Wiring a Reverse Loop in DC - not DCC

[learmoia]

Flipping the track polarity AND the throttle polarity will cancel each other out.  Your reverse loop polarity would be unchanged.

Technically yes from the viewpoint of the locomotive.. but in terms of the Layout as a whole.. polarity on the loop is changed.

While in the reversing loop.. Flipping the track polarity sets you up to exit the loop in reverse polarity from when you entered.
--- It also reverses the locomotive direction.
Flipping the throttle polarity keeps the locomotive moving in the intended direction.
--- It 'DOES' Flip the reversing loop polarity.. but it also flips the Main Line polarity at the exit point.

I think that the CTI Electronics Train Brain system works by essentially having a computer controlled block assignment system that assigns a throttle to the occupied block and the one ahead. It tracks the direction of travel by monitoring the polarity of the track, but it’s basically an on/off relay coupled to a throttle routing relay... if I understand the literature.

https://www.cti-electronics.com/index.htm

..WOW.......... That... is..................................................one solution...

You'd have to re wire your entire layout.. and add sensors, and RFID Chips everywhere to make it work..
(I'm actually intrigued, and will read more about it....)

Here is another... (1 per reversing loop.)
https://www.modeltrainstuff.com/circuitron-800-5401-ar-2-automatic-reverse-circuit/


~Ian

[CRL]

This is layout pre-planning so nothing is built or wired yet... have to build the house first. The Circuitron auto reverse unit works fine with a small layout with only a single block on the mainline. You can’t run more than one train at a time using this unit. That’s not what I intend to build. I hope to accommodate 2 operators on the mainline and one operator in the yard.

[CRL]

I just received a reply from CTI, and it appears you don’t have to “program” their system if you use RR&Co Traincontroller software to control the CTI system. So the choice is basically Smart Layout vs Smart Locos. Since it would cost about $50 per loco to install DCC decoder or $12.50 to control each “block” on the railroad if I’m reading the CTI manual correctly. The sensor costs are comparable for DCC & CTI, so it’s going to depend on the number of locos vs number of layout blocks.

[peteski]

I just received a reply from CTI, and it appears you don’t have to “program” their system if you use RR&Co Traincontroller software to control the CTI system. So the choice is basically Smart Layout vs Smart Locos. Since it would cost about $50 per loco to install DCC decoder or $12.50 to control each “block” on the railroad if I’m reading the CTI manual correctly. The sensor costs are comparable for DCC & CTI, so it’s going to depend on the number of locos vs number of layout blocks.

You can do DCC installs for less than $50/loco. Many new locos already have decoders installed.   And DCC is way more flexible (you can set up consists, or have full control of multiple locos on the same track. Plus DCC offers all sorts of lighting options (headlights, Mars Ligths, etc) But of this will be a moot point if you have simple layout and just run one train at a time, IN that case installing a complete CTI system seems to be a waste of money. Just wire the reverse loop and manually toggle that reverse block switch.

[MK]

Digitrax decoders are around $30 each.

[learmoia]

I did a quick cost comparison to 'fully' implement each system on my layout..

DCC is a command station and booster, with 2 throttles.. (Additional throttles via Wifi phones)
The DCC system is minimally blocked to allow a single operator to run 1 DC locomotive at a time.

Train Brain is full system.. blocked like a DC layout, with 1 sensors at each end of Each block
and RFID chips on each loco, with RFID sensors on each main line block.
Train brain assumes that people are operating the train, so the only 'controlled' switch is the reversing loop.

Here is the layout in question. 
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Here is the cost comparison.
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If you only intend to operate a 2 cab DC Layout:
Each $12 block controller can be replaced with a $0.50 DPDT toggle switch.
You can wipe out all the sensors and sensor readers, RFID chips and RFID sensors.

If you want a walk around throttle system.. since Aristo Radio is out... you might as well do a DCC system, then you have compatibility with other operators.

You can run your layout DC with a DCC control system as follows.:
Install the DCC system.
Take the DCC Command outputs to a DPDT toggle switch for each cab, AND Two 1.5amp DCC Decoder..
Run the Motor output of each 1.5A DCC Decoders to the other side of the DPDT toggle for each cab.

Your DCC Decoder is acting as a DC throttle.

Cab 1
Up = DCC to track blocks.
Down = DC to track blocks (from decoder 1)

Cab 2
Up = DCC to track blocks.
Down = DC to track blocks (from decoder 2)

Then each of these circuits need to run to your track blocks.. (just like an old fashioned DC system)

Then for each block..
Another DPDT toggle switch: (Cab 1 vs Cab 2)

I'm planning to do this on my layout to a certain extent due to my big collection of vintage stuff where I don't want to install decoders and I don't want to run on '00' DCC (Analog on Digital)

~Ian

[learmoia]

Another thought I had with the whole Reverse loop thing....

