Insulated joint and gaps

[mrmel0]

I'm guessing no difference in concept, but that "insulated joints" are where tracks are joined with plastic instead of metal, and gaps are actual "gaps" cut into the track.

Close?

And further more, if "frogs" need gaps and/or insulated joints around them (no matter what the case), why don't manufacturers already make them with gaps?

[Maletrain]

First, "gaps" are just one type of "insulated joint" so far as track wiring is concerned.  You are right that plastic rail joiners are true "insulated joints."  They both join the rails together physically and isolate them electrically.  By design, they actually prevent the rails from moving together by putting a thin plastic material between the rails.  They are most commonly used with sectional track as the sections are joined together.

On the other hand, "gaps" are more commonly used with long pieces of "flex track" that is laid (instead of many pre-formed sections of track) and cut to fit.  Gaps are usually just that, cuts in the rails wherever an electrical isolation is needed.  But, layouts have a tendency to expand and contract as the temperature and humidity change, so rails tend to slide a bit, and can close a gap that is not filled with an insulator, causing short circuits.  So, many people put a bit of plastic in the gaps they cut and then file it to the shape of the rails so that it is not noticed.

Switch (turnout) frog isolation is a lot more difficult to explain because there are so many different types of construction on the market.  Basically, there are the pre-DCC designs that often just use plastic frogs with the conducting rails coming very close together so that electrical contact with wheels is not lost for very far.  They were fine when used with DC power, even though the often created short-duration short circuits as extra-wide metal wheels passed over them, because DC power systems are not so sensitive to shorts as are DCC power systems. The Atlas code 80 turnouts are one example of this type of construction.  Turnouts designed for DCC have frogs that are either larger plastic sections that keep the out-of-phase rails farther apart, or frogs that are made out of metal and electrically isolated from both rails.  The idea with the isolated metal frogs is that they can be set up to be provided with the proper phase of power with an electrical switch that works in conjunction with the movement of the turnout. This allows locos to go through the turnouts very slowly without stalling for lack of power at any point. There are some sectional track products like Kato that have this already set-up for you, and others like Atlas code 55 track where there are just attachment points for you to use to electrically power the frog with a wire that you need to connect to an electrical switch that you provide and set-up yourself.

[jward]

Most switches come with the frogs already insulated. On some, the frogs are plastic which itself acts as an insulator. Others use a metal frog which is insulated from the surrounding rails. There is often a provision for metal frogs to be powered in some way if you desire. This is accomplished by a set of contacts that throw at the same time as the switch itself. the contacts may be built into the switch itself, or use an external relay that is wired in parallel with the switch motor.

The advantage of a powered frog is that the locomotives  with short wheelbases that tend to stall on plastic frogs will run smoothly through a powered frog.

I know some of the HO EZ track switches have frogs that are powered internally, but don't know which ones off hand. Likewise all HO Atlas custom line switches have a metal frog that can be powered by an external relay.

[mrmel0]

Can you create a block/zone simply by running wires to a toggle from one side of the plastic rail gaps back to the other side - to isolate a spur for example?

[Maletrain]

Yes, you can do that to allow you to control the spur power.  It is often done when the spur will be the place where an engine or lighted cars will sit for a long time without being used, such as a enginehouse track or a passenger car yard.

Just recognize that there are a lot of historical implications for the words "block" and "power district" that don't really apply to that situation.  For example, it the days of DC, "blocks" were intended to allow operation of locomotives independently of each other by putting them in different blocks.  So, the voltage and polarity of the tracks was set-up to be controlled independently in each block to control locomotive speed and direction.  With DCC, that type of track parameter control is not necessary to control locomotives independently, so it is not used for different isolated sections of track.

Another aspect of electric supply to a block is whether it has a circuit breaker that is set up to control just that block (or maybe a group of blocks that is not the whole layout).  If so, then that block is a "power district."  A short circuit in a power district causes all of the locomotives in that district to stop, but the locos in other districts (with their own circuit breakers) will keep running.

One place where you do need to control the power to a block is on a "reversing loop", where the track configuration makes a locomotive end-up going in the opposite direction on the same track (loop or wye).  In that case, there will be some point along each of the rails where the DCC power phase (or polarity for DC) will need to change, at an electrically isolated rail joint or gap.  If you do not have at least one isolated joint in each rail of a reversing loop, you will get an immediate short circuit as soon as power is supplied to the track.  But, you really need two gaps in each rail for a reversing loop to work, because a locomotive picks up power with more than one wheel on each rail. So, whenever the locomotive crosses an insulated gap, it will be picking up current from both sides of the joint at the same time.  If the polarity/phase are not the same on both sides of the gap when the locomotive crosses it, there will be a short circuit.  So, the trick is to have two gaps in the rails of a reversing loop that isolates a section of the rails that is longer than your train, or at least the part(s) of your train that pick-up electric power.  The isolated section needs to have a double-pole-double-throw switch set-up to reverse the polarity on that section when it is thrown.  That way, it can be set to have the rails match phase as the train enters one side of the reversing section, and, then while the train is in that section, the phase is reversed with the dpdt switch so that the phase also matches when the train leaves.  That can be done with a manual switch, or, these days, there are special circuit breakers that will reverse the polarity of the rails instantaneously to clear a short circuit (and, if that doesn't clear the short, it then acts like a regular circuit breaker and cuts-off power to the rails).  The track plan posted by the OP in a companion thread does not include a track configuration than makes a reversing loop, so this part of my reply is for others, or for the OP at some later time when he decides to make a more complicated layout.