The controller switches are designed to handle currents up to a 1000 A.

The switch arms are made of 16mm square copper bar (from www.nfm.co.za).

The copper nuts and bolts are M10. (from www.screwman.co.za).

The switch base board and the isolator tips on the switch arms are made of 4.47mm P1 SRBP bakelite sheet (from wilec.co.za).

The layout of the switch is shown in the Figure below:

For dimensions, open this file:

Switch Schematic

The side arms and the centre arm of the switch swivel around the bolts which keep them in place. The plungers of the solenoids hit the two arms from each side of the switch in the centre where the two arms touch each other. (the contacts). This construction creates maximum force over the contact area in order to break it lose in the event of contacts that are welded together. The construction of the switch is shown in the following pictures:

Top View

Side View

Bottom View

The shape of the copper bolts are shown below. The flat surface is 16 mm and the length is 60 mm.

A fuse is provided in each switch. See picture above. The fuse is made of 15 strands of normal home electric earth wire (x3).

The tips of the two side arms of the switch must be isolated to prevent a short circuit. The isolators are cut from the bakelite board, shaped and screwed on as shown.

The detail of the side spring installation is shown above. “How to make the Spring” is described in the Springs Chapter (see site menu).

The centre arm spring is attached to a L-shaped support bracket as shown below. The other end of the spring fits over the head of a M4 bolt that screws into the centre arm copper. Again,  “How to make the Spring” is described in the Springs Chapter (see site menu).