10 with DCC chips in them.  

But, its probably a diversion from your actual aims, so lets stick with those aims: how to make the existing setup do what you want. 

 

 

23 hours ago, rynd2it said:

Trackside detectors and a control circuit is probably the way to go and something I will need to look into in detail. I'm familiar with Arduino programming as I use them for the semaphore signals and for point control on another layout. Integrating this into the existing controls for reverse loop polarity change might be interesting. There is another idea I'm playing with - a switchable series of resistors and diodes in the slow-down area which would gradually reduce the voltage over a few inches of track. This is the most attractive option as it is independent of rolling stock. Much research and thinking required :)

 

 

 

 

Arduino approach, which I think ought to be fine if you've used them before.  Need a motor "H-bridge" output module to drive the track.  The unit then becomes one of your CAB controllers.   Programmatically, I'd break it down as follows:

version 1 - input to the Arduino (a speed potentiometer and direction switch or button) can directly control the H-Bridge output, and thus drive a loco (thus you've built a train controller).

version 2 - add binary inputs to stop a train.  Manual push button to restart train.  

version 3 - use a timer to hold train after stopping with input from v2.

version 4 - write code which causes acceleration and deceleration to be gradual (ie. taking say, 6 seconds to move between stop and running speed). 

 

Then, whatever buttons and switches you think are necessary to do the control you need.   For example, is a general "stop" different to a "stop and reverse" instruction, and thus needs a different input ?   etc..     I think having a manual speed control is useful, as you can just dial the appropriate speed for the loco under automated control, and can stop it if needed by turning the knob down.

 

 

- Nigel

 

 

 

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Having come across this in my own search, I would certainly welcome the ability to be able to automatically slow down a train as it nears the buffers.

 

I have a terminus on an upper level towards the back of a layout which is still in the process of having its track laid, so now's the ideal time to try and fit something. Two of the terminus lines will effectively be hidden behind a station building, so although I will be able to send in a train at a low and slowing speed (manually), I won't really know where the lead loco is until it smacks the buffers. Easing to a stop from that manual slow speed would solve that problem.

 

I'm certainly interested to know whether a solution been found.

Failing that, even the originally-unliked sudden stop would be better than nothing, especially if the speed is already slow. I was looking at this with the eye of someone who is almost clueless about electrics: http://www.blocksignalling.co.uk/index.php/train-detector-with-relay-bod2-rly

Peter

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Hi

 

As you have a DC operating layout, I'm wondering if any of the existing Heathcote Electronics modules would do what you're after?  They offer normal running, slow to a stop and slowly accelerate away options all operated via Infra red detection devices. If none of their existing modules do exactly what you're looking for then I would recommend emailing Clive Heathcote to enquire what if anything he recommends or can do for you.  Link to web site... Heathcote Electronics

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23 hours ago, CarriageShed said:

... I would certainly welcome the ability to be able to automatically slow down a train as it nears the buffers.


... even the originally-unliked sudden stop would be better than nothing, especially if the speed is already slow.

That's easy, if the requirement is 'always slows and stops' (which the OP didn't want).

 

For slowing, with the last rail feed before the gap(s) all you do is gap one rail, and bridge with a pair of diodes in parallel head to tail. The voltage drop resulting slows the loco. (You can put in more than one diode pair bridged gap for progressive slowing if required, but if a slow approach setting is used on the controller, that's overkill.

 

For stopping, a gap bridged by a single diode to only conduct for the reversing away from the buffers direction.

 

It will need some experiment to find the controller setting that finesses the result, such that the loco slows enough that the final stop isn't too abrupt.

Edited by 34theletterbetweenB&D
clarification.
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On 25/05/2019 at 08:32, rynd2it said:

 

If there's no room for a chip where do you suggest I put a flywheel?  These locos are tiny and the bodies are full up with motor & gears etc,

 

Several of my N gauge locos, steam and diesel have flywheels. If it'll go into N, then maybe OO9 isn't such a problem??

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2 hours ago, Brian said:

Hi

 

As you have a DC operating layout, I'm wondering if any of the existing Heathcote Electronics modules would do what you're after?

 

It literally is the slow to a stop that's all I need, and the simplest-possible solution is likely to be the one I go with because my ability to understand electronics seems to be very limited. But I'll certainly give Mr H a buzz if a solution doesn't present itself here. Thanks for the suggestion.

 

1 hour ago, 34theletterbetweenB&D said:

That's easy, if the requirement is 'always slows and stops' (which the OP didn't want).

 

For slowing, with the last rail feed before the gap(s) all you do is gap one rail, and bridge with a pair of diodes in parallel head to tail. The voltage drop resulting slows the loco. (You can put in more than one diode pair bridged gap for progressive slowing if required, but if a slow approach setting is used on the controller, that's overkill.

