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.
The main spotting features of the old brick are
the axle extensions at each wheel. This is a late version of the "old"
brick. 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.
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.
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
Most Aristo diesels are smooth running engines, but there are some
that are unsteady at low speeds. This is caused by the motor bricks,
which are inside each truck, running at different speeds. 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
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
Whatever lubricants that you use MUST be plastic
compatible. Many general lubricants, like 3-in-1 oil, will eventually
Before you tear into the bricks test your loco to see if you
actually should do anything.
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.
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
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
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
Lubricate the shaft end with a small drop of heavy
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
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
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
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
Lubrication of the 2nd Axle
Lubricate the second set of axle bushings with heavy gear oil or
Lubricate the worm gear with a small drop of heavy gear oil or gear
Lubricate the end of the shaft with a small drop of heavy gear
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
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
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
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.