Stay alive

[Eagle_one]

Hi all,

My first query on here.

I’m just starting a new layout, my first in dcc, I have a controller and lots of chipped motive power. Reading up on fitting dcc, my query is simple.

Will stay alive if fitted, be enough to ensure the loco drives across insulfrog points?

[Suzie]

Generally yes if there is sufficient storage in the stay alive, but if streamline Insulfrog the momentary short circuits are likely to be disruptive to smooth running if you don't use insulated joiners on the frog rails.

[The Johnster]

Not a DCC person, but as I understand it a stay alive is basically a sort of capacitor, which will store power for a short time and release it in a controlled way over a few seconds; the motor is kept running, though it starts to slow down until the normal supply is restored.  If the normal power is not restored, the loco comes to a smooth 'overrun' standstill not a sudden brickwall stop.  They are, of course, A Good Thing.

 

How effective they will be in preventing stalls on dead frogs is another matter.  They will certainly do no harm, but are probably not a cure-all.  They depend on the capacitor part being charged, and if a loco has been at a standstill and moves off to encounter a dead frog within the first few inches, typical of most station starts, chances are that the cap will not have had time to charge fully as there is no spare power for it; the loco is using it all to accelerate away with it's load.  A stall will result if pickup is interrupted in the same way as a DC model, and now I'm on familiar territory!

 

You will be able to minimise and hopefully eliminate such stalls by ensuring that:-

 

1) the track is level, especially in the vicinity of pointwork.  Check your baseboard joins; they have a tendency to sag in the middle and form peaks at the edges, just where there is a join in the track.  

 

2) the track is laid smoothly at the joins; you want your locos to run through pointwork at the best angle to aid pickup.

 

3) pickups are clean and bear evenly on the rear of the wheelrim taking into account any sideplay.  Both sides' pickups must do this on all the wheels that they are fitted to simultaneously at all times, when your loco crosses an insulfrog or any dead section it cannot pickup from the wheels that are traversing the frog and must rely on others to supply continued current, which needs to be given the best chance it can get.

 

4) wheels are clean.

 

5) track is clean.  Dirty wheels and track go together, the dirty wheels spreading crud over the track and the track re-supplying it to the clean wheels; clean your wheels, pickups and track at the same time.  Clean them all scrupulously if the layout has not been used for a while; one of the most effective methods of keeping things clean is daily use.

 

6) Some locos have just the right wheelbase for pickups on more than one set of wheels to be over dead frogs simultaneously; the only way around this is to eliminate the possibility at the planning and tracklaying stage, or relay.

 

7) Ensure that flangeways on your points are clear of ballast or other debris; they are a natural place for it to collect, and will lift the flange clear of the railhead when the wheel runs over them, interrupting vital pickup continuity.  I have a set of pound shop kid's toy paintbrushes which are no use for painting but, with their stiff plastic bristles, just the thing for clearing flangeways.  They are cheap enough to be disposable and replaceable, and get used for all sorts of stuff, including applying superglue, after which they are only fit for an exciting new career in the landfill industry...

 

My layout, Cwmdimbath (check it out on Layout Topics under 'South Wales in the 50s' unless you've got a life), uses Peco Streamline insulfrogs and one Hornby curved turnout.  Some Pecos are medium radius, and have quite long insulfrogs, and the Hornby curved is even longer; I have used this method in the interests of wiring simplicity and hence reliability, and my running is very near 100% reliable over the entire layout so long as everything is kept clean; there are a total of 4 soldered electrical connections which have, so far, not failed.

 

Running failures on insulfrogs have all been isolated to be pickup problems or chassis not sitting square on the track, i.e. on the locomotives, and all have been addressed and eliminated.  I have to comment that Hornby's chassis have needed more work to ensure reliable running than Bachmann's, or even an antediluvian Airfix large prairie, and I include recent Hornby products in this comment, but good running is achievable with them.

[Harlequin]

Not a DCC person, but as I understand it a stay alive is basically a sort of capacitor, which will store power for a short time and release it in a controlled way over a few seconds; the motor is kept running, though it starts to slow down until the normal supply is restored.  If the normal power is not restored, the loco comes to a smooth 'overrun' standstill not a sudden brickwall stop.  They are, of course, A Good Thing.

 

How effective they will be in preventing stalls on dead frogs is another matter.  They will certainly do no harm, but are probably not a cure-all.  They depend on the capacitor part being charged, and if a loco has been at a standstill and moves off to encounter a dead frog within the first few inches, typical of most station starts, chances are that the cap will not have had time to charge fully as there is no spare power for it; the loco is using it all to accelerate away with it's load.  A stall will result if pickup is interrupted in the same way as a DC model, and now I'm on familiar territory!

 

Mr. Johnster, sir,

 

Most of your advice is sage wisdom for both DC and DCC systems but stay-alive capacitors don't work in quite the way you describe.

