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Author Topic: Wiring tips  (Read 2045 times)
Desertdweller

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« on: November 25, 2011, 11:22:33 PM »

Although my model railroad is N-scale, I hit upon an idea that will work for any scale layout.

It is a fairly large railroad for N-scale with 40 power switches, about the same number of blocks, two turntables, and a large passenger terminal and three small yards.  Most of my wiring is for the switches.  Track wiring is minimized by the use of "common rail".

I have a double track mainline.  Beneath the layout, a wire bus line follows the route of the mainlines above.  Frequent feeder wires jump off this bus to connect to the common rail side of the circuit.  To simplify this wiring, I used "suitcase connectors" to connect the jumpers to the bus.  These are marketed by 3M under the "Scotchlok" brand.  They are also available at auto supply stores.  NAPA sells their own clones of these.  These will work on wires of 18 gauge or slightly smaller, but they should be stranded core wire.  The connector is placed over the bus wire, the jumper wire is inserted (be sure you use the right hole!) and the connector is squeezed shut with a pliers.  A slotted blade inside the connector pierces the insulation on both wires and makes the connection.  Once these are in place, they cannot be removed.  This eliminates the need for distribution terminals for half the rails, in effect "hard wiring" them to the control system.

The other rail is gapped, and each gapped segment (power block) is wired to a DPDT switch in the form of an Atlas Selector.  Each Selector contains four DPDT switches.
So, each gapped rail in common rail wiring requires its own feeder and DPDT switch.

Each power turnout requires three wires: a wire each for each direction, and a common return.  Since the control wires for the powered switches are too short for a big railroad, I cut each three wire cable in two in the middle, and attached the wires to a terminal strip (sold at Radio Shack as a "barrier strip").  Of course, you will need a "barrier strip" for each end of the cable you cut.  These are available in a variety of lengths.
The other end of the three wire cable is attached to the switch controllers as usual.

The same can be done for the power wires running to the gapped rails.  I fastened the barrier strips to the underside and legs of the layout with wood screws.  An electric drill is very valuable for this!

All the wires were attached to the barrier strips by stripping the insulation away at the ends, and wrapping the wires around the screws on the barrier strip.  The wires are attached to the Atlas switch panels and switch controllers the same way.  When I returned after a two-year job assignment, I had a lot of trouble with poor power supply to the switch machines and open circuits to both the switch motors and track.  I was able to trace almost all the trouble to poor wire connections at the barrier strips and electrical panels.
Especially difficult were the very delicate wires used on the switch machines.  After you strip away the insulation, there isn't much wire left!

I found the solution at the local Radio Shack.  This little town doesn't have a hobby shop, but it does have a Radio Shack!  They sell a product called "Telephone Spade Lugs", part number 6403070.  These aren't what I call spades, they are more like little two-tined forks.  The package is labelled for 26-22 gauge wire, but I have used them successfully on up to 18 gauge wire.

These things come in a package of 24, price works out to about 10 cents a lug.  If you attach these to the wires (you crimp them on with a crimping tool or long-nosed pliers, you don't need to solder), you can have a nice, positive connection to the barrier strips.  It gives a very neat solution to poor wire connections.  The only drawback is the lugs are too big to pull up through the holes drilled through the layout for the switch machine wires.  If I have to remove a switch from the layout, those three lugs will have to be cut off to pull the wires up.

A bigger problem came when attaching the lugs to the Atlas electrical gear.  The forks are just a little too wide to fit the terminals on the Atlas equipment.  I could not find smaller ones, however, it was easy to modify the Radio Shack lugs.  I clamped them in my bench vise and, one at a time, narrowed the forks by trimming off a little material from each tine with a Dremel Moto Tool.  Use the drum sander attachment with coarse sandpaper.  The narrowed tine can be compared with one of the Atlas "bridging connectors" that are used to gang the Atlas panels.  If the milling leaves a sharp edge, a couple wipes with 400-grit sandpaper will smooth it right off.

I am in the middle of this project.  I still have several hundred to install  (but only about 60 more to modify, the rest can be used "as is".

Les
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Jim Banner

Enjoying electric model railroading since 1950.


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« Reply #1 on: November 26, 2011, 12:58:33 AM »

Using barrier strips for wiring layouts is classic and makes trouble shooting easier.  But those of us in a hurry and/or wanting to save a few bucks often just strip the wires, solder them together, and insulate them with shrink tubing.  For joining fine wiring like switch motor extension wires, tie them together first using a square knot, or better, a double fisherman's knot.  Then strip the ends, twist them together, and solder.  Use enough shrink tubing, installed on the wire before joining, to cover the knot and the joint.  This technique takes all the stress off the solder joint and if you use the double fishermans knot, is as strong as the wire itself.

Properly soldered joints never fail unless you use acid core solder or let the wire flex right next to the joint.

Jim
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Growing older is mandatory but growing up is optional.
Desertdweller

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« Reply #2 on: November 26, 2011, 06:29:34 PM »

Jim,

Good idea!

The use of terminal strips may be "old school", but it does make it easy to isolate trouble spots.  And, if the layout ever has to be disassembled (God forbid!) the wires can be taken off and re-installed.  Wire tags would be handy in that case.

For a "hard wired" (no terminal strips) layout, the Scotchloks might be a good substitute for soldering wires and using shrink wrap.  But they would not work for the little switch machine wires.

I also solder my feeder wires directly to the sides of the rail.

Les
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Ken G Price


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« Reply #3 on: November 26, 2011, 09:22:29 PM »

desertdweller:
Do you have any photos of you layout or a link to them on this or any of the forums? Huh?
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Ken G Price N-Scale out west. 1995-1996 or so! UP, SP, MoPac.
Pictures Of My Layout, http://s567.photobucket.com/albums/ss115/kengprice/
Desertdweller

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« Reply #4 on: November 26, 2011, 09:48:44 PM »

Ken,

No, but if you PM me I'll e-mail them to you.

Les
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