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Auto Reversing Problem still, a year later

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Auto Reversing Problem still, a year later
Posted by CPbuff on Wednesday, June 24, 2020 2:51 PM

Well its been a year since I posted a problem with the MRC Auto reverser on a balloon track. Since then I have changed the layout to leave only one reverse loop or balloon track and a slight problem still exists... The loco enters the loop over the Auto reverser(Gap A) and everything is fine, it proceeds around the loop but when the loco goes over the gap (Gap B) to leave , it stops... If I enter the loop the opposite direction it enters over the gap (Gap B) and proceeds around the loop over the AR leaving the loop(Gap A) theres no problem... I have tried 3 AR's , 2 of which are brand new! I have sent the control unit back to the manufacturer for testing as we thought there was a problem with voltage supplied to the track and they say all is good! I also send a diagram of the layout to the manufacterer and they see no problems. Should I look at stay alive capacitors? Or just be happy with a loop around with no capability of reversing directions?

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Posted by richg1998 on Wednesday, June 24, 2020 3:08 PM

It might help if you post the diagram here. You look fairly new so you will need a photo hosting site for the photo if not aware.

Rich

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Posted by floridaflyer on Wednesday, June 24, 2020 3:41 PM

Does this happen with multiple locos?  When you approach gap B the rails are out of phase and the reverser corrects that problem. If you run a loco over B and bring the rails in phase, and then place another loco in the loop and run it through B  (with the rails already in phase) does the loco still stop? Trying to see if other factors are in play. 

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Posted by gregc on Wednesday, June 24, 2020 4:02 PM

richg1998
It might help if you post the diagram here.

which model AR and how it is wired

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Posted by wjstix on Wednesday, June 24, 2020 4:28 PM

I had a similar problem at one time, trains went thru one direction OK but not the other. Turns out one of the feeders for one rail in the reverse loop got connected to the 'regular' wiring for the rest of the layout in error. Going one way, the polarity matched, the other, it didn't. I'd suggest going over or even re-doing all your wiring relating to the reverse loop to be sure something like that isn't happening.

Similarly, it could be one insulated rail joiner has gone bad, or a rail gap has somehow closed together over time, so one rail is no longer insulated. It would have a similar result, trains would only work one direction.

In either case, it's possible to have a trickle of power that's not enough to trip the short circuit detector, but is enough to mess up the reverser.

Stix
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Posted by jjdamnit on Wednesday, June 24, 2020 5:05 PM

Hello All,

I don't know if this has been asked/answered...

Are you running DC or DCC?

Hope this helps.

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Posted by floridaflyer on Wednesday, June 24, 2020 5:15 PM

Agree with Stix, given that you have tried multiple AR's, possibility of other causes increases.

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Posted by gregc on Wednesday, June 24, 2020 5:41 PM

wjstix
Similarly, it could be one insulated rail joiner has gone bad, or a rail gap has somehow closed together over time, so one rail is no longer insulated.

wouldn't there be a short across the closed gap when the section matches the polarity at the other gap?

 

wjstix
I had a similar problem at one time, trains went thru one direction OK but not the other.

CPbuff
The loco enters the loop over the Auto reverser(Gap A) and everything is fine, it proceeds around the loop but when the loco goes over the gap (Gap B) to leave , it stops...

If I enter the loop the opposite direction it enters over the gap (Gap B) and proceeds around the loop over the AR leaving the loop(Gap A) theres no problem.

so the problem is only leaving the loop at gap B?

is there a short, either from the booster or the AR?

how far apart are the gaps at both ends from the AR connection to the mainline?

 

greg - Philadelphia & Reading / Reading

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Posted by BigDaddy on Wednesday, June 24, 2020 6:21 PM

jjdamnit
Are you running DC or DCC?

The OP's original thread

He is running a MRC Prodigy Advanced. 

gregc
which model AR and how it is wired Ad

Currently MRC only lists one Reversing Unit and there are only 4 wires to deal with.

As I understand it, MRC has checked his Prodigy, looked at his track plan and 3 AR's don't work in one direction on the reversing loop. 

Seems unlikely that MRC doesn't know how to make an AR compatible with the Prodigy.  The unidrectional operation of the AR ought to be telling us something, but I don't know what.  Maybe Stix nailed it.

