I probably am reinventing the wheel for the millionth time, but I just had to try to figure this out on my own. I may be way off, and maybe at least I will give some forum members a good laugh on me!!! I lifted the pic from @ADCX Rob post in a different thread, and replicated/edited to make the attached pic.

I have watched the "I Love Toy Trains" show on the RFD channel many times. One episode had an operator that said he operated his Lionel postwar engines with DC (in usual three rail power distribution of one polarity to center rail, and other polarity to outside rail). He said he converted the engine by removing the e unit and adding a bridge rectifier, and this allowed him to control direction by the polarities he supplied to the rails (ex, DC plus to center rail, DC ground to outer rail, go forward - DC ground to center rail, DC plus to outer rail, you go forward).

I decided I had to try and figure out what he did, as he never showed a schematic. So the pic I have attached depicts, on the upper left side, how the AC power goes from roller to ground for one direction, and lower left side, how the AC power goes from roller to ground for the opposite direction. I noticed that in either direction, the current going through the field coil is the same for both directions, ie. when the AC is at plus max voltage, the current in the field coil is always going "down" regardless of the direction of the loco.

So on the right side of the pic is my schematic converting the loco to DC power/direction control. The bridge rectifier always keeps the current in the field coil going in the same direction irregardless of the polarity of the DC being applied to the motor.

#### Attachments

Images (1)
Original Post

Close! Here is the diagram for DC on the track direction control.

Other than being unique is there any value in doing this?

Thanks @ADCX Rob - in my mind I did erase the segment you did to correct my DC schematic, I just overlooked doing it. I am just glad I was able to figure it out.

@necrails Per the guy on the show, as I remember his comments, you eliminate having to deal with some unreliable characteristics of the mechanical e units (in his opinion), eliminates the buzz of the e units, and the motors run cooler and perform better.

The downside for me is that you lose the neutral position often necessary for operating cars on the UCS/RCS track sections.

@MED posted:

The downside for me is that you lose the neutral position often necessary for operating cars on the UCS/RCS track sections.

Wire UCS/RCS sections to operate on auxiliary power and the problem is solved.

Many years ago I built a heavy-duty [DC output] "Transistor" throttle with a walk-around control. I then wired a bridge rectifier as shown in Rob's schematic in a Pullmor-motor engine. It worked beautifully for switching operation because reversing was accomplished with a direction switch on the walk-around.

I use DCS but if someday all five of my extant PS3 boards have let out the pretty blue smoke and GRG can no longer find the bits with which to repair them I will build a DC walk-around throttle and keep railroading. Since MTH engines all have DC ["can"] motors I won't even need a bridge rectifier.

Any CONVENTIONAL O three-rail Pike can be easily converted to DC power by installing a bridge rectifier (and DPDT direction switch) on the AC Transformer output and a bridge rectifier (as per Rob's schematic) in each Pullmor (universal motor) locomotive.

Ok you have my attention.  Now I have a further question, if I were to convert my open frame conventional locos to DC as described with a bridge rectifier and my TMCC locomotives operate fine with an AC transformer why convert the track power to DC?

I have very few locomotives left with a mechanical E unit but now that I think about it eliminating that buzz is worth the effort.

@necrails the circuit I was try to "re-invent" is based on the polarity of DC applied to the tracks to control the direction of the engine. Example: + DC to center rail, DC ground to outer rails, engine goes forward --- then reversing polarity so DC ground  to center rail, +DC to outer rail, engine goes in reverse.

This is what the guy on the "I Love Toy Trains" show said he did, and I was trying to create the circuit as an engineering exercise.

This circuit arrangement comes up for discussion about five time each year. To obtain direction control of a universal motor via track DC polarity, the time tested bridge rectifier circuit described in this thread is the answer. One benefit to this alteration is that universal motor based locos run very smoothly on DC.  There is another circuit method, but it's not near as nice.

Connecting the DC outputs of the bridge to the brushes works equally well as the alternate circuit arrangement. The other circuit I used very early on used a DPDT relay triggered by negative DC  track voltage to reverse the motor connections.  A low voltage relay (5V) protected by a -5V fixed regulator chip worked fine.  The bridge circuit is simpler.

@BOB WALKER posted:

The other circuit I used very early on used a DPDT relay triggered by negative DC  track voltage to reverse the motor connections.  A low voltage relay (5V) protected by a -5V fixed regulator chip worked fine.  The bridge circuit is simpler.

This method is better! Without the rectifier in the circuit the motor will have much more power... I've tried it both ways.

The value in doing this for my friend is two-fold.    First he has no digital control system now - is just building his layout.    He says he says 40-50 older locos that he wants to run.     Locally our group is all DCC with one other 3 rail layout using DCC.   All others 2 rail HO and my O.     So the local control systems he deals with are all DCC and he likes what he is using.    And he could get lots of help and advice with DCC but none if he got into one of the other systems.

The second big reason is with all these locos, he doesn't want to remotor them, but he wants to run them on a Digital control system.     So he is thinking if he can just install DCC decoders with some other circuitry, it would be cost effective and give him very nice control.    And could even get decoders or receivers for the various Lionel and MTH systems were he to chose one?

