Falling Derrick Method of Tilting Up a Tower
N6RK, March 28, 2004
I used a homemade 16 foot "falling derrick" to tilt up my 50 foot high, 18 inch wide Glen Martin aluminum tower (weight: 175 lbs). The pulley schematic shows the basic principle. The rope was 3/8 polypropylene and the wood was 2x12's. A cradle was used to push the tower up rather than tying ropes to the tower rails directly. This prevents a concentrated point of stress, and also eliminates the need to climb 16 feet up the tower to untie the ropes when finished. The tower and derrick had temporary rope side guys at about 12 feet (mandatory).
The greatest opportunity for Murphy to strike in the falling derrick method has to do with the derrick bowing. Always do a test raising where you lift the tower a foot off the ground, then stop and inspect the derrick. The first time I tried to raise the tower shown here, the 2x12 bowed badly. Fortunately, the tower had just raised a few inches off the sawhorse at the end. I added a 2x6 brace to the derrick at right angles to make a "T" crosssection. That fixed the bowing problem. I also tied the cradle to the tower half way up to prevent it from bowing [front view][rear view]. After I got the tower up, I discovered some bolts stuck out and
caused the Hazer to bind, so I ended up lowering and re-raising the tower two more
times with the derrick.
After the tower was up, the Hazer was used to put a 4 element Steppir Yagi at the top.
We used an Alfa-Spid rotator. Both the Yagi and rotator have been excellent and
I would highly recommend them. The Hazer is a good concept, but the implementation
is not great and the price is too high; I only got it because I bought it used at
1/3 of the new price. I think if you are skilled enough to build a falling derrick
setup like this, you can build your own Hazer.
Photos:
On the ground, view 1
On the ground, view 2
On the ground, view 3
Ropes are taught, liftoff imminent
Just lifting off the ground
Halfway up, view 1
Halfway up, view 2
Tower in fully upright position, ready for antenna
Tower with 4 element Steppir Yagi
The white posts in the lower left corner are the supports for my 850 foot open wire line to the 90 foot vertical in the rear (barely visible in photo).
Closeup of 4 element Steppir antenna
Rope details
My 60 foot irrigation tubing mast with inverted vee's is visible on the left side of the photo.
Pulley closeups
Ground pulley closest to tower
Ground pulley farthest from tower
Base pivot
Pivot detail
Cradle, front view
Cradle, rear view
Closeup of cradle
Cradle attachment to bottom of tower, view 1
Cradle attachment to bottom of tower, view 2
Cradle on ground, view 1
Cradle on ground, view 2