This is a listing of frequently asked questions and general information concerning the collection, operation and repair of collectable model railroad equipment. For more info on this FAQ see part 1. Additions and corrections are always welcome. E-mail to:
(Christopher D. Coleman)
This FAQ contains the following topics:
This is a basic list, see REPAIR AND MAINTENANCE TIPS for applications.
Specialty tools available from parts suppliers:
- bottle of track cleaner and rag
- standard screwdriver set
- miniature screwdriver set
- miniature wrenches or nut drivers
- linesman pliers
- needlenose pliers
- TV Tuner (non lubricating) or Zero Residue spray cleaner
- pipe cleaners
- fine sandpaper
- lithium grease
- light machine oil
- test lamp (or multi-meter)
AF Diesel truck rebusher
- track pliers
- wheel puller
- arbor press (step up from a vise)
- spring bender
Whistle Stop Hobbies
258 Rt 356
Apollo, PA 15613
Train Parts Tumbler (media polisher)
618 Cumberland St
Lebanon, PA 17042
Arbor Press and other tools
Hobby Horse Products
PO Box 543
Kendallville, IN 46755
Track Pliers, Wheel Puller, etc
1805 Hoffnagle St.
Philadelphia, PA 19152
For oil 3in1 MOTOR (not regular) oil is sufficient, but light machine oil for electric motors is best. For grease, light lithium grease in a small tube is good. The rule of thumb is to oil bearings and grease gears. Never use more than one or two drops of oil or a thin coating of grease. Excess will simply accumulate or fall on the track, collecting dirt and making electrical contact worse. Never lubricate needlepoint bearings or solenoid interiors. These are designed not to be lubricated and it would just gunk them up. Lubrication of older truck bearings is usually not needed except under extreme operating conditions. One small drop on either side of rollers periodically is a good idea. For the loco interiors see the next section.
There are many possibilities. First take your test light or multi-meter, or a lamp post or other small accessory with two leads. With the power on, first test directly at the transformer. If there is no result, there is a defect in the transformer. Transformer repair can be dangerous and should not be attempted by an amateur. Check next at the track. If no response you have a bad connection to the transformer or dirty track. If this tests OK check your engine wheels for dirt or grime caked on. If all these test OK you may conclude it is your locomotive.
To start working on your engine the first thing you need is an engine cradle. You can make one by assembling some 3/4" plywood strips to form an upside-down U or trough about 12" long and an interior of 4" wide and 4" deep. Coat the interior with clean foam rubber or thick felt. This provides a soft cradle for the top of your loco when you're working on the bottom. Next you need an exploded diagram for your loco. Greenberg has books of these for many makers. There are many different designs employed in locomotive construction so the following procedure is necessarily vague to cover many types of locos. It gets progressively more mechanical from here.
To access the interior of larger steam locos there are often four screws under the frame screwed upward into the shell. Many mid-sized Lionel steamers use a rod through either side of the shell, just above the rear driver, to keep the shell on. To remove it use an appropriately sized punch and hammer to GENTLY drive it in one side and out the other. Drive in the direction in which it moves most easily. Newer diesel shells have two screws, one in each end of the plastic shell just above the frame (visible). Older style diesels have a rotating tab connected to a screw head under the frame at each end of the body shell. Rotate them 1/4 turn counterclockwise to disengage the tab from the shell. WHOA! Don't remove that shell yet. On many locos there will be a wire connecting the light in the shell to the frame. Be careful of this. On many Diesels the stamped steel railings will scratch a deep grove in your precious shell. Insert 3X5" cards on either side of the cab between the shell and railing first.
After removing the shell you should see the motor and sequencer (Flyer's sequencers are in the tender, if steam). Find the lead that comes from the roller or insulated wheels. Run a wire directly from the transformer to it before the sequencer and connect the other to the frame. If the motor now runs you have bad wiring in your pickups. If not try the field lead not connected to a brushwell (see motor diagram below). If the motor runs either the sequencer or sequencer's wiring is awry. If it does not run then the problem is with your motor. For sequencer trouble, see the sequencer section below.
