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The heavy altazimuth mounting which came with the dish was in fair condition. Except for the elevation screw. Which had rusted badly over the years. Two of the three nuts could be turned with great difficulty. The third was stuck fast despite repeated applications of penetrating oil.
If I was to replace the entire elevation adjustment screw I needed the two alloy pieces which formed its pivots. I finally decided to sacrifice the rusted rod and cut it where I could remove the alloy fittings with least effort.
I left a stump of rod below the top pivot piece to grip in the lathe chuck. This allowed me to centre drill and bore out the rusted stud in the top pivot piece in the lathe.
The alloy had originally been threaded to hold the top of the screwed rod. Rust had taken its toll and I could not remove the rod from the alloy fitting.
By the time I had freed the threaded rod with careful boring there was no thread left in the alloy piece. I thought I could easily overcome this problem by fitting another nut on top of the pivot piece. For the modest dish elevation angles, which I would be using, the nut should never get in the way.
An image of the top elevation pivot fitting after drilling, boring, cross-drilling and a new, hot galvanized elevation screw (stud) fitted. The top shows the dealer's colour coding paint rather than rust.
The pivot bolt itself passes right through a cross drilling in the threaded rod. Which I drilled in the vice on the bench drill after tightening the two security nuts.
I also turned a slight flat on the top of the alloy pivot piece. Just to give the nuts more surface to work against and to lower its profile.
Lower elevation screw, pivot piece. The alloy is a clearance fit on the large elevation screw. The ends are threaded for the two pivot screws. A cross drilling would just lock the elevation screw in the fitting. All the visible nuts seen here are used as lock nuts. Dish elevation requires one of the large galvanized nuts to be loosened so that the other can be turned. Fine adjustment for elevation is then possible. Major changes in elevation would require one nut be backed well off to allow the elevation screw to slide freely through the fitting.
Here is the fine azimuth adjustment on the main crossbar. Azimuth can be roughly adjusted by loosening the holding screws on the pole and turning the whole mounting (and dish) but this can be far too coarse an adjustment. Particularly with larger dishes. Which have a very narrow signal acceptance angle.
Most of the screws on the dish mounting are badly rusted and should be replaced with either new, hot galvanized screws and nuts or stainless steel.
One of two dish elevation brackets pivots on this bolt screwed into the end of the main cross arm. Again rust has taken its toll and the screw should ideally be replaced.
Do not confuse hot galvanized with electroplated zinc. The latter finish is bright and attractive in the shop but rusts rapidly out of doors. Hot galvanized is very dull grey and often shows surface "crystals."
While a hot galvanized finish can protect steel for decades any damage can weaken the protection. Even applying a spanner/wrench to a nut or screw head can cause a break in the protective surface. Chemical reactions can also occur at screw threads. Which may break down the protection and cause rust to form.
Click on any image for an enlargement.
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