It quickly became clear to me that my
braking system was not correct. I had a go-kart/motor bike disc
braking system with a caliper system to clamp down on it. This
certainly worked. The cable ran down the side of the pole down to
the ground to a lever. I realized that as the assembly yawed with
the wind, the cable began to wrap around the pole. Soon it became
tight and activated the lever on the brake. Going down the center
of the pole would not work either because the cable would rotate around
the electrical cable which was stationary due to the rotary
switch. It would wrap around the wire instead of the tower, but
the effect would still be the same.
Then I had an idea as I worked the problem out with a friend at
work. I would fashion a tube to just slip over the top tube of
the tower. I could pull this down with my cable. A spring
would push it back up when I realized the cable line. I would use
a sealed bearing at the top to which I would attach the cable that went
to the caliper lever. All I had to do was use my lathe to get the
right tolerance for the bearing and brass pipe (brass was used for the
ease of lathing and low friction) and press fit the two together.
Steel bands would hold the actual cables. So far the system works
great. I let the blades free spin in 20-25mph winds and by
pulling on the cable I could bring the rotation to a quick stop.
When I released the cable the blades would start to rotate again.
Here are the pictures.
The brass tube is 2" ID and just fits over my 1.875" OD tower
stub. The brass has been machined down to allow me to press fit
the bearing on top with a vice. At the bottom I carved out a
groove to lock the bracket in place that you see in the next picture.
Steel brackets hold the cables in place.
Here is the system on the top 1' section of my tower. The spring
is made from coat hanger steel. The tower pipe gets bigger after
the first 1' and this forms a floor for the spring.
The cable to the left goes to the ground cable. On the right it
connects to the lever that activates the disc caliper. The brass
tube easily slides over the tower and the spring makes sure it doesn't
jam in the locked position. As the assembly turns it turns the
bearing, while the tube stays stationary.
I found over time, though, my initial design was flawed. I was unable to find stainless steel 55mm bearings. Over a few rainfalls the bearing began to rust and get stuck. It wasn't long before failure. The solution, that has worked so far, is very simple. I took a 2L coca-cola bottle and cut off the top so it just fit over the 1 7/8" diameter tubing at the top. I also cut off the bottom. I burned a small hole for one of the cables and now I have a waterproof cover. For protection against atmospheric moisture I coated the bearing with marine triple grease, which is the blue substance covering the bearing in the pictures. I have had rain and snow and the bearing has remained dry.
