Thanks to all who replied. Two useful suggestions came of it. One is
KE7JA's below. The other occurred to me as I was using a come-along to
pull my car up onto a trailer. Looking at the X2 force increaser pulley
for the come-along, it uses a grade 5 (three tick marks) bolt, is rated
at 2,500 lb, and is at least one size smaller than the hole on the tower.
For those who suggested a falling derrick, that was always the plan. My
falling derrick is my tractor, a falling derrick with hydraulics.
John Ammeter wrote:
> Get an AN bolt. Bolts designed for aviation use will not "break" yet
> are quite strong.
> John KE7JA
> Art wrote:
>> I'm about to pull a HWS671 vertical. There's a pad welded on the
>> outer section. For those with an erection fixture it was used to
>> install a pulley wheel to winch up the tower. I don't have a fixture,
>> but I do have a tractor that I intend to pull it up with. The plan is
>> to use 1/4 inch 7x19, same stuff the tower uses, on a thimble around
>> a bolt through the pad ordinarily used for a pulley with the erection
>> The question is, what grade of bolt do I buy that will pull it up and
>> not break? I see it as a fight between ductility and brittleness,
>> grade 8 being brittle for shear loads like this. The hole is for a
>> 5/16 -- which seems a bit small to yank up this tower. I'm sure it
>> used to work when these towers were new 30-40 years ago. The
>> alternatives are, drill out the hole for a bigger bolt or use a
>> chain, either one putting the galvanizing at risk.
>> HWS671 is a 4 section 71 ft middling strong crankup weighing about
>> 1400 lb.
>> 73 Art
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