Question on basic wiring of control blocks and use of switches in home layout

Size of the layout is not necessarily a determination if you need dual (or more) cab control. If you have two speed controllers (cabs), then you need cab control, unless you plan to NEVER have the train cross from one controller to the other. Since you mention crossovers in your post, I'll assume that this is not the way you'll be running. Otherwise, you'd need to get up enough speed in your train for all the locomotives to cross from one to the other without stalling between controllers.

As an example, if Cab A controlled the outside main and Cab B controlled the inside track, you'd have difficulty crossing from the outside to the inside loop. With Cab control (all electrical sections of track or blocks, have a selector switch to set them to either Cab A or Cab B) any block can be set to either cab. There is no additional wiring on the layout, this is all done at the control panel. Normally, you'd use Cab A to pull your train out of the yard on to the outside main. Then if you want to switch to the inside track, you'd set it to Cab A, cross over, and continue running. You could then switch the yard and outside main to Cab B and run a second train.

I hope you misunderstood what the "local club guy" told you about wiring. Each section of track should have a feed wire to it, but only requires insulation (plastic rail joiners) where you want to electrically isolate the blocks from one another. Elsewhere, use metal rail joiners. The fed wires to each section of track will give you more reliable electrical feed, because the metal rail joiners will corrode or get dirt in them over time and lose their conductivit, giving you dead spots. This usually happens right after you ballast the tracks (yes, that's how I know).

A DPDT switch can be a selector between two cabs, or a polarity reversing switch, depending on how you wire it. As a Cab selector, you feed Cab A wires into the pair of terminals on one side, Cab B to the pair on the other side, and the feed to the block comes off the center pair. For polarity reversing, you connect the outside pairs of terminals togetner with the wires crossing from top to bottom terminals (making an "X") on the back of the switch. The fees come into either side, and the output comes off the center pair. For eventual conversion to DCC, you'll want to insulate both rails, and feed each block on both sides. For that you'll need DPDT switches. As cab selsectors, I'd recommend the type with center off, so you can also turn a block off.

 First thing.  DPDT switches don't cost much more than SPDT switches.  Check All Electronics.  A DPDT switch can be used as SPDT or SPST, so if they cost the same, you might as well buy DPDT switches 'cause they are more versatile. 

Second thing.  You are going to want switches to cut the power on sidings and spurs and other places so you can leave a locomotive on a spur and have it stay put while you run another loco on the main line.  

Third thing, the wiring will be easier to under stand and trouble shoot if it is done the SAME way everywhere.  Since you are planning a double track main line and thinking about running two trains at the same time, you are thinking about having two power packs.  If you wire every block the same, cab control style, the standardization will pay off in the long run.  You want to make one main line track a block, the other mainline track a second block, and all the sidings and spurs independent blocks.  If the main lines are long enough you might divide each one into a number of blocks.  

   The most flexible way to wire your blocks is put the track block to the center contacts of a DPDT switch and put the first power pack (Cab A) on one side and the second power pack (Cab B) on the other side of the switch.  Assuming center off toggle switches, then each block can run from Cab A , or Cab B or be turned off.  Wire every block this way and it will be easier to operate the layout 'cause every block works the same as every other block, and easier to wire and troubleshoot, again 'cause every block is wired like every other block. 

   Second benefit of this plan.  If in the future you want to try DCC, but be able to switch back to DC 'cause not all of your locomotives have decoders, the two cab wiring makes it simple.  Just replace one DC power pack (say Cab B) with a DCC supply.  To run DCC throw all the toggles to Cab B and you are done.  To revert to two cab DC running, put the Cab B DC supply back in place and there you are, back where you started from. 

  Third thing to think about.  Location of the block toggle switches.  If you locate them on the fascia, near the block controlled by the toggle, it facilitates walk around operation.  If you centralize them on a control panel with a track schematic, it will take somewhat more wiring to make everything work.  

 

  I would add to the wiring advice above in that You make a detailed schematic of your wiring as You go, believe me , this will be a great help in the future in case of trouble, I learned this the hard way .

swhite10539

My design is basically a dual oval layout with the outside oval being my mainline and the inner oval will service various industry spurs and such.   I do not believe I need or want dual cab control, I just don't think my layout will be big enough for this.  But, I do plan on having two MRC power packs so that I can run trains on both ovals at the same time, independant of each other.

Easy peazey.  But the size of the layout has nothing to do with whether you would want dual cab control or not.  For many years I used triple cab control on a 2x4 layout.  The deciding factor is how you want to control the trains.

If I understand wiring enough, then I really need to make sure that the outside oval is insulated from the inside oval where turnouts allow one track to cross to another.

