2-25-15 Impact of wheels on P2K tests

I really didn’t realize how true the title of the last post actually was. The activity at this time of year has always been at the yearly high. This year has started really very good.

The rate of engines being tested has dropped to less than one per day. Most of these have been “sold” engines.

The last variation in the five engine P2K engine study was completed this afternoon. The data on the last three tests are in evaluation and the whole activity summarized.

My initial partial assessment is as follows:

1- The real surprise is that very little positive impact occurred in the steps.

2- The previous conclusion about “upgraded wheels” was repeated in this series.
The best performance occurs with the stock wheels.
The Athearn RTR wheels perform the worst.
Most of the loss was in the reduced draw bar force due to the reduced friction coefficient of the polished wheels.
The NWSL version also was a significant debit on the engine performance. Better than the RTR, but still significant.

Because the track is cleaned before each test, the electrical benefit that may be associated with these wheels does not show through.

Some discussion on the Atlas rescue forum indicated that the stock P2K engines have diodes that control the brightness of the lights. In the process, this is supposed to keep the motor from starting before four volts. The data indicates that this not precise. Not getting into the why’s of that choice, this limit is likely having an interesting impact on the results. If you focus on the velocity voltage function, reduction of drag or voltage loss in the system will lead to the engine running faster at a given voltage. This by itself looks like a loss in the goals for performance. The hope is that the starting velocity would go down with a tune up. Without the diodes in place, the starting voltage and velocity would be less. In this case the voltage may stay the same and the velocity goes up. Fortunately, the torque and thus the draw bar force should also increase with the tune up, so a net improvement should still be possible, but the limit has a modulating effect on the assessment. More to ponder.

The total engines tested has grown to 121 units. One of these is the recently released Bowser C626. This unit was tested after the original trucks and fuel tank were replaced by Bowser at no charge. The engine is a beautiful model. It has some performance short falls, but still falls in the good range.

More later.

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