Templot Club Archive 2007-2020                             

topic: 1918Track Construction using C & L Components
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posted: 10 Apr 2012 19:11

from:

David Yates
 
Walsall - United Kingdom

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I am about to start track construction for my permanent, 7mm Scale7 layout, Staircliffe Exchange Sidings, using C & L components.

In order to avoid using multiple droppers for connecting track sections together, standard track lengths being 210mm ( i.e. a scale 30ft) I've been contemplating using etched brass fish-plates soldered between sections of track rather than wire connections below the baseboard. I'm also contemplating using strategically positioned brass chairs to solder the feed droppers to, to get the power to the track.

My question is, has anyone out there tried this method and if so, have you found any pitfalls with this method?

Regards,

Dave

posted: 10 Apr 2012 19:22

from:

Raymond
 
Bexhill-on-sea - United Kingdom

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I'd have thought that they woould work exactly the same of droppers.
Regards
Raymond

posted: 10 Apr 2012 20:08

from:

Martin Wynne
 
West Of The Severn - United Kingdom

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Hi Dave,

A general engineering principle is that you don't use a mechanical fixing as an electrical connection.

Mechanical fixings are subject to the stress of thermal expansion/contraction, timber shrinkage, vibration, etc.

The original Protofour riveted plywood track system used an electrical feed through one of the rivets, and it was always unreliable. When a soldered rivet fractured due to thermal expansion, guess which one it was? :( Most users soon abandoned the system.

A suitable wire for short droppers is bare 1/0.5mm solid copper wire from old telephone cables. If you drill a 20 thou hole through the web of the rail*, the wire can be neatly soldered into it using a smear of 179deg solder cream, and after painting the connection will be barely visible.

*very much easier to do before construction, but it does require some forward planning and an immense feat of memory. :)

regards,

Martin.

posted: 10 Apr 2012 20:20

from:

David Yates
 
Walsall - United Kingdom

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Hi Martin,

Many thanks for your comments, which have been duly noted. It will be interesting to see what else comes from this thread.

Regards,

Dave

posted: 10 Apr 2012 22:25

from:

Chris Mitton
 
 

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David Yates wrote:
I am about to start track construction for my permanent, 7mm Scale7 layout, Staircliffe Exchange Sidings, using C & L components.

In order to avoid using multiple droppers for connecting track sections together, standard track lengths being 210mm ( i.e. a scale 30ft) I've been contemplating using etched brass fish-plates soldered between sections of track rather than wire connections below the baseboard. I'm also contemplating using strategically positioned brass chairs to solder the feed droppers to, to get the power to the track.

Why use such short rails and a multitude of power connections?    My method (borrowed largely from Jim Smith-Wright) is to use long rails - for example, a metre length, trimmed to 960 mm, can represent four 60-foot sections and runs across most of a four-foot baseboard.    Mark on each rail (accurately) the "real" rail-joint positions from your Templot plan - and don't mark one from the other, mark both from the plan - even gentle curvature will stagger them significantly.     Cut through the rail head, as far down as the web, to simulate the intermediate joints.   Slide the chairs onto the rail (suggest Mozart as accompaniment!), then solder cosmetic fishplates into the web.    Don't forget to group the chairs in sections first - you can't slide them past the fishplates once they're on.    For electrical connection, I use brass lace-making pins (about 0.6mm diameter), pushed through tight holes in the sleepers and bigger holes in the trackbed and baseboard, then wired underneath.  You need exactly two such droppers on each rail section - on adjacent sleepers so that expansion between them is miniscule, but avoiding a single point of failure.   Solder the rails to these - in 4mm the pin head leaves the rail height above the sleeper exactly matching the plastic chairs, although in your 7mm this might not be the case.    Splitting the chairs that go on these sleepers in half and cementing them, cosmetically, in place leaves the droppers totally invisible.

The virtue of this approach is that it leaves the rails securely fastened transversely, as they must be, and free to move longitudinally, as they need to be to allow for thermal movement.    [I also prefer some vertical play, for much the same reasons as the full-size railway, but that's another tale.....]    The temperature range in my loft, with the expansion coefficient of nickel silver rail, means that I need to allow about 2/3 mm across a baseboard length, which with the use of expansion joints* at the "actual" rail joints and baseboard junctions can be lost fairly inconspicuously across three or four joints per board.   Granted I've still got three baseboards to fill with track, so maybe in a decade or two.......

Hope this helps,
Regards
Chris

* I did put some thoughts on expansion joints on the ScaleFourum a year or two back - I'll elaborate here if it's of any interest.


posted: 11 Apr 2012 08:53

from:

Stephen Freeman
 
Sandbach - United Kingdom

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It all depends on the layout's location. You are more likely to experience expansion/contraction problems if it is subjected to direct sunlight. I can't say that I've ever seen any severe problems where this not the case. Do not, however rely on soldered fishplates for electrical continuity, it's asking for trouble.

posted: 11 Apr 2012 12:09

from:

LSWRArt
 
Antibes - France

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If you are using the usual C&L track construction method with ply baseboards, glued granite chips or ash ballast on cork or rubber - can you use bare wire for the droppers?