If you put a Switch machine that has a DPDT switch built in on the Reversing Loop Switch.. The switch position can dictate track polarity, and (at least for DCC) an Auto Reverser can dictate Switch position.

For DCC:
Pull through your loop, and when you hit the double gap at the switch, the AR changes your switch and the switch changes your polarity.
since it's DCC you don't need to worry about direction control.

For DC: you don't even need the AR.
Pull into your loop - Loop polarity is set by the switch position at enterence.
Before you exit, throw the track switch for exit position... Switch motor flips your polarity, then change your direction switch to keep the train moving. (you can stop to avoid the F-R-F jerk).
.. I WOULD make sure that the Enter/Exit point of the loop is in the same block as the loop itself..

I keep thinking in my head.....
'Were trying to debate the pros and cons of 2 supercomputers to purchase.. so we check our Gmail...'

All the while.. the devise we currently own and are using to have this debate.... can also check our Gmail...

~Ian

[CRL]

Hmmm 🤔...

Some good thoughts there from both posts. CTI system does require occupancy detectors in each block, but current detection is supported. The RFID option is only necessary if you want to ID, ala Railcom, each locomotive &/or car, which doesn’t matter to me.

Bottom line, I think the Locomotive / Block ratio will be the major cost determining factor. So, I’ll have to design the layout, then make the comparison.

Thanks for all the input.

[djconway]

One thing I did not see in your analysis is the number of locomotives that "could" be operated at one time.  With DCC even a minimal system will give you more than 8 locomotives at one time, to control up to 8 locomotives at one time with a traditional cab system you are talking 8 power supplies / throttles and a 8 position double stack rotary switch (last time i looked (1996) the switches were about $14.00 each.

Design your RR for how you want to operate in 5 to 7 years. 
Are you going to be the only person running it?
Switching sidings while someone is running a main line train.
One train only.
Automated operations?

Just some things to think about.

[learmoia]

One thing I did not see in your analysis is the number of locomotives that "could" be operated at one time.  With DCC even a minimal system will give you more than 8 locomotives at one time, to control up to 8 locomotives at one time with a traditional cab system you are talking 8 power supplies / throttles and a 8 position double stack rotary switch (last time i looked (1996) the switches were about $14.00 each.

Design your RR for how you want to operate in 5 to 7 years. 
Are you going to be the only person running it?
Switching sidings while someone is running a main line train.
One train only.
Automated operations?

Just some things to think about.

AGREED!!!!!!...   Also consider other operators who may want to bring locomotives to run..

Bottom line, I think the Locomotive / Block ratio will be the major cost determining factor. So, I’ll have to design the layout, then make the comparison.

That's pretty much the determining factor... (It may also be worth asking them (CTI), if you can design 2 isolated systems that just handle each reversing loop..)

Another aspect of cost comparison..
If you equate CTI Block controls to DCC Decoders as a cost comparison..
For CTI you need to buy your Command station and ALL of your 'decoders' up front to make your layout work.

For DCC you just need to buy the Command Station, and you can buy Decoders over time to expand your locomotive fleet..
-And wiring is much simpler.
-And you don't have to 'Program' it with computer code to make the Layout Go.
-And if a Decoder goes dead or out of whack.. it's just that locomotive, not that portion of the layout.

(And as I said before, you can build in backwards compatibility in DCC for older locos that don't have decoders.)
Wiring is 'more' complex than normal DCC.. but not as complex as blocking for CTI.

Good discussion.. ~Ian

[learmoia]

I did a bit of Googling...

Here is another thing to look at..
http://www.azatrax.com/automatic-reverse-loop.html

They are taking the same approach as I mentioned earlier.. (The loop is normal, and the rest of the world gets reversed.)

~Ian

[peteski]

Digitrax decoders are around $30 each.

Hmm . . . I thought the smaller Digitrax decoders cost around $20. Or was that long time ago (I haven't looked recently).

[MK]

Hmm . . . I thought the smaller Digitrax decoders cost around $20. Or was that long time ago (I haven't looked recently).

I don't know but you may be right.  The $30 is for plug-n-play ones.  The hard wired tiny one are probably cheaper.

[peteski]

I don't know but you may be right.  The $30 is for plug-n-play ones.  The hard wired tiny one are probably cheaper.

Yup, DZ125 on eBay for $22.
https://www.ebay.com/c/1900170440

DZ126 from Tony's Trains: $17.55  (not $30).
https://tonystrains.com/product/digitrax-dz126-wired-mobile-decoder

Far from $30.  But those are do-it yourself installs. Having one installed professionally would likely be over $50.
But installing the DC block control system is also a D-Y-S job and just as complicated (or even ore so) than installing a decoder.

[learmoia]

But installing the DC block control system is also a D-Y-S job and just as complicated (or even ore so) than installing a decoder.

But you don't have to do frame milling to make space for the decoder.. 

~Ian