DC (not DCC) operating system

[eric220]

One thing though that I can't get straight with DCC.....cutting gaps in switches. Is that a requirement? Nothing mentioned about that in this thread.

With Atlas switches, no.  I suppose this might be a concern with power-routing switches.

[railnerd]

One thing though that I can't get straight with DCC.....cutting gaps in switches. Is that a requirement? Nothing mentioned about that in this thread.

FACT: THERE IS NO SUCH THING AS A DCC TURNOUT

It is about making a switch that will run smoothly with wide wheel sets, and more equipment without causing momentary short circuits.

Basically, because DCC typically dispenses with blocks, any short circuit in the same power district screws anyone trying to drive their trains— not just the guy who shorted out on a switch.

BTW: Running against a switch will still screw everyone operating on the same booster, regardless of whether or not you have "magical pony" turnouts.

[DKS]

FACT: THERE IS NO SUCH THING AS A DCC TURNOUT

Fact: some turnouts are more "DCC friendly" than others. Not all behave the same way. The biggest thing to watch for is the way the points are powered. If both points are the same polarity (e.g. Peco, Kato), then they need to move away from the stock rail when open far enough to avoid the backs of wheels touching them, thus causing brief shorts. Another problem caused by this sort of switch is timing: a Tortoise switch machine used to power the frog and point rails can cause a short because the machine can sometimes throw the electrical contacts before the points have moved. Other switches have points that match the polarity of the stock rail (e.g. Atlas), in which case there are no worries.

Another concern is the frog. Some Peco switches with plastic frogs have the rails leading up to them so close together that wheels can bridge across the ends and cause shorts. Isolated and separately-powered frogs must be powered in such a way as to avoid any possible shorts. For DCC layouts, electronic switching circuits (e.g. Frog Juicers) are recommended since they will avoid shorts under all circumstances--including accidentally running against the switch.

As for gaps... again, it depends on the way the switch is made. If the frog is powered and there are no gaps between the frog and the track connected to it, then gaps are required in order to isolate the frog, although most commercial switches with metal frogs will already have gaps. Some switches are "power routing" (the track to which the switch is not thrown is made dead) and will need to be dealt with accordingly; since DCC is not in need of any sort of power routing, then disabling this feature will avoid undesirable power losses or shorts. Cutting gaps may be necessary in order to disable power routing.

There are other caveats that I'm sure others will mention.

[peteski]

One thing though that I can't get straight with DCC.....cutting gaps in switches. Is that a requirement? Nothing mentioned about that in this thread.

First of all, it is not just the switch that we are taking about. Since the shorts often occur at the frog, we will be discussing the entire turnout (yes, that is the proper name for that track arrangement).

Several complicated and detailed explanations were already given.

But I feel like the basic things needs to be mentioned. Electrically, there is no difference between DC or DCC signal in the tracks.  Both supply voltage of opposite polarity to the track (at any given time one track is positive, the other track negative).


The only huge difference is that in DC, if the locomotive traveling through a turnout which is designed or wired in such a way that the metal wheel will cause a momentary short, the inertia of the loco will allow it to coast through that brief period of electrical short, and continue on its way.  That's because most short circuit protectors in DC throttles have fairly slow response time - they are  not tripped by that short, which lasts only few milliseconds.  In most cases, the DC operators aren't even aware that their turnouts have this problem.

With DCC, the power booster is equipped with a very fast acting (electronic) short circuit protection. That is there because there is a greater need to protect the output transistors of the booster from burning up.  So, the same short-duration short which occurs on DC layouts, caused by the loco wheels traveling through a poorly designed turnout, will cause the DCC short circuit protection circuit to trip and remove power for the track for quite some time (half a second or more).

This causes the DCC locomotive to stop abruptly.  Then, when power is restored (the loco was already stopped by then), and assuming that the wheel has traveled past the short, the decoder in the loco will have to reinitialize (after all, it is a micro computer).  That also takes some time (depending on the decoder brand). Only then the loco will begin moving again. Some decoders gradually increase the speed, resulting in even more of a noticeable delay.   Repeat this cycle 4 or 6 times (depending how many loco wheels will have to run across that short), and you have a major hiccup while traveling through that turnout.  That is why it's important to make sure that a turnout used for DCC is not prone to those types of shorts. If it is, steps (like cutting gaps in certain areas) have to be taken to make the turnout DCC-friendly.

