So far, the data for the motor test series has been focused on running a given test bed engine with different motors. In that case, the only variable is the motor. Where possible everything else is held constant.
The test bed engines are basically Athearn Blue Box models. This was chosen for convenence, cost and availability considerations.
In the process of doing this a given motor is run a number of times in different test beds. Here, the only constant is the motor (and fly wheels). Everything else is varying. The results are quite interesting.
For this reason the potential variables include the following:
1 Shaft length
2 Shaft coupling type
3 Truck design
a 2 axle
b 3 axle
c inside frame
d outside frame
4 Wheel material
b NS RTR
5 lubrication age and amount
6 wheel condition
7 gear bind
8 gear teeth condition
9 gear burrs
Items 5-9 are condition issues that may or may not be controllable.
A sample of this is shown in the following figures:
The first figure describes the known similarities and variables. All wheels were cleaned and polished in a similar manner. All truck gears, bearings and drive worms were cleaned and lightly lubricated. An attempt was made to minimize these influences. As shown in the second figure, certain configurations appear to be influencing the results.
Some statements that can be made:
1 Inside Frame trucks start at the lowest voltage. The velocity tend to be mixed. This comment is made relative to Athearn type trucks. In this case, the outside frame includes a bearing in a metal side frame. These bearings tend to be not aligned with the axle causing additional friction drag.
2 Six axle trucks have more pulling force. The inside frame version on the SD40-2 is clearly the best. The question is why is the 4 axle GP38-2 so bad? The RTR wheels are definitely part of the problem. These lose 20 to 25 percent of the driving friction force. This would not achieve the SD40-2 level, but may beat the other two.
3 The velocity voltage result indicates the Trainmaster version has significant resistance at all power settings. The other three also exhibit more variation than expected.
Based on these results, some additional testing may be in order. For the GP38, stock wheels, tuned and deburred gears and tuned or improved tower worm gear. For the Trainmaster, the gears and bearings should be worked appropriately.
For now, this work will be delayed because there test bed engines have additional motors to be tested in the current condition.
A full report on this motor, including the full set of results and additional insights will be available for download in the near future.
Thanks for looking.