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Capacitance for reliability [Video] (stay-alives and alternatives)


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I have uploaded a new video this evening about stay-alive capacitors, why they are needed, some alternatives to installing them in some cases, different types of capacitor, the need for charging circuits and more.

 

Watch the video here:

 

981324858_Capacitanceforreliabilitytitle.jpg.4d5a4215fd9755f82ef2e9eec58be557.jpg

 

Particular thanks to Jennifer E. Kirk, who kindly gave me permission to use some of her archive footage in the video.

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19 minutes ago, WIMorrison said:

Properly laid track doesn’t need stay-alive fitment.

 

"need" probably not.   "benefit from",  yes it does.   

 

I'll use as evidence a number of finescale layouts I'm involved with, using handlaid track in 2mm, P4, EM and Scale7.   

I think the track builders are good and know what they're doing.  In many cases they were sceptical of the benefits of fitting stay-alive units into locos.   I did a few demonstration fittings.  They now want them in all their smaller locos.     

Why?  because occasional stalling doesn't happen anymore, and control of that loco shifts from "will it stall over that cross-over" to "I'll just run it into the siding and buffer up to the wagons".  

 

The effects are more marked in locos with fewer pickups, so 0-4-0s and 0-6-0s.   By the time one gets to bogie diesels the effect is tailing off because of more wheels to pickup. 

 

 

- Nigel

  

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Something to be careful of when fitting stay alive capacitors is inrush current on layout power up. Any short circuit device should be capable of handling this inrush current.

 

another factor to be considered is track voltage needs to be adequate, even 1 volt lower can cause the stay alive not to charge.

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5 minutes ago, Andymsa said:

Something to be careful of when fitting stay alive capacitors is inrush current on layout power up. Any short circuit device should be capable of handling this inrush current.

 

another factor to be considered is track voltage needs to be adequate, even 1 volt lower can cause the stay alive not to charge.

 

All the commercial kits I know have charging circuits to limit in-rush.   Anything I build from components has such a circuit. 

 

I don't understand your second point, I've never seen a circuit which won't charge from a lower track voltage.   
There are situations where over-voltage is an issue; when a trade-off for run-time against rated voltage has to be made.   Sometimes I'll go close-to-the-wire on voltage limits (as do quite a lot of commercial stay-alive devices), whereas the theorists on electrical circuits want a much larger head-room on rated voltages.   

 

 

- Nigel

 

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20 minutes ago, Nigelcliffe said:

 

All the commercial kits I know have charging circuits to limit in-rush.   Anything I build from components has such a circuit. 

 

I don't understand your second point, I've never seen a circuit which won't charge from a lower track voltage.   
There are situations where over-voltage is an issue; when a trade-off for run-time against rated voltage has to be made.   Sometimes I'll go close-to-the-wire on voltage limits (as do quite a lot of commercial stay-alive devices), whereas the theorists on electrical circuits want a much larger head-room on rated voltages.   

 

 

- Nigel

 


I recently purchased a viessmann maintenance loco, it was factory fitted with a stay alive. I found that the stay alive wouldn’t charge on certain sections of the layout. When I check track voltage there was a difference of 1 volt between Booster districts. Once I adjust the voltage in the problem area the stay alive would charge ok.

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2 hours ago, WIMorrison said:

Properly laid track doesn’t need stay-alive fitment.

 

May I suggest watching the video for an experimental demonstration of the accumulation of insulating oxide deposits on track? Well laid track can certainly reduce stalling compared with poorly laid track, but cannot eliminate it.

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I don't have issues with anything stopping on track or turnouts and as I work in H0e I would be much more susceptible to any of these issues that you mention than other scales and gauges due to the size of the wheelbase and weight (lack off) in H0e locos. Yet with good track-laying, proper wiring and a regular cleaning regime I do not suffer any of the issues these units are designed to rectify. 

 

Strangely enough, until the commercial trade started advertising these units heavily, others didn't have the issue that these correct either. What people now use them to mask is the problems, rather than address the root cause.

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10 minutes ago, WIMorrison said:

I don't have issues with anything stopping on track or turnouts and as I work in H0e I would be much more susceptible to any of these issues that you mention than other scales and gauges due to the size of the wheelbase and weight (lack off) in H0e locos. Yet with good track-laying, proper wiring and a regular cleaning regime I do not suffer any of the issues these units are designed to rectify. 

 

Strangely enough, until the commercial trade started advertising these units heavily, others didn't have the issue that these correct either. What people now use them to mask is the problems, rather than address the root cause.

 

I refer to Nigel's response above, and also to the experimental demonstration in the video of the build-up of insulating oxide deposits on track. It is factually inaccurate to state that stalling can only ever be an issue on improperly laid track.

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1 hour ago, WIMorrison said:

I don't have issues with anything stopping on track or turnouts and as I work in H0e I would be much more susceptible to any of these issues that you mention than other scales and gauges due to the size of the wheelbase and weight (lack off) in H0e locos. Yet with good track-laying, proper wiring and a regular cleaning regime I do not suffer any of the issues these units are designed to rectify. 

 

Strangely enough, until the commercial trade started advertising these units heavily, others didn't have the issue that these correct either. What people now use them to mask is the problems, rather than address the root cause.


Since the contact pressure of the wheel on the rail is, probably, a key factor here I have to say that while I have not yet found the need for SA’s in the larger scales such as 7mm, or as Nigel says in smaller scales with stock having multiple wheel current collection and plenty of weight, I have found them to be a distinct advantage in many cases with 4mm, and most particularly with 2mm. The difference is, in some cases, like night and day if you value decent and reliable running, which I always have. 
 

I seem to recall having such current collection problems well before commercial SA’s appeared, before DCC existed even, all my modelling life of over 50 years really, yet I don’t think I am too lax in my track construction, loco building, or cleaning regime. You don’t have to use them, the choice is yours, but home produced ones, which is all I use, are fairly easy and cheap to make, so why not? Nothing to loose, plenty to gain. 

 

 

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