Getting the Power through
a Ball Thrust Bearing.
by John Ince
There is enough room, 11mm, between the upper and lower plates of a Ball Thrust Bearing, P/N 168, to install a simple commutator to enable a power supply to be taken from the engine room of a crane to the driving wheels at the bottom of the tower.
The commutator rings are made from 0.5mm copper sheet and are 5mm wide. The outer one is 44mm o/d and the inner one 24mm o/d. They are held in place by tabs soldered to the rings and bent over under the ABS plastic disk. For my brushes I used scraps of brass from old electrical terminal blocks. These already had a tapped hole and a small bolt. They are trimmed down to the thickness of a Meccano Nut and screwed to the disk. The spring brass brushes are of similar origin and are cut to size, bent and soldered onto the brass base. Once they are in the correct place and alignment, use a bit of double sided Sellotape to prevent them from moving. Another option would be to use the contact strips from a dismantled relay.
The upper ABS disk is held by Bolts passing through the outer round holes of the upper Ball Race plate. An extra nut between the plate and the disk gives enough space for the head of small bolts holding the brushes in place. The 3/4" Bolts also secure the plate to the crane superstructure. The brush holding bolts have the supply wires attached to them. Cover with insulating tape to avoid a short circuit.
The 1mm ABS disk shown below has brass or copper contact rings fixed to it with tabs passing through holes in the disk. These tabs are folded to lie in the slots in the ball race. Solder a connecting wire to one tab on each ring and cover with insulating tape. The two Bolts secure the ABS disk to the Ball Race bottom plate.
