Saturday, 30 January 2010

Yet Another Point Tie-Bar Mechanism - 2

Here is how the mechanism described in my previous post is fitted below the baseboard and the point. Remember, the point blades are fitted with operating wires, formed using the Easitrack bending jig, so the point has two vertical operating wires dropping down near the ends of the point blades. Two small slots are drilled and carved in the baseboard surface before gluing the point down. The slots are wide enough to allow the brass tubes from the operating mechanism to pass up through them, with enough sideways throw to allow operation of the point. This photo shows the point in position. When it is ballasted, there should be very little of the mechanism visible, I hope:

The mechanism is glued underneath the point. As it is put into position, the two operating wires dropping down from the point must be threaded into the two tubes of the mechanism. The ends of the tubes will be just below the top surface of the baseboard when located properly. Some rigid brass wire with an omega loop formed in it is hooked into the hole drilled at the end of the PCB in the mechanism. I am using servo mechanisms to operate the points. These are very cheap on Ebay. I have some MERG Servo4 electronic kits to drive them (each board will drive up to 4 servos) and the first of the MERG CBUS kits will be used to control them. More on the electronics will be in a later blog posting. I had hoped to glue the wooden blocks that the servo is mounted on to the baseboards, but the glued joint was not strong enough, so small countersunk screws have had to be added which will have to be covered by the scenery.


Howard said...

Have you seen the method of mounting servos on the MERG forum

It uses aluminium angle & attaches the servos via cable ties. Very quick & simple and surprisingly rigid.


Ian Morgan said...

Yes, Dave Harris is a colleague at the Basingstoke model railway club. The aluminium strip still needs to be connected to the board somehow though.