Modifying Kato Unitrack Turnouts

[JXC]

Has anyone modified a Kato turnout so that electrical routing is DPDT rather than SPDT? On the surface this seems like a silly question as it would require gapping both rails on the diverging legs and one of the key benefits of Kato Unitrack for me is that it doesn't need any wiring so works well for temporary layouts - I live in a downtown hi-rise so have limited space. I have an idea that by converting the existing electrical routing arrangement (SPDT) so that both stock rails are powered via a switch (DPDT) and gapping them on each diverging leg with saw cuts on the turnout module itself it would be possible to power the throat route from the diverging route selected by the turnout. That is, power routing into the throat instead of the usual out of the throat. Such a turnout would make it possible to include reversing loops and wyes in trackplans without requiring any wiring.

Jan

[PED]

I assume you are talking N scale? Have you ever opened up the back of a turnout and examined the interior?  The connection for power routing is a very light weight arrangement and would only carry a limited amount of power. Not very suitable for powering much track beyond the turnout especially is you are running several locos.

If you really wanted to do this, I suggest you come up with a relay approach where you use the power you want to trigger a relay that can carry the load you want.

[JXC]

Yes N scale and its a DC system that gets set up each time. These two constraints mean there is only ever one loco at a time anywhere on the layout. Regardless, the DPDT power routing would only be to a reversing track so would only supply one loco at a time.

 

I haven't looked inside an N turnout but I also have an HO unitrack setup and I have had those turnouts apart and I'm assuming N and HO are similar. My HO setup is DCC and I've had no problems with 2 locos simultaneously operating using the standard unitrack power routing turnouts. I have track runs of 20 feet from the power feed point.

 

The problem with using a relay is that it would require a power supply which means additional wires, complexity and setup time. This is my grandson's setup so I'm trying to keep it simple.

 

Jan

[SeeYou190]

If I am reading your question correctly, you are trying to wire a reverse loop (section in a wye track arrangement) using the contacts built into the Kato Unitrack turnouts so you can use this track arrangement with no other controls than the Kato turnout controllers.

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My gut feeling is no.

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Am I understanding the question correctly?

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-Kevin

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[ROBERT PETRICK]

There is a Kato Unitrack Yahoo Group with several thousand members. This topic has been batted around for at least 15 years that I know of. It is one of their favorite dead horses.

There is a guy over there named George Stilwell. He is an electronic whiz and is their version of rrinker. He gave away wiring diagrams regarding the DPDT debate. Unfortunately he passed away late last year (2017) at the age of about 90. I don't know who, if anyone, picked up his mantel, but surely there are many on that forum who could answer the OP's question. Or at least provide info as to where to look. All you gotta do is mention those four magic letters . . .

Good luck.

Robert 

[JXC]

Yes Kevin that's correct. This is a one-loco DC system, not DCC.

I've dug a little deeper since posting the question and have some new doubts. First of all I didn't realize how different the design concepts are for different Kato turnouts. #6 N scale is not like #4s or the HO versions. And #6N has some very questionable features such as the fragile way electrical connections are made to the power routing switch and the metal bottom cover which will short out any internal electrical parts which are not fully "tamped down".

But I haven't given up. What are your doubts?

Robert: thanks for the suggesiton. The only group I find under Kato Unitrack on Yahoo Groups is Ntutorial which has moved to Groups.io. I have joined and posted to that group but no response.  I am not surprised That DPDT has been brought up before (its actually 3PDT because the frog needs powering too - it is half the length of the turnout) but I can't find any threads anywhere on modifying Kato turnouts.  The only info I have found is Allan Gartner's wiring for DCC website which discusses how to make Kato #6 N half DCC friendly by cutting off one of the contacts on the power routing switch.

Jan

[SeeYou190]

JXC

What are your doubts?

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Inside the Kato turnout roadbed there is a circuit board with the electrical circuit. I model in HO. On the HO turnout you can change the function from power routing to non power routing by moving two sheet metal screws. It is a simple and effective design. I assume N scale products are similar.

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In the power routing function, each turnout is basically a SPDT swicth. You could wire both turnouts together to possibly get a DPDT switch, but that would require a lot of jumper wires from one turnout to the other.

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This even assuming they function like a Shinohara "non-DCC" or Peco Electrofrog turnout where all rails to the frog switch polarity with the point position. The Kato frog is plastic, so this might not be the case. It might just turn power off to the non-aligned rail. In fact, they must do this because I do not get short circuits on passing sidings when the turnouts are not alligned properly.

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You also need wiring to the isolated section of track. All this would break your rule for a lot of external wiring, if it is even possible.

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-Kevin

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[JXC]

Kevin: Actually, for some strange reason, Kato Unitrack #6 N is entirely different electrically to #6 HO. #6 HO and #4 N are quite similar in allowing setup for either power routing or non-routing (let's call them Type A). However, #6 N allows only power routing and I understand (from Allan Gartner's website) #4 HO is similar (let's call them Type B). Type A turnouts are DCC friendly with the two point rails electrically separate however the Type B turnout design has both point rails joined together electrically. It almost looks like Kato redesigned half their product line with the advent of DCC and then stopped. Jan

[JXC]

Kevin: On frongs - Type A turnouts have plastic frogs but Type B have metal ones that are powered by the internal power routing switch - hence the reason they cannot be changed to non-power routing (without surgery). Jan

[JXC]

Here's what I will try and do - all onboard an N-scale unitrack #6 L turnout.

