[TowerTalk] Tower mast..

[Jim Lux]

At 07:22 AM 9/19/2006, Chuck wrote:
>Grab the kids old bicycles or any off a junk heap to cannibalize the 
>pedal sprockets. Have the machine shop mill out the center of one 
>sprocket to fit around the mast at window level. Weld the sprocket 
>to the mast. Drill two holes in the window base to allow the chain 
>to run through the window.
>
>Take the second bike and cut the sprocket hub off with sections of 
>the bike frame still attached so you can use hose tie down clamps to 
>mount to a flat surface next to the desk. Attach chain and manually 
>rotate the antenna.


Chain drives aren't so hot for bidirectional loads.  You need some 
slack in the chain to account for mechanical movement, stretch, etc., 
so you wind up with backlash in the system.  You can put a tensioning 
system in, but that adds a level of complexity.  Chain drives also 
have trouble when the chain is running sidewise (if it goes slack, it 
tends to fall off the sprocket, just like a derailleur on a bike).

But chains work well in other applications, good idea...