 

On a DCC system a loco is receiving full power all the time, whether moving or not and whether currently addressed by a controller or not. (The DCC decoder chip decides how much power to feed to the motor.) So a stay-alive capacitor will be almost always be fully charged and probably only takes a fraction of a second to charge up anyway.

 

Another detail is that a stay-alive stores power not just to keep the motor running but to also to keep the decoder chip, lights and sound-generators running.

 

Most DCC suppliers and installers recommend using the biggest capacitors (in terms of energy storage capacity in Farads, not size) that you can fit inside your loco body. The more energy storage, the longer your loco will run while disconnected from the DCC power and control signal. I.e. the more reliably it will traverse dodgy pointwork.

Edited July 28, 2018 by Harlequin

[ba14eagle]

I have a couple of 0-6-0 tanks that are fitted with Olivias Trains dcc sound and stay alive capacitors - they will run for over 2 seconds after a break in power - long enough to negotiate pointwork smoothly.

[The Bigbee Line]

Not wishing to sound ‘pythonesque’ but I have a Minerva Pecket that will keep going for at least 10 seconds. Spooky when it’s still making sounds as it goes in the box.

Edited July 28, 2018 by The Bigbee Line

[The Johnster]

Mr. Johnster, sir,

 

Most of your advice is sage wisdom for both DC and DCC systems but stay-alive capacitors don't work in quite the way you describe.

 

On a DCC system a loco is receiving full power all the time, whether moving or not and whether currently addressed by a controller or not. (The DCC decoder chip decides how much power to feed to the motor.) So a stay-alive capacitor will be almost always be fully charged and probably only takes a fraction of a second to charge up anyway.

 

Another detail is that a stay-alive stores power not just to keep the motor running but to also to keep the decoder chip, lights and sound-generators running.

 

Most DCC suppliers and installers recommend using the biggest capacitors (in terms of energy storage capacity in Farads, not size) that you can fit inside your loco body. The more energy storage, the longer your loco will run while disconnected from the DCC power and control signal. I.e. the more reliably it will traverse dodgy pointwork.

 

Thank you for this, Harlequin; I am a Luddite and do not understand DCC fully, but it bit of digging in the memory bank would have told me that full voltage is available all the time...  I have to wonder if something similar to the 'analogue' type of system I mistakenly described could be applied to DC, but DCC has effectively frozen development of DC control in the late 80s despite the advances in electronics since then.

[Eagle_one]

Thanks for all the replies.

Regarding the checking of levels of point frogs, if they are found to be proud, what methods are recommended for levelling, a) in situ (ie laid and fixed) or b) free reign?

For b) I would file off, well away from anything that wouldn’t like the dust, and finish with 320 grit up to 1000 to tidy up.

However in situ, the dust issue seems tricky if filing. Is shaving possible? A Dremel style tool would spread the mess everywhere.

 

If they aren’t proud, but sunk, can they be successfully raised, or does the whole thing need to be junked? I’m struggling to think of how to raise them without bending the whole unit in the vertical plane, which would surely cause running issues by crowning the running rails.

[34theletterbetweenB&D]

...Regarding the checking of levels of point frogs, if they are found to be proud, what methods are recommended for levelling, a) in situ (ie laid and fixed) or b) free reign?

For b) I would file off, well away from anything that wouldn’t like the dust, and finish with 320 grit up to 1000 to tidy up.

However in situ, the dust issue seems tricky if filing. Is shaving possible? A Dremel style tool would spread the mess everywhere.

 

If they aren’t proud, but sunk, can they be successfully raised, or does the whole thing need to be junked? I’m struggling to think of how to raise them without bending the whole unit in the vertical plane, which would surely cause running issues by crowning the running rails.

 Points typically bow upwards slightly, largely from forces exerted by the formed curved rails trying to straighten, I have never had to deal with a sunk crossing on a RTR point. Fix any bow at time of laying if possible so that the track piece lies flat. Once installed, shaving a plastic crossing to slightly reprofie is possible, just vacuum off the swarf.

 

...  I have to wonder if something similar to the 'analogue' type of system I mistakenly described could be applied to DC, but DCC has effectively frozen development of DC control in the late 80s despite the advances in electronics since then.

 Well actually it's not DCC that froze the development of DC, it's rather that DCC emerged to overcome the intrinsic 'dead end' of DC control. Fundamentally, staying with pure DC supply to the loco, there is no way to discriminate on board the loco between 'no power to motor = intentional stop', and 'no power to motor = failure to pick up'.  If you want to have electronic stay alive on DC, then a command signal is required so that some onboard electronics receive instructions independent of the state of the DC power supply. That could be achieved by a  superimposed AC signal, or radio in some form.

 

DCC neatly achieves this by putting the command signal in the power supply, and thus enables 'stay alive' among much else.

