[TowerTalk] Any recommend material to use for a mast drive shaft.

[Roger (K8RI)]

Eugene Jensen wrote:
> The rotator will set in a cage approximately 20 feet from the thrust bearing 
> until it drives a 20 ft section of 2" Chrome Molly Mast that will hold 
> approximately 30 