This section covers universal AC/DC motors not DC only can motors. Can motors are a steel can with plastic ends. Universal motors are open on one side and have the wire wrapped field coil on the other and are much larger. See the motor sections for more details on this. Lionel universal motors come in two types, spur and worm geared. Worm geared motors will usually be mounted vertically or diagonally and have a corkscrew gear on the armature that mates with a gear with diagonal teeth. Spur geared motors are mounted horizontally and are usually used in mid-range to cheap steamers and cheap diesels. They use only gears with straight teeth. Some motors are more readily disassemblable than others. If it's won't come off, chances are it was never meant to. Worm gear motors are usually easier to service than spur gear motors.
To service your motor, first remove screws or nuts holding the brushplate on. BE CAREFUL when you remove it. There is a delicate wire connecting it to the field coil. If you break it off at the coil you've ruined the motor. Also the spring loaded brushes will pop out, so be ready. You can now see the three segment copper commutator. Inspect it for dirt or pitting. Clean it with zero residue cleaner or track cleaner, or if it is worse a soft pencil eraser. NEVER use anything harsher or abrasive. Clean the ruts between plates with a toothpick. Similarly inspect and clean the brushes, springs and brush wells. If pitting has occurred the part must be replaced.
Not all armatures are removable but if yours is, do so and look into the gear cavity (for worm-gear motors). Remove old dirty grease as best you can and apply a thin coat of fresh grease. Look for worn gears. The gear that meshes with a worm gear is the most common to wear out. If you have a spur gear loco (mid to cheap steam locos) the spur gear of the armature is likely exposed in the opposite side of the loco from the brushplate. Again, remove old and apply new grease to all gears, including those on the wheels.T T screws ___O__^__O___ brush wells and armature bearing |_____________| brush plate O O brushes ____|____ commutator | | | | armature windings |_|___|_| I I armature shaft O armature gear H H mounting studs +==============+ motor housing (field core) |==============+--------+ |==============| | field coil +==============+--------+ GENERIC UNIVERSAL MOTOR - EXPLODED VIEWReassemble the reverse of how you disassembled but watch to mesh gears properly and if the brushes have grooves for the brush springs make sure they are properly aligned and right-side-up. When reconnecting plastic shells DO NOT OVERTIGHTEN!!! This will cause the shell to crack immediately or over time.
DC can motors are generally unserviceable and should be replaced if they fail. They are usually mounted in the trucks. A drop of oil on the end bearings will help if they are exposed.
Similar procedures can be used when servicing motorized accessories and whistling tenders.
If your loco jerks as it runs or runs much better in one direction than the other, and you have eliminated all electrical problems, it likely needs a new motor armature. Most toy train motors have three pole armatures so if one is failing, the motor will push for two thirds of a spin and be dead weight for one third, causing jerking.
A loco that makes a "jjjjjsssshhhiinnnngggg" noise may have worn gears. Inspect the gears. If the edges of the teeth are straight and angular they should be OK. If they have become curved and dulled they have become worn and will only get worse. Replacing gears and wheels may be expensive and difficult, especially on steamers.
When traction tire equipped locos slip on grades, run your finger across the rubber tire. If this soils your finger the tire should be replaced. Grime sticks to the tires and reduces traction. Replace, don't clean them. They don't cost much, but are tricky to get on. If a magnetraction loco slips, the permanent magnet may have failed. A sharp blow can weaken a permanent magnet so dropping locos doesn't help magnetraction much. DON'T try to replace the magnet yourself! It takes special adhesive to connect them properly.
A loco that jitters or stalls under light loads is saying "clean wheels, rollers and track!"
Lionel's whistles/horns use an often testy relay to trigger them. Normal track current is AC which causes the solenoid to reverse directions of "pull" 60 times a second causing the unit to buzz slightly in neutral (see MOTOR DESIGN for further discussion). When the whistle activator is pushed some current is diverted through a rectifier and converted to DC. This DC supply superimposed on the AC causes a constant field on the solenoid, pulling up a contact arm to its contact. The contacts form a switch between the battery and horn or the track and the whistle motor. Diesel horns use a vibrator permanently enclosed in a metal casing while steam whistles use a motor driven impeller in a resonance chamber.to coil frame +-+ coil supply and supply to whistle/horn =============== |-------------| +- supply to whistle/horn |-------------| | + coil supply |----coil-----| | | |-------------| | | |-------------| | | to coil frame =============== |__ upper contact I__________________ lower contact arm hingeThe whistles on Lionels are located in the tender and horns in diesels and electrics may be in either the powered or unpowered unit. Follow the discussion above for removing shells. FIRST if you have a diesel or electric check the battery. Never leave a battery in a diesel for extended periods since it can corrode and destroy your locomotive with battery acid. Check the battery's charge.
