Stopping train without E unit reversing?

First when you say “legacy” and “Marx” in the same sentence, I take that to mean older conventional running trains, not Lionel’s LEGACY system. I don’t have an answer for you other than this is part of the reason we have command control systems like TMCC, LEGACY, DCC, and DCS. I think there are too many variables to try and design a circuit to do this reliably, especially without some software smarts doing some of the work.

The E-unit in older toy trains is basically a electromagnetic coil that holds the position until the voltage drops enough to let it move. Then a spring moves it to the next position. The problem is, the exact voltage that engages the coil vs. the voltage that makes the motor move are variable from locomotive to locomotive. The reason is the exact resistance of the coils are always slightly different, and track and pickup roller conditions affect this too.

A mechanical solution could be in order though. One that is between the rails, like a ramp that just lifts the locomotive enough that it loses traction. The E-unit should stay engaged as long as the center roller stays in contact with the center rail and there is a path to ground through either the tender or leading/trailing trucks. Much harder to do with diesels I’m afraid.

A simple way is a reed switch in the locomotive triggered by a trackside electromagnet that just interrupts power to the motor.  The E-Unit still having power will retain it's setting.  When you de-energize the magnet, the motor runs again.

Half joking - convert to DC. Direction is then determined by polarity. But I think what will happen is various coils will start over heating. I can't remember how to make a series wound motor change direction based upon polarity but pretty sure it involves diodes. Then for unmodified pre-war and post-war engines can run on DC, but the E-unit will get warmer; the coil in the E-unit was optimized for 60Hz, not zero. So, you can start with certain engines, then can still run un-modifed for a short period of time.

If you use a bridge to make sure the armature or the field get a constant polarity, direction will be determined by the track polarity.

In my sample of one, I was able to get this to work as requested on a single Pullmor motor diesel with a 2 position e-unit by maintaining a constant 3.5VAC on the track.  Granted as @rplst8 points out, this may not work for every engine you may have, but it may be possible that the hold voltage could be adjusted for each, maybe.  AFIK, it should also work for a 3 position mechanical e-unit.

My test set up is as follows:

PW ZW C output set to ~14 volts fed through a Normally closed momentary push button switch (for intentional direction control) then through a 12.5 Ohm resistor array (4x 50 Ohm 100W wire wound resistors wired in parallel).  This gave a measured 3.5 volt constant voltage on the tracks.  Note: at this voltage the 14V incandescent bulb in the engine is dimly lit and the motor and e-unit hum noticeably.

PW ZW D output provides stop/start and speed control from slow to fast.

Voltages measured on the track:

• 3.5 when stopped
• 6.1 starting slowly
• 18.5 full speed

Was there a solution to this in one of those Lionel Bantam books? Something where it "leaked" power to the center rail while stoping the train to prevent the e-unit from cycling?

Sample two.  Using a low end Lionel 1990's vintage dual can motor electronic e-unit locomotive, I was able to get essentially the same results.  With this locomotive's overall higher impedance I did have to lower the ZW's C output to around 8 volts to maintain about 3.5 volts on the track with the D output turned off.

@BobbyD posted:

Was there a solution to this in one of those Lionel Bantam books? Something where it "leaked" power to the center rail while stoping the train to prevent the e-unit from cycling?

That's what my experiments did.  With a constant 3.5 Volts, the two e-units I tested remain the in same direction.

My thinking with the positive switching is having a more certain stop where you want it, I'm assuming this is for something like station stops?

@SteveH posted:

In my sample of one, I was able to get this to work as requested on a single Pullmor motor diesel with a 2 position e-unit by maintaining a constant 3.5VAC on the track.  Granted as @rplst8 points out, this may not work for every engine you may have, but it may be possible that the hold voltage could be adjusted for each, maybe.  AFIK, it should also work for a 3 position mechanical e-unit.

My test set up is as follows:

PW ZW C output set to ~14 volts fed through a Normally closed momentary push button switch (for intentional direction control) then through a 12.5 Ohm resistor array (4x 50 Ohm 100W wire wound resistors wired in parallel).  This gave a measured 3.5 volt constant voltage on the tracks.  Note: at this voltage the 14V incandescent bulb in the engine is dimly lit and the motor and e-unit hum noticeably.

