Bob
The Big Loop Saga Continues - Part 4
You may recall from part 3 that it was decided to use carabiners at the corners of my big
loop antenna, to avoid the problems with pulleys (axle comes unscrewed, wire comes off
wheel, and pulley breaks). But later It was discovered that the wire sticks to the carabiner
and does not allow free flow of the wire to equalize the tension in all legs of the loop.
So back to the pulley, but with an improved design. This time they are metal instead of
plastic so they cannot break, the axle is held with a pin instead of a screw and a special
washer is manufactured to prevent the wire from coming off the wheel.
The new pulley looks like this:
The wire is supposed to ride on the wheel, like this:
But witih changing loads, the wire inevitably manages to come off the wheel and get stuck
around the axle:
The way to avoid this problem is to make the wheel “thicker”, so there is no space for the
wire come off the wheel. This is done by manufacturing a washer of just the right
dimensions to fit into the pulley, block the wire from coming off the wheel, yet not increase
the turning friction of the wheel.
I purchased some thin aluminum sheet of just the right thickness to easily slip in between
the wheel and frame. Then using a drill for the center hole and a chassis punch for the
outer diameter, a washer was cut out.
When the washer comes out of the chassis punch, it is not flat, so I pounded it flat with a
hammer on a flat anvil. Now as you can see here the wire cannot come off the wheel, after
the washer is installed.
Since I have 3 pulleys, I made 3 washers. That left a lot of aluminum sheet, so if you would
like to have washers made for your pulleys, I would be glad to help you.