[TowerTalk] Joining sections of aluminum mast

[Pete Smith N4ZR]

I'm also deeply skeptical of just using U-bolt clamps to do this job - 
far better to pin the joints with grade 8 bolts, so you never have to 
worry about their working loose through seasonal temperature changes and 
wind forces.

73, Pete N4ZR
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On 8/20/2022 7:29 PM, Grant Saviers wrote:
> A lot depends on what rotator and how tall is the tower?
>
> I would recommend machined internal sleeves either of solid 6061 or 
> tubing with enough wall thickness to machine the od to fit the mating 
> tube id's.  I don't think slitting and expanding 6061 is practical 
> with adequate wall thickness - min 1/8".
>
> With a top thrust bearing, there will only be the tube or pipe weight 
> on the bottom rotator.  That tube will only have to handle the 
> rotation torque loading, no side bending from wind.  Probably 1-1/4 
> NPT pipe would be strong enough, backyard engineering. Threaded 
> couplers with a 3/8 gr5 thru bolts in drilled holes to prevent 
> unscrewing.
>
> However, I'm not in favor of adding a long torque tube spring to an 
> already complex tower-rotator-mast-boom-elements dynamic system.
>
> Grant KZ1W
>
> On 8/20/2022 16:08, Dave KØEKL wrote:
>> To ease maintenance I want to relocate my rotator to the bottom of my 
>> tower.
>>
>> The existing mast is 2" diameter ¼" wall 6061-T6 aluminum tubing. The 
>> rotor is 8 feet below the top of the tower / thrust bearing.
>>
>> What is the best way to join additional lengths of tubing together to 
>> reach the bottom? I'm thing about buying tubing that is 2" ID, 
>> cutting it into 18" or 24" sections, slitting it and slipping it over 
>> the 2" OD sections to be joined and clamping with SS U-bolt clamps 
>> like those sold by DX engineering. Will this provide enough coupling 
>> friction between sections to prevent slippage?
>>
>> Also, can I get away with using 1/8" in wall 2" OD tubing from the 
>> existing mast to the base of the tower or should I use ¼" wall all 
>> the way to the bottom.
>>
>> Thanks.
>>
>> -Dave K0EKL
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