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Posted by rrinker on Wednesday, June 24, 2020 6:35 PM

 A track diagram would help. If it's a diagonal cutoff type of reverse loop, is the train entirely within the reversing section before crossing the exit gaps? That would definitely cause an issue where the train can enter the loop either way, but fail to exit cleanly.

 If it's a loop in the sense that the diverging leg of a turnout comes back to the straight leg, it pretty much has to have the whole train fit inside the reverse section, or the engine would hit the tail end. However - what brand of turnout is used here? 

 When the train halts existing the loop - does the breaker in the main system trip? This could indicate something like the issue of one feeder crossed, or a bad gap, or simply inadequate feeders in the reverse section.

                                           --Randy

 


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Posted by SouthPenn on Wednesday, June 24, 2020 8:03 PM

Are the gaps in the rails straight across from each other?

South Penn
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Posted by gregc on Wednesday, June 24, 2020 8:24 PM

rrinker
This could indicate something like the issue of one feeder crossed

if it is adjacent to a gap, either it always causes a short when a loco bridges the gap it's adjacent to or the loco stops on it when approaching from the opposite direction, not at the gap.

 

CPbuff
when the loco goes over the gap (Gap B) to leave , it stops

does "goes over the gap" mean 

  1. when metal wheel bridges the gap
  2. the truck/wheels are just across the gap with the gap under the loco

 

what happens if the reversing section turnout frog and diverging rail up to the gap are powered and the turnout is not thrown correctly when exiting the reversing section

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Posted by chenxue on Wednesday, June 24, 2020 8:30 PM

How are the points being set? And how are the point rails powered? I mean, that may cause a difference between entering and exiting scenarios.

Cid    (Memphis, Tennessee)

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Posted by chenxue on Wednesday, June 24, 2020 8:32 PM

Also, I notice in that AD520 manual, the bus connection is not to the main rails, but connected past the turnout toward the loop. This does not jive, to me, not quite sure why. Just not consistent between the entrance and the exit. 

Cid    (Memphis, Tennessee)

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Posted by rrinker on Thursday, June 25, 2020 8:52 AM

 It's essentially the same thing. The main would be connected to the bus, so the input side of the AD520 needs to be powered from the main track, bus or some manner. Electrically it is the same. Main power in, the loop must be fed ONLY by the output side of the AD520.

                                            --Randy


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Posted by jjdamnit on Thursday, June 25, 2020 12:53 PM

Hello All,

BigDaddy
The OP's original thread He is running a MRC Prodigy Advanced.

Thanks for the clarification, didn't see the original post.

In the MRC AD520 instruction sheet, it notes that both the Red (feeder) wires to the unit are connected to the track between the turnout and the gapped (insulated) rails on the straight section. The Yellow (polarity shift) wires go to the reversing section on the opposite side of the gapped (insulated) rails.

It doesn't matter which red or yellow wires go to which track polarity.

On the wye on my pike I originally put the feeder wires on the track between the two legs of the wye and attached the polarity shifting wires on the point end of the wye turnout.

The turnouts to the wye are #2 PECO insulfrog (unpowered) turnouts. When the points are thrown to the main power is not transmitted to the diverging line.

When the points are thrown to the diverging route both the main and diverging routes have power.

Both legs of the wye are gapped on all rails at the first joint past the diverging points of the turnouts.

This configuration didn't work.

I moved the feeder wires to the AR unit "outside" the legs of the wye and VIOLA! Success!!

For the OPs situation, a baloon track, I would move the feeder wires to the point end of the turnout, keep the gaps (insulated rail joiners) on the tailing ends.  

My point...

If the feeder wires to the AD520 are between the turnout and reversing section on the diverging side, and the turnout is a power routing- -no power to the diverging route when the points are thrown to the straight section, then no power will get to the AR unit when entering through the straight track.

When the points are thrown to the diverging track (where the AR unit is fed from) then the power will energize the AR unit and the polarity successfully reversed.

Unfortunately, I am unable to post a diagram so a verbal description will have to suffice.

Hope this helps.