@prrjim posted:

The value in doing this for my friend is two-fold.    First he has no digital control system now - is just building his layout.    He says he says 40-50 older locos that he wants to run.     Locally our group is all DCC with one other 3 rail layout using DCC.   All others 2 rail HO and my O.     So the local control systems he deals with are all DCC and he likes what he is using.    And he could get lots of help and advice with DCC but none if he got into one of the other systems.

The second big reason is with all these locos, he doesn't want to remotor them, but he wants to run them on a Digital control system.     So he is thinking if he can just install DCC decoders with some other circuitry, it would be cost effective and give him very nice control.    And could even get decoders or receivers for the various Lionel and MTH systems were he to chose one?

Well the first is, are others locally doing this exact scenario (postwar style high amperage pulmor AC motors) on that track and thus DCC infrastructure? Example- what boosters or track power supply do they have?

We loosely examined one side of the equation- the loco and the decoder, but you also then have to worry about multiple power hungry locos and the infrastructure (wiring, power sources, DCC boosters) to power all that.

Others are running 3 rail DCC.    I don't think anyone else is converting PW locos.    but that is not any different than old MG brass with series wound motors.

Also some of us are doing 2 rail DCC with older stuff that draws more than 2 amps.

So the answer is no and  yes.    No one I know is doing the exact same scenario, but some of  us are doing similar things.    And the entire round robin group uses DCC so there are "experts" for each of the control systems to help with install and answer questions.     My experience was that it took me about a month to understand how things were working.   It was great to h ave some people to ask when I had questions.

DCC is not any harder than any other system to get set up.    The complexity comes when you are installing on a large layour focused on operations.   If you are running simpler loops of track, it is basically 2 wires to the track plus jumpers like old Lionel AC.

One way to try this is simply power the track with DC and see how much current they draw. You could use any transformer with a full wave bridge (preferably rated for at least ten amps)  between it and the track along with an ammeter.

Then look for DCC supplies and decoders that can handle at least that much current.

Pete

@necrails posted:

I have very few locomotives left with a mechanical E unit but now that I think about it eliminating that buzz is worth the effort.

Can't you just install electronic E units to replace the mechanical ones, to eliminate the buzz? If that's your goal, it seems much simpler.

@breezinup posted:

Can't you just install electronic E units to replace the mechanical ones, to eliminate the buzz? If that's your goal, it seems much simpler.

Eventually all mine will get an ac commander.  Just responding to the OP.

Wow this is an old thread.  Jim, please see my reply on your other thread.  There might be a few DCC receivers that were made in the '90s for Marklin trains that output AC.  But most DCC decoders used in G scale, 2-rail O, etc., are designed to operate DC motors, and reverse them by reversing polarity to the motor.  So yes, along with installing a decoder, you would probably have to install a rectifier to make the old Lionel motor "look like" a DC motor.

Did you mention the D408SR decoder?  What do the specs in its manual say?  Is it equipped from the factory to drive a "Universal" motor with a separately wound field?

Post  War motors are Universal motors. They will run on either AC or DC. If you apply power through the E unit it will reverse just by reducing voltage using the decoder just as it does using track power.
Best leave the motor in its series wired configuration. If you try to make it more like a parallel wired DC motor with fixed DC across the field and polarity reversal across the armature, your current draw will double.

Pete

@Norton posted:

If you try to make it more like a parallel wired DC motor with fixed DC across the field and polarity reversal across the armature, your current draw will double.

Only if the field is parallel wired... this keeps it series wired:

Only if the field is parallel wired... this keeps it series wired:

My reply had to do with driving the motor with a DCC decoder, not using DC on the rails.

Pete

Pete we're not disagreeing with you.  No one is recommending connecting the armature and field in parallel (shunt.)  Rob's schematic fixes the direction of current through the field, so the rotation of the motor can be reversed simply by changing polarity to the brushes.  To the decoder it "looks like" a can motor!

@Norton posted:

My reply had to do with driving the motor with a DCC decoder, not using DC on the rails.

OK, fixed.

I was pondering if it was possible to run the pictured motor off a dcc decoder and searching these forums hoping to find answers, when I came across this thread. Great infomation here. However in my limited experience installing dcc they typically (if I remember correctly) require the motor to be isolated from the locomotive frame and/or frame ground. So a question for you more experienced modellers, would that alone make this idea a no go?

Thanks

Bobby

#### Attachments

Images (1)
@BobbyDing posted:

Great infomation here. However in my limited experience installing dcc they typically (if I remember correctly) require the motor to be isolated from the locomotive frame and/or frame ground. So a question for you more experienced modellers, would that alone make this idea a no go?

Well, it must be floated if that's what you're asking. Neither pole of the motor can be at frame ground.  We haven't even gotten into the issue the current demands of the Pulmore motor.  If you really want to go with DCC, I strongly recommend a motor transplant for a DC can motor.

Thank John, I have sent a couple emails with photos to Timko inquiring about the cost of upgrading to a can motor, but have gotten no responce (been a few days). I'll try calling tomorrow.