Yes this is true.  However this design of two independent controlled loops has some sever problems. Specifically when the train crosses from one power supply to the other they have to be syncronized almost perfectly.  Even then power feeds from one pack into the other while the train is crossing the gap.  Depending on the exact scenario this probably won't happen, but it could fry the loco, the light bulbs in the locos and passenger cars/cabooses, one or the other power packs, or all of the above.  If you really want to do the two loop, two separate power supply route then I would NOT put any crossovers between the tracks.

The local club guy is recommending that I insulate each two to three foot segment with feeder wires to a main bus.  In my case, I guess I will need two main buses, one for the outside oval and another for the inside oval and its rail spurs.  Does this sound correct to the extent I have explained what I am doing?

It sounds like way over kill for what you are trying to do.  The three foot segments would be for dual-cab control that you already stated you did not want to do.   A 16'  loop of N-scale track might at most need two sets of feeders. One right next to the MRC power pack and the other to the opposite side of the loop.  Done.  Only if the train slows down somewhere in the sides of loop (not due to a grade) then think about adding another feeder at that point.

Also, under what circumstances would a home layout, as small as mine, need to use SPDT or DPDT type switches?  I think I understand that a DPDT switch will basically reverse the polarity on a track segment and a SPDT switch will basically turn power off on a track segment, like a rail spur?  Is my basic understanding correct?

For this conversation, no your understanding is not correct.  The advice being given is getting into a debate over something called "common rail" or "dual rail insulation" for dual cab control.  You already stated you did not want to do that, so in essence it is irrelevant.  While dual cab control can seem intimidating if you want crossovers between the two loops then I recommend it.  The catch is that there have been entire books written on the subject, so it is hard to help someone with only a few words on a forum post.

Why is it that you do not want to go with DCC?  It would make all of these design considerations irrelevant.

Ok, these posts have been very helpful. I have looked at the NMRA web site on Dual Cab control and with these posts, I think I understand some of the benefits and even need for this type of set.  So, if a segment of track is controled by Cab A lets say...what happens if a train using Cab B crosses into the segment controlled by A...does the train just stop?  Can two trains run on the same track on the same Cab or is this too much for one power pack to handle?  Each oval I have will strech about 16' from end to end, so would I need maybe two segments per oval and then segment off the turnouts for any inner spurs?  I can see this will take some careful thought and I plan on doing some testing first before I lay a stitch of track so I understand the concepts!  Now, what the club guy mentioned was dual insulation of both rails between segments as opposed to just one rail for common rail.  They said every two to three free to avoid current loss and I thought they said this was necessary for DCC? 

The reason I have not consider DCC was it sounded more expensive to start with and getting into the decoders for the train...I was afraid that this was getting more complicated than I wanted for a newbie.

I see your point...in effect, the train on one loop controlled only by ONE controller, would have to cross to the other loop controlled by a second controller which would have to be ON or adjusted to try and match...plus, this scenario sounds like you could burn out a train possibly or cause a short since it would be possible for one set of wheels (lets say front) to be on one loop controlled by Cab A power pack, and then the back wheels to still be on a segmant ran by the Cab B power pack.  The use of the switchs makes sure everything the train runs on is controlled by "A" particular cab.  Thus, why this would not work, unless I simply did not cross over anywhere from one track to the other which would not seem to be very realist to me but could be done if simplicity is the only consideration.  So, it sounds like dual cab is the way to go and double insullation of rails in preparation for DCC...correct?  Then use DPDT switches to control each segment.  Now, the next question will be what is a logical division of my layout into segments and whether or not to place the switchs near each location or on a central control board?

I like the idea of being able to switch into DCC down the road with your idea!!!! With my dual oval, each oval being almost 16' from end to end (L shaped), how many segments would make sense?  With lets say cross overs from the outside loop to the inside loop in two places (forwards or reverse directions) and the inside loop has just three turn outs, what might make rough sense?    Segment the outside loop where they cross to the inside loop, so maybe two segments on the outside, then similarly for the inside loop along with isolating the three turnouts?  

 As I have asked before, with dual cab control, what happens if a train crosses from track controled by Cab A to track controlled by Cab B...even accidently...does the train just stop or what?  This part is a little confusing?  You can see how inexperienced I am!  Thank you!

"...whether or not to place switches near each location.."  You may not be ready to go down this road yet (frequently called walk-around control)...but I personally recommend it.  In truth, your preferred operations scheme should dictate your control architecture and your layout design - not the other way around.  With walk-around control, you follow the train.  You adjust speed as necessary for the track conditions.  You make switching decisions at the site to be switched.  You throw turnouts and uncouple cars as needed - on the spot - for the train.