Test the relay. One common problem is that the relay's lower contact arm is not reaching the upper contact arm. Place the unit on the track and try to activate it manually with a small screwdriver (you will need track power for whistles, but not for horns). If it sounds, there is a problem with the relay or the wiring to it and if not it is with the horn or whistle or the wiring from the relay to the whistle or horn. If the coil does react to the activator, but the contacts do not reach each other, the arms may be CAREFULLY bent closer if needed, but not too close or it will contact at every bump in the track. If there is no response from the coil from different activators, try connecting the supply directly to the coil supplies (not the contacts) and throwing the activator. If this fails to activate the coil, it is likely burned out and needs to be replaced. If it alleviates the problem, your track pickups or wiring to the coil are at fault.
To test the whistle apply transformer leads directly to the inputs to the motor (one may be the frame)(throwing the activator is NOT necessary). If it runs, the whistle motor is not the problem. If on the other hand you trace the problem to a whistle, test and repair it just as described in the locomotive motor repair above. The same basic motor design is used. DO NOT TRY TO OPEN THE RESONANCE CHAMBER! You will destroy it. You may remove the motor and flush plastic ones with water but usually not metallic ones.
To test the horn use a couple of jumper wires to connect the battery terminals directly to the horn leads (one is a common ground with the locomotive's frame ground). If it operates, the wiring is at fault. If you trace it to the diesel horn, there is a small adjustment screw on the underside of the horn with a locking nut. It adjusts the play in the vibrator that creates the horn noise. Try various positions with battery power applied. If you still get no response replace the horn unit. Replacements are available.
There are three kinds of whistle triggers available. The first, original, and oldest is the electromechanical whistle/horn relay discussed earlier. It does not care which way the superimposed DC current goes, just that there is one. The transformers designed to activate these use a diode to rectify part of the AC signal. A resistor was in parallel with a diode to allow most of the AC through to power the train, and rectify only enough DC to trigger the whistle/horn relay. The result was a sine wave modified to a sine wave with attenuated (smaller) peaks on one polarity. This is not a true DC offset, but does change the RMS (average) voltage to a non-zero value. That is sufficient for whistle relays of that era. The higher priced models used a two position trigger in which the first intermediate postion, all current passes through the diode, and in the second, the bypass resistor is introduced. This provides an initial strong DC 'current' to activate the relay and then a smaller one to sustain it in its position. These models also usually cut in a 5 volt 'booster' coil that compensates for the additional current drain placed on the transformer by the whistle motor.
The second trigger emerged in the early Fundimensions era of Lionel and is electronic. It uses a circuit board to sense the presence of a net DC current. Because these units are electronic, they are more sensitive and discerning of input signals. They were designed for use with solid state circuits. The older diodes used for mechanical relay triggering were ineffecient and noisy. This tends to confuse the electronic detector. Often it is necessary to hold older controllers in the intermediate position (all current through the diode) in order to get enough DC to trigger newer triggers. Additionally the electronic triggers are polarity sensitive. One polarity activates the primary function (whistle for steamers or horn for diesels or electrics) and the opposite polarity for an optional second feature, usually a clanging bell sound. The correspondence of available power to this trigger arrangement will be discussed in a moment.
The third type is part of the TrainMaster Control system. This system uses encoded digital signal transmitted on the track to trigger decoders mounted in the locomotives. This uses wholey unrelated methodology. TM is, however, equipped with a retroactive horn/whistle and bell activators for track blocks. This presumably works the same as the previous electronic activators.
Now back to the original and its diodes.
