As discussed in the post on Life Like P2K performance, these engines have a fairly wide range of overall performance. Reviewing the work of others online indicates that there are techniques that can improve the results. I have included a link in my favorite links post that identifies the major part variations and some potential reasons for the performance fall off.
I have several engines that have been tested and several others that are poor runners or not running at all. To better understand this performance a systematic step by step evaluation was performed to identify the benefits of various tune up features. This is similar to the work done on the Athearn blue box units tune up process earlier.
In this case, some think problem is associated with the factory applied lubricant that was used on P2K unit. Over time or due to environment variations this lubricant hardens and has an adverse impact on the performance. The shortfall that has been observed is consistent with excessive internal engine loads. Increasing the sustained starting voltage and adversly impacting velocity and current draw. It will also reduce the measured draw bar force.
This is on top of the mandatory replacement of the Athearn clone axle gears. As indicated in the info link, not all P2K units suffer from the gear issue, but the all can have the lubricant issue. If the original owner was diligent and replaced the lubricant, then the engine may not have a problem or may not show improvement. Because of these potential variations, a number of engines need to be followed before a conclusion can be drawn.
Another design issue that can cloud this performance is the electronics that was built into all P2K engine models. In order to ensure a bright light when the engine was running, diodes were used to control the voltage where the motor would start. Generally this is around 4 volts. The problem with this is two-fold. First, the electronics has variation, so it is possible to see more than a volt variation in motor start because of the electronics. In addition, the electronics puts a floor on where the engine will start. Doing tune up work typically increases the velocity and the current draw at a given voltage. The arbitrary voltage floor does not allow the engine to run at the potentially lower values of a lower starting voltage.
The plan followed for these of tune up steps was as follows:
(Using the Simplified engine only test sequence.)
1- run an “As Received” test. If the configuration is the Athearn clone, the axle gears were replaced. If required additional minimum tweaks will be applied the get the unit running.
This is shown in the following figure:
2- the motor bearings will be cleaned as best can be done and lubricated.
This Process is shown in the following figure:
3- the tower gear bearings of step 2 will be cleaned & lubricated
This is illustrated below:
4- the truck gears and internal truck surfaces will be cleaned and lubricated.
As shown in the following:
5- the stock wheels and new gears will be replaced with Athearn RTR wheels and new gears.
6- the wheels and axle gears will be replaced with an appropriate set of NWSL wheels and new gears.
These last two will quantify the value to the system performance of wheels that are intended to have better conductivity when the “dirty track” environment prevails.
The initial tests went well. All of the units showed a need for tune up. The starting voltage and speeds are high and the 12 volt velocity is low. Generally the draw bar force is adequate, but not outstanding.
The five engines being tested in this series is shown in the following figure:
These include, A BN GP30, a NP GP18, a NP GP7, a NP GP9 and a Susquehanna GP18.
One of the units, a NP GP9 quit running at the end of the first test series. During the 8 volt stall current test. This is not a critical item, so it was decided to fix the unit on the next test step. All of these units are used, some more used than others. Upon tear down to do the initial repair and do step 2 of the series it was discovered that this engine had a digitrak decoder in place. This was either forgotten or never known. The stall testing likely fried it. These, NP units, are part of my collection. Fortunately, A second GP9 of similar vintage is also part of the collection. The second units shell was removed to verify that this unit was a stock configuration. It is, so it replaced the original unit in the series.
In the process of this work, it became clear that the drives are three variants of the same fundamental drive. The two GP18’s are from the earliest release. These are represented in the following figures:
In this version, the shells were held on by tabs that would break off with removal. The drives were not designed to be easily worked on. In order to get at the truck towers, some wires had to be cut so the weight could be moved out of the way to get at the parts underneath.
The GP9 engine drive has the modified chassis where the couplers screw on. This screw holds the shell in place. I call this version 2. I am not sure that is correct, but that is how I am referring to it. This version also has a light card added and the wire lengths have been increased to allow the weight to be moved so the maintenance can be done easily. This drive is shown in the following picture:
The GP7 and GP30 drives are from a later vintage (version 3) where they have been made DCC ready with the addition of a plug for the decoder on the light board. Otherwise, the drives are visually similar to the GP9. These are shown in the following charts:
As previously stated he construction of the two early units is enough different that it is difficult to get at the motor or the truck towers. In trying to clean and lubricate the motor for the second round of tests on one of these units, a wire came loose from one of the truck towers. In addition the upper clip on the motor came off. Because of this, only two units were tested for steps 3 and 4 separately. This was done on the GP30 and GP7 only. For the other three engines, a limited step 3 and 4 was used. Here the truck tower bearings were oiled from the outside. The Truck gears and surfaces were cleaned from the bottom. The shafts holding the gears were oiled and a light amount of grease was applied to the gears also only from the bottom.
While this is not the same as the individual steps, the concern about the variation caused by potential repeated repairs was the deciding factor.
The results of this test series are summarized in the following chart:
Unfortunately, these results are not a crisp as I would like. The best case appears to be step 2. The other steps tend to reduce or have only a slight impact on the performance criteria 1 parameter. Here the starting voltage varies from 3.9 to 5.2 volts. While some of the steps did have an influence on this parameter, the engines tended to hover around different starting voltages. This is likely due to the electronic restrictions mentioned earlier.
These results bring up the question about the bearing and truck gear lubrication in general. In the case of the GP30, the truck work was detrimental to the performance. This implies that for this unit, the cleaning and new lubrication cause a bigger problem than the preexisting condition.
For the GP7 the truck gear cleaning and lubrication yielded the largest improvement. The preexisting condition here was causing a performance problem. In this case the motor clean and lube had little impact. This unit is part of my collection and was purchased on e-bay as new. So maybe it actually was new. If so, the half hour running before the test may have put the motor in its best condition. Any additional cleaning did not show a benefit.
The other three engines showed a good benefit for the motor cleaning step. The impact of the modified truck lubrication was again mixed. Two of the engines showed a benefit and the other showed a loss.
Based on these results, both steps are worth doing. If the engine is used, cleaning and lubricating the it will likely show the largest benefit. Most discussions about Athearn clone truck lubrication indicate that less is more. These results are mixed, with 3 of the 5 engines showing a healthy improvement.
The 12 volt velocity benefited from these tuneups. Some of the engines were excessively slow runners. While not getting up to a competitive speed, these demonstrated around a 10 SMPH increase.
As has been shown in earlier tests, the wheel changes from the stock P2K wheels showed a significant loss in draw bar force. This drop was not compensated for in the other factors, so the four engines where this change was tested all showed a performance loss for the wheels.
1- Cleaning the armature and lubrication the motor bearings are a critical step for a used P2K engine tune up.
2- Cleaning and lubricating the Athearn Clone truck gears and bearings are probably a good step. a resistance check is in order to make sure there is a problem to cure.
3- Because of the substantial loss in performance for the upgraded wheels, one has to question if they are worth doing. That will depend on your experience and situation.
4- These P2K engines show more variation than one would expect. The best varies between 30 and 85 in PC1 depending on the unit. The starting voltage and starting velocity variations were also significant. On one hand we have the GP30 that starts at 4.5 volts running at 1.5 SMPH compared to a GP18 that starts at the same voltage at 3.8 SMPH. The difference grows to the point the there is a 10 SMPH difference at 12 volts. While these numbers may seem small, a control card is going to required to put them in consist.