I have always used insulated wire, but wonder if this is really necessary?  With multiple drops, would there be much leakage through the baseboard and ballast - especially at the high frequencies of DCC?

Thanks, Arthur

posted: 11 Apr 2012 12:19

from:

Stephen Freeman
 
Sandbach - United Kingdom

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Hi,

Never used insulated wire for droppers even with DCC, never been a problem.

Stephen
LSWRArt wrote:
If you are using the usual C&L track construction method with ply baseboards, glued granite chips or ash ballast on cork or rubber - can you use bare wire for the droppers?

I have always used insulated wire, but wonder if this is really necessary?  With multiple drops, would there be much leakage through the baseboard and ballast - especially at the high frequencies of DCC?

Thanks, Arthur


posted: 11 Apr 2012 12:29

from:

Martin Wynne
 
West Of The Severn - United Kingdom

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LSWRArt wrote:
With multiple drops, would there be much leakage through the baseboard and ballast - especially at the high frequencies of DCC?
Hi Arthur,

You would need very much higher voltages to detect any leakage. Bare wire is fine for droppers at 18 volts, and much easier to hide in the ballast.

If there was going to be a problem, it would be much more likely to occur where the rails contact the ballast, or are buried in roadways, goods yards, etc., and no such problems have ever been noticed.

regards,

Martin.

posted: 11 Apr 2012 14:22

from:

LSWRArt
 
Antibes - France

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Great! That is one task simplified :-)
All the best, Arthur

posted: 11 Apr 2012 14:54

from:

Roger Henry
 
Brisbane - Australia

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      If you are using the tradional white-glue to secure your ballast you might be surprised at just how  low the insulation resistance of a track section is. I did some experiments a couple of years ago and, although I don't have the figures to hand, I seem to recall that even a yard or so of track was down to about 20,000 Ohms rail-to-rail.

    As I operate with DC (Analog) this was of no concern to myself, but I did wonder if,during humid weather,  it could cause erratic operations of some kinds of track-detection circuits and, possibly, DCC.

    The measurements were taken using the high-Ohms scale of a typical hobbyist's multi-meter.

Roger,

Brisbane

 

 

posted: 11 Apr 2012 16:53

from:

LSWRArt
 
Antibes - France

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20,000 ohm at 20 volts is a leakage current of only 1 milli-amp and we have may be 10 droppers on a section so say 10 milli-amps, so with typical motors drawing 1/4 amp (?) that is only 4% leakage, so I would not have thought it would be significant. As Martin said we happily bury our rail is plaster, etc for inset track and have ballast touching the rails, so if that works OK, I think he and Stephen are correct in saying that it should not be a problem.

posted: 11 Apr 2012 21:41

from:

PRChappell
 
United Kingdom

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Hi

Using a dropper giving a 1mA leakage is probably ok but by 10mA all my track circuits will be lit! I usually bond around fishplates with bare wire but do not take the wire into the ballast.

Regards

Peter

posted: 11 Apr 2012 22:11

from:

Martin Wynne
 
West Of The Severn - United Kingdom

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Roger Henry wrote:
I seem to recall that even a yard or so of track was down to about 20,000 Ohms rail-to-rail.
Hi Roger,

Per yard of track? I've seen such a low figure only for a whole roundy-roundy layout (with all stock removed), using bare droppers throughout.

Admittedly that was using latex adhesive and non-mineral ballast.

Were you by any chance holding the test probes in your bare hands? That sort of figure is typical for skin resistance hand-to-hand.

regards,

Martin.

posted: 11 Apr 2012 23:41

from:

David Yates
 
Walsall - United Kingdom

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Hi Everyone,

To all those who have replied to my original question, a big thank you, for pointing out the pitfalls in the scheme I was contemplating.

To all other contributors who have taken this discussion into new territory, an equally big thank you for sharing your experiences with us. All very helpful and educational.

Regards,

Dave

posted: 12 Apr 2012 14:12

from:

Roger Henry
 
Brisbane - Australia

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    Bother. A retraction and a clarification. I unearthed my original e-mail. to another group, and it pertained to drying times of diluted white-glues as used in/on ballast.

    What I had measured was the conductivity of the diluted glue in the jar, which is quite high, and then how the conductivity fell as the glue dried out. The 20K figure was measured after several hours. It did take several days before the figure reached a couple of Meg-Ohms.

     I have just run the meter over my trackwork and the needle doesn't even lift off zero, which, of course, explains why no-one has experienced any problems with their electronics.

     So my apologies if I have got anyone excited with my earlier post.

Roger,

Brisbane

 



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