But, and this is a big but, the implications of adopting walk-around control are not trivial.  If you have only walk around controls it can be difficult to sit back in an easy chair, beverage in hand, and watch the trains run while changing their path with a simple push of a button.

For walk-around control, you need hand held throttles, with or without tethers.  In DC, there are very few hand-held throttles available commercially; most build their own.  It's not difficult to build your own throttle, though it is another task.  In DCC, there are plenty of commercial walk-around throttles, both wireless and tethered.  But building your own DCC throttle is not so simple.

If using DC, location of the block toggles has to be thought about.  You want to be able to reach the block toggles while following your train - from either direction.  Switch machines can be manual throws or powered with controls located near the turnout in eithe case.  Uncoupling is actually much simpler with walk-around control - you can use skewers or other manual uncoupling devices instead of guessing whether the car is over the magnet or not from a distant control panel.

Walk-around control definitely favors linear track plans with the track located within arm's reach of the benchwork edge.  Loop-de-loops and turnbacks are relatively awkward to follow your train by walking.

"...logical division of my layout into sements..."  Setting up blocks used to be well understood, but the advent of DCC has reduced the universal need for understanding of block control.  My rules of thumbs for establishing blocks are:

1) Each continuous loop needs at least 4 blocks to allow 2 trains to follow each other without stopping.

2) Making each passing siding a separate block(s) enables one to have a train(s) wait on the siding while another train goes by on the main.

3) Each spur or branch where you will want to "park" or operate a locomotive or train while other locomotives or trains are running on other track needs to be a separate block.

4) Ideally, blocks should be at least a train length long.  However, this is not always possible while meeting the other 3 rules.  Trains that span more than one block require a little more consciousness of where block boundaries and other trains are.

5) DCC is ideal for controlling multiple locomotives/trains simultaneously on small layouts due to the absence of worrying about block boundaries and toggles.  That said, I am still a DC user at present.  But I normally operate by myself, and only one train at a time.  The other locomotives/trains are "parked" while I operate the one train.

my thoughts, your choices

Fred W

swhite10539

Ok, these posts have been very helpful. I have looked at the NMRA web site on Dual Cab control and with these posts, I think I understand some of the benefits and even need for this type of set.  So, if a segment of track is controled by Cab A lets say...what happens if a train using Cab B crosses into the segment controlled by A...does the train just stop?  Can two trains run on the same track on the same Cab or is this too much for one power pack to handle?  Each oval I have will strech about 16' from end to end, so would I need maybe two segments per oval and then segment off the turnouts for any inner spurs?  I can see this will take some careful thought and I plan on doing some testing first before I lay a stitch of track so I understand the concepts!  Now, what the club guy mentioned was dual insulation of both rails between segments as opposed to just one rail for common rail.  They said every two to three free to avoid current loss and I thought they said this was necessary for DCC? 

The reason I have not consider DCC was it sounded more expensive to start with and getting into the decoders for the train...I was afraid that this was getting more complicated than I wanted for a newbie.

If you cross from track controlled by one cab to track controlled by another another and the speed is low enough, your locomotive will probably stall. If you're going fast enough, it may drift across the gap an be controlled by the other controller. Controlling two trains from one controller has a different problem. Most power packs have nough power to do it, but both engines may not respond to the control the same. One will run faster and catch up to the other.

The breaks for gaps would be determined by the operation, track length can be pretty much irrelevent. The main part of the loop should be one block, and the crossover area should be another. With the Cab selector, you can control any block from either Cab A or B.

swhite10539

how many segments would make sense?  With lets say cross overs from the outside loop to the inside loop in two places (forwards or reverse directions) and the inside loop has just three turn outs, what might make rough sense?    Segment the outside loop where they cross to the inside loop, so maybe two segments on the outside, then similarly for the inside loop along with isolating the three turnouts?

Well, at least 2 more than you would think.    That is a simple loop should have at least 4 segments.  Lets call the segments block A, B, C, and D.   There are trains in A and C.  Train #1 and #2  Block B has to be set up to the same controller (called a cab) as block A is, so it is ready to receive train #1.    Block D has to be set to the same cab as block C is in order to receive train #2.  As soon as the trains move into their new respective blocks the switches have to be flipped so that A is set the same as D to receive train #2, and block C has to be switched to receive train 1.  To do this one has to be constantly on the block switches flipping them quickly.  With six blocks (E and F) there is a little more breathing room so one doesn't have to be as quick with the switches, likewise with eight blocks there is even more breathing room.

It might sound like this is not applicable with your double loop, but every time a train wants to cross over there will be two trains on either the inside or outside loop at least for a short time.  So the concept remains the same.   Fewer blocks = more frantic switch flipping.  All this is on top of turning the throttle to actually move the train.

This is why people consider cab-controls to be controlling the track rather than the train.