 

For stopping, a gap bridged by a single diode to only conduct for the reversing away from the buffers direction.

 

It will need some experiment to find the controller setting that finesses the result, such that the loco slows enough that the final stop isn't too abrupt.

 

Yep, 'always slows and stops' is precisely what I'm after, and why I was a little hesitant on posting my question here even though it seems to be roughly along the same lines as that of the OP.

 

Given that my electrics abilities are very basic, I'll need very simple words to be able to understand any solution! With that in mind:

     - There is already a rail break on one side of the tracks, with a feed wire on either side of it so that the train loco can be isolated and the coaches removed by the station pilot.

     - Would the feed to the buffers side of the break be suitable to use in your solution?

     - Would the solution work automatically or will it need a switch?

     - If the diode(s) are part of this feed, how will that effect the power when the train has been removed and the train loco can leave the isolated area near the buffers?

     - If the arriving loco has already been slowed down by the controller, but the stop is still abrupt, is it simply a case of adding another diode to 'top-up' the slowing effect?

 

Apologies for the simplistic questions, 34... I can see how great it would look in practice but I need to plug the gaps in my knowledge of how to set it up. I do want to know, though.

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17 minutes ago, CarriageShed said:

...There is already a rail break on one side of the tracks, with a feed wire on either side of it so that the train loco can be isolated and the coaches removed by the station pilot...

That's easy, no need for the diode at the 'stop' rail break, just leave the switch open, close it only when the loco is to reverse away. Best type of switch is one which springs  to the open position; 'push to make', so the rails immediately before the bufferstops are normally dead, thus always stopping the loco.

 

21 minutes ago, CarriageShed said:

... If the arriving loco has already been slowed down by the controller, but the stop is still abrupt, is it simply a case of adding another diode to 'top-up' the slowing effect?

If you want some automatic slowing before the loco reaches the dead section, another rail break before the dead section, with the pair of diodes arranged across that rail break will automatically produce that effect. You will have to experiment to determine how to achieve an effect that satisfies you.

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6 hours ago, 34theletterbetweenB&D said:

That's easy, no need for the diode at the 'stop' rail break, just leave the switch open, close it only when the loco is to reverse away. Best type of switch is one which springs  to the open position; 'push to make', so the rails immediately before the bufferstops are normally dead, thus always stopping the loco.

So the normal isolating switch is left 'open' (ie. isolating) at all times, and is only turned off (supplying power) when the loco is reversing away from the buffers...? If that's right then it sounds easily workable.

I already have a DPDT On-On switch installed for this (although no wiring is in place). It wasn't my design of course, but the idea is that it isolates two roads at a time. When it's switched off only one of those roads will be supplied with power anyway, depending on which way the points are set. Will a DPDT On-On switch be suitable?

 

6 hours ago, 34theletterbetweenB&D said:

If you want some automatic slowing before the loco reaches the dead section, another rail break before the dead section, with the pair of diodes arranged across that rail break will automatically produce that effect. You will have to experiment to determine how to achieve an effect that satisfies you.

No, no, that's absolutely fine. Happy to slow down the loco manually (and keep things as simple as possible). The buildings that will obscure the buffers will only be located across the last quarter of the platform length, so the train will be pretty slow by the time I lose sight of the loco.

 

What's more, the isolated section is pretty generous in length, so that it can accommodate a train loco and potential pilot. I'm not sure how that affects things if one loco is being slowed down while the other is still gently pushing forwards until it also gets across the isolating gap in the tracks. Or if there's no pilot and the train loco has a double-loco length in which to slow to a halt.

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  • RMweb Gold

A few strategically placed "little people" on the  visible part of the platform could indicate where (say) the second or third coach should stop to have the loco close to the buffers.

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10 hours ago, Colin_McLeod said:

A few strategically placed "little people" on the  visible part of the platform could indicate where (say) the second or third coach should stop to have the loco close to the buffers.

Possibly, although that supposes that all coaches are the same length. In scale terms, I already have two 44ft conversions from Farish suburbans, plus a couple of 57ft conversions that haven't been shortened, a 47ft ex-royal saloon, and plenty of 54ft conversions on the schedule. The passengers would have to be positioned according to carriage lengths, but would still need to shuffle around for mixed trains. Hmm... I see a snag!

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Isn't that something along the lines of 'if a tree falls in a forest and no one hears it, does it make a sound?'. ;)

 

Nope, the train doesn't need to stop *exactly* at the buffers but it does have to fit inside the isolated section, and if it has a pilot loco in front of it then both have to fit inside the isolated section which brings them within two or three centimetres of the buffers. With the best will in the world, sooner or later something is going to hit the buffers unless I can auto-stop it.

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