# Reverse unit too sensitive



## ChopperCharles (Jan 3, 2012)

The reverse unit on my 21085 trips for next to nothing. My trackwork is fine, none of my other locomotives have problems, but in this one area, on a banked curve on a light grade, my 21085 will trip the reverse unit right at a track junction. 

I've connected a lock-on with power to both track pieces. I've soldered the track together and then carefully sanded the solder down flush with the rails, so there's no lip at all. I've gone to great lengths to scrub the track spotless with a green scotchbrite pad. I've gauged the tender wheels, and scrubbed them until they shine like the noon-day sun. Still it trips the reverse there. I'm at a loss as to why...

Charles.


----------



## ChopperCharles (Jan 3, 2012)

Also, another bit of wierdness. I have an Alco 360/361. Inside the 361 shell I gutted the original horn and added an ooooold railsounds horn board. When that alco pulls a full load of cars up the incline, and the B unit goes over that one track section, the horn sounds briefly. Any idea why? Unloaded this doesn't happen...

Charles.


----------



## gunrunnerjohn (Nov 10, 2010)

Sounds like you have a high resistance joint. It's somehow seeing a DC offset that triggers the horn. The *fully loaded* would suggest there's more load, thus more current, and that might be enough to trigger the high resistance to cause the issue. Might explain the E-unit as well.


----------



## ChopperCharles (Jan 3, 2012)

Waht would cause that? The track is clean, and I have lockons for all the track sections, and I SOLDERED THE JOINT. 

Charles.


----------



## gunrunnerjohn (Nov 10, 2010)

Hard to say, but that's the indications. Are you saying you've soldered the track sections on both sides of this problem area, and you did both rails?


----------



## ChopperCharles (Jan 3, 2012)

I soldered the specific track joint that was giving me problems, both rails, and powered both sections with a lock-on. 

Charles.


----------



## gunrunnerjohn (Nov 10, 2010)

I'd put a load of a few amps on the track section in question with a large load resistor, then measure voltage drops to adjacent track sections on both sides. There has to be something unique going on there.


----------



## ChopperCharles (Jan 3, 2012)

How would I do that? I just went up there with my multitester and the resistance between all track sections is 0.3 ohm or less.

Charles.


----------



## tjcruiser (Jan 10, 2010)

That's a gravity-based e-unit, right? If the e-unit is tripping, that indicates you've lost power to the e-unit momentarily. Sounds to me like the loco pickups are somehow losing contact with the rails for a breif moment?

TJ


----------



## ChopperCharles (Jan 3, 2012)

That is possible. It's pulling a long train on a banked section of track up a grade... and the 21085 doesn't have any weight in the tender. (The base is cast though, so it's heavier). I will try loading that sucker down... I don't have any fishing weights, but a couple rolls of quarters should fit in there.

Charles.


----------



## flyernut (Oct 31, 2010)

Swap out the tracks in question with different ones.Could be that some of your insulating pieces of fiber board are bad. When the weight of the train goes over it, they might short, almost acting like a track trip.


----------



## ChopperCharles (Jan 3, 2012)

The wheels lifting off the track is definitely the problem. Adding some weight or reducing (or eliminating) the number of cars being pulled makes the problem disappear, and I found that if I put the B unit on the tracks without turning the power off, the moment all wheels hit the track the horn sounds briefly. If I nudge the B unit so the wheels come off the track and then come back down, the horn with briefly sound then too. So it's definitely a problem with too many cars, too little weight in the tender. 

However... the reverse unit in my 21085 really is WAY too sensitive. In my other locomotives I really have to crank the juice for it to switch sometimes. (or the train will move a foot before it catches). The 21085 can run over a tiny piece of schmutz on the track, and trip. And it trips directly from forward to reverse, with no neutral, which tends to derail cars  Is there a way to adjust this one? I know there's not with the drum type...

Charles.


----------



## flyernut (Oct 31, 2010)

ChopperCharles said:


> The wheels lifting off the track is definitely the problem. Adding some weight or reducing (or eliminating) the number of cars being pulled makes the problem disappear, and I found that if I put the B unit on the tracks without turning the power off, the moment all wheels hit the track the horn sounds briefly. If I nudge the B unit so the wheels come off the track and then come back down, the horn with briefly sound then too. So it's definitely a problem with too many cars, too little weight in the tender.
> 
> However... the reverse unit in my 21085 really is WAY too sensitive. In my other locomotives I really have to crank the juice for it to switch sometimes. (or the train will move a foot before it catches). The 21085 can run over a tiny piece of schmutz on the track, and trip. And it trips directly from forward to reverse, with no neutral, which tends to derail cars  Is there a way to adjust this one? I know there's not with the drum type...
> 
> Charles.


No adjustment, and there's no neutral. That's the way the 5-digit series engines are. I have a 21105 Atlantic, and although the problem isn't as bad as yours, it does the same thing occasionally.And it's the only 5-digit engine I have, no many problems with the reverse units on those.. Just get a 283, same engine, different reverse units.


