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Improving Performance on Athearn Locomotives - by John Waitkus

Athearn locomotives, while of a good basic design, suffer from some shortcuts involved in the manufacturing process.   Here are some solutions to those problems.    None are terribly difficult to do, and you will have a much better running locomotive if you decide to do any or all of them.  Read through all of the choices below and you will see that they can all be done at the same time rather easily (and they are laid out so that one procedure leads into the next).

Basic repairs for some manufacturing deficiencies
Wheel replacement for better electrical pickup
Tuning the motor for better performance
Hardwiring the motor eliminates a lot of problems

 

Basic Repairs - Checking the Driveshafts and Gear Endplay

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Begin by removing the body and test running the chassis on a section of track.    Look at the drive shafts and universal joints.   Do they seem to be turning out of round?  If so, they are due for a replacement.

Use a small screwdriver and pry the top of the gear tower on the trucks.  Be careful as these are what hold the truck to the frame.  With the top clip off the tower you should see the worm.   See if you can move the worm forward and backward while it is in the truck.   A small amount (.010") is ok, but any more and you will need to add a thrust washer between the worm and the square bronze bearing.

 

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Carefully remove the driveshafts, universals, and the worm, being careful not to loose the bronze bearings (they come off very easily).

Take one of the universals and check for any flash and remove any you find with a hobby knife.   While you have the universal out, carefully pry the tabs apart slightly with a small screwdriver by putting the shaft of the screwdriver between the tabs an twisting very slightly.    Test the fit on the ball of the universal.    You want the least resistance you can get.   When connected, they should 'flop' when you turn it in your hand.

When satisfied, replace all the components, unless you are going to do the motor tuning in the section below.

 

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Wheel Replacement For Better Electrical Pick-up

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Athearn locomotives are manufactured with a steel wheel.   For best performance these should be replaced.    Aftermarket nickle-silver wheels are made by several manufacturers.

Begin with the body removed from the locomotive.   Carefully remove the sideframes from the trucks.   There are pins on the back of the sideframes and these are a press fit into the truck.   Carefully pull the sideframe off the truck straight out.

Turn the locomotive or truck over so that the bottom is facing up.   Carefully remove the bottom truck cover using a screwdriver to release it from the four small pins on the sides of the truck.


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Remove the wheel assemblies.   Remove the stock wheels by twisting slightly while pulling apart.   Be careful not to lose the square bronze bearings.

Place the bronze bearings on the new wheels and press them into the axle gear, twisting slightly in the reverse of how they came apart.

Check the axle gear to see if it is split.    If it is split, you will need to purchase a replacement wheel assembly from Athearn as the gear is not available separately.

Check the gauge using a NMRA or comparable gauge.   If you don't have a gauge, check against another wheelset known to be in gauge and make a note to get a gauge.


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Place the wheelsets one at a time on a section of track and apply power.  Check to see if there is a short circuit.   If there is, remove the wheel set and pull apart slightly and retest.   Recheck the gauge.  If it is too wide, you will have to file off some of the material on the end of the axle that goes into the gear. (Note: this is a rare occurrence)


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Put the wheelset back in the truck, making sure that the square bearings fit into the slots on the truck.   Replace the bottom cover.

If you are not going to do the motor hardwiring, replace the sideframes.      If a sideframe appears to be loose, carefully 'squish' the pin slightly with a pair of pliers to make it out of round.    It should then go in with more resistance.


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Tuning the Motor for Better Performance

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With the driveshafts and universals disconnected from the motor, check to see if the armature (the part with the wires on it) moves forward and back.   A slight amount (.010") is ok, but if there is more you may need to add thrust washers to the armature shaft.

Adding motor thrust washers: This involves removing the flywheels and partial disassembly of the motor.   If you are not comfortable with this, please seek the assistance of someone with more experience.

NWSL makes thrust washers to fit the Athearn motor.  They should be placed on both ends of the motor shaft to get armature centered in the motor and no more than .010" of endplay.


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The commutator on the Athearn motor is often manufactured with burrs on it.   This causes the motor brushes to hop and spark as the motor rotates.

The easiest way I have found to repair this is with a piece of Briteboy or other track cleaning block (I like Peco for this).


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Apply a moderate amount of current  (8 -10 vdc) to the motor to get it turning freely.  Apply the end of the track cleaner to the armature from the side.   You should see the armature get shiny in a short time.  There should also be less sparking.

From time to time, the commutator gets dirty from brush wear.  You can use this same method to remove the crud.    Rubbing alcohol on a Q-tip works well for this also.


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The brushes and brush springs should be replaced if they are excessively worn, or the springs are blue in color.

When satisfied, reconnect the driveshafts and universals to the motor.


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Hardwiring the Athearn Motor - Improving the Electrical Circuit

Hard wiring the motor is one of the simplest solutions to performance problems.   The schematic drawing at the left shows one way to do this, along with how to build a directional constant lighting circuit, but there is a better way.

Some will say that all you need to do is remove the metal bar that goes from the motor to the trucks and connect wires from the motor to to tabs that protrude from the trucks.   This is good, but there is a better solution.


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The procedure described here will isolate the motor from the frame, making the unit DCC compatible.   It also eliminates one of the weak points in the circuit, the connection from the trucks to the frame.   Crud can build up on the top of the truck, and/or the frame, causing intermittent operation.   This procedure will eliminate that problem.


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With the sideframes removed from the truck, solder a small (22-30 gauge) wire approximately 10" long to the outside of the brass rivet on each side of the truck.  Be careful not to get solder inside the rivet (it is what holds the sideframe on).

Run the wires through the frame so that they don't interfere with truck movement.

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Remove the motor from the frame.    Note which way the motor is oriented.   Put a piece of electrical or adhesive tape along the strip where the paint has been removed from the frame under the motor (we want to insulate it).   Be careful not to cover the holes in the frame that hold the motor mount


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Carefully remove the brass clips on the top and bottom of the motor, making sure that the brush spring stays in the motor (this clip holds them in - under pressure).

Solder a short (3-4") piece of small (22-30 gauge) to outside of each of these strips.

Using a pair of pliers, flatten the two tabs on the one strip so they lie flat with the rest of the clip.   Replace the clips on the motor, putting the one with the tabs on the top.


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Replace the motor in the frame, aligning it in the direction it was removed.   Bring the wire soldered to the bottom clip alongside the motor but away from the metal 'can' part of the motor, and the wires that are inside.

Temporarily connect the wires (twist the wires together) from the same side of each of the trucks to one of the leads coming from the motor.   Do this to the other side of the truck to the other motor lead also.   Test to see that the loco runs in the proper direction.  If it does not, switch the leads from the motor.

(Note: for DCC operation, the decoder will be connected between the motor wire and the truck leads)

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Constant lighting: If you want a constant lighting circuit installed, it should normally be inserted between one of the motor leads and the truck leads.  Test for proper orientation, and reverse the unit if necessary.
(Note: never test the lighting circuit without having the motor connected)


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Trim the excess wire and solder the connections when you are satisfied that the locomotive (and constant lighting, if installed) operates properly.    Insulate the connections with shrink tube or electrical tape.

I like to then tape the leads down to the top of the motor  with a piece of electrical tape, from one side of the motor to the other.   This makes for a neater appearance, and helps keep the wires where they should be.


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Replace the sideframes, body, and any other components you removed (except the metal bar) and enjoy your locomotive.  It should run vastly improved over what it ran like before we started.   Maybe even well enough that you will have to do this to your entire fleet.   :)

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