"Morris Dovey" wrote in message
...
MikeWhy wrote:
"Morris Dovey" wrote in message
...
in a trough-type reflector tracking mechanism subject to (mostly)
unpredictable wind loading.

I haven't actually ever made a hob, but know of the general principles.
If your gears are non-metallic, wood or GRP, the problem might be even
simpler. Better still, if the geartrain is a worm gear, a simple tap --
the things used to cut internal threads -- are perfectly serviceable hobs
for cutting the worm wheel.

Your suggestion is appreciated, but this thing needs to be thermally
driven (as opposed to motor driven) - and if I need to use a geared
approach, it will probably be a sliding rack with one or two simple spur
gears.

It's one of those problems that /seems/ like should have a simple and
inexpensive solution, but every attempt so far has led to unacceptable
complexity and/or cost.

Locking against heavy loading would seem to suggest a worm. PV? A
Stirling pumped "hydraulic" motor/water wheel? I know... complexity.