1. Cut gaps in the stock rails on the diverging legs to create two extra rail sections called "stock extensions" in the diagram
2. Replace the existing PC board with a new custom one which includes contacts to all rail sections on the turnout, including the new stock extensions
3. Add a new wiper arm (red in the attached) to the existing wiper arm (black in the attached) such that the two wiper arms are mechanically joined but electrically insulated from each other

The following diagram is scaled up by 4 and does not show PCB traces to connect the various switch pads to solder pads for connections to rail sections. It also does not show the attachment pads for connecting the operating coil to the external control wire. The diagram is with the turnout upside down with the bottom cover plate removed.

https://www.dropbox.com/s/2ro3so5sy71c3tq/job_688%20Turnout%20routing%20switch.pdf?dl=0

Among the challenges I see are

• soldering new connections to unitrack rails without melting the whole thing
• working with the 2mil copper foil used for the wiper
• making the PCB
• ensuring the modified switch rotor moves as freely as the original while maintaining adequate pressure on 4 contact points instead of 2 while also making sure the pivot bolt touches the black wiper (to power the frog and point rails) but not the red wiper.

I'll let you know how I get on but in the meantime, all suggestions gratefully received.

Jan

[ROBERT PETRICK]

JXC

Among the challenges I see are

• soldering new connections to unitrack rails without melting the whole thing
• working with the 2mil copper foil used for the wiper
• making the PCB
• ensuring the modified switch rotor moves as freely as the original while maintaining adequate pressure on 4 contact points instead of 2 while also making sure the pivot bolt touches the black wiper (to power the frog and point rails) but not the red wiper.

I'll let you know how I get on but in the meantime, all suggestions gratefully received.

Jan

About the only advice I can offer is regarding your first concern: use heat sinks. Place heavy blocks of metal as close to the joint as possible without interfering with the solder process. I use machined blocks (about 2"X2"X2", solid steel) or small- to medium-size sockets. Heavy washers or coins will do in a pinch.

But if you're fabricating a home-made PCB, you probably don't need my advice. Good luck. Add photos.

Robert 

[JXC]

Thanks Robert. Don't sell yourself short. Your advice and suggestions about heat sinks for soldering are very helpful.  The other advice I was given at my local electronics shop was to use Kapton tape to protect areas around the soldering from heat. I don't think Kapton is a particularly good thermal insulator but it is very heat resistant so I guess it acts a shield against radiant heat from the iron.

I've never made a PCB so that's a learning experience too. What I need is very simple and crude compared to most PCBs (single sided, single layer, no solder shield coating) and it looks like I can more or less spray or brush paint the mask needed for etching right onto the copper clad board using paper stencils cut from patterns printed on self adhesive paper labels.

Jan

[JXC]

I’ve done it by completing the following 3 changes:

• making the diverging routes double gapped by cutting an additional gap on each of the diverging stock rails
• adding an extra brass wiper to the internal switch
• substituting a new PC board in the internal switch.

The extra wiper is used to connect the two new electrical sections beyond the new gaps on the diverging stock rails and the new PC board adds contact pads for these rail sections.

Photos are on https://flic.kr/s/aHsmntCFhQ  (note that I wanted only manual turnout so did not reconnect the solenoid wires for remote operation)

A few tips from my experience are:

• To cut and create the contact dimples on the new wiper, sandwich 0.002”  brass shimstock between two pieces of slightly larger 1/32” styrene sheet and clamp it there by gluing the styrene pieces together around the edge. Cut and drill the sandwich instead of the brass directly. This prevents the cut edge of the wiper from crinkling or bending and also allows making holes by using ordinary drills instead of using punches on the brass itself. The dimples can be formed by pre-drilling a hole through the sandwich before putting the brass in and then pressing a ballpoint pen tip through one hole from one side to deform the brass into the hole  on the opposite side which acts like a die.
• Apply self-adhesive Kapton tape to the mating face of each wiper and join the two wipers together with CA glue (which works better on Kapton tape than it does on brass). This electrically insulates the two wipers from each other. Be sure that the pivot hole on the new wiper is bigger than on the original wiper so that it does not contact the pivot bolt (which energizes the frog casting). Put the new wiper between the original wiper and the PC board so that the original wiper continues to contact the pivot bolt.
• Use 1/32” single sided copper clad board not the far more common 1/16” which does not work because the pivot bolt, frog casting, circuit board and wiper have all been dimensioned to ensure good electrical contact without overloading the turnout actuating mechanism due to excessive spring tension in the wiper. I could only find presensitized board which is intended for using UV light for transferring the etching mask artwork photographically. I used household paint remover to remove the UV sensitive layer and a Sharpie pen to hand draw the etching mask.

Jan