Problem with RailPro Reversing Loop

[MtRR75]

First, a little background.  I am relatively new to RailPro.  I have a small layout and about 10 locomotives.  Two have been converted to RailPro, and another is in the shop getting converted.  But it will be a while before all of my locos get converted.

So, I am still running on my DC layout -- complete with block switches and two cabs.  I have a TPDT (tripple pole, double pole) switch that switches the layout from DC to RailPro.  The first 2 poles switch between CabA and RailPro.  The other pole disconnects CabB whenever RailPro is on.  There is no way that I can run the both systems simultaneously, which is exactly what I want.  I never leave RailPro locos and DC locos on the layout at the same time.

The problem comes with the reversing loop.  If I am only running one RailPro loco, I use my CabA directional switch to reverse the polarity of the Main Line while the loco is on the reversing track.  This works fine.

However, if another RailPro loco is moving, the sudden loss of power (from the center switch position) as the polarity changes causes the 2nd loco to stop suddenly, then restart -- but in the correct direction.

I know that RailPro makes a reversing loop module that will automatically deal with the polarity change that the 1st loco encounters.  I assume that the 2nd loco is unaffected and continues to run correctly.  So this is the obvious solution to my problem.

BUT.....

What about when I switch back to DC?  I doubt that the RailPro module will switch the polarity of a DC system.  It seems like it might be necessary to figure out how to toggle between the RailPro reversing loop module and my DC directional switch -- at the same time that I toggle between power sources.  I have some wiring skills, but I am not an expert.  So I am having trouble figuring this out.

I seem to recall that there are others who have DC vs RailPro switchable layouts.  Any ideas on how to deal with this?

[Alan]

Place another DPDT switch in the wires going to the reversing loop. Use it only for RailPro operation. Mark it so you know which way to flip the switch (and leave it there) when operating with DC.

[MtRR75]

Thanks for the idea.  Sorry about the long delay in responding -- family has been visiting and other stuff happened -- very little train time lately.

I studied your suggestion and compared it to my wiring diagrams.  I already have a DPDT reversing switch in the line that sends power to the reversing track.  My problem is that I have been using a different reversing switch to reverse the MAIN LINE polarity while the loco is crossing the reversing track.  The problem is that the OTHER loco (the one on the main line) feels that polarity reverse and stops momentarily.

Are you suggesting that I install a RailPro reversing module, then use the reversing switch on the reversing track to flip the polarity of the reversing track while the loco is running through it?  Would the RailPro reversing unit sense this change smoothly and reverse the polarity a 2nd time while the loco was running across the reversing section, thus not disturbing the main-line polarity?

[William Brillinger]

You could simply use a regular toggle switch with an AR-1 on the loop, so when you are using the layout in RAILPRO mode, you switch the reversing loop to use the AR-1, when you are in DC, you remove the AR-1 from the circuit with the toggle.

[Alan]

Are you suggesting that I install a RailPro reversing module, then use the reversing switch on the reversing track to flip the polarity of the reversing track while the loco is running through it?

No RP reversing module needed if you are okay with flipping a switch. Yes, install the second toggle and flip the polarity of the reversing loop while a train is in it (only while running RP). That way there is no effect on any other trains on the layout. The train on the reversing loop may skip a beat while you are flipping the switch. All depends how fast you can flip the switch.

Bill's idea will work also if you want to buy an AR-1.

I doubt that the RailPro module will switch the polarity of a DC system.

The AR-1 may work on a DC system. A RP power supply is just a DC system at wide open throttle. The only issue may be the ugly waveform DC power packs put out. We know the AR-1 works great on clean DC. It would be a $39 gamble to find out.

[MtRR75]

Thanks for the replies.  I do realize that this is sort of a “much ado about very little” situation.  The problem only shows up when I am running a train continuously on the main line (my outer loop) AND at the same time moving a loco across the reversing diagonal that connects the two sides of my inner loop.  I had RailPro for a year and a half before I tried this situation, so it is not common to my operations.

By far the easiest solution is to have the loco on the reversing diagonal stop briefly, while I flip the existing DPDT directional switch for the reversing diagonal, then resume its motion.  It will continue to go forward because RailPro direction is determined by the setting on the HC-2, not by the track polarity.

This is actually a prototypically realistic solution.  The diagonal track has several yard spurs coming off of it.  It is realistic that one of those yard turnouts might need to be switched before proceeding through the yard.

BUT, I like to know precisely how things work, and I would like to know how to allow continuous motion of both locos in this situation – even if I decide not to build the fix.

SO, I have been playing with wiring diagrams and switch position situations, and I may post something here when I think I have got it figured out.

BUT, FIRST I HAVE A QUESTION.  (I put this in all caps so that you can find the question among my ramblings.)  I want to be sure that I understand exactly how the AR-1 works.