- Cathode-----|<------Anode +
The anode is positive and the cathode negative, and since current runs from positive to negative, it runs only in the direction the arrow points. This is an electronics convention. For our discussion we will use the common Lionel ZW and 1033 as examples. The ZW is usually wired with the common U terminal wired to the common outer rail, and the 1033 with terminal A wired to the common outer rail. According to Lionel's schematics, when the whistle is triggered, the 5V booster coil (which compensates for the whistle motor and diode loss drain) is put in series with the variable coil and a diode-resistor combination. According to the Lionel diagram the anode is positioned toward the center rail terminal.Lionel's questionable diagram: common common 1033 +--------- A --+ ZW +----------- U --+ | - + | load | - + | load +--|<----- U <-+ +--|<------- A or D <-+ diode power diode powerThis would imply a negative charge on the power rail relative to the common rail for a current to flow in the direction the diode indicates (Current always flows positive to negative). Another way to look at it is that since the diode is conductive in the direction of the current shown, the diode 'pulls' the power rail negative. Concluding from the diagram, the horn trigger uses a center rail negative DC current, but this is not the case. There are three test that confirm this.
- Testing continuity with a silicon diode in series with the copper Lionel diode. The combination will only conduct when the two are anode to anode or cathode to cathode (according to the Lionel diagram). This can be done with a plain diode and a continuity testor or with two AAs and a LED. Same results.
- The horn of a current direction dependent locomotive can be activated just as the built-in whistle controller does by adding a silicon diode in the circuit to the track. The successful direction of the diode is the opposite of that shown in the Lionel diagram.
- Inserting a AA into the circuit to the track activates the horn of a current direction dependent locomotive when the positive end of the battery is contacting the center rail. The battery would, in effect, add a positive offset to the AC from the transformer. This is a positive offset on center relative to outer. The reverse configuration does not activate the horn.
A modern MRC 027 transformer is reported to actually use negative center rail DC for horn activation. This may have resulted from 1) MRC taking Lionels diagrams verbatim or 2) not caring which way the DC current went, as where it is irrelevant for electromechanical whistle relays.
It has been reported that MTH (QSI) do use positive center rail DC for whistle/horn activation and negative for bell control. MRC and the Lionel schematic drawers made mistakes.
This is a generic defect and most corral sets suffer from it. It is caused by the fact that the car vibrator does not work as well as the corral vibrator. Sometimes adjusting the spring on the car vibrator plunger will help, but no reliable solution has been found. If yours works count your blessings.
Remove the shell and milk can ramp cover. Early shells are removed by first removing two wire clips under the car which pass through the frame and shell on both sides. Later cars have screws on either end of the car. Clean every trace of dirt, oil and grease from inside the milk can ramp. This will usually solve the problem. Also make sure your platform is set to the correct height for O or O-27 track using the appropriate slots for the metal platform.
This too is normal. You can play with the vanes and sometimes increase performance, but this is why Lionel replaced it with #494. Make sure the top is balanced by carefully adjusting the pin inside the top. The 394 has to be running for a couple minutes before it generates enough heat to turn the top.
There are two types of vibrator motors. The first is used on rotating accessories like the 494 Beacon, spotlight cars, and rotating radar antenna. These use a method similar to that in the corral cars. A coil with an iron core is supplied with AC so it vibrates 60 times a second. A rubber ring with angled fingers sets on the coil and with each vibration the fingers loose contact with the surface for an instant and when contact is made again the fingers push in the direction of their lean. Doing this 60 times a second causes a (nearly) smooth motion. For the fingers to grip these motors they should never be lubricated.
The second type is used in the culvert loader and unloader and in the aquarium car and animated gondola. It uses a coil near a flexible steel strip. Similarly it pulls and pushes the strip 60 times a second. Connected to the strip is a nylon cable wrapped around a pulley. As the strip moves toward the pulley no force is exerted. When it is moving away the cord pulls slightly on the pulley. The result is smooth motion (noisy though). The pulley surface should not be lubricated but its bearings and gears may, depending on the material from which they are made.
A sequencer is the device that controls locomotive direction. The "E-Unit" was originally developed by Ives. It was a trademarked name I believe, where the generic name for the device is a sequencer. When Ives went bankrupt in 1931 Lionel bought it principally to acquire it's superior sequencer. Until then Lionel had used a simpler and less reliable two position sequencer. Ives' was the three position seen in 'modern' tinplate locos. During it's classic era Lionel designated locos with E-units as -E such as the 300E and 700E. Flyer never owned the right to use the name E-unit specifically, but their sequencer is the same principal interpreted differently. I believe the E stood for Electronic unit. Although it wasn't really electronic by today's standards, it must have seemed that way in those times before transistors, and vacuum tubes were the cutting edge.