[eric220]

There are other caveats that I'm sure others will mention.

Or we can get back to discussing DC controllers...

[Chris333]

One thing though that I can't get straight with DCC.....cutting gaps in switches. Is that a requirement? Nothing mentioned about that in this thread.

Believe it or not this thread is about DC.

[Loren Perry]

Or we can get back to discussing DC controllers...

In case you're interested, my illustrated article on installing and using the GML DC system on my Hollywood Railroad appeared in the March/April 2010 issue of N-Scale magazine (Vol. 22, No. 2.) It also covers designing and building DC control panels for yards and engine terminals. I believe the GML system is the most modern state-of-the-art and user-friendly DC system on the market today.

[mmagliaro]

Or we can get back to discussing DC controllers...

Why in the heck would you want to do that?  It's not like the person asked for suggested DC
products and setting up a DC system or anything.

DCC must be the "electronics K4".

There's yet another DC throttle product option, the "Cooler Crawler", which I think is still available.
You can find it on the web. I have never operated one, so I can't vouch for it.

[rodsup9000]

 unittraincoal
 There was some miss information on the Aristo throttles. With Aristo going down the tubes and reorganizing to "Polk's GeneratioNeXt" the Revolution went back under the "Crest" brand and are still available. You say you will have return loops so I assuming these will be reverse loops. I haven't done DC for over 20 years so I don't know if there is a circuit available now to do the reverse polarity(I'm sure somebody has). If not, you'll have to flip a switch every time a train goes through the loops.

[unittraincoal]

Thanks for all that have answered some questions regarding DC throttles...    Im hoping the new MRC throttle will show up this year sometime. If the Aristo craft unit is still be produced I likely will go with that.

The 180 feet of mainline is a dog bone for continuous running. The dog bone will create the "illusion" of a double track mainline.  The "loops" (not return loops) will be "hidden"(easily accessible) 21.5" radius curves at each end of the layout.  A 50 car train will never be visible turning back on itself. (most trains will be 30-42 cars). There will be a total of 5 switches off the 180 feet of mainline.  The dog bone will be one electrical block, yup just ONE! The layout is being built with minimum amount of switches for less problems with long trains.    Minimum radius on the layout will be 21.5". All curves will have easements..... It will be extremely easy to wire, and extremely easy to change to DCC at a latter date if I desire.....


The Utah Railway portion of the layout which will be built at a much later date will have a visible yard and more switches. Perhaps by the time I get around to building the UTAH, DCC will be replaced...lol 

[kalbert]

Had the first post contained the detail of the 54th we may not have had a DCC debate first 

[alhoop]

There's yet another DC throttle product option, the "Cooler Crawler", which I think is still available.
You can find it on the web. I have never operated one, so I can't vouch for it.

I can - been using one for years.
http://home.roadrunner.com/~jimngage/TRACTRONICS/PRODUCTS/price_1.htm
















Al

[nkalanaga]

Given that description I'd say you have it made.  Since you can apparently only run one train at a time I'd keep it as simple as possible.  Use the heaviest bus wire you can reasonably find, to avoid voltage losses, and make sure you have plenty of track feeders.  If you ever do switch to DCC, you'll be thankful for the current capacity.  There's no need for two cabs if you can only run one train. 

For the spurs? sidings? I wouldn't bother with power routing turnouts, although powered frogs are nice.  I would put gaps or insulated joiners on the siding end and power the track through an on-off toggle.  That way you can easily store an engine there if you like.

If you do use power routing turnouts, you'll still have to gap the mainline to prevent shorts, but that won't require any extra wiring.

[Scottl]

I have a DC back up system when I am too lazy to plug in my DCC.  It is super simple, no wiring or switches.  It is an old 9V battery.  Sits on the rails perfectly.  Want to reverse?  Flip it around! 

[Rossford Yard]

FWIW, Model Train Stuff just sent an email with all MRC products on sale for another 10%. If you can pull the trigger rather than waiting for the Aristocrat (or current named) it might be worth checking out.