DCC friendly turnouts or not

[GMD-1]

I am still at the planning stage for my layout. I would like to get an idea whether DCC friendly turnouts, as in insulated frogs, are necessary with Railpro. Although I do not have Railpro yet (I'm just DC for now) It is my plan to go with it, rather than DCC

[Dean]

My layout is a mix of DCC friendly turnouts and older non-DCC friendly turnouts. With the non-DCC turnouts, I have a small gap between the diverging route and the track. I also leave a gap between the main route and it's track. The turnout gets power from being attached to the main at the throat of the switch. No extra wiring, no 'juicers', no relays, no extra switches. Just install and enjoy.

[G8B4Life]

Welcome GMD-1 (name?)

I don't think you'll be displeased in any way if you do go with RailPro.

DCC friendly means a bit more than just insulated frogs. Either insulated or live frogs will do you ok and both are/can be DCC friendly.
Many like live for the reason of better pickup capability but if the insulated frog section isn't overly long insulated should work for you if you prefer it.

What you don't particularly want is the points (you may know as the switch) rails to be connected together electrically. There's much more out there on DCC friendly turnouts that I could ever type in here so a couple of good links to get you going.

DCC Wiki (start with this one) http://www.dccwiki.com/DCC_Friendly_Turnout

Look at the drawings section, even if you don't run power buses and the frog is insulated (pretend the frog is not coloured red or green) this is really the type of electrical path you want with the turnout's you get.


Alan Gartner's Wiring for DCC http://www.wiringfordcc.com/switches.htm

Alan's site is much more complex but contains a wealth of information on wiring turnouts.

So to sum up and hopefully I've not clouded things for you, DCC friendly in essence is not necessary but you certainly won't be doing yourself any disfavours if you do use them, in fact if you add power buses it'll probably maker your life much easier for you and remember, insulated or live frog isn't the only defining factor in the term DCC friendly.

- Tim

[GMD-1]

Thanks Tim. I meant to sign off with my name but forgot. I probably should have said isolated frogs, like Microengineering's ones, rather than insulated. I was planning to go with Microengineering turnouts as I like the look mostly (and the price). But I find the gaps on each side of the frog unattractive. So I was wondering about turnouts where the frogs are part of the rail. I gather then that old Shinohara/Walthers turnouts would be bad. The ones where both points are joined together with a metal piece. I have a few I bought years ago and never used.

Richard

[Alan]

RailPro is a DC system as far as track is concerned. The only difference is the amount of power available from the track. DC regulates loco speed by regulating the amount of power available from the track. RP has the track at full power all the time.

In a perfect world where all wheels are in gauge, flange thickness is correct, switches have sufficient stock/point rail clearances, and derailments are rare there is no need for DCC friendly. Sadly, we are playing with Made in China toys so such assurances can not be relied upon. A short circuit with a DC system rarely causes any real problem. The power pack is slow to respond, wiring gauge is relatively small, and the amperage is generally low. DCC and RP on the other hand are high amperage units using low loss wiring with fast acting internal circuit breakers that shut down quickly from a short thus disrupting fun for all. If the shorting current is not high enough to kick the breaker then it is possible to build up a lot of heat resulting in melted plastic parts. A short on a DCC/RP layout is electrically the same as a short occurring on a DC layout with a high amperage power pack set at wide open throttle connected to the track with fat wire.

So, DCC friendly switches with RailPro are in essence an insurance policy. What is your risk tolerance?
 

[GMD-1]

Good points Alan. I have been considering dipping my toe in Railpro by getting a TC2 & PWR-56 and a couple decoders to use with a little 4.5 x 6 'portable' layout I threw together for a local modelling show last year. Thing is I used salvaged old style shinohara turnouts. I could tolerate the occasional short as long as it does not destroy anything. Would I be right in expecting the over current protection to kick in quickly enough on such a small layout? As for the future layout, well pretty much all the main commercial turnouts are DCC friendly anyways. I will just choose the ones I like the best.

[Dean]

99% of my turnouts are the old Shinohara or the Walthers/Shinohara turnouts. I think I have two Peco turnouts on my layout. The frogs are powered on them. Electrofrog?
I understand why you wouldn't want the older Shinohara turnouts with the connected points. But honestly, I have never had any problems with them. I have more problems with the copper contact that is on the bottom of the points.

[G8B4Life]

I probably should have said isolated frogs, like Microengineering's ones, rather than insulated.

Isolated is good too, in fact probably the best as they can be either dead or made to be live; it's usually up to you. Making them live to switch polarity probably doesn't have to be expensive either, if Alan gets some free doodling time one day he might be able to pen down a circuit that was discussed here a while back that should be cheap to build (remember that voltage divider network frog polarity changer Alan?).

Regarding the gap in the rails of the isolated frog variety of turnouts like Micro Engineering's, here is an idea adapted from an old issue of Railroad Model Craftsman - Fill in the gaps with little thick grey epoxy (make sure non conducting) and then neaten up with needle files etc, looks like Thermit welds after painting and no more ugly gaps.

