Performance results of Athearn loco’s rev 1-3-15

Of the HO Engines that I see in a year, about a third are Athearn older Hi Fi and blue box models. These ran the range from rubber band drive Hustler yard loco’s to 9-44CW with the rectangular motor with brass fly wheels.

As time and opportunity has it, modern RTR and Genesis models will also be included

As with the other engines that I see, I will perform a limited set of tests.

In this case the engines will be combined in common sets:

1- Hi-Fi models (Unique models will be highlighted)

2- metal side frame models with a round motor

3- Inside frame models with a rectangular motor

4- Unique models with a round motor

5- Unique models with a rectangular motor

6- RTR models

7- Genesis models

This post will document these results. As time and testing progresses, these results will be updated as appropriate.

The initial data will be for engine only level surface testing. As the facilities are put in place, the grade and car load variations will be added.

Initially, five basic functions will be presented:

1- current draw vs voltage with the engine operating on rollers
This will give a stable current level at any voltage. It will imply the engine health variation.


This chart shows the current draw for the round motor (black), rectangular motor (green) and earlier models (red). The RTR model is shown in orange, and the Genesis models are shown in purple. Clearly the round engine currents are generally higher than the other engines tested. This chart demonstrates that the Athearn models have current draws that cover range of all the engines tested. The progress in reducing the current draw is apparent, with the a Genesis models showing on the lower side.
The results show significant variation between similar units. This can happen because of varying maintenance, reduced magnet strength or just natural differences due to the cumulative manufacturing tolerances of the system.

2- current draw vs voltage for the engine only operating on straight and level track.


The scale changed between these two charts, but the current draw increased due to the loco have to deal with the track resistance where the rollers had very little resistance. Interestingly, the relationship between engines changed with the track resistance.

3- scale speed vs voltage for the engine only operating on straight and level track.


In this parameter, The Athearn units are spread across the set. The round motors tend to be high in speed at high power as do the Hi Fi units. At four volts, the differential in speed across all of the engines tested is relatively small. The round motors are still high relative to the group. The speed-voltage slope is higher for the round motor and Hi Fi units. The rectangular motor units have the low power speed of the group of tested engines. The speed-voltage slope is interesting in that it starts out like the round motors. but then flattens out at high power. At intermediate power they are running faster than the average of the group.

The dashed black lines are two units that have Ernst type gears added to the trunks, with the intent of slowing them down. They definitely do that. Compared to the desired speed range shown in the reddish brown dashed lines, the Athearn units tend to run slower at four volts and higher above 9 volts. The exceptions are these Ernst type geared units and a couple of the Genesis units. A couple of the Genesis units were produced in the late nineties and some are recent production models.

4- The following chart shows the maximum draw bar force Generally the Athearn engines are in the mix. The high ones may be C-C units as that has not been differentiated at this time. That will be clarified in the next revision. The two units with the lowest pull force are questionable engine health.


(Revision 11-23-14)

As was the case with the cumulative post an additional set of plots were identified beyond figure 1-4.
These are:

5- voltage at minimum sustained velocity. This is the voltage setting that is required to start the engine from dead stop and achieve sustained movement. This is a constant DC voltage, no pulse wave at all. This is a bar chart, one bar per engine.


6- The minimum sustained velocity, SMPH


7- the variation in the minimum sustained velocity, as defined from three runs.


8- the current level at the minimum sustained velocity.

(This chart is not available at this time)

And based on the discussions in the performance criteria post a critical chart is:

9- the Performance criteria parameter for each engine. This is the second parameter defined in the above post.


As shown, two of these engine are off the chart and would have to be considered exceptional performers. At the same time several of the engines are in the suspect zone. This includes one of the Genesis engines. A detailed parameter examination will reveal that most of the engines in the suspect area have sick motors.

Additional charts will be included as they are developed in later revisions along with the results of additional engine tests.

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