[TowerTalk] Adjustments to Tower Base Pier J-Bolts
Roger (K8RI) on TT
K8RI-on-TowerTalk at tm.net
Sat Jul 22 13:23:15 EDT 2017
If it were me, I'd make some flat plate adapters from 1/4, 3/8ths, or
1/2" plate for the hydraulic jacks to push against. 1/4" should be
strong enough. Pushing against the threads could be risky. There are
some mechanical engineers on here who might be able to give specifics,
but heat will weaken the bolts substantially. Still, they "might" be
strong enough for temporary, no wind use. (Engineer input?)
Be careful, pushing one bolt against the other. one may bend more than
the other. Even with bolts that size there is some spring, so you
"MIGHT" need to take them a bit extra.
In the future, people using long rods should consider two templates with
one at the normal location and a second at the top of the bolts.
The "lots of grease and use the bottom nuts to force the template up"
MIGHT work, but it might bugger up the threads.
73, Roger (K8RI)
On 7/22/2017 Saturday 11:49 AM, K7LXC--- via TowerTalk wrote:
>> Got a nasty situation here that needs some brain power to resolve.
> this year, I poured two base piers for a pair of Pirod self-supporting
> towers. The 140 ft. tower base has the problem. Unfortunately, the base
> J-bolts on two of the three equilateral triangle points are bent inward,
> toward the base center by 1/8". That 1/8" may not seem like much, but it
> is. In fact, the template used during the pour cannot be removed. During
> the pour, the J-bolts were double-nutted, one on top and the other below
> template. Still, the force of the concrete pour managed to push out the 6
> ft. J-bolts. As that was settling, I quickly moved the crew to the other
> tower as sunset was minutes away. I did not go back and take a level to
> bolts, thinking the template would keep them perfectly straight.
>> Each 6 ft. bolt is exactly 1-7/8" in diameter. Each protrudes 12"
> above the
> concrete surface. Moving these huge bolts even 1/8" will take a Herculean
> effort. The template holes are the exact same diameter and made that way
> minimize shift of the type that occurred anyway. The tower base section
> mounting holes that are exactly 2.0" in diameter. So, there's just a small
> amount of wiggle room. If we can get the template off, then I know that
> tower base will absolutely go on without trouble.
>> Some options:
> 1) Use an oxy-acetylene torch and apply heat at the point where the J-bolts
> exit the base, then pound with a sledge hammer. Trying it now without heat
> is futile; we've tried and the bolts are going nowhere. I have no idea
> heating will do to the strength of the J-bolt.
> 2) Use a telescoping hydraulic cylinder (a.k.a. hydraulic ram jack) to
> the two J-bolts against each other since they are both leaning in by the
> same amount. What I don't know is how much adjusting precision I'll have
> when expanding the cylinder. Do these things move in very small
> What cannot occur is the cylinder "jerking" the bolts to anything beyond
> 1/8". These cylinders are capable of pushing 30,000 lbs. and are typically
> used on large earth-moving front loaders
> Heating the bolts should be okay. I don't think it'll appreciably
> cause a problem - but I'm not an engineer, just a tower builder. Use a 6' or so
> piece of pipe as a lever to help move them.
> The other thing you could do would be to enlarge the leg holes to
> accommodate the slight off-set. That'd be what I'd do.
> Cheers & GL,
> Steve K7LXC
> TOWER TECH -
> Professional tower services for amateurs
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> TowerTalk at contesting.com
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