When a loco enters or exits an AR-1 isolated block and finds that the polarities of the two blocks are opposite, it quickly flips the polarity of one of the blocks.  Am I correct that it always (whenever needed) flips the polarity of the AR-1 block, regardless of whether the loco is entering or leaving the AR-1 block?

[Alan]

Am I correct that it always (whenever needed) flips the polarity of the AR-1 block, regardless of whether the loco is entering or leaving the AR-1 block?

Correct. The AR-1 is not concerned with direction of travel. It simply flips polarity anytime a polarity mismatch is detected.

Be aware if a train is longer than the reversing loop track (train is on the 1st main - reverse - 2nd main) and the isolation gaps are such that a wheel can contact both rail ends at the same time (unfilled rail gaps) there exists the possibility the AR-1 may not set correctly due to there being no correct polarity solution. If the train is moving this situation is unlikely to cause a problem. If a train were to stop with the wheels on each end of the reversing section touching the corresponding main rails there could be a problem. In this event the RP power supply circuit breaker would likely trip.

[MtRR75]

Thanks for the response.  I have decided not to install an AR-1 at this time.  I figured out were I could connect it into my circuitry so that a new DPDT switch would route power to the reversing loop either via the AR-1 or via the original DC block lines.

The problem is that I would have to make sure that EVERY time I flip my TPDT switch (DC or RailPro power), I would ALWAYS have to remember to flip the new DPDT switch, as well.  If I switch to DC power on the main TPDT power switch, but forget and leave the new DPDT switch on RailPro, the main line would be DC, but the reversing track would be RailPro, and a loco moving into the reversing track would connect the two power supplies together – NOT a good idea.

I have designed my hybrid DC-RailPro system to be idiot-proof.  Adding the AR-1 in this manner would circumvent that level of protection.

Some day, when I get all of my locos converted to RailPro, I will go back and install an AR-1 for the reversing track.  In the mean time, I will use the low-tech solution that I described in a previous post – just pause the loco and flip the direction switch for the reversing track.

[Alan]

You could use a 4PDT relay controlled by a single switch to change the entire layout, including the reverse track setup, between RP and DC. That would ensure the whole system is either DC or RP. Then you could use the AR-1 or toggle switch for the reverse loop without worrying.

http://www.mouser.com/ProductDetail/Omron-Automation-and-Safety/MY4-DC12S/?qs=sGAEpiMZZMtSzCF3XBhmWx3JwO0RjjQeeLqWlf15lmQ%3d

Another possible solution if you want fully automatic operation with both RP and DC would be a simple logic circuit and IR sensors across the reverse track entrance and exit. Place one sensor before the rail gaps and another sensor after the rail gaps on each end of the reverse track. The logic circuit would use a truth table comprised of the output from the four sensors to determine the correct polarity of the reverse track i.e. is a train entering or leaving the reverse track and in which direction is it traveling. You could even get a bit fancy by adding an additional row to the truth table that detects if three sensors are triggered at the same time (meaning train is longer that reverse track) that would shut down the power to prevent a short circuit.

[MtRR75]

You could use a 4PDT relay controlled by a single switch to change the entire layout, including the reverse track setup, between RP and DC. That would ensure the whole system is either DC or RP. Then you could use the AR-1 or toggle switch for the reverse loop without worrying.

Another possible solution if you want fully automatic operation with both RP and DC would be a simple logic circuit and IR sensors across the reverse track entrance and exit.

I had thought about getting a 5PDT switch (if such a thing exists).  The 5th pole is for disconnecting Cab-B whenever Cab-A is switched to RailPro -- part of my idiot proof plan -- in case I accidentally toggled a block to Cab-B AND I had accidentally left the Cab-B transfomrer on AND had bumped it dial to some positive voltage.

But I have decided that both the 5PDT approach and your automated operation option are far too much work for what is essentially a temporary fix, that rarely occurs.  This problem will go away when I get all of my locos converted to RailPro -- 2 done, 1 in the works, and about 4-5 more to go after that.  I'm hoping that the conversion will be complete in a couple of years.

Thanks for your help.

[PatP]

You could use a 4PDT relay controlled by a single switch to change the entire layout, including the reverse track setup, between RP and DC. That would ensure the whole system is either DC or RP. Then you could use the AR-1 or toggle switch for the reverse loop without worrying.

Another possible solution if you want fully automatic operation with both RP and DC would be a simple logic circuit and IR sensors across the reverse track entrance and exit.

I had thought about getting a 5PDT switch (if such a thing exists). 

Hello, not sure if you've given up on this or if you're still contemplating, especially if it's going to be a couple of years. While I've never seen a 5PDT switch, however you can stack relays and control them with a single switch. As in a 4PDT or 2-DPDT and a SPDT make a 5P. Could be as simple as flipping a switch (simple is my favorite too).

Just a thought,
PatP