[TowerTalk] [SPAM] Re: Recommendation for mast on bottommountrotator

[K8RI on TowerTalk]

>>
>> ------------ REPLY FOLLOWS ------------
>>
>> Good idea about the flanges. The flanges could be welded to the pipe
>> but bolted to each other. That way you'd have the security of welds
>> and yet be able to disassemble when needed.
>>
>> Thanks!!
>>
>> Bill, W6WRT
>
> What you need is a sliding joint in the mast near the top to take the 
> weight
> of the mast off the tower. A set of square tubes that telescope inside 
> each
> other, a couple of feet long, welded into the mast (or coupled with 
> flanges)
> would do the trick.
> Look at a tractor supply store like "fleet farm" for PTO drive shafts that

Hit up the junk yards.  They have all kinds and sizes of splined shafts 
*cheap* compared to PTOs. and they will be close to the same size.

> go between the tractor PTO and the equipment behind the tractor. This is 
> how
> they are built. They can slide in and out several feet to accommodate
> different equipment distances. They usually come with U joints on each end
> which would not be needed for this application. They are built to transmit
> many horse power.

Balers and a lot of other equipment use this arrangement so you can turn 
corners with the shaft spinning.  Again you might be able to find some old 
junked out equipment, or get the splines from busted shafts.

>
> With a sliding coupling like that the top thrust bearing could fully 
> support
> the antenna weight and the rotor could support the mast and no worry about
> keeping loads balanced,
>
Jim had a good idea with the square tubing in another post, but that tube 
needs to be a snug slip fit.  That means using some kind of tool to smooth 
the weld on the inside of the outer tube.  I use a lot of this stuff from 12 
Ga to 1/4" wall in making fixtures for holding large parts, but the price of 
steel has doubled in the last six months. Still it's a lot cheaper than 
copper.

After smoothing that weld down flat put lots of grease on the mating 
surfaces.  The white Lithium grease works well and you are less likely to 
get thigs stuck while fitting, but it is one whale of a mess. Be sure to 
debur the things too.  That can save a lot of pain and lost precious bodily 
fluids.

73

Roger Halstead (K8RI and ARRL 40 year Life Member)
N833R - World's oldest Debonair CD-2
www.rogerhalstead.com (Use return address from home page)


> I am in the process of acquiring a tower with the rotor mounted at the
> bottom with a water pipe run to the top. I need to figure out the same
> thing.
>
> 73
> Gary  K4FMX