[TowerTalk] Building a Tower Trailer
jimlux at earthlink.net
Mon Jun 26 16:41:39 EDT 2006
At 12:32 PM 6/26/2006, Kelly Johnson wrote:
>I would like to mount a Force12 LPT tower on a trailer. Anyone have
>any experience building a trailer for a tower (or otherwise)? I am
>looking for design/construction tips. In particular, I need a trailer
>that is small and reasonably inexpensive. In particular, I would like
>the trailer to be as narrow as possible yet still stable enough for
>towing. I'm thinking something with retractable/removable struts.
We have a couple tower trailers we've used for FD ops at the JPLARC/CITARC
operation. Both were essentially homegrown..
Here's some comments, for what they are worth..
Consider using a hydraulic ram to push the tower vertical. By the time you
fool with pulleys, lift arms, winches, etc., you'll wish for the simplicity
of hydraulics. You can use inexpensive ag cylinders/rams (about $100 each,
brand new) like they use on tractors, and a small electric motor driven
pump. Look at the gear sold to put snowplow blades on pickup trucks, for
Big advantage of hydraulics: you can limit the speed it moves: in both
directions. No sudden, whoops there it goes over the balance point.
If you have a crankup style tower, you can get a hydraulic motor to run the
winch. Hydraulics are wonderful this way.. by selecting the different
displacements in the pump/motor, you essentially get gearing for free.
The CITARC trailer has a boat winch type hoisting apparatus, and it's
*exciting* every time the mast goes up and down, for a whole raft of reasons.
You WILL need outriggers to make it stable in any sort of wind. You can
make them telescoped (we have a series of 4' nested sections of square
steel tubing, but it takes a while to unnest, put them into the sockets,
drop the pins, etc. And then you still have to fool around with jacking
and tensioning them appropriately. Some sort of hinge arrangement seems a
good idea, and isn't much more complex to build, IF you have someone around
to do the welding..
Even with outriggers, odds are you'll need temporary guying anyway, so, do
some analysis and don't make your outriggers bigger than they need to be.
Find a good welder to work with.
Make sure the CG of the system is low when the mast is in the stowed
position. W4EF can tell you some hair raising stories about the
instability of the CITARC trailer on the freeway, largely due to
underdamping of a high CG (the tower sits a good 6 feet off the ground in
the horizontal position) interacting with the tow vehicle and the
aerodynamic forces (which are considerable at 60 mi/hr).
You need some sort of positive lock to hold the tower in place after
erection. The lock should not involve reaching into somewhere to insert a
pin in a close tolerance hole.
Assume that the tower WILL get bent sooner or later, and you're still going
to need to get it retracted and stowed.
You need some big "footpad" plates to spread the loads of your jacks and
outriggers. You need somewhere to store those plates on the trailer, where
they're not buried under tons of stuff. Think about the sequence of
stopping, pull the plates out, run down the jacks, unhook the tow vehicle,
deploy the outriggers, etc.
Consider storage of stuff on the trailer. You need a way to secure it to
the trailer so it a)doesn't fall off when towing and b) doesn't get stolen
off the trailer when it's stored/parked/unattended. It's also nice if you
don't always have to be reaching down into bins or climbing up on the
trailer to get at stuff.
It's definitely worth looking at what grips/gaffers in the movie business
use. They spend a lot of time and energy lugging heavy stuff around on
locations. Check out things like "taco carts" and "cable dollies". The
former are nifty rolling carts with slots/cubbies that exactly fit standard
plastic tote bins, and a bar across the front to hold them in.
Consider where your generator(s) are going to be located on the trailer,
and that they can be run with the tower up or down (or, for that matter,
providing power to move the tower). Power distro panels are also
nice. Cable trays and guides keep you from severing that coax at an
>My LPT1242 worked out extremely well for FD this past weekend. I'm
>hoping to make it even more convenient by mounting it on a trailer.
>Unfortunately, I have limited space at my home for a trailer and thus
>need it to be small, narrow, and light enough that I can push it along
>the side of my house into the back yard.
>Any advice would be appreciated.
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