This thread posted an interesting challenge, using a DCC decoder to drive a universal motor. I am going to try out using the Blunami4408 DCC decoder which has a 4A motor current capability to drive a universal motor using the time tested AC/DC bridge based conversion circuit.

Bob, I look forward to your results.

Bobby

@BobbyDing the requirement to isolate both sides of the field from chassis ground does NOT make the conversion a no-go.  Sometimes it's inconvenient to access one end of the field winding, but it can be done, and Lionel DCC conversions have been done before.  At least a handful of postwar locos, including the 1656 0-4-0 switcher didn't have its field connected to ground from the factory.

I'm pretty sure that 4A will be enough motor current capacity for normal use.  I wouldn't use the decoder to control smoke, lights, etc., just the motor.  If it's a metal loco with rubber tires, that complicates things because attempting to pull a heavy train, the motor may draw more than four amps before the wheels slip.

You might also need to install shunted brushes with capacitors as Lionel did in many of their AC-motored TMCC  and Legacy locos.  Sparking at the commutator (and the pickup rollers, etc.) creates electrical noise.  This could interfere with the DCC signal, and a local snubber network would help minimize that.  I believe that robust tolerance of electrical noise in existing AC layout environments was the main reason that Neil Young and others went in their own direction with TMCC with its track signal "halo," etc., instead of adopting the open-source DCC, which had already been around for a couple of years when TMCC hit the market.

If you choose to do a DC motor "transplant," that simplifies a lot of things.  But the way most postwar Lionels are geared, they benefit from a motor that has very high starting torque.  A couple of folks on this Forum expressed disappointment with the performance of their 736 Berkshires after installing the Timko motor.  Diesels seemed to fare better.  The root of the problem is the gear ratio, it's just too fast.

No matter what you decide, you and your friend should temper your expectations.  Even if you get DCC in there, don't expect a 75-year old toy to run like a purpose-built scale model.*  A RailKing steamer has the "look" of a postwar toy train, but some of them have much better gear ratios, and if it has Proto-3, DCC is already built-in.  My \$.02.

*Edit: the 773 Hudson, prewar 0-6-0 switcher, dual-motored F3 might be capable of near-scale performance.

Last edited by Ted S
@BOB WALKER posted:

This thread posted an interesting challenge, using a DCC decoder to drive a universal motor. I am going to try out using the Blunami4408 DCC decoder which has a 4A motor current capability to drive a universal motor using the time tested AC/DC bridge based conversion circuit.

Bob, I seem to remember a youtube video, from a couple of years ago, where someone was powering a postwar O-27 loco with a BlueRail board.  Was that you ?          j

Last edited by JohnActon

Spoke with Frank Timko today. I'm purchasing a dc can motor/flywheel for it. He said he only had the one type of motor for it. I don't think it's a Pittman. Whatever it is I'm sure it will be up to the job. Now on to the smoke unit!

Bobby

Note for future Timko buyers: My emails never got to him. However he answered the phone immediately when I called.

Last edited by BobbyDing
@Ted S posted:

@BobbyDing the requirement to isolate both sides of the field from chassis ground does NOT make the conversion a no-go.  Sometimes it's inconvenient to access one end of the field winding, but it can be done, and Lionel DCC conversions have been done before.  At least a handful of postwar locos, including the 1656 0-4-0 switcher didn't have its field connected to ground from the factory.

I'm pretty sure that 4A will be enough motor current capacity for normal use.  I wouldn't use the decoder to control smoke, lights, etc., just the motor.  If it's a metal loco with rubber tires, that complicates things because attempting to pull a heavy train, the motor may draw more than four amps before the wheels slip.

You might also need to install shunted brushes with capacitors as Lionel did in many of their AC-motored TMCC  and Legacy locos.  Sparking at the commutator (and the pickup rollers, etc.) creates electrical noise.  This could interfere with the DCC signal, and a local snubber network would help minimize that.  I believe that robust tolerance of electrical noise in existing AC layout environments was the main reason that Neil Young and others went in their own direction with TMCC with its track signal "halo," etc., instead of adopting the open-source DCC, which had already been around for a couple of years when TMCC hit the market.

If you choose to do a DC motor "transplant," that simplifies a lot of things.  But the way most postwar Lionels are geared, they benefit from a motor that has very high starting torque.  A couple of folks on this Forum expressed disappointment with the performance of their 736 Berkshires after installing the Timko motor.  Diesels seemed to fare better.  The root of the problem is the gear ratio, it's just too fast.

No matter what you decide, you and your friend should temper your expectations.  Even if you get DCC in there, don't expect a 75-year old toy to run like a purpose-built scale model.*  A RailKing steamer has the "look" of a postwar toy train, but some of them have much better gear ratios, and if it has Proto-3, DCC is already built-in.  My \$.02.

*Edit: the 773 Hud@son, prewar 0-6-0 switcher, dual-motored F3 might be capable of near-scale performance.

@Ted S, All points taken. I'll be keeping the Pullmor around just in case. Also, I only run leds and opto isolators from dcc function outputs. I have a favorite SSR for turning on/off the smoke unit(s). Those large scale dcc cards are too expensive to gamble with.

Bobby