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Posted by chenxue on Thursday, June 25, 2020 7:36 PM

Haha, I think that's exactly what I was worried about, jj Big Smile

I think gregc was looking at more or less the same issue, or similar...

Cid    (Memphis, Tennessee)

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Posted by gregc on Friday, June 26, 2020 6:51 AM

it would be good to hear from the OP if the turnout to the reversing switch is power routed

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Posted by jjdamnit on Saturday, June 27, 2020 1:50 PM

Hello All,

gregc
it would be good to hear from the OP if the turnout to the reversing switch is power routed

Seems we've been "ghosted" again Huh?ConfusedHuh?Confused!!!

Hope this helped

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Posted by gregc on Sunday, June 28, 2020 7:51 AM

jjdamnit
gregc
it would be good to hear from the OP if the turnout to the reversing switch is power routed

Seems we've been "ghosted" again Huh?ConfusedHuh?Confused!!!

Hope this helped

gregc
what happens if the reversing section turnout frog and diverging rail up to the gap are powered and the turnout is not thrown correctly when exiting the reversing section

i wonder if the OP realized all his problems: trying 3 types of ARs and sending units back to the manufacturer -- were simply caused by a power routing tunout positioned incorrectly.

yes this might be embarassing, but we all make mistakes.   knowing if this is the cause would solve the mystery and be a great learning experience for all of us

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Posted by BigDaddy on Sunday, June 28, 2020 9:08 AM

I didn't see where the OP told us what turnouts he was using.

He is not a prolific poster and if you read the original thread, people asked him to post a picture, offered to post a picture for him but the thread just ends with no more information.

Maybe he will get back to us in another year.

Henry

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Posted by CPbuff on Sunday, June 28, 2020 5:19 PM

Thanks everyone for all your information (overload)... I beleive I may have figured it out ! Spent the last two rainy days gapping and measuring(VOM) and working on it...

Each time the loco went to leave the loop at Gap B , I finally saw the sparks fly as the loco crossed the gap (dull and dark made it easier to see) , shorted and then stopped!

What  I ended up doing was adding an addition gap outside the reverser on the red (track power side) but the same short happened again and sparks flew so obviously the loco didnt like the wrong polarity so I added a second auto reverser just up the track from the first one but with two turnouts between them... So essentially I think I tricked the original AR into beleiving its getting track power on the red side when in fact its getting track power from other side (yellow)of the second reverser!

I will try to figure how to post the track plan in the next few weeks for those who may be interested!

Some other answers are: DCC, Atlas track and turnouts, happened to all locs, Prodigy Advanced system, no feeders required inside the loop as the AR supplies the power !

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Posted by BigDaddy on Sunday, June 28, 2020 5:32 PM

CPbuff
I will try to figure how to post the track plan in the next few weeks for those who may be interested!

I for one, would be interested and need a track plan to understand this.   Please show the gaps too. Atlas turnouts are not power routing so we can get rid of that red herring.

It sounds like you are telling us you needed an auto reverser before the reversing loop. 

pm sent, I will be happy to post your track plan

Henry

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Posted by gregc on Monday, June 29, 2020 5:47 AM

CPbuff
I will try to figure how to post the track plan in the next few weeks for those who may be interested!

can i suggest the following diagram until then

the top 2 loops illustrate a conventional reversing loop, one for each loop polarity.  mainline polarity in red/green and corresponding loop polarity in yellow/cyan.   with train moving counter-cockwise (CCW) thru loop, yellow and red polarity match on outer rail.    as train exits loop in 2nd drawing, loop polarity switches, and outer rail polarity matches green and cyan.

 

bottom set of drawings (3, 4, 5) attempt to illustrate how 2 ARs are used, the 2nd AR illustrated in blue and orange

as train moves CCW thru loop, 2nd AR polarity matches mainline rails, red/orange and green/blue.   rev section polarity is also shown as matching yellow/orange/red and cyan/blue/green.

drawing 4 illustrates when train exits loop, 2nd AR switches polarity, yellow/orange on outer rails and 1st AR remains unchanged.

drawing 5 illustrates trains returning to mainline.  2nd AR switches polarity, cyan matches green.

i would think the lengths of both rev sections need to be long enough for a train.