 

But here's the thing that might just appeal to the Luddite tendency. The loco is still a 12V DC loco at heart and needs to be proven competent ofn 12V DC before a decoder is fitted. The only difference is that some of the control electronics are relocated from a 'before the rails' control box to inside the loco. As a long term DC user with a regular switched section cab control layout which was satisfactory in operational reliability, the gain in reliability in smooth slow speed starting especially - which in DC requires very low power on the rails - was immediately noticeable. The DCC equipped loco is always on power at 'full voltage', and the benefit of this is very great, the loco starts every time as smoothly as the mechanism is capable of. (And the customisation of decoder set up to the mechanism means that a good DCC decoder wrings every bit of available performance out of the mechanism too.)

 

One of the appealing features of DCC when I first read up on it, was the Lenz USP 'stay alive' and I imagined that this would probably be handy for small locos with intrinsically limited pick up. But no! Over fifteen years from deploying DCC, no stay alive yet required. If the layout track has been carefully laid and locos have the adequate pick up arrangements long proven for satisfactory DC operation, they simply work yet better on DCC with no further assistance in the way of 'stay alive' required. (I have nothing smaller than fair sized six coupled tank engines, possibly if I had tiny four coupled it might be different, but not explored.)

[The Johnster]

You don't have to sell me on the benefits of DCC; it's a marvellous idea and clearly The Future.  I described myself as a Luddite, but the real reason that I use DC on my current layout, likely to be my last as I'm well into my 60s, is that I am familiar and comfortable with DC, and do not really want to 'learn' a new system (my attitude to Kaydee couplers is similar), and, as an impoverished pensioner, cannot really afford it.  I am happy with my slow running over dead frogs.

 

I experimented, unsuccessfully, a bit back in the 80s with lashed up capacitor and diode circuit stayalives for DC, and designed, though never built, a servo system for controlling battery powered locos that picked up current from the track; the idea was to give a more realistic 'driving experience' and needing something more than just turning the power  off at the controller.  My understanding of electronics was not sufficiently developed to give any of this much of a chance of success; advice from friends who knew electronics always failed to take into account a model railway's need to reverse polarity, unlike car wiring.  Perhaps it is just as well that DCC (Zero 1 had just come out then and I thought it would be just a gimmick to be honest) came to the rescue!

Edited July 30, 2018 by The Johnster

[young37215]

Hi all,

My first query on here.

I’m just starting a new layout, my first in dcc, I have a controller and lots of chipped motive power. Reading up on fitting dcc, my query is simple.

Will stay alive if fitted, be enough to ensure the loco drives across insulfrog points?

 

My experience with DCC and streamline insulfrog points was that I had no problems with electrical continuity on a fleet of sound fitted diesels with BoBo and CoCo wheel configurations. I did have a power BUS and regular feeds to the track but stay alives were not required at any time. Where power problems arose I found that an additional link from the offending track area to the power BUS was the solution.

 

Clearly if you have short wheel base locos then it is potentially more of an issue although my 4 wheeled Bachmann OWB ran without problems. My suggestion would be that unless you have chips with stay alives built in, you try your locos out before you incur the time and cost of adding stay alive. So long as you have reasonably laid track with regular power connection to your controller/power BUS, I doubt that you will need stay alives.

[Izzy]

Hi all,

My first query on here.

I’m just starting a new layout, my first in dcc, I have a controller and lots of chipped motive power. Reading up on fitting dcc, my query is simple.

Will stay alive if fitted, be enough to ensure the loco drives across insulfrog points?

 

Having now fitted stay-alives to a few items it has to be said that it is a distinct advantage, but.... in many cases you have to add the stay-alive to decoders by soldering wires on yourself, with some it isn't possible because useful connections on the decoders just don't exist, and to get the kind of extended 'dead rail' running that is possible (seconds etc) you need a very large capacitance. This needs quite a bit of space and/or is expensive.

 

Izzy

[Suzie]

...useful connections on the decoders just don't exist...

 

This is where PluX decoders are king - the socket in the loco has the connections for the capacitor so that there is no need to wire anything direct to the decoder. 

[DCB]

While very much a DC user I am DCC curious! and I suspect the problem with certain versions of peco and Dead Frog points is that the two Frog rails

converge to form the frog and have just a sliver of insulated plastic between them Exactly the same as the Live Frog in fact, and metal wheels can

bridge the insulation at the point frog causing momentary short(s) The answer as in post #2 by Suzie is to put isolators on the frog rails and obviously

additional droppers beyond. That's why I don't go DCC Life (Available modelling time) is too short to add all those droppers.

 

The new "Unifrog" points neatly sidestep the issue.

 

I think the future is on board batteries and Radio or Infra red control. Present plan is R/C banker/ pilot on DC layout, DCC is a dinosaur in heath

and safety terms with typically 4 amps where 0.5 amps is I believe the legal limit for toys.