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POINT CONTROL

September 13, 2009

 

I have decided to use the Hoffmann point motors as supplied by Finney and Smith. These are superb motors which can be adjusted lo give slow action. They have positive charge over contacts for changing the polarity of the frogs and are easy to install. However the total throw of the motor is much more than I need for my points. I therefore had to find a way to restrict the throw and also allow fir easy adjustment.

I have therefore adapted a method of point control described by Neil Rushby in the Railway Modeller in April 2008. He uses a point drive bracket fabricated from ‘chocolate block’ connectors clamped on point rodding made from bicycle spokes with further connectors to act as stop blocks for the amount of throw.

The operating bracket is made from the brass insert of a connector block. A piece of brass shim is soldered to it and a piece of brass tube is soldered to this. The tube is the right diameter to accept the 12BA screw coming from the false point tie-bar. A further small tube is soldered across the bade of the connector. This will take the operating wire from the point motor. See below.

 

The mechanism is then built up on a plywood base. The operating bracket runs on a piece of 1/16" steel inserted through blocks of wood glued to the sub-base. The motor is then screwed to the base and the operating wire runs through the tube with a connector block on either side.

A recess is routed out of the baseboard and the whole unit is glued in place with NoNails with the operating tube engaged with the screw form the tie-bur,

To adjust the point the molar is thrown fully over, the point operating bracket is pushed over and secured with one of the adjusting blocks. This process is then repeated with the point motor thrown the other way. This whole system allows for the excess travel of the point motor and it is easy to adjust the throw in the future.

Once installed, the motor was wired up to the main wiring loom and feeds connected to the frog from the running rails, It was there tested from the control panel and any adjustment at throw made.

This method seems to give a good positive throw of the point but doesn’t put any excess pressure on the tie-bar. Time will tell how robust it is.

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