Tuning impact on Athearn BB Engines Rev 11-27-14

During the initial engine testing phase the results of various tune up features were examined on three Athearn blue box engines. All three of these engines were previously well used to varying degrees.

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These engines are as follows:

1- Pennsylvania SD9 with round motor and grey fly wheels. The truck side frames are metal and the wheels are outside frame.

2- a Stewart shell FTA on a F unit frame. It has a rectangular motor with brass fly wheels. This motor can be called gold-colored, but I have also seem them in a black color. The truck side frames are plastic and the wheels are inside frame. The truck gears had previously been changed to the Ernst type. The result of this is a change in gear ratio at the expense of additional load due to the drag of the extra surfaces. The data shows is a significantly reduced top speed and a higher starting voltage

3- a Conrail GP35 with a rectangular motor with brass fly wheels. With plastic side frames and the wheel have inside frames.

The tests performed were as follows:

1- As received condition. This is the first test performed on all engines. No tune up is done unless it just doesn’t run. If that is the case, the minimum tweaks are made to get the unit to run. These tests are initiated with an engine running on rollers at 16 volts for 15 to 20 minutes. This insures that the loco is as loose as possible.

2- in this series the second feature is polished wheels. In this case each row is polished with a Kadee wheel cleaner for 20 counts.

3- in this series the unit is grease, oiled and non wheel contact surfaces are cleaned and polished.

4- in this test series the modified five wire scheme is applied. In addition, the screw motor mounts and upgraded wheel sets are included.

This sequence was varied in later tests, but for these three engines this was the general sequence.

Not all of these steps were used on all three engines. The FTA was tested as described in steps 1-3. The GP35 was only tested twice, step 1 and 3. It got the polished wheels, but was not tested with that change only. The SD9 was tested on all four steps.

Athearn WP RTR GP40-2 Engine

Athearn END model 40 RTR Engine

The results of these tests are shown in the following figures.

For the FTA:



The third step led to zero delta velocity across the whole range. Thus the tuned FTA does not suffer from torque wobble. In general, tune up steps tend to increase the velocity level at a given voltage.
The dashed lines on the delta velocity represent the average of the 31 engines tested as of this writing, and an established goal of 1 SMPH at any voltage setting.

The current story will be included in an update.

For the GP35:



As was the case with the first engine, the velocity irregularity at a voltage level was significantly reduced.

Athearn GT Bicent RTR GP38-2 Engine

Athearn SP RTR GP40X Engine

For the SD9:



The best delta velocity result occurred at testing step three. When the 5-wire plus features were added, the performance seemed to retard slightly. Because this step is accomplished by taking major parts of the engine apart, including the motor. The motor clips are removed and wires are soldered to them. This activity apparently changed the performance. In this case it was a negative result.

(revision 11-27-14)
As indicated in the Engine Health and other posts, a better way to compare engines is using a performance criteria parameter. This parameter is defined as foloows:

PP1 = (Pull Force max – base) / ( Volt min * Velocity min * current min )

where base is the pull force required to pull a train of a minimum requirement as defined in other posts.

Five Atheran Blue box engines have been tested varing various tune up features. Actually more than that have been ested, but they appear to have sick motors and the benefits of these features are questionable. That includes the Conrail engine described earlier in this post.

The engines compared here are identified in the following chart:

Athearn tune features1

Athearn tank train car

Athearn NS RTR F7A Engine

A bar graph of these results is shown below:

Athearn tune features2

These data favor the stock wheel with a simple polish and the G&O features. Switching wheels to the NWSL or the Athearn RTR both seem to be very detrimental to this performance parameter. This seems to support the on line statements that these wheels have a 20 percent lower friction coefficient. It begs the question as to the benefit of “upgrading” wheels. These are supposed to provide improved electrical contact. In this environment, that is not showing a benefit. Treating the track with graphite or other treatment is supposed to do the same thing, and in a more cost effective manner. These will be tested in a later set of tests.

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