Sunday, 14 April 2013

Scam 12 Develops Air Leak

Scam 12 Maintenance and Repairs

Available on the market and used by a lot of amateurs is the scam 12 telescopic mast made by Clark. Created in the  mid 1960's to provide
 the military with a versatile field and vehicle mounted mast for vhf/uhf antennas then in use.
I purchased mine in June 2011 and installed it not long after with my G-600RC rotator and my Cushcraft MA5B
 mini beam mounted on the top. It worked great every time I came to use it with no hassle. After a break of a year
 from radio I came to use my equipment again pumping the scam 12 up. The top section I had left fully extended on
 my break thinking nothing of it. When using the mast I noticed the top section the 2 1/2" tube (item 3 in the
 diagram below) would not come down it was stuck up even when all the air released and collar slackened off to let
 the tube down. When pumping I could hear air escaping from the top tube and the mast would not pump up. After
 taking the mast to pieces here is what I found. The top Piston (Item 6 on the diagram below) had an issue with the
 screws corroding causing them to break inside the piston (item 50 in the diagram below) which then made the
piston insecure causing an air leak when trying to pump the mast up. Also upon inspection the inner tubes had
 gathered a residue of dirt and grit which eventually would have worn the tubes, seals and O' rings (Items 42 & 46
 on the diagram below) A lot of wear was present on the top 3 pistons (3 1/2", 3", 2 1/2") so they was to be replaced along with the seals. You can read the full write up by clicking here


1 comment:

  1. Hi Dave I have had a SCAM 12 for a few years now - it's been great - apart from the leak I'm yet to sort. However after the first front - I can to swap out the 70cm beam for a 6m beam for UKAC this week - the threaded screw that you tighten the clamp that holds the mast (that you put the antenna on) at the top sheared off.. oh bggr! Do you have any data of threads so I can get a replacement part - assuming I can extract the old snapped off one. its part 15 Thanks Dave H G0CER