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Posted by rrinker on Monday, June 29, 2020 7:15 AM

 I can't see why you would possibly need two ARs back to back like the second set of drawings, unless between the blue/orange and yellow/cyan section there are other turnouts that are not properly gapped and form a track shortcut to elsewhere within the yellow/cyan. 

 For example, two turnouts off the main, the diverging routes of which come together at a turnout in the loop, and then joins back to the main as a single track. Either the isolated loop section needs to be made shorter, or the diverging side of BOTH turnouts need gaps.

 There is definitely more going on here than a simple loop if two ARs are needed to solve the problem.

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Posted by gregc on Monday, June 29, 2020 8:51 AM

is the 1st even needed with the 2nd in place?

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Posted by wjstix on Monday, June 29, 2020 2:45 PM

BTW I believe the MRC reverser doesn't have an way to adjust the sensitivity, while others (like the Digitrax one) does. I've found using the Digitrax AR1s that it's very helpful to be able to adjust the sensitivity to get things working right. Could be switching to an AR1 reverser could solve the problem - assuming everything else in the track wiring etc. is OK.

Stix
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Posted by jjdamnit on Monday, June 29, 2020 3:16 PM

Hello All,

Thank you for the diagrams gregc.

After my experience of wiring this exact MRC AD520 unit to a wye I believe the culprit lies in where the AD is drawing power from- -Red Wires. (Wiring a Wye for DCC)

Referring back to the instruction sheet of the AD520 it shows the unit being powered- -both Red wires- -after the turnout but before the gapped rails on the straight section.

I submit that both the Red wires to power the AR should be attached before the turnout on the facing point end, NOT- -as the instructions show- -on the straight section on the trailing end before the gapped rails.

By powering the AR unit before the turnout this should remove the variable of the power routing of said turnout.

All the rails should be gapped per the first two examples in gregc's diagram.

The Yellow wires (polarity shifting) then can be attached to any point within the gapped (isolated) track (loop).

The addition of a second AR doesn't make sense IF indeed this is a simple loop or ballon as gregc has diagramed.

wjstix
...assuming everything else in the track wiring etc. is OK.

That's a big assumption at this point.

Hope this helps.

"Uhh...I didn’t know it was 'impossible' I just made it work...sorry"

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Posted by gregc on Monday, June 29, 2020 6:25 PM

jjdamnit
Referring back to the instruction sheet of the AD520 it shows the unit being powered- -both Red wires- -after the turnout but before the gapped rails on the straight section

if there's a DCC bus from a command-station/booster with feeders to track, why wouldn't you connected the AR to the bus and from it to feeders in the rev section?

 

just to summarize the problem:

it works fine in one direction, but in the other direction, the loco stops "when the loco goes over the gap (Gap B) to leave"  (from this thread)

 

the other thread has other interesting comments (paragraph breaks and underlining added by me):

I have a problem with what essentially is a balloon track that I have an auto reverser on ...

the loco goes through the balloon track and passes the required gaps and loco continues on to the next gap (not related to the balloon track) and the loco has the front wheels passed the gap then if any of the following railcars trailing, cross the AR gap back in the balloon track , the metal railcar wheels short out the AR gap shutting down the loco(s) as it recognises a short...

Is this a call for another AR at the other gap not related to the balloon track or should I move this gap further out beyond where my longest train would be past the AR in the balloon track?

 

 Yes, the loco does exit the loop and is across the third gap, when the following cars cross the gap between the wires of the AR when the wheels of the cars make the short...

The AR has switched the polarity to allow the loco to pass over safely a few seconds previously!

Yes the third section is a reversing loop also after goes away for a while to the rest of the layout... 

If I run the loco by itself over this third gap it continues on because the polarity is correct at the third gap...

Its just the trailing cars that cause the shutdown...

We are  out of the loop and its gaps when the problem occurs...

The loco and a couple of cars travel fine for a foot or so before reaching the third gap!

CPbuff
no feeders required inside the loop as the AR supplies the power !

"3rd gap" and only one connection to the AR??

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Posted by rrinker on Monday, June 29, 2020 7:17 PM

 Yes, you normally would connect the input of the AR to the main bus. MRC likes to 'simplify' their instructions, which can lead to consequences.

                               --Randy

 


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

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