PW ZW D output provides stop/start and speed control from slow to fast.

Voltages measured on the track:

• 3.5 when stopped
• 6.1 starting slowly
• 18.5 full speed

Perfect, exactly what I was asking for (or at least providing usable building blocks to help me arrive at an answer)!

After posting, I did a few more calculations, based upon some other random information I'd collected from other projects. First, it was my recollection that legacy E-10 base bulbs drew about 1/10th amp, and had a resistance of roughly 150-200 ohms. Thus, my unsuccessful experiment with two parallel bulbs would have added roughly 75 to 100 ohms to the circuit, so I needed to go below that threshold to avoid triggering the E unit. A few minutes' search on Amazon, and I discovered relatively high-power rheostats in the right range for around $20, but then found a ten-pack of ceramic resistors (10 ohms and 10 watts each) for about $8, delivered by Monday! I figured the ten-pack would suffice to build a cheap man's power rheostat by chaining them together as needed (10-20-30 ohms, etc., even fine-tuning by putting a couple in parallel in the chain, if needed) to find that elusive sweet spot. Your real-world results should enable me to rapidly target the voltage I'll need.

And yes, "legacy Marx" is completely redundant, since there's been no other kind of Marx equipment since they went out of business, but I wanted to emphasize the "old school" nature of my quest, and yes, there are many potential ways to control direction, but I need one that did not involve modifications to the engine and which can be remotely controlled by an electrical relay, like old-time electro-mechanical block control systems (e.g. https://youtu.be/2L6wg7gx_zo). The reason is that I'm trying to replicate or improve on the clever block control simulation Marx created in their "Twin Train" set. Here's what that looked like in action:

<iframe width="560" height="315" src="https://www.youtube.com/embed/crHm2elsEjU" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>

@Steve Tyler posted:

Here's what that looked like in action:

Whoops, sorry -- here's the link: https://youtu.be/crHm2elsEjU

@gunrunnerjohn posted:

My thinking with the positive switching is having a more certain stop where you want it, I'm assuming this is for something like station stops?

My immediate objective, as detailed in another reply, is to replicate/improve on the block control simulation Marx built into the signal control "brains" of their now rare (and expensive!) "Twin Train" sets, and their earlier 1405 block control system. But yes, if I can crack this nut, I fully intend to explore using the potential for other ways to emulate prototype functioning (I'm looking at you, trolley loop!). As a 'legacy' guy (in years *and* model train preferences!), I delight in finding simple, electro-mechanical solutions that don't necessarily involve microprocessors, computers or smartphones -- not a Luddite, really, I just enjoy the challenge! It's a bonus to me when I can used recycled or repurposed materials in the process -- go ahead, ask me what you can do with discarded chains of small incandescent Christmas lights!

@illinoiscentral posted:

I can't remember how to make a series wound motor change direction based upon polarity but pretty sure it involves diodes.

If you already have DC, no diodes needed … as long as you bypass the E-unit. Motors that use an electromagnetic field are called “universal motors.”

https://en.wikipedia.org/wiki/Universal_motor

@BobbyD posted:

Was there a solution to this in one of those Lionel Bantam books? Something where it "leaked" power to the center rail while stoping the train to prevent the e-unit from cycling?

Yes.  Indeed.  This is from "How to Operate Lionel Trains and Accessories" (1954), p. 31:

The guide itself can be found at:

     How to Operate Lionel Trains and Accessories (1954)

or on the same page of the 1956-57 version, which can be found here:

     Lionel 1956 Instructions- searchable } Quietman

Mike

@Mellow Hudson Mike posted:

Yes.  Indeed.  This is from "How to Operate Lionel Trains and Accessories" (1954), p. 31:

The guide itself can be found at:

     How to Operate Lionel Trains and Accessories (1954)

or on the same page of the 1956-57 version, which can be found here:

     Lionel 1956 Instructions- searchable } Quietman

Mike

Interesting, Mike, and very much aligned with the results of both JohnH's experiments, and my musings! It's interesting that the "10 ohm, 10 watt adjustable resistor" recommended is exactly the value I ended up with for my fixed-value resistors -- looks like I may have to use two or three resistors in parallel (for 5 or 3-1/3 ohms, respectively) or some cascading combination if I need to go below 10 ohms, but I'm hoping just one will be close enough to hit that sweet spot. It's also interesting that they warn the control block needs to be somewhat longer, presumably because the engine will slow before stopping and thus need more room to come to a complete halt within the block, which is an effect I'd already anticipated as a later track design factor. Stay tuned . . .