Most sequencers work by means of a rotating drum and contact fingers. The drum has copper contacts on its surface arranged so that there will be connections made between different fingers for different positions of the drum. The circuitry of this is explained in MOTOR DESIGN. An electric coil plunger engages a series of teeth on the drum and pulls it a fraction of a rotation each time the coil is energized.
The most common problem with sequencers is a lack of proper contact between fingers and drum, or a failure of the coil to properly position the drum. The contacts are best cleaned with Zero Residue or TV Tuner spray cleaner. If this fails you may carefully clean the drum in place with an eraser. Be careful not to touch the contact fingers. THEY ARE VERY DELICATE so BE CAREFUL. If the drum is pitted or damaged it needs to be replaced. Disassembling a sequencer is VERY tricky and delicate. For Lionel units the sides of the unit must be forced apart to remove the drum, and a pair of external snap ring pliers are good for this. The drum and finger assemblies will pop out. When reassembling press the assembly together by hand first and gently finish it in a vice. If the fingers are damaged it may be possible to re-bend them with precision pliers, but replacement is the best option. If your coil plunger is sticking do not oil it! The oil will "clog" it up. A pipe cleaner is useful here to clean the interior of the coil, as is spray cleaner. When the interior is clean, the plunger should slide easily. If not, the coil case is likely warped, so replacing the unit is the best solution. This same procedure may be used for accessories using the coil plunger system, such as crossing gates.
APPEARANCEThe best thing for keeping your old trains tidy is MILD detergent and water. A SOFT bristle paint brush is useful for occasional dusting. I've heard of using petroleum jelly but never tried it. Also there is: Toy and Train Cleaning Solution
Hampton Hobby Products --- also has many other useful supplies
2475 Hitching Post Drive
Allison Park, PA 15101
It is advisable to test any cleaning solution on less valuable stock and/or an unexposed region before committing to it. Avoid using any type of cleaner on decals and if you get them wet be very careful. They can easily tear, disintegrate or slide out of place.
Modifications are not covered here as where they change the service routine from the predictable factory norm. The most common addition is that of modern electronic sounds and sequencing. Here are a few makers of add-on electronics.
ADD ON ELECTRONICSQSI
2575 N E Kathryn St #25
Hillsboro, OR 97124
10 Witmer Road
Lancaster, PA 17602
PO Box 2093
Warrendale, PA 15086
Electronics for Trains
1225 Johnson Ferry Road, Building 400
Marietta, GA 30068
Hyde-Out Mountain Live Steam
89060 New Rumley Road
Jewlet, OH 43986
Ott Machine Services, Inc
118 E Ash St
Lombard, IL 60148-8701
Train America Studios
Both original new and used, as well as reproduction parts are available. Below is an incomplete listing of sources. Alfra Engineering
7910 Poplar Hill Drive
Clinton, MD 64138
Bowser - Standard Gauge Wheels
PO Box 322
Montoursville, PA 17754-0322
Brasseur Electric Trains
4215 South Wayside Drive
Saginaw, MI 48603
6 Como Trail
PO Box 472, RD 3
Lake Hoptacong, NJ 07849
PO Box 158
Hubertus, WI 53033
Classic Model Trains - supplies custom mixed paint to match original colors
PO Box 179
Hartford, OH 44424-0179
18025 8th Avenue, NW
Seattle, WA 98177
Doctor Tinker's Antique Toy Trains
Parts and Service
1 Belfry Terrace
Lexington, MA 02173-4909
William J Doomey
Model Engineering Works
PO Box 1188
Ramona, CA 92065
East Coast Train Parts
PO Box 604
Englishtown, NJ 07726
Phone/Fax: 732-972-8263 Tues-Fri 11-5:00
(Confirmed in business 10-2001)
7910 Poplar Hill Drive
Clinton, MD 20735
Fred's Train Parts
2102 Concord Road
Chester, PA 19013
(confirmed in business 10-2001)
The R.F. Giardina, Co. - AF new and reproduction parts
PO Box 562
Oyster Bay, NY 11771
The Robert Grossman Company
857 East 237th Street
Euclid, OH 44123
