Kato Amtrak P42 truck power test results

Normally a multiple sample set of tests is required before any statement can be made with certainty. However, recently a Kato P42 Amtrak engine with the motors in the trucks was made available for testing. This same engine is being used as part offense other parameter impact series.

The results of this engine’s initial tests were such that a summary of this single test was justified.

While looking at individual parameters the uniqueness may not stand out, when looking at the performance overall the unit is in a class by itself.

This engine running on the test rollers is shown in the following figures:


The bottom and the bottom of the trucks are shown in the following:



This discussion will focus on the performance measurements of the unit. The basic test requirements are as follows:

1.) Powered with DC voltage with no pulse wave modulation

2.) Running on a level surface, measured and adjusted as required weekly.

3.) The same 8 foot segment of track is used for all the basic tests.

4.) the track is cleaned before each test.

5.) the unit is run without external load for all but the max draw bar force tests.

6.) Each track running data point is the average of three measurements.

The accuracy of the shell, the location and nature of the details or the lettering are left to others.

To appreciate the results, the question of relative to what always comes to mind. For this reason the engine is compared with the full set of nearly 200 engines tested up to this point. In addition, the data is compared with all the results of units manufactured post 2000. To further highlight the comparison, a specific second engine is also shown in the comparisons of post units. This second engine is an Atlas Master Train-master model. Like the P42, it was new out of the box at the time of the testing. It is no longer available for pictures and further testing.

Basic function results are presented in the following charts. The first chart in each category is the total set of engines. The second chart is the post year 2000 comparison. Note, the voltage function curves do not show the minimum voltage data. That data is shown on the weight function charts.

1- current draw vs voltage with the engine operating on rollers

This gives a stable current level at any voltage. It implies the engine health condition.
Because there is some additional voltage drop across the rollers, the four volt current is usually for the unit just sitting on the rollers, not running. This is approximately the stall current at actual voltage potential of the roller surface.

p42allcurrent on roll

The post 2000 results are:

p42current on roll

In both charts the P42 is clearly shown to be a low current draw machine.

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



As before, the P42 current level is near the lowest level measured in the series. It is significantly lower than any other post 2000 engine. That is a bit of a surprise. It has two motors where all the others have one.

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



In these charts a reference line is shown that is intended to represent the goal of best speed voltage function. Basically, the unit needs to crawl as slow as possible at low voltage and be able to replicate the full size unit at high-speed. For this purpose, 80 smph at 12 volts was chosen as the value. One could argue that it should be higher. True, but without any external load, why would it be lower? Notice a significant number of engines, particularly post 2000 run slower than this goal level.

The P42 engine defies the general trend of the post engines. It clearly runs faster at all voltage settings. The Atlas Master unit follows the goal line almost exactly. That is interesting, because the position of the line was created long before these results were known.

A number of parameters are shown in a weight function chart. There is one data point per engine. In this case the pre and post 2000 engines are shown on the same chart. The pre engines are shown in grey. The post engines shown in blue. The Atlas master engine is green and the P42 engine is red.

4- maximum pull force.


It is interesting to note that the P42 pull force is very good for the post 2000 engines, but does not achieve what the average pre 2000 engine.

5- Current draw at maximum pull force.


So fully loaded, the current draw is still low. Other recent engines do as well on current draw, but do no do as well on force.

6- 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.


Both the P42 and the Atlas Master engines fall near the bottom of this data.

7- the minimum sustained velocity, SMPH

For this data, the engine was required to sustain movement for six feet. The speed measurement was taken at the end of that distance.


In this case, the P42 tends to be average where the Atlas master is competitively low.

8- the variation in the minimum sustained velocity.


This chart shows the measured variation in velocity for the three data samples taken for each engine. Running over the same track at the same voltage setting, all things being equal this should be zero. Any value above that implies the existence of some torque wobble. In this case, the P42 is comparatively low. The Atlas master is excellent. Note, the number of pre and post 2000 engines that have large speed variations. This is not fully appreciated at this point, but it is implying something. The larger the number, the less smooth the operation.

9- the current level at the minimum sustained velocity.


As with the other current draw charts, the P42 unit current draw is distinctively lower than the other engines. The Atlas master is competitively low, but higher than the P42.

10- Engine only velocity at 12 volts


As has been indicated, the P42 speed is high relative to most of the other engines. This is indicative of the two motors resulting in a high power design. Considering that the unit was intended to operate on sharp curves, this is a good result.

Kato AMTRAK P42 engine 1

Kato AMTRAK FP40PH engine

Bachmann AMTRAK GG1 engine

Kato AMTRAK P42 engine 2

11- Engine only current draw at 12 volts


As has been seen, P42 is setting the standard for current draw.

12- the performance criteria parameter for each engine.


Using a combination of the measured parameters, that was defined in the performance criteria post, The P42 engine set the standard. The current draw is dominating this result.

Heretofore, a PC2 value of 50 or above was considered to be an excellent engine. Both the Atlas Master and the P42 are well above that level. The P42 clearly sets the standard for performance of engines tested so far.

The only draw back is that it may not crawl as slowly as desired. But how slow is slow. Particularly if you impose a PMW signal.

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