Reversing Loop

[BenjiGranddad]

I'm making a fairly large layout which will run up to 5 DCC locos and 1 analog loco.  There is about 80 feet of track.  I have two issues:

1.) Will I need more power than I can get from a standard DCC controller to run efficiently?  That is, will I need the 5 watt power boost to get the most out of this layout?

2.) I plan a reversing loop in this layout.  Is the best way to avoid the reversing polarity with DCC to use the Bachmann reversing loop module and the insulating track sections?

These q's are probably pretty old, but any help will be greatly appreciated!!!

[renniks]

What DCC controller are you using and how many locos will you actually be running at the same time?

Eric UK

[sparkyjay31]

I have about about 100' of track.  I have had no problem running a BLI Mikado, Spectrum 2-8-0, and a Roundhouse 4-4-0 all with sound.  All at the same time.  My NCE Power cab has been flawless.  I don't know enough about the Bachmann dcc systems to know if it is comparable.  But mine is considered a "starter" dcc system and is great!  Jay

[BenjiGranddad]

What DCC controller are you using and how many locos will you actually be running at the same time?

Eric UK

I hope to run up to 5 at one time.  I have the Bachmann DCC EZ Controller.  Thanks.

JJB

[Jim Banner]

(1) Five locomotives, working by pulling cars, will draw about 2.5 amps.  For sound, add another 1.5 amps or so depending on sound system.  To run all that, you would need a booster.

(2) A reverse loop means the polarity of the DCC on the rails has to be reversed to avoid short circuits.  You can do it manually with a toggle switch or automatically with an auto reversing module.  Sometimes you can do it automatically with a switch or contacts tied to a turnout - this depends on the details of the reverse loop.  Unlike dc, you do not need two polarity reversing switches - with DCC you reverse the polarity of the loop OR the polarity of the mainline while with dc you have to reverse the polarity of the loop AND the polarity of the mainline.  It is easier than this makes it sound,.

Jim

[jward]

it might be splitting hairs, jim, but the description of how a reversing loop works on dc contains a fundamental error. it is true that the loop requires its own direction switch, but the purpose of that switch is to set the polarity of the loop before you enter it, and to reverse the direction of the train while in the loop itself, if need be. a properly wired reversing section needs only the main direction switch thrown while the train is in the loop. to wire in this manner requires that your loop wiring bypass the power pack's direction switch, in favour of wirong the loop and its direction switch directly off the power supply rheostat.

what you are probably thinking of is a common shortcut where people don't bypass the direction switch on the power pack, and wire the loop switch in series with that switch instead of in parallel. only if you wire your loop this way would you have to throw both direction switches while the train is in the loop.

[Chris350]

2.) I plan a reversing loop in this layout.  Is the best way to avoid the reversing polarity with DCC to use the Bachmann reversing loop module and the insulating track sections?

While I'm not familiar with the Bachman unit, your basic premise is correct for DCC.  You want to use a reverse module and insulate both ends of the loop from the main.  I have used the Digtrax AR-1 reversing unit, and the PSX-AR from DCC Specialties (my current favorite).  You will not, however, be able to run the DC loco through the reverse loop with out some additional wiring.  I did it once, it was kind of funny to see the loco bounce off the reversed section like a tennis ball off a wall.

[Jim Banner]

Jeffery,
I usually avoid suggesting that people open up their power pack and start modifying it.  Instead, I suggest they use the usual dc method of a reversing switch for each loop, another reversing switch for the main, and leave the reversing switch on the power pack for actually reversing the train.  This has the advantage that the power pack reversing switch then changes direction relative to the locomotive, not relative to the track, and the other "reversing" switches are used only for polarity matching.  This method works best when the polarity matching reversing switches are on a control panel that includes a track plan.  To go along with that, I usually recommend that they add signal lights connected across the gaps and located appropriately on the control panel to tell them whether the polarity is matched or not.  This is nothing new - Lynn Westcott was writing about it 50 years ago, even before he was editor of M.R.  And I believe it was old technology even then.

The only time I ever recommend a single trackside reversing switch that has to be thrown simultaneously with the power pack switch is as a stop gap measure when the person plans an almost immediate conversion to DCC.

When walk around control became popular a few decades ago, I designed a third system where the walkaround throttle has two direction switches, one for east/west and the other for clockwise/counter clockwise.  They are used with the main and the loops respectively.  That left the reversing switch on the power pack for setting the train to run eastward when the remote direction switch was set to east.  Once set, it was usually left alone except for the occasional reverse wired locomotive.  As an aside, I built these throttles with the power handling components in the base unit, including direction relays, so the hand helds are light, do not warm up, and require only light weight telecom wiring.  The people I built them for love them.

Chris350
If you read your quote carefully, you may come to the conclusion, as I did, that BenjiGranddad wants to avoid reversing the polarity.  You cannot avoid reversing the polarity.  Either you have to do it yourself manually or you have to use one of the methods that will do it automatically for you.  The most basic manual method will work for both dc and DCC.  Whatever method he chooses to begin with, I am guessing he will want to use an automatic method eventually, along with converting that dc locomotive to DCC.  Is that a good guess BenjiGranddad?

Jim

[BenjiGranddad]

Jim Banner, you have it right.  I wanted to avoid reversing polarity, but still have the loop.  You summed it up well and I will proceed in this direction.  Thanks, much!

JJB

[Chris350]

JB good catch, it was late.. I see now.  I assume by not reversing the polarity he looking to try to run that DC unit through the loop?

[CNE Runner]

Having an intimate association with track plans that require reversing polarity (such as a Peco SL-E193 Electrofrog crossing or the Peco SL-E199 threeway Electrofrog turnout) I recommend the Digitrax AR1 Single Automatic Reversing Section Controller @ $29.99 MSRP. Should you be wiring something like the threeway Electrofrog turnout, and require more than one reversing circuit, the Digitrax PM42 will accomplish that task on as many as four sections...and has four section circuit detection built in...@ $79.95 MSRP.

Other than the circuitry described above, you would be restricted to using multiple SPDT or DPDT mechanical switches. The mechanical method is definitely cheaper - although more tedious to operate.

I hope this helps,
Ray

[BenjiGranddad]

Thanks to all.  I think I've got it now.  I'm sure other things will come up.

JJB