Hobby Surplus Sales
287 Main Street
PO Box 2170
New Britain, CT 06050
131 W Washington Avenue
PO Box 381
China, TX 77613
E C Kraemer Reproductions
105 Hollywood Avenue
Fairfield, NJ 07006
Leventon's Hobby Supply - AF supplies
PO Box 1525
Chehalis, WA 98532-3707
Lionel Classics Service Center
9693 Gerwig Lane, Unit A
Columbia, MD 21046
Locomotion Service Center
4887 132nd Ave
Hamilton, MI 49419
1915 West Fort Street
Detroit, MI 48216
Mike's Trains & Hobbies
104 West Ocean Avenue
Lompoc, CA 93436
(reported to be out of business)
Model Engineering Works
12600 Frost Road
Kansas City, MO 64138
Model R.R. Centre
90 Saxon Bay
580 Humiston Drive
Bay Village, OH 44140
L M Olsen
2192 McKinley Avenue
Lakewood, OH 44107
Stanley Orr - attends York meet
PO Box 97
Stormville, NY 12582
P K Train Parts
220 Trouville Road
Copiague, NY 11726
Doug Peck Port Lines Hobbies
6 Storeybrooke Drive
Newburyport, MA 01950-3408
David G Reinhert
The Train Cellar
1416 3rd Street
Trevose, PA 19047
240 163rd Place, SE
Bellevue, WA 98008
Mike Sabatelle - not recommended, experienced order trouble
PO Box 040136
Brooklyn, NY 11204
Richard J Sapetelli
390 Dartmouth Street
Wyckoff, NJ 07481
Joseph Schwingl - Recommended, good service
92-61 246 Street
Bellrose Terrace, NY 11001
PO Box 46238
Philadelphia, PA 19160-6238
105 David Lane Lansdale, PA
Spencertown, NY 12165
O, O-27, Standard Gauge; Lionel, AF, Ives, Erector
(Confirmed in business 10-2001)
That Train Place - Only place for NEW Marx parts
56644 C R 3 South
Elkhart, IN 46516
Tom's Trains / Triple S Supplies (Flyer parts)
Shoppes of Nobb Hill
288 Lancaster Ave
Malvern, PA 19355
(Confirmed in business 10-2001)
Town and Country Hobbies
PO Box 584
Totowa, NJ 07512-0584
(Confirmed in business 10-2001)
The Train Shop
Preakness Shopping Center
Wayne, NJ 07470
The Train Tender
135 Hamptom Way
Penfield, NY 14526
Phone: 716-381-0705 (eves and weekends)
Trains and Things
209-1/2 W Clark Street
Champaign, Illinois 61820
Richard A Trickel
PO Box 262
48 Sunset Drive
Paoli, PA 19301
Triple "S" Supplies - Flyer S Parts
PO Box 343
Secane, PA 19018
PO Box 841
Sparta, NJ 07871
Phone: 201-702-7001 e-mail (temporarily) DWALD86426@AOL.COM
Warren's Model Trains - good list, attends York meet
20520 Lorain Road
Fairview Park, OH 44126
Some basic parts can be found at your local hardware or electronics store.
Light bulbs:Lionel # GE # base type Radio Shack # 47-300 47 6.3V bayonet 272-1110 50-300 50 7.5V miniature screw 272-1133 52-300 52 14V bayonet 272-1117 53-300 53 14V miniature screw 272-1127
What follows is a technical description of the situation in as much layman's terms as possible and still be accurate. There are three basic types of electric machines in use today:End of the Tinplate Train FAQ, Part 3 of 4
DC MACHINES: These have a non-moving field coil on the stator and a moving armature on the rotor. It uses a commutator, which is a segmented plate which constantly redirects the current direction in the armature. This change in current causes a change in a magnetic field so that it keeps pushing against the field produced by the field coil. The more current, the more field, the more push, the faster the motor goes and no matter how fast it goes the commutator keeps the fields opposing each other, thus the variable speed.
SYNCHRONOUS AC MACHINES: These have a non-moving armature on the stator and a moving field coil on the rotor. Since the field is constant, it has a solid slip ring instead of a commutator and relies on the change in the AC voltage supplied to it's stator to create the changing field and hence the motion in the machine. Because of this IT CAN TURN AT ONLY ONE SPEED at a given AC frequency for which it has been designed, usually a factor of 60, the frequency of standard AC current. (frequency can be varied by specialized electronics)
INDUCTION AC MACHINES: These are a variation on synchronous machines that rely on induction to supply current to the rotor field from the stator armature (slip rings are then not needed), but are otherwise pretty similar.
