[AMRadio] Gin Pole for folding tower question - OT


Jack Krisel wa9nqw at nconnect.net
Thu May 11 15:08:09 EDT 2006


Hi Brian,

Your may want to consider what Hy-Gain (before MFJ) did. Run a chuck of 
cable at a 45 down the back side of your pipe into an earth anchor or 
other suitable support. The one I have works great.

73,
Jack
WA9NQW

On May 11, 2006, at 1:58 PM, Rick Brashear wrote:

> My personal opinion is it will not withstand the first half of the 
> lift.  I had a similar situation and it did not work.  You might 
> consider using "drill stem".
>
> Rick
>
> Brian Sherrod wrote:
>
>> Sort of off topic, however I know there are some really smart guys on 
>> here
>> that may know the answer to this;
>>
>> I've got a Rohn bx48 (48' light duty tower) that I would like to be 
>> able to
>> fold over/up for any maintenance.  It will have a Ham IV rotor/3 el.
>> tri-bander and dipole pulley at the top.  I plan to mount in the 
>> concrete
>> base a 25' steel pipe 4 1/2" diameter with 1/4" walls directly behind 
>> the
>> tower for raising and lowering to tower.  The pipe will be 20 feet 
>> above the
>> ground level with 5 feet embedded in the concrete tower substructure. 
>>  It
>> will have a pulley at the top of the pipe and a hand crank at about 4 
>> feet,
>> with steel cable attached to the tower at the 20 foot level.  
>> Question is;
>> will 1/4" walled 4 1/2" steel pipe be able to withstand the foot lbs.
>> required to raise and lower this tower below the 45 degree mark 
>> without
>> buckling?  Seems I can not find any pipe this size with larger wall 
>> diameter
>> around here.  I could guy the pipe in the opposite direction if 
>> needed...
>>
>> Any mechanical engineers out there know the answer??
>>
>> Thanks,
>>
>> Brian / w5ami
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>
>
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