Steve,

We'll be standing by.

Good luck.

Mike

@Mellow Hudson Mike posted:

Steve,

We'll be standing by.

Good luck.

Mike

Actually, a couple more data points I've recalled since posting: first, the OEM Marx "Twin Train" had a rheostat built in to adjust the power running to the track section just before the control block, to slow (but not stop) any train approaching the back of the halted train ahead; and second, an excerpt from a '50's boy's how-to book was posted in a prior discussion, and among the articles was a suggestion that you could automatically limit the speed of a model train approaching a curve by -- you guessed it -- adding an adjustable resistor in series with that section, after isolating that track section (rinse and repeat for each problematic curve). So again, there's apparently nothing new under the sun, merely the need to get your SPF level right . . .

@rplst8 posted:

If you already have DC, no diodes needed … as long as you bypass the E-unit. Motors that use an electromagnetic field are called “universal motors.”

https://en.wikipedia.org/wiki/Universal_motor

Guess again.  The motor will run in the same direction for either track polarity, try it.  To reverse a universal motor you have to change the phase relationship between the field windings and the rotor windings.

If you use a bridge on the field, that will maintain the field polarity while the armature polarity changes.

My conventional controlled layout has had two loops equipped with 5 ohm 25 watt variable resistors to keep the eUnits from tripping when operating two trains on each loop for 44 years.  It works great.

Both the inside and outside loop were wired for two trains to operate on each loop, by using 12 vac relay and 5 ohm 25 watt variable resistor for each loop.  Each loop already had a section of 4 or 5 track sections at each end of the both loops.  A train sensing track was make by modifying a section of track to have one outside rail insulated from the metal ties with electrical tape and a insulated plastic pins were installed in each end of the insulated section and a wire was soldered to each insulated rail track of the section.  This insulated track was installed on bottom straight part of each loop to act as the switch to trigger the 12 vac relay to cut the selected isolated track section to have a reduced voltage do to the 5 ohm resistor being in that circuit.  This will make the behind train, that is over taking the train on the insulated track section, causing it to stop but still have voltage to not let the e-unit cycle.  When the front train passed the insulated track section, full voltage is applied to the rear train and it resumes running.

Below:  5 ohm, 25 watt variable Resistors for two train per loop operation to keep e-units from cycling when idled by the relay.

Two loops of 2 trains on 1 track and the Operating Car train on New train board

Charlie

@gunrunnerjohn posted:

Guess again.  The motor will run in the same direction for either track polarity, try it.  To reverse a universal motor you have to change the phase relationship between the field windings and the rotor windings.

If you use a bridge on the field, that will maintain the field polarity while the armature polarity changes.

Ah, makes sense. I read it wrong thinking illinoiscentral was just talking about making it work at all on DC.

Since most universal motors that run on DC have a switch to reverse directions I ASSumed it was the same as an HO transformer ...  I never realized there was more going on inside.

What am I missing in this dissusion?

Just get the engines moving forward and flip the lever to disconnect the e unit. The engine will allways run forward after a interuption of power.

Paul,

Nothing ...

Except that the whole thread has been about maintaining forward direction without using the lever.

(This is most likely because the OP wants to be able to back the train up at some point by cycling the e-unit, just not every time.)

Mike

@choochoopaul posted:

What am I missing in this dissusion?

Just get the engines moving forward and flip the lever to disconnect the e unit. The engine will allways run forward after a interuption of power.

Uhh . . . because most engines don't *have* a "lever" to throw?

*None* of my legacy Marx or Lionel engines has one, for instance. I've heard that some engines came with such a feature, but I've never seen one personally.

Steve

For engines for post war and conventional control:

Engines with the two way eUnits, like some Lionel and most Marx, the cycle is F R F R etc.  Most two way eUnit motors do not have eUnit lock out switches including Marx engines.

Engines with the three way eUnits, used on most better Lionels, the cycle is F N R N F R etc.

The point being an interruption of the current to the eUnit will make it cycle as like a step relay.

