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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. Below the parts diagram is photo's in detail of the repair of the mast and faults found when
The pictures above show the machine screws broken off and rusted inside the piston which caused the piston to
come loose inside the tube causing an air leak at the top which stopped the mast being pumped up. Look at the
difference between a brand new piston on the right of picture 1 and the old piston on the left.
Above a look down the inside of the tube when taken apart for maintenance. As you can see there has being a build
up of residue and grit which would cause problems with the seals and cause wear to the inside of the tube.
The above pictures show the seals, ptfe strip, collar rings and collar which were found to be very dirty and need of
cleaning and fresh silicone grease putting on. The collar item 10 in the diagram above had allot grit in the circle
groove which can be seen in the 4th picture.
All the parts above shown after a good clean ready for grease and reassembling back together.
After repairs carried out myself and friend Devo put the mast back together, bellow a few pictures taken while doing this. I would just like to say it was allot easier putting it back together than taking it apart when the parts were cleaned and re greased it was a pleasure after it was finished to be able to get back on the air working the world again knowing the antenna and mast were fully serviced ready for the summers dx.
My thoughts after taking my scam 12 apart to repair it would be that if you buy one of these impressive masts
before installation check all the above are of good working order and it is cleaned and fresh silicone grease applied.
Then it will need very little maintenance afterwards possible re grease or wipe of the tubes to keep them clean.