A gin pole during raising may be loaded in compression more than the tower is, depending on how far away the tow point is when you're first starting up. It needs to be strong against bending (unless you also guy the MIDDLE of the gin pole, which is getting silly). So you want a large diameter pipe to be strong against bending.
The good part is that the forces on it are strongest just at the start, so if you're not hoisting irregularly it's more likely to fail right away rather than once your tower is halfway up.)
As for lifting force you can figure that out from the tower weight, top-load weight, the lengths of the tower and gin pole, the angle between the tower and gin pole, and a little trig. If the tower is tapering you'll also need to find its center of gravity, rather than assuming that's halfway up. The shorter the gin pole the higher the forces on the hoisting guy(s) at the start of the raising / end of the lowering.
Yeah, the woww was meant to bend, and the way it bent, when it happened I couldn't see it happen because it bent straight away towards the tower from me so I couldn't see what happened, only knew that the jenny and blades hadn't lifted off their cradle.
This gin pole was guyed both to the side at the top and the middle, and from the middle to the tower, nothing other than the lifting cables to the tow point.
And you think I can figure the lifting forces, sorry, math (Trig) and I really don't do well together.
Thanks for the reply, Skip [ Parent ]
Yeah, it's hard to do a middle guy to the tow because the two cables would have to change lengths as you raised the tower. Gotta keep it straight by making it stiff.
Take off the unopposed guy from the middle of the gin pole to the tower. It contributed to the bending of the pole, big time. The pole might not have been stiff enough to avoid bending anyhow. But the extra pull from that guy greatly raises the stiffness needed to avoid the bending, by giving the pole the initial slight bend that starts the collapse.
You probably want to remove the side guys at the middle of the gin pole, too, and just guy it at the tip. With it guyed against bending failure in only one plane any inequality in the side guys will start it bending, though they will also limit the amount. But a slight asymmetry will let the bend also occur in the other plane (where it's not opposed) and the pole will continue to fold up. The more it bends the weaker it gets against bending in a positive feedback collapse.
Post the measurements and we'll go over 'em.[ Parent ]
Thanks for the comeback.
I must have raised and lowered this tower 20 times or more over the years of it being up with the other jenny... ahhh well, the weight was certainly less.
Anyway, what I have is:
tower 65'6" (the attaching point is at 60')----- 350lbs
jenny & 12' blades and mounts -------------- 170lbs
miscellaneous hardware (cable, 4 AWG, elec box, clamps etc) -------- 50lbs
tail and mount ------------------------------ 40lbs
Total Weight of all parts 610lbs
4 sets of 4 guys at 15' 30' 45' 60'
Anchors set in a 30' circle around center point of tower hinge, not center of tower.
The weight of this set up is mostly at over 60'. The 60' cables are 5.5' down from the very top of the jenny and as you can see in the pictures, everything is pretty much above that except for 65' of 4AWG 4wire, attaching hardware and about 130lbs of the mast.
side view view of top view of top 2 view of top 3
Hope this is enough info and thanks again, Skip[ Parent ]
I think that's where your problem came from. I would suggest making all attachments to the tower from the top of the gin pole.
With any amount of stretching of cables and flexing of the tower, that middle of the gin pole connection would've taken nearly the full brunt of the pulling force.[ Parent ]
