I understand all the issues you are mentioning. If the 2x4 makes you
nervous then 1. don't watch carpenters raise walls with them or Amish
raise barn walls with them and 2 nail two of them (or 2x6) together at
right angles to reduce bending. I understand the simple leverage
issues. Hence using the "pole" to push at a higher level than the man's
height. If using 2x6 at right angles then stagger the boards and use
maybe 12 footers to make a 24 ft or longer pole for better leverage.
Patrick NJ5G
On 3/9/2015 9:07 AM, Grant Saviers wrote:
nope, as you walk in, more of the weight of the tower is behind you.
Another way to think about this is what size torque wrench would you
need to raise the tower if it was attached to a hinge bolt? Ans:
HUGE. A 300# 85' tower needs a torque (moment) of 300*42.5= 12,750
ft-lbs to move it just up from horizontal. Assuming the sections are
uniform, we can use a mass one half the length, so with a tapered
tower it will be less. Or you can weigh each section, and use the
distance to eacg section center when assembled and add up the moments
for a fairly accurate approximation of the initial raising moment.
Yes, the lifting load at the end is only 1/2 the weight (less for a
tapered tower), but as you walk in the force needed increases. At 45
degrees a little geometry will show where you will be trying to hold
the tower up. Then calculate the load - from the 12,750 ft-lbs of
moment (actually not quite accurate since the changing geometry helps
a bit).
A 16' 2x4 has very poor buckling strength, perhaps a recipe for disaster.
A walking or fixed derrick is the way to go.
Grant KZ1W
On 3/9/2015 6:29 AM, Patrick Greenlee wrote:
Say what? If the tower were not tapered (lets look at a simple
model) and you picked up the top then you would support 1/2 the
weight and the ground via the hinges would be holding the other half
of the weight. The higher the top of the tower goes the greater the
portion of the weight is held by the ground/hinges until when
vertical the ground holds all the weight.
Buy a 16 ft 2x4 and either notch one end and apply duct tape to
secure it to about 16 ft above the tower base or otherwise secure it
with wire or...
Then as you lift the tower the 2x4 can take the load while you rest,
change hands, take a break or ... Once the tower is lifted so high
the 2x4 is not securing the tower very well grab hold of the 2x4 and
use it to push on the tower. The increased leverage pushing at the
16 ft level rather than at your head height or so will make a
considerably easier time of it.
Archimedes said something like given a lever long enough and a place
to stand he could bend the lever (move the Earth) or some such.
Patrick NJ5G
On 3/8/2015 11:45 PM, Richard (Rick) Karlquist wrote:
On 3/8/2015 5:36 PM, Hans Hammarquist via TowerTalk wrote:
If you don't put to much heavy stuff on the tower before you walk
it up it should be OK. Just for your comparison, I have an 85 feet
aluminum tower and the total weight of the tower, empty is 300 lb.
It's tapered so the heavier section are at the bottom. No, I didn't
walk this tower up but I easily carried around the top 40 feet
during the assembly of the tower and could, probably have raised
the by myself as a 40 foot tower, had I done that.
Hans - N2JFS
I made some calculations and determined that the
force you have to apply to a 40 foot tower of
uniform cross section with nothing on top works
out to 1.7 times the weight of the tower. And
you have to be able to apply this force using
one hand at a time while you "walk". It all
depends on the weight of the tower and the
strength of the walker. Can you hold an 85
pound barbell over head and pass it back and
forth between your hands? Then you can walk
up a 40 foot tower weighing 50 pounds.
Rick N6RK
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