Charlie

@Choo Choo Charlie posted:

My conventional controlled layout has had two loops equipped with 5 ohm 25 watt variable resistors to keep the eUnits from tripping when operating two trains on each loop for 44 years.  It works great.

Ding, ding, ding, we have a winner!

OMG, Choo Choo Charlie, you've just confirmed that I'm some 44 years late to the party!

To be fair, the 'truck' I've been metaphorically chasing (the Marx "Twin Train" set functionality) has been rolling along for nearly twice that long (the basic low-tech approach was also in Marx's pre-war 1405 signal block system), but you've confirmed both that the solution I sought was in fact a simple one, and that with the help of others, I was well down the same path you'd traveled so long ago. Just curious: where did you get the idea for the design of your system?

Technically, I've been pursuing a slightly different goal, since the "Twin Train" set incorporated a figure-8 configuration with a crossover (similar topographically to my layout's embedded double-loop figure-8), and in fact apparently used a sort of "bump and run" form of control (the train approaching the stopped train from behind would trigger the 'release' of the leading train from the de-powered control section, rather than a true forward-looking block control system like yours) that *requires* both trains running to operate at all (by all indications I've seen, running only one train on the "Twin Train" set would cause that train to stop in the control block, and with no following train to release it forward, it would just sit there). However, it always was my eventual goal to translate the "Twin Train"-type control into something more accurately representing a true block control system like yours, usable with multiple trains on each loop and potentially more closely mirroring early electro-mechanical prototype block control systems. Thanks for the confirmation I was on the right trail, though a bit late to the chase!

Steve

I am glad some of my comments helped you.  I got the idea of operating two trains on one track from the book below.

“Operating O and O27 Trains”   by Maury D. Klien and Bruce C. Greenberg , 1976, 242 pages.  This is a "must have book" and my main, best layout building book.  It has track plans, details on homemaking turntable, round house, coal mine, and sand station and details how to wire a layout to run two trains on one track loop.  Ironically it was published one year before I built most of my layout in 1977.

It also lead be to block every section of track on the layout except the 33 Marx switches.  Most blocks are 5  to 10 track sections long , allowing parking trains anywhere on the layout.  It was then simple to add a track section, with isolated outside rail on one rail to act as a switch ahead of the blocked section, to operate the two relays that control one of the blocks, with the wire going to that section to have the 5 ohm, 100 watt resistor in it, to not let the eUnits cycle.  In fact, each loop has one isolated track section and two blocked sections, one on each ends of the isolated track section after 5 or 6 sections of track normally blocked, so the 2 trains on 1 track can operate in CW or CCW directions.

Control panel with switches for 2 trains on 1 track are below labeled Relays is used to activate the 2 train on one track system and IN and Out switches select the direction of train travel.

More details are on OGR links below including how I built the whole layout:

https://ogrforum.com/...68#60417098708129468

The next link leads to Page 1 of my write up on how I built my layout, including a $5 homemade turntable and table of content is at the end of Page 1.

https://ogrforum.com/...ra-027-layout?page=1

Charlie

The Greenberg book by Peter Riddle, Wiring Your Lionel Layout, Intermediate Techniques has a discussion of this on page 35. Its a great book with lots of information on two train control, operating accessories from control rails and etc. Might be worth your looking for a copy as you are trying to operate "old school" and the book is filled with information like that.

@Steve Tyler posted:

Ding, ding, ding, we have a winner!

...

As a footnote, back in the day before semiconductors became cheap and ubiquitous, variable high-power resistors (25 Watts, 50 Watts, etc.) were the only game in town for the application at hand.  Today though, the diode-dropping method might be a candidate.  Discussed in various OGR threads this method uses the relatively fixed voltage drop of a diode to reduce AC voltage.  That is, a resistor drops voltage proportional to the current.  Of course that's the purpose of the "variable" in variable resistor - to fine tune the voltage drop.

Above photo hijacked from another OGR thread about the voltage dropping method.  If patient, old-school high-power variable resistors can be found for a song at a train swap meet or eBay, but if those are not options then using bridge-rectifiers to drop AC voltage can save some serious coin.

