Aristo Power Brick Tune-up

All the pre-1999 Aristo diesel products use the same truck assembly which is modeled after an AAR type B truck that was often used on Alco and early GE equipment. The information on this page applies equally well to the U-25B, FA-1, FB-1 and RS-3 manufactured roughly through the end of 1998.

This brick was from one of the latest locos made with the non-ball bearing brick, a 2nd generation RS-3. There is only one connector on the brick itself, a blue/green pair for the motor only. Power was conducted to the frame from wires connected to the sideframes. The motors on this version used a 3 pin connector that plugged into the bottom of the frame. The power (usually a black/white pair) used a similar 2 pin connector that also plugs into the frame.

One version older bricks (usually black box locos) used red in-line connectors for both the motor and power. The motor wires were still blue/green but the power wires could either be black/red or black/white. These then plugged into a 4 pin connector on the board inside the loco.

Even older versions (mostly blue box) didn't have the red in-line connectors. The wiring harness from the brick and sideframes went directly to a 4 pin connector inside the loco.

The main spotting features of the old brick are the axle extensions at each wheel. This is a late version of the "old" brick taken off an RS-3. The even older versions have lash screws at each end of the brick to set the axle play as discussed below. Even older versions don't have the plastic hub on the wheels.

The axle ends fit into brass bushings on the truck sideframes. The engine is actually suspended from these axles and bushings via the sideframes and some springs. The axles are also used for power pickup via the bushings and some wires connected to brass straps on the sideframes that contact these bushings.

The older bricks may have a brass or plastic universal joint. Be careful when you take it out, sometimes the metal rods in the universal fall out.

As of 1999 a new design appeared that is significantly different. The new design has ball bearings and the axles do not extend to the sideframes. The wheels are held on with screws at the center of each wheel. This page is relevant only to the older design.

The newer bricks pick up power via the ball bearings inside the trucks. The engine is suspended via the tabs on the sides of the bricks and the sideframes are for decoration only.

This brick is taken from a Doodlebug that does not have frame mounted connectors. There are pigtails hanging out from the bottom of the Doodlebug to make contact with the red connectors. The connectors are keyed backwards so that it is not possible to mis-connect them.

Newer locos with a distribution board and DCC socket inside usually have the 2 and 3 pin connectors facing downward from the frame to connect the bricks.

The new brick differs significantly inside too. This brick has ball bearings at each wheel and power is picked up through the bearings. Therefore, there are power contact straps inside and an extra pair of wires leading from each brick. The motors have a noise suppression capacitor already installed. This brick doesn't seem to suffer the same binding issues as the older one so the notes below have little importance for this design.

If you have a U-25B, FA-1, FB-1 or RS-3 with the older bricks and one or both are too far gone for remedial work, you can get a replacement ball bearing brick that will fit your loco. These also fit the RDC and Doodlebug. The ART-29351 is a brick/sideframe assembly with wiring harness that fit both the older and newer types of locos. If you loco is really old, it MAY require some wire splicing but the brick will still fit.

These bricks run at the same speed as the older ones so they don't have to be changed out in pairs. A single assembly as shown in the photo can be found for about $50 at various online retailers.

I have this one wired to test as an individual brick. My intention is to use it to replace the brick under a Bachmann trolly.

Most Aristo diesels are smooth running engines, but there are some that are unsteady at low speeds. This is caused by the motor, which are inside each truck, running at different speeds due to changes in loads on that brick. One brick wants to run faster than the other and they fight each other. This does not have to happen and with a little work, gear grease, heavy gear oil and a few scraps of thin styrene, EVERY brick can be made to run very well.

A major problem with some bricks is that the brick case halves pinch the motor bearings adding unnecessary drag. This can be prevented by shimming the case halves apart with the aforementioned styrene scraps, although any small piece of shim material about 20 mils (0.5 mm) thick will do.

Sometimes an Aristo brick will develop a loud squeak. This is usually caused by a dry joint between a motor shaft and a lash screw. You should lubricate the brick, but to temporarily solve the problem, try to determine which truck the squeak is coming from and turn the lash screw furthest from the rocking gearbox counterclockwise about 10 degrees. If this doesn't do it, try the other lash screw.

There is a universal joint inside each brick. Sometimes this joint comes loose and slips on either the motor shaft or a gearbox shaft. There were two types of universals used in various production runs, a metal one and a plastic one. The metal one is the most likely to slip. Slippage is indicated if the axle in the rocking gearbox does not turn at all. The universal has two very small setscrews on it, one or both of them often tends to loosen. These screws are so small that it is easy to damage them. Before you go in there and gouge up a setscrew, find a jewelers screwdriver that fits the full length of the screw slot and is thick enough to just fill the slot. If you use the wrong screwdriver, you'll likely damage the screw requiring a replacement IF you can get the old damaged screw back out.

To do internal work, you'll need to have some lubricants handy. You can get away with just three types.

General oiling can be done with LGB 50019 Special oil which works very well for all light oiling applications such as shaft bearings and bushings.

Gear lubrication requires a heavy gear oil or grease such as LGB 51020 gear grease or HobeLube HL655 gear oil.

Electrical contact lubrication requires a conductive lubricant. There are several types available from Bachmann, AristoCraft and others.

Whatever lubricants that you use MUST be plastic compatible. Many general lubricants, like 3-in-1 oil, will eventually attack plastic.

Before you tear into the bricks test your loco to see if you actually should do anything.

