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Know your Nuts!

Discussion of large prime focus satellite dishes used for C-Band signal reception.
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The Professor
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Know your Nuts!

Post by The Professor » Fri May 26, 2017 11:58 pm

Section 5.8 added to The Comprehensive Guide to C-Band Dish Installation

5.8: Importance of Locking Nuts and Washers

At this point it is worthwhile to mention a few things about the nuts and washers you use
to assemble your dish. Most of the assembly will be done with standard hex nuts and flat washers shown below. However, for critical bolts and screws, we highly recommend using either Nylon Insert Locks or split lock washers.

A dish as large as the one you are installing will experience significant wind resistance over the years. This will cause stress and vibrations on the dish. If your dish is motorized, extra stress will be felt by the pivot bolt on the elevation arm. These vibrations will add up incrementally over the years and eventually lead to the loosening of bolts and screws.

Initially, this loosening will show up as 'play' and cause minor satellite tracking problems. If the play is not immediately addressed, it will get worse and worse until it becomes impossible to track the satellite arc. Of course, this will be the least of your problems. If high winds should hit your dish at such a vulnerable time, the entire dish may start shaking uncontrollably on the pole and if the winds are strong enough, the dish may be thrown clear of the pole altogether!
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know_your_washers.jpg
To avoid such damage, we highly recommend that you use nylon insert locks and/or split lock washers for critical bolts and screws on your dish mount. These special nuts and washers are designed to exert either a frictional force against the bolt thread or a spring force between the fastener's head and substrate. In both cases, there will be significant resistance to rotation and loosening.

Therefore, we highly recommend that you study the dish mount below and use locking nuts and/or washers where recommended. You can do this after installing the dish and getting it properly aligned, but you must eventually do it in order to avoid serious damage to your dish, especially if you live in an area that gets hit with gale force winds. There is no reason why your dish can't withstand 100 mph winds and survive just fine, if you just take the time to install locking nuts/washers.
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PhD in TVROSat

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