----------



## gunrunnerjohn (Nov 10, 2010)

You could always rip out the E-Unit and replace it with an electronic one, problem solved.


----------



## ChopperCharles (Jan 3, 2012)

I could, but these are my father's old trains, and I want to keep them as original as possible. Plus, it's really kind of cool to operate trains made nearly 60 years ago. Who owns anything electronic, and still uses it daily, from 60 years ago? By the time I leave these to my kids, they'll be over 100 years old.

Charles.


----------



## NIMT (Jan 6, 2011)

I can't believe that all you seasoned model train buffs have not told ChopperCharles the answer how to fix his reverse unit problem!
What is Reckers and Stillakid on vacation???

OK ChopperCharles here is how to fix it:

_Send that Reverse Unit to Sensitivity Train-ing_!:laugh::laugh::laugh:

Sorry could not resist!:lol_hitting:


----------



## T-Man (May 16, 2008)

It leads me to think you have a bad center roller contact. With only one working you will switch when contact is lost,


----------



## NIMT (Jan 6, 2011)

T-Man said:


> bad center roller


 Wait there's supposed to be a center roller? 

Has your morning coffee not kicked in yet?:laugh::laugh:


----------



## ChopperCharles (Jan 3, 2012)

heh 

Charles.


----------



## gunrunnerjohn (Nov 10, 2010)

The center roller bounces off the ties, it's the sound for those locomotives.


----------



## tjcruiser (Jan 10, 2010)

Center roller?

Huh? 2-rail AF track, right???

In terms of a potential fix for the sensitive e-unit, didn't we have a thread a while back where someone added a capacitor (or something) to the e-unit circuit to prevent premature solenoid drop-down / e-unit toggle ??? (Fuzzy memory here ...)

TJ


----------



## gunrunnerjohn (Nov 10, 2010)

You'd probably have to run the E-Unit on DC to add a capacitor, adding a cap for AC wouldn't do much.


----------



## tjcruiser (Jan 10, 2010)

Bridge rect plus cap? Over my head, but I thought someone tackled this somewhere ...


----------



## gunrunnerjohn (Nov 10, 2010)

Yep, that would be the plan. You can make the cap as large as you like, bigger means more transient protection.


----------



## T-Man (May 16, 2008)

NIMT said:


> Wait there's supposed to be a center roller?
> 
> Has your morning coffee not kicked in yet?:laugh::laugh:


I sensed the bad vibes and returned. I would go with a bad wiper connection in the tender.

I did use a cap trick to light a tender.

It helped but I wonder if it would work for the reverse unit.

l


----------



## ChopperCharles (Jan 3, 2012)

Looks to me like you lit a caboose, not a tender 

Charles.


----------



## NIMT (Jan 6, 2011)

T-Man said:


> I sensed the bad vibes and returned. I would go with a bad wiper connection in the tender.


Just more proof the members on MTF are Human!


----------



## gunrunnerjohn (Nov 10, 2010)

The cap works fine on a reverse unit, but you need the bridge to create DC. Truthfully, sometimes it makes sense to use a single diode to minimize the voltage. Reasoning here is that the DC resistance of the E-unit coil is lower than the AC impedance, so more current will flow (and more heat will be produced). You have to experiment with the slow speed to see if the single diode provides enough power to keep the E-unit engaged at your minimum speeds.


----------



## flyernut (Oct 31, 2010)

Oh, I get it,lol. Time to bash REAL toy trains, ones that run on 2 RAILS!!


----------



## gunrunnerjohn (Nov 10, 2010)

Bashing? I thought we were trying to solve a real issue. However, if that's considered bashing, I'm outta' here. I must have taken a left turn at the wrong door.


----------



## flyernut (Oct 31, 2010)

gunrunnerjohn said:


> Bashing? I thought we were trying to solve a real issue. However, if that's considered bashing, I'm outta' here. I must have taken a left turn at the wrong door.


Hey, I'm only kidding...With the crack about the center roller, I assumed the person was having fun, meaning a third or center rail, so I jumped in and tried to have a little fun.. Sorry...


----------



## NIMT (Jan 6, 2011)

flyernut said:


> Hey, I'm only kidding...With the crack about the center roller, I assumed the person was having fun, meaning a third or center rail, so I jumped in and tried to have a little fun.. Sorry...


TWO RAIL RULES!
Now we just gotta fix your AC problem!


----------



## ChopperCharles (Jan 3, 2012)

I don't have an ac problem. I LIKE ac


----------



## ChopperCharles (Jan 3, 2012)

Well, the problem was the tender having no weight in it. I wrapped a cam chain from a CX500 in plastic and tossed it in the tender, along with a regular tender weight... probably 6 pounds in the tender now. It rarely misses a beat now, but will occasionally trip the reverse unit on the same piece of (brand new straight) track that causes my lighted caboose to flicker. No idea why that happens, but it's a rare, occurrence now so I'm not going to worry too much. Weight is your friend.

Charles.


----------