I realize this discussion is about conventional control, but there is a related application where you want a COMMAND engine to stop but not shutdown.  In this case you want to drop track voltage to the point (i.e., to the voltage) where the electronics stays "on" but the motor does not spin.  Using a variable resistor with its proportional voltage drop can be tricky since the voltage drop depends on, say, whether smoke is turned on or off.  The diode-dropping method provides a relatively constant voltage drop independent of load.

@Choo Choo Charlie posted:

Steve

I am glad some of my comments helped you.  I got the idea of operating two trains on one track from the book below.

Thanks for the recommendation, Charlie! I found an inexpensive used copy of the book you mentioned, which (except for the reference to the "Big L" in the title instead of Marx!) is exactly the type of source material I was looking for, and I look forward to rummaging through it for more "old school" projects for my layout.

Speaking of layouts, that's quite a layout you've built over the years -- I look forward to perusing your construction details after I can clear the clutter from my own labors!

And speaking of labors, my project is continuing to move forward. I dug out some more old track, and extended the basic figure-8 test bed to closer resemble the elongated figure-8 used in the Marx "Twin Train" setup. I also visited the local hobby shop to pick up a pack of insulating pins (I know I have most of the remainder of a pack somewhere, but haven't been able to find them, and hey, they're cheap, right? ), and while I was there I found and negotiated a cash deal on two legacy signal lights: a Lionel 151 with a broken semaphore arm, and a rusty Marx 454 with a defunct switch. Somewhat to my surprise, the 151 actually functioned, after a shot of lubricant (I'll just need to fabricate a replacement semaphore arm), but I decided the best plan for the 454 was removal of the switch and a rewire so I can light each bulb separately from the relay, and a quick rattle-can coat of flat black. I plan to drive both signal lights from the relays I got the other day. Oh, and the power resistors arrived, so I can start experimenting, designing and bread-boarding my prototype legacy block control system. It's even odds as to whether I can get it to work before the book I ordered at your recommendation arrives!

Again, thanks for the confirmation that what I was seeking was indeed possible within the constraints I'd set for the project.

@stan2004 posted:

As a footnote, back in the day before semiconductors became cheap and ubiquitous, variable high-power resistors (25 Watts, 50 Watts, etc.) were the only game in town for the application at hand.  Today though, the diode-dropping method might be a candidate.

Thanks for the info, Stan. As you note, I *am* looking for an old-school solution in this case (and think I'm on the trail of one, thanks to Charlie and others!), but I'm not adverse to using more modern technology when appropriate or necessary, and I appreciate the annotation for the benefit of others who might be inspired to attempt a version with updated materials and methods!

Steve

Another very good source of post war Lionel train wiring with an isolate track section as the trigger and ways to keep the eUnit from tripping is below:

"How to Operate Lionel Trains and Accessories for 027, O and Super O" published by the Lionel Corporation in 1965.  It must have been available on line for free as I have a home copied edition.  Ebay also has some copies for sale.  It is about 31 pages and is a summary of installing Lionel track and accessories and maintaining Lionel trains.

Some of the track plans use a Lionel 153C contactor in place of a relay.  It even shows how to make an insulated track section to use as the trigger like I did.

I also have the book Scottie recommended above, Riddles book "Greenberg's Wiring Your Lionel Layout".  On pages 45 and 46 they describe, "Automatic Two-Train Operation" using the Lionel 153C contactor.

None of these sources describe my exact system but they should help.

Charlie

@Choo Choo Charlie posted:

Steve

Another very good source of post war Lionel train wiring with an isolate track section as the trigger and ways to keep the eUnit from tripping is below:

"How to Operate Lionel Trains and Accessories for 027, O and Super O" published by the Lionel Corporation in 1965.  It must have been available on line for free as I have a home copied edition.  Ebay also has some copies for sale.  It is about 40 pages and is a summary of installing Lionel track and accessories and maintaining Lionel trains.

Some of the track plans use a Lionel 153C contactor in place of a relay.  It even shows how to make an insulated track section to use as the trigger like I did.

I also have the book Scottie recommended above, Riddles book "Greenberg's Wiring Your Lionel Layout".  On pages 45 and 46 they describe, "Automatic Two-Train Operation" using the Lionel 153C contactor.

None of these sources describe my exact system but they should help.