99% of my turnouts are the old Shinohara or the Walthers/Shinohara turnouts.

Dean, I am glad your not having any issues with the turnouts that have both point rails the same polarity, All the planets must be lined up for you    I wish I could say the same for others out there. Actually the webpage in the next paragraph explains the issue better and why they might be working well for you.

Here is another page that tells a bit on this DCC friendly term and what it means to turnouts. Some people love the guy some do not but what's on this page is good info none the less. Note, the list of turnouts is probably quite old. http://www.members.optusnet.com.au/nswmn/y_dcc_friendly_MG.htm

- Tim

[GMD-1]

That is good to hear Dean. And I know what you mean about the copper contact strips. A lot of mine have broken, so I use our forum hosts manual switch machines with a DPST slide switch to do the power routing.
Another good article Tim. I only use B-B diesels on this current mini-layout, so perhaps I will be lucky like Dean. But not if it means risking frying decoders.

Richard

[Alan]

I could tolerate the occasional short as long as it does not destroy anything. Would I be right in expecting the over current protection to kick in quickly enough on such a small layout?

Size of the layout is not the determining factor. Total resistance is.

Shorts always do damage. The question is how much. At the very least, micro pitting of wheels and track will occur. Enough pitting at the same spot over time will be a problem especially on thin metal such as point rail taper. At the very worst, a wheel set becomes a toaster and melts truck frames and ties. On a positive note, unlike DCC, RP modules seem unaffected by shorts on the rails so module damage is unlikely.

As you know the trick is getting the breaker to sense and act fast. This requires an extremely low resistance electrical path between PWR and loco. Here is the issue... train equipment caused shorts are not zero resistance. In fact, they may not be anywhere close to zero resistance. Bus wiring is not zero resistance either. Total current flow will be determined by the sum of the two resistances. As resistance goes up current goes down. It is quite possible for the equipment short resistance and bus wiring resistance to add up to a value that causes total amperage to be less than the circuit breaker trip point. For example: RP PWR is 14.8v and trips at 4 amps. This translates to a resistance of 3.7 ohms. A 4 ohm short circuit will not trip the breaker. Instead, 55 watts of power will flow continuously. Hold a 50 watt light bulb against a plastic truck frame to see what will happen. Not good. Now imagine this situation with a poorly wired layout. Let's say small gauge wire and poor connections add 2 ohms resistance. A short circuit now has to be less than 1.7 ohms resistance to trip the breaker. It is very likely you will have shorts from time to time that have more resistance than 1.7 ohms.     

That is a long winded way to answer your question with a solid maybe.

You can increase the odds the breaker will protect you by using healthy size buss wire and sufficient number of track feeders i.e. make the bus resistance as close to zero as possible. There is much bantering about regarding wire gauge and number of feeders. Personally, I think it is an argument not worth having. Use 12 gauge buss wire period. Use 20-24AWG feeders 12" or less in length spaced no further than 3' apart on the track. Make sound electrical connections (solder). With this arrangement, regardless of layout size, you are guaranteed a near zero resistance path and thus the highest probability the breaker will protect your equipment.

[GMD-1]

Thanks Alan, advice taken!

[Dean]

That is good to hear Dean. And I know what you mean about the copper contact strips. A lot of mine have broken, so I use our forum hosts manual switch machines with a DPST slide switch to do the power routing.
Another good article Tim. I only use B-B diesels on this current mini-layout, so perhaps I will be lucky like Dean. But not if it means risking frying decoders.

Richard

I have been using Penetrox A on the copper contact strips. [ https://www.amazon.com/Burndy-P8A-Oxide-Inhibiting-Compounds-Container/dp/B008KLX2RY ] In my 40+ years in the electrical field, this is the only joint compound I have ever used. On the copper strips it's a lubricant and enhances conductivity.
You can also use Penetrox A on light bulb bases to keep them from galling into the socket. You can use it on the battery terminals on your car to prevent corrosion. It also prevent threaded aluminum and stainless steel from galling together. 
Some of these other uses help justify the cost of Penetrox A.

[GMD-1]

My problem with the contact strips is that they broke or bent and bunched up behind the point rails. No Pentrox A is going to help there. It is just a temporary layout though, so no big deal.

[Alan]

I am not a fan of relying on the internal shunts of commercial switches. Too many horror stories like the ones in this thread. Even though my layout uses exclusively Walthers Shinohara 88xx series DCC friendly switches which have no sliding electrical contacts, I still don't rely on the internal connections. Every rail, no matter how short, has a feeder. If you use WS 88xx switches here is an easy way to power the point rails - solder feeders inside the rivets on the throw bar.

Soldered rivets:


Point rail feeders from below:


With switch machine installed:


Often I hear people say they have a feeder on every piece of rail. I suspect they are talking flextrack. To actually live up to the feeder on every rail claim requires a boatload of feeders on turnouts. A regular turnout requires 9 feeders. A 3way requires 14 feeders. The feeders at switches begin to take on a look like this: