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106 Chapter Eight

1
3 / 2 in

1
1
4 / 2 in 4 / 2 in

32 in

3
3
4 / 4 in 4 / 4 in

1
9 / 2 in
1
1
Figure 8.26 Top dimensional view of bumper fabricated from � ­in � � ­in �
8
2
32­in aluminum bar.
5-40 nuts
Aluminum bumper

1-in-long aluminum bar

5-40 machine screws
Figure 8.27 Cutaway close­up of aluminum bracket used to secure the open ends of
the bumpers.

The second half of the tile switch is comprised of a 1­in 6­32 plastic machine
screw and three 6­32 machine screw nuts. One nut must be brass with a wire
soldered to it (see Fig. 8.31). Figures 8.32 and 8.33 are close­up photographs of
the finished bumper switch. The assembly is adjusted so that the brass nut on
the top of the 6­32 machine screw lies just underneath the upper aluminum
bracket without touching. When the upper bracket tilts forward, contact is
made between the aluminum bracket and brass nut, which is read as a switch
closure.