[TowerTalk] Why are gin poles so expensive?

[Roger (K8RI)]

John wrote:
> Try and make one - you'll understand. It needs to have fasteners that can  easilly release the fixture, yet secure as to not kill someone. It has to have a hinge. It requires tubing and a locking mechanism to hold the pole itself. And all parts must be welded. Did I mention liability?
>
>   
I built my own and didn't find it difficult ... to build that is. 
Finding the parts was something else.
I have about $20 in it. Today it would take about $40 to $50.  It's all 
steel and heavy.

I used a bit of innovation  instead of hinges and it is very strong. 
Stronger than the ones you'll purchase, BUT it 's heavier and not quite 
as handy (or pretty) as the ones with real hinges. It attaches to the 
tower leg in two places nearly a foot long to distribute the stress. 
OTOH it's almost as fast and has been tested at over 800# live weight 
which is far greater than I'd ever put on it.  I do a lot of welding so 
that wasn't a problem. I also have it set up with a pulley at the base 
of the tower so no one works under it but they should all be used that 
way. I have a set of strict rules when working on the tower and any 
helpers are briefed before we start. OTOH  I want helpers who know what 
they are going to do.

Using two support clamps allows me to loosen the clamps to mast and 
tower on the top clamp, slide it to the top of the next section. and 
attach to the tower section. Tighten clamps. repeat with the bottom 
clamp. Then loosen the mount to mast clamps while holding the mast/pole, 
slide the pole up to the desired height and tighten the pole to mount 
clamps and it's ready to go again. That way I never have to lift more 
than the pole, or a single mount. The rope goes up through the pole, 
over a pulley, through a second pulley and then connects to the end of 
the arm which rotates.  This gives me a 2:1 mechanical advantage and 
with the capability of swinging the arm makes positioning the next tower 
section easier.

No, I don't loan it out. <:-))


> -John, N9RF
>   
<snip>
>   Why are gin poles for assembling for example, Rohn 25, so expensive?
>
>   The Rohn one is over a thousand dollars and even the kits are $250 and don't
>   include the tube.
>   
Strength and liability.
>    
>   Isn't it just a pulley, rope, pipe, and some clamps?
>
>   
That have to be strong enough to do the job plus a good safety factor.
>   Do I need to know anything important if I fashion my own from hardware store
>   materials?
>
>   
How much stress will be put on each part so you can figure the proper 
ratings.  Regular pipe is going to be too heavy with out the desired 
strength and it bends easily. It's unlikely you will find the desired 
pulleys at a hardware store.  Although you can find pulleys rated to 
750# at Lowe's, I'd not consider them appropriate for the job as the 
wheel is plastic. Gin poles take a beating and are a safety item.  If 
you don't have the design and welding skills I'd either get some one 
else to build it, pay the long dollar, or try to borrow one.

OTOH  (this is not a recommendation!) for something simple and light 
I've used nothing more than a piece of steel masting with a pulley on 
one end, u-bolted to the tower leg.  You still have to know how much 
stress you'll be putting on said pole. 

One added note: NEVER pull sideways on a Gin Pole.  If it starts to 
spring sideways, stop, rethink and set things up for a vertical lift.
Run the rope through a pulley of the proper rating at the base of the 
tower so the helpers can be well away from anything that might fall. 
This also allows them the pull horizontally. The arrangement should be 
such that even if the pulley breaks the rope can not come away from the 
tower and apply a horizontal pull to the Gin Pole.


73

Roger (K8RI)