The Universal motor in operationEssentially all model engine motors are DC machines. The difference is in the field. Traditional Lionel, Flyer and Marx locos use an electric field coil. When DC is applied, the armature current goes one way and the field current goes one way. It pushes the motor in a particular direction.
If the terminals of a universal motor are reversed, the motor still spins the same way. The current through BOTH the field and armature are reversed so the field RELATIVE to current in the armature is the same. The two must change RELATIVE to one another to reverse the motor. This is why sequencers (E-Units) are used to reverse the field current RELATIVE TO the armature current.
Now, AC current changes direction 60 times a second (50 in Europe). It is just like reversing the terminals 60 times a second. When AC is applied, the field current changes direction right in step with the armature current so that they are always flowing in the same RELATIVE direction. The force stays in the same direction.
These motors are conceptually designed for DC but will usually work fine on AC too, as is the case in tinplate trains. It is, however, common practice in the hobby to call them "AC" or universal to indicate that they CAN run on AC, unlike "can" motors. I'm not trying to change this, but rather show how it all really works.
The Can motor in operation"Can" style motors are used in N, HO, G and some Lionel offerings use a permanent magnet instead of an electric field coil. When DC is applied, the current in the armature runs one way and the permanent magnet substitutes for the field with current running one way. It pushes the motor in a particular direction.
If the terminals of a can motor are reversed, only the armature is reversed (remember the field never changes). The armature has changed RELATIVE to the field so the motor direction reverses.
Now, if AC is applied, the field of the permanent magnet does not change direction when the armature does. The RELATIVE directions change with the AC. The motor tries to change direction 60 times a second causing it to just shake violently.
Below is a table which tries to graphically show the different behavior of these types of motors under AC and DC. 1 is a magnetic field in one direction and 2 is in the opposite direction. When they point in the same direction the motor will spin one way and the opposite way for opposing fields (here I arbitrarily chose the directions of rotation as clockwise CW and counter-clockwise CCW).ELECTRIC FIELD COIL reverse motor leads (universal) | time (sec) 1/60 2/60 3/60 4/60 5/60...| 1/60 2/60 3/60 4/60 5/60... DC supply | field 1 1 1 1 1 | 2 2 2 2 2 armature 1 1 1 1 1 | 2 2 2 2 2 result CW CW CW CW CW | CW CW CW CW CW | AC supply | field 1 2 1 2 1 | 2 1 2 1 2 armature 1 2 1 2 1 | 2 1 2 1 2 result CW CW CW CW CW | CW CW CW CW CW | PERMANENT MAGNET FIELD (can) | DC supply | field 1 1 1 1 1 | 1 1 1 1 1 armature 1 1 1 1 1 | 2 2 2 2 2 result CW CW CW CW CW | CCW CCW CCW CCW CCW | AC supply | field 1 1 1 1 1 | 1 1 1 1 1 armature 1 2 1 2 1 | 2 1 2 1 2 result CW CCW CW CCW CW | CCW CW CCW CW CCWDC can motors can be used with AC if it is converted into DC through a rectifier or other means. This is done with many new offerings from Lionel and MTH. However, this requires a slightly different type of sequencer.
The cheapest Lionel offerings are equipped with non-rectified can motors without sequencers. These are provided with DC power packs and require a polarity change from the power pack to reverse, as in HO, N and G scale. They are incompatable with the rest of the AC powered line. (you get what you pay for)
Conversely, you can run universal motor equipped locomotives on DC. However, since whistle, horn and bell activation relies on DC signaling (except the TrainMaster System), DC power cannot be used on a locomotive so equipped.
Also, smaller size can motors require less current to run and hence smaller transformers. I have several HO transformers I use to run lights and most do not generate enough current to run tinplate trains with universal motors. The current limitation of DC power packs has traditionally been linked to the inability to rectify large amounts of AC house current to DC. Also, can motors have traditionally not been as powerful as universal motors and only in the past 10 years have they been considered to have enough power per size to use in the better Lionel offerings.
As a result of all this, AC power and universal motors have been the system of choice from the 1890's through the 1990's. Still today, many of the best units have universal motors, albeit with five poles rather than three.