Charlie

Indeed they did, Charlie! I was easily able to locate the Lionel publication you referenced, and I've attached the copy I downloaded. You're absolutely right -- exactly the kind of electro-mechanical block control I've been seeking is described in detail, even down to dealing with the E-unit reversing issue!

Speaking of which, a bit more progress: after entirely too much fiddling with the innards of the signal sets I just bought, I turned back to the test track, and the attempt to find the correct resistor value to keep the E unit from cycling when the engine is stopped. As it happens, just one 10 ohm, 10 watt ceramic resistor in series with the power feed was perfect to stop my Marx 666 smoker almost immediately, and then allow it to resume moving without reversing direction. The resistor got a bit warm in operation, but not dangerously so -- the worst warming occurred when the train briefly shorted out. A bit of back of the envelope calculations indicate a dead short of track voltage across one of those resistors *could* easily exceed its wattage rating (check my math: 15 volts across a 10 ohm load should draw an amp and a half, and an amp and a half at 15 volts would be 22 and a half watts, right?) if left for an extended period (Note: I have an external 5 amp circuit breaker on each throttle circuit on my layout, but I don't think one would trip at the roughly amp and a half the resistor would draw even if there was a dead short), so I may end up installing four of them (two parallel pairs in series) which will quadruple the wattage at the same resistance. Or, I may just use (and risk burning out) a single resistor, and locate it somewhere it won't set anything on fire!

@Steve Tyler posted:

Uhh . . . because most engines don't *have* a "lever" to throw?

*None* of my legacy Marx or Lionel engines has one, for instance. I've heard that some engines came with such a feature, but I've never seen one personally.

I'm pretty sure nearly every Lionel engine I have from 1948 to 1991 has a "lever" to lock out the e-unit.  Most every engine i've seen in that time period had a lever unless they had an electronic e-unit.

Back in the day and I mean way back I wired the e unit to the horn relay. That way the e unit only activated when you blew the horn.  Engine ran quieter as well because the e unit was silent..

@aussteve posted:

I'm pretty sure nearly every Lionel engine I have from 1948 to 1991 has a "lever" to lock out the e-unit.  Most every engine i've seen in that time period had a lever unless they had an electronic e-unit.

Well, I'm happy to concede the point, since at this point I have only one "Big L" engine which AFAIK doesn't have such a lever (at least, not one I've noticed or verified -- and come to think of it, I believe that engine runs on DC and thus may not *need* an E unit!), and I *do* know none of my small fleet of legacy Marx engines (333, 666, 999, 1095,1666, 1829, 6000, etc.) has one. If you *do* have one on each of your engines, great, no problem, just lock out the E unit and go, but even Lionel added an "avoiding triggering the E unit" design option in their publication, discussed above, so at least when it was published (about 1965?), E unit reversal was still a live issue, even for those running Lionel gear.

Gilbert American Flyer made a Lock Out Eliminator for accessories that stopped the train but let just enough current flow so the E Unit would stay in reverse. I imagine you can find them in ebay and I believe the Greenberg manuel had instructions on how to make one which was simple. I remember making one from Radio Shack parts which was i think was only a resistor.

@Gene H posted:

Gilbert American Flyer made a Lock Out Eliminator for accessories that stopped the train but let just enough current flow so the E Unit would stay in reverse. I imagine you can find them in ebay and I believe the Greenberg manuel had instructions on how to make one which was simple. I remember making one from Radio Shack parts which was i think was only a resistor.

Dunno about the AF gear, but yes, so far all the various solutions I've found or heard about from others to prevent an active E unit from cycling when a legacy engine is halted involve adding some form of resistor in series with the power feed while the power remains on, keeping just enough current flowing to prevent the E unit from activating when the engine stops.

Side thought: I don't believe I've ever heard why they call it an "E unit" -- anyone know where the term came from?

@Steve Tyler posted:

Dunno about the AF gear, but yes, so far all the various solutions I've found or heard about from others to prevent an active E unit from cycling when a legacy engine is halted involve adding some form of resistor in series with the power feed while the power remains on, keeping just enough current flowing to prevent the E unit from activating when the engine stops.

Side thought: I don't believe I've ever heard why they call it an "E unit" -- anyone know where the term came from?

It was about the size of a accessory button and you only had to connect it to the center rail.