Working on restoring a 474 engine.  I'm more familiar with wiring Lionel Engines and E-Units.  I've been using colored high lighters on the wiring diagram and still can't quite figure it out - diagram attached.

From my understanding, The Lionel E-Unit changes which rail goes to a specific brush and the other brush goes to the other rail.  The coil is in series with the later line going from the brush to the rail.

From tracking the diagrams, the AF reverse unit changes whether the rear truck goes to one side of the coil, or the other.  The flow through the brushes appears to be the same - sketch attached.  If I have that right - I get how how power flows through the brushes, but the coil seems to leave one side open.  I'm sure I am missing something.

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Original Post

Looks like you have a dual motor Alco PA set. Go to the rfgco.com website. The wiring diagrams are posted there. The one you want is listed as General Alco Diesel. The field is wired in series with the armature for each motor. The reverse unit changes the direction of the current flow through the field relative to the armature.

all you have to remember is that the field coil is in series with the motor armature , so in order for the motor to reverse , you have to reverse the filed coil in relation to the armature and the direction will change or reverse  the field back again and the ac motor will reverse again !

 

 

Alan

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Last edited by Alan Mancus

Thanks for the help.  Still confused based on how the reversing unit is working.  I have a single motor Alco, but the wiring drawings work since the motor wiring is identical.  I color coated the drawings to show my problem.  When I'm in position 1, the blue pickup is tied to red coil and yellow brush.  Green brush is tied to the other pickup.  The purple coil is left open it would appear.  In position 2, the blue pickup is tied to purple coil and yellow brush.  Green brush is tied to the other pickup.  The red coil is left open it would appear.  I'm definitely missing something.

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The 474/475 PA/PA Rocket set has a dual motor powered 474 PA and an unpowered 475 unit with a diesel horn in it. A few 474’s were made in 1955 with a single motor but they have a diesel roar unit in the engine as well, so that will have wiring for powering the roar sound. If the chassis has one motor and no diesel roar unit it appears something was changed by a past owner.

Pardon my sloppy sketch, here is a diagram of what the reverse unit is doing. The bulb is wired across the two pickups no matter the position of the reverse unit. The armature and the field are in series. In one position the connections as shown in red are made, in the other position the connections as shown in dotted blue are made. The reverse unit is a four position design so it cycles F-N-R-N. The field connections are not completed when the reverse unit is in the N positions. Regrettably I do not have one of those diesel reverse units handy to show a picture of which wires go to which finger in that specific reverse unit.

It's possible that this is a '55 unit.  There is a round indention in the frame where the roar unit would go, but it isn't there.  Since there has been some "modifications" to the unit - it makes me wonder if there is something wrong with the reverse unit.  I've tested the motor and it works as expected, both direct and reverse.  I've ohmed out the reverse unit so I don't have a short - in N everything is open.  Here's how the drum works.  I intentionally left off the wire colors and where the coil for the reverse unit ties in.  Does anyone know if this is correct?  If so, any ideas how to wire this to accomplish the sketch from AMFLYER?  Maybe I'm too close, but I just don't see it.  I don't believe it is following the wiring diagrams from rfgco.com or my K-Line Service Manual.  Any help would be greatly appreciated!!  Thanks!

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I picked up a single motor Rocket last year and just assumed someone switched out the twin motor chassis for a single one. Just checked the date stamp on it and it shows as March 1955. So what did this come with as a set then?

Here is a picture of the business end of the reverse unit.

Lower yellow goes to a brush, black next to it goes to motor field, red on top goes to motor field, two blacks to left of red go to reverse unit field and the other one goes to front power chassis and is soldered to top of unit which is power pick up, wire pick up from rear dummy truck goes to other reverse unit field which also has the green with it which is the other motor brush.

F08970A3-8595-42F0-B42D-AB4447D6652F

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I bought a Rocket about 20 years ago from '55 that had one motor as well.  Always thought someone had swapped shells....maybe not??

I added another motor to mine and it works well.

I found the problem - user error!  Embarrassed to say I had the lower fingers parallel to the upper fingers, not perpendicular - rookie mistake.  Works amazingly better now!  Sorry for the confusion and thanks for all the help!  Learned a lot about AF!

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