• Testing
  • Connect your loco to a power pack which has very good low voltage control. A Bachmann pack will not do. Nor will a Train Engineer because the slowest speed step is just a little too high. A conventional pack like an MRC pack will do fine. The easiest way to connect power to the engine for testing is to use two clip leads and clip to the lugs on the inside of the side frames. Do this with the engine on its side or cradled upside down.
  • Run the engine at very low speed. If all is well, both trucks will start at the same time and run very slowly without stalling. If you can run the wheels at 10 RPM (one wheel turn in 6 seconds) or less, you can stop because it doesn't get any better. If the trucks won't run that slow or run at different speeds, or if you just want to do some preventive maintenance, then proceed.
• Brick Removal
  • Remove ONE brick from the engine. Depending on the model and the vintage, you may have to remove the shell to unplug the wires. If you can pull enough wire out of the body so that you can work with the brick, then you don't have to remove the shell either.
  • Remove the side frames by removing three screws from each side frame. If the engine is a 1997 model, be careful when removing the side frames as there is a spring and contact in each axle bushing. Note the power pickup wire that fits under one of the top screws. You'll have to get this wire back in the right place when you reinstall the brick.
  • Remove only one brick at a time. You'll want the other one in place to give you a clue as to how to reinstall the brick. Note that the bricks are apparently reversed from each other (the motors and gearboxes are on different ends) AND that the wires leading to the lugs which contact the brass contract strip on the back of the side frames are apparently reversed as well. This is the way it is supposed to be.
  • Pull the brick out a little ways. If a set of connectors comes out of the hole in the body or more than 6" of wire comes out, you're in luck, you don't have to remove the shell. If not, take off the shell so that you can disconnect the brick from the loco.
• Brick Disassembly
  • On each brick case, there should be six screws and two more holes for two screws that are not used. Remove the screws. Carefully separate the case halves. The motor and the axle in the rocking gearbox should remain in the piece that has the wires coming out from it. The axle nearest the motor should remain with the other case half.
• Motor and Universal Joint Lubrication
  • Lubricate the motor bearings with a small amount of medium weight oil.
  • Lubricate the commutator (visible through holes in the motor can on some motors) with a VERY SMALL amount of light conductive oil.
  • Lubricate the worm on the end of the motor with heavy gear grease or heavy gear oil.
  • Lubricate the universal joint with heavy gear oil.
• Gearbox Lubrication
  • Gently remove and disassemble the gearbox and lubricate the worm inside and the axle and drive shaft bushings with heavy gear grease or heavy gear oil. If your brick has a metal universal joint, be sure not to lose either of the two pins in the universal. Some units have plastic universals that do not have metal pins.
  • Lubricate the shaft end with a small drop of heavy gear oil.
  • Reassemble the gearbox.
• Gearbox Lash Adjustment
  • Adjust the gearbox lash by rotating the input shaft and tightening on the lash adjustment screw on the end of the gearbox. Tighten until you feel some drag and then back off just enough so that the drag goes away. It may be necessary to further loosen the lash screw in the next step.
  • Reinstall the gearbox and the universal joint. Rock the wheel to see if there is any lash in the universal joint. There should be just a little. If not, loosen the lash screw further until you can JUST start to see the universal lash just a little.
• Intermediate Testing
  • Connect the brick in its partially disassembled state back to the engine and run it. The one wheelset installed should run REALLY slowly and smoothly. If not, take the gearbox back out and try to run the motor alone. If it won't run slow, then the motor may be bad. Due to the magnetic detenting in the motor, it may seem a little jerky even if it is in good condition but it should run steadily. The motor by itself won't run slower than several revolutions per second.
  • If you ever want to install radio remote control, you might want to solder a 0.1 micro farad capacitor across the motor terminals at this point. If you are going to install DCC, do not install this capacitor.
• Lubrication of the 2nd Axle
  • Lubricate the second set of axle bushings with heavy gear oil or grease.
  • Lubricate the worm gear with a small drop of heavy gear oil or gear grease.
  • Lubricate the end of the shaft with a small drop of heavy gear oil.
• Final Adjustments
  • Reassemble the brick but don't put in the screws. Try running it again. It should still run real slow. If not, something is binding. Find the problem and fix it.
  • Now install all six screws and tighten them one at a time while the brick is running slowly. You may find that tightening one or more of the screws (most likely the center ones) causes the brick to bind. If you find that the brick doesn't run as well as it did when it was apart then loosen all 6 screw about one turn and pull the case halves apart as far as you can. Low speed operation is probably restored.
  • Here is where you will need the shims. Place a shim on each side of the motor between the case halves, right next to the center screws and tighten them again. If all is well, the brick still runs smoothly. Tighten the end screws and check again. If low speed operation is lost, then another shim between the case halves is needed. Tighten the screws one at a time to find where the binding is and shim near that screw.
  • When the brick is properly shimmed, tighten the other lash screw (the one away from the gearbox) with the brick running slowly until the speed decreases then back it off until it doesn't affect slow speed performance.
• Brick reinstallation on the Loco
  • After the brick is running right, reinstall it. Note that the orientation of the brick and the power pickup wires are opposite the other brick.
  • Be sure you get the lugs on the wires still hanging out of the engine under two of the side frame mounting screws so that they touch the brass strip on the back of the side frame.
  • If your side frames have springs and contacts in the bushings, be sure to reinstall them. Its a little harder to get the newer side frames back on, but it can be done with a little practice.
  • Place a small drop of conductive oil on each axle bushing where the axle extends into the sideframe.

Do the same to the other brick if it needs it.

When you are all done, the engine should run with no hint of hesitation or jerky operation.