Re: [TowerTalk] Tower Trailer Safety;maintainence

[Jim Lux <jimlux@earthlink.net>]

You might want to talk to Michael Tope (W4EF@dellroy.com) or Marty Woll 
(N6VI) about CalTech ARCs tower trailer.  It has outriggers, a crank up 
tower, etc.

At 11:04 AM 1/14/2005, you wrote:
> Folks:
>
> I am refurbishing a State Highway Department (Caltrans) floodlight support 
> trailer for re use as a ham radio tower trailer.  The trailer has a HD 
> Tristao 60 ft tower, with two motorized pivot (to vertical) and 
> telescoping (3 20 ft sections) cable drives.  The trailer is weathered, 
> but inspection shows only localized surface rust of parts of the frame and 
> erection fixtures.  I want to clean up and paint, possibly repair 
> gavlanized surfaces, and replace lifting cables.  There will be a 
> generator mounted aboard, and cabinets for equipment storage.  The tower 
> is in excellent shape and has a HAM 4 rotator.  The trailer has two 
> pivoting outriggers that are simple pipes, angled to the ground with 
> footing plates, and a turnbuclke cable to bring the outrigger foot to 
> bear  pressure on the ground. Pictures exist for anyone interested in 
> discussing improvements, safety issues.  I see no locking features for 
> each section, when extended.  How can this be made safe?  Is it safe to 
> climb to each joint, and insert a block?

For the CITARC trailer, you shove a bar in across the tower section to 
prevent the tower from retracting, then crank it down onto the stop, so the 
cable hoist isn't bearing any load.  Hardly a fully engineered solution, 
but it seems to work.

The CITARC trailer uses square steel tubing for outriggers.
http://www.luxfamily.com/events/fd2004/
has some pictures of the trailer.  In some of the pictures you can see the 
outriggers; take a look where the tower is being winched up vertical.



> I am reading case histories of crane and tower accidents on the web, and 
> have found a number of crane accidents (often fatal) that were caused by 
> crane outriggers failing for a variety of reasons, often by putting more 
> than allowable PSI on the ground, resulting in earth shifting, unbalancing 
> the crane, and causing collapse.  Or outriggers that were not of 
> sufficient radius to ensure stability.   Not wanting to experience this 
> firsthand with the tower trailer, I want to learn more about outriggers, 
> scrutinizing the adequacy of  the two existing ones at the rear of the 
> trailer..  The trailer is only a single axle, is about 18 ft front to 
> rear, approx 7 ft wide, and
> the tower is very close to the rear, when vertical, with the two 
> outriggers, about 15 ft long, pivoted and producing a triangular footing 
> comprising the outriggers, the road wheels, and the trailer tongue  screw jack.
> Hopefully the ascii char drawing comes out OK below...
> I am looking for feedback wrt safety issues, and surface rust 
> refurbishment techniques..


I did some quick calculations on overturning for a tower attached to a car, 
and the quick thing is that if the wind comes up, your in a heap of hurt, 
even with a tower trailer, unless your outriggers are comparable in length 
to the height of the tower.

Try this: http://home.earthlink.net/~w6rmk/antenna/mastcar.htm

Jim, W6RMK 


_______________________________________________

See: http://www.mscomputer.com  for "Self Supporting Towers", "Wireless Weather Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with any questions and ask for Sherman, W2FLA.

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