Point Motors

Webmaster's Note: This article is not from the original Sough Lea series. Sough Lea uses Seep point motors which were installed in virtually the same way as Richard describes below.

Points can be operated manually, provided they are within easy reach, but you can't beat the 'hands off' control of motorising them and operating them from a control panel. This article show you how to attach a Seep point motor to a Peco point, as well as wiring the live frog using the accessory switch.

The Seep point motor has been available for a few years now, and as such is a tried and tested design that is still going strong. It can be used with all the major makes of point work and with a little care is easy to install. It is available either with or without the accessory switch, the version with a switch being cheaper than the Peco alternative, where the accessory switch must be purchased separately, an important consideration if your layout has a lot of points or you are on a tight budget.

How Does A Point Motor Work?
A point motor consists of two solenoids, coils of wire that become magnetic when an electrical current is passed through them. A steel bar is passed through both coils, and by passing current though each solenoid in turn, the bar can be pulled one way and then the other. Connecting this bar to a point via a rod enables the point to be thrown one way then the other (see Photo below).

A seep point motor

Fixing The Point Motor
The first thing to do is attach the point motor to the point. Peco points have a hole on both sides of the tie bar into which the rod on the point motor fits, moving the tie bar to move the point. First, position your point where it will go, and check that there are no parts of the baseboard frame underneath that will interfere with the location of the point motor. If there are, you have a number of alternatives. You can move the point to another location, the simplest but perhaps not the best! You can put the point motor above the board, hidden under a building or scenery. Or you can put it under the board away from cross members but use a link to join it to the point (see later).

With your point temporarily in place, put a sharp pencil though the hole in the tie bar and move the point back and forth. When you remove the point, you will have a pencil line showing where the rod from the point motor will come through the board. Note that the line is actually an arc not a straight line. You can drill a series of small holes along this arc or one bigger hole, as large as the arc. I prefer the latter as it ensures that the baseboard will not interfere with the point motor rod, an important consideration when lining up (see later). However, you do have a bigger hole in your baseboard!

Correct Alignment
It helps for the next stage if you can turn the layout over, or at least on its side. If not, then it's a crawl underneath job! Hold the Seep point motor in place, with the rod through the tie bar; this rod extends underneath the motor, enough to hold it to throw the point as if the motor was working. Check that the action is smooth, and that the rod is at 90 degrees to the tie bar. Also check that the contacts on the motor for the accessory switch positively locate on one or the other contact, and that it does not stop in between, which would be a short. Once you are satisfied that the motor is in the correct position, use a pencil to mark the locating holes. I drill small pilot holes and then use short round headed screws, easily available from DIY stores. The two screws together provide a very solid fixing.

Cutting the Rod to Size

You will probably find that the rod from the point motor extends above the tie bar more than it needs to (see photo below).

The rod from the point motor extends above the tie bar more than it needs to

It is simple enough to cut off but do not do what I first did, which was to use a slitting disk in a mini drill on the rod in the tie bar as the heat from the abrasive nature of the Carborundum disk nearly melted the tie bar! I now use a file with a thin edge to mark the place on the rod to cut (see photo below) and then remove the point motor completely and cut it out of harm's way. Alternatively, you could use a heavy duty pair of side-cutters.

Use a file with a thin edge to mark the place on the rod to cut

Attaching Wires To The Motor
Having located the point motor, it is time to remove it and fix the wires. Unlike the Peco motor, the Seep motor requires wires to be soldered directly to the contacts on the circuit board. This is not as daunting as it may seem. The first thing to do is hold the motor securely. You could screw it to a scrap piece of wood; I used the invaluable Helping Hands, available from all model tool suppliers. Next, tin the end of the wire you are going to attach; this simply means using the soldering iron to put a thin coating of solder on the end of the wire. This will make it easier to solder to the contact. Simply hold the tinned end of the wire on the contact, quickly apply the soldering iron to the wire and you should find that it has soldered the wire to contact (see photo below).

One wire soldered on

Now do the other five (see photo below)!

6 wires soldered on

I cut these six pieces of wire to about an inch in length and then screw the ends into a piece of terminal block. This is done so that the wires from the control panel do not have to be soldered directly to the motor which would be awkward. All soldering is done more easily on the work bench. Also, in the unlikely event that a motor fails, it can be easily swapped for another without the need for the soldering iron (see photo below).

Terminal block

Get Connected
Electrical connections can now be made, but first you need to decide how you are going to operate the motors on your control panel. The simplest method is the stud and probe, whereby a light touch of the two makes the connection (Figure 1).

Figure 1

Peco make all the necessary parts, and they come with good advice on wiring (see photo below).

Peco studs and probe

However, they are simple enough to make from screws and an old biro with a metal rod inside. The wiring is a bit simpler but when you are operating, one hand is permanently occupied holding the probe. Push-to-make switches will do the job, there's no probe to hold but there's a few more wires involved (Figure 2).

Figure 2

The accessory switch on point motors is so called because it can be used to operate an accessory such as a signal when the point is operated. However, the more usual use for these switches is to change the polarity of live frog points. You do not need to wire the frogs on a point as they will get their power from the point blades, but therein lies the problem, for the blades act as switches, and rely on the contact of the face of the blade with the face of a rail which is not the best contact; they can get dirty and be difficult to clean. Wiring a feed to the frog overcomes this problem and ensures better electrical continuity. However, depending on which way the points are set, the frog will be either positive or negative; it needs to change its polarity when the point changes (Figures 3 and4).

Figure 3Figure 4

There's all the information you need in the instructions with Peco points and with Seep point motors. Also, refer to Section 6 of your N Gauge Society Handbook. It's best to include a Capacitor Discharge Unit (CDU) in the circuit as this helps to smooth the action of the motor.

Awkward Locations
Finally, what if you cannot put the point motor where you need to? I had two points close to one another such that the Seep point motors would over lap under the board; in other words, one would have to go over the other. I tried this, suspending one of the motors over the other on a kind of shelf, but it meant that the rod was too long and tended to just bend when the motor was worked rather than moving the point. Mark Two consisted of a new rod from a piece of wire, bent at 90 degrees and soldered into a piece of brass square section which had a hole drilled in its bottom surface to accept the rod from the point motor (see photo below).

A new rod from a piece of wire

The motor itself was suspended over this on some small pieces of wood strip. Only one screw could be used to hold the motor, but this has proved to be enough (see photo below). A similar procedure could be adopted above the baseboard, with the motor being hidden in an adjacent building.

Motor fitted to small supports

This article first appeared in N Gauge Journal 2/03. Members can purchase back copies of Journals.