Peco Point Motors and Switches


Background

Over the years we have heard many people mention reliability problems with Peco point motors and switches, particularly the latter.
So what problems are people having with these products ?
In this article, we look at the products and provide answers.


Peco Point Switches (PL13)

Peco point switches are a self contained two-way switch. Sometimes, they can be quite stiff to move. This can be fixed by dismantling and re-assembling or by opening out the slot in the PCB a little to free the movement.


In general, we found the switches to be quite reliable.


Peco Point Motors (PL10)

Peco point motors in themselves are actually very reliable. They are light, the movement is free and they readily clip to Peco turnouts, making them an ideal choice:


The Problem and Symptoms

Apparently, there is a widely held belief that the PL13 switch is unreliable, so we decided to investigate.
What we found was that the most common problems people reported was that of the switch appearing not to operate. The symptoms of the problem usually manifested itself as one or more of the following:

  • A common croosing on a live frog turnout is electrically dead when the turnout is in one or both directions
  • Accessories connected through the PL13 are electrically dead when the turnout is in one or both directions

Switches which do not make contact can only be an indication that the switch is not working properly or not being operated correctly.


Problem Investigation

Firstly, we believe that the problem with these products is widely misunderstood. Both products do actually work well, however, when they are put together, the problems start...

The problem is actually caused by the point motor. It's armature slides in tubes in the coils which are somewhat larger than the armature itself. This means that not only can the armature move side-to-side, it can also move up and down and this is the cause of the problems.

The following two pictures are exagerated to demonstrate what we found on a sample of Peco point motors:


The diagrams represent a cross section of a Peco point motor, taken through the coils (denoted in black).
Note how the coil tubes through which the armature (red) passes through is much larger than the size of the armature. The result of this is that the armature can move up and down inside the coils.

When the armature moves up and down inside the coils, the movement of the actuating rod (blue) is affected. In the diagrams, we have shown it affecting the tip of the rod at the top of the diagrams by causing reduced movement - the tip of the rod doesn't move the full distance that the armature does. This translates to reduced tie bar movement and switch blades which don't move their full distance. This problem becomes even more pronounced when the actuating rod is extended and this results in very little movement at the tip of the rod - the turnout doesn't change at all. This is compounded by the fact that the actuating rod and its extensions are slightly flexible.

If the movement of the armature causes reduced movement at the bottom tip of the actuating arm, this translates to reduced movement of the PL13 switch.
When we experimented with Peco components in order to compile this article, we found that this generally only happened either in the left or right position, but not both, but the result was a PL13 switch not being fully moved and therefore, not making contact in one direction. This caused live frogs to be 'dead' when a turnout was in one position but not the other.
We also found that the mounting of the switch on the point motor could have an impact. The switch is not a firm fit and must be glued to attach it - this is a really cheap and nasty fixing method! If there was any movement, the whole assembly became out of adjustment.

The 'Principal of Levers' determines that the moment of rotation will always be around the most 'fixed' part of the assembly. Therefore, if the switch is stiff, it will act as the point about which the whole armature and actuating rod move.

In tests, we found that the Peco turnouts themselves offer a lot of resistance, due to the spring, and with the Peco extension to the actuating rod, it was actually possible to move the armature fully in both directions and have no motion at the tie bar end of the rod - the turnout did not change at all!


Conclusions

The basic design of the point motor and the switch is sound, provided it is manufactured correctly, however, where the whole product is let down mechanically is in the size of the tubes through the coils. If there is no slack, the motor works fine, but we found in a large collection of motors, that most exhibited tubes which were too large and had armature 'slop'. This must have been a problem for years given that the 'reliability rumour' is so widespread.
The actuating rod is made of a metal which is slightly flexible. This contributes to the problem, especially with extended rods.


Solutions

The Peco switch is very susceptible to the manufacturing quality of Peco point motor coil tubes. Provided the switch is attached to the motor centrally and tested prior to fitting to a layout, we found that they were generally reliable.

Peco need to tighten up on the manufacturing quality of their point motors and ensure that the tubes are the correct size.
The actuating rod needs to be made of a much less flexibile steal, like the equivalent part on Seep point motors.
Peco need to modify the switch to have a proper clip fit to their point motors in the same way that the PL15 microswitch set does.

Extended actuating rods are susceptible to mechanical issues and really should be avoided if at all possible. If they really must be used, we would recommend Seep motors instead which do not suffer the problems of Peco point motors. Certain Seep motors also have an integrated switch.


Peco's Response

We have raised the issues presented in this article with Peco. They advised that they have been making the products mentioned for more than 35 years and that we were the first to report a problem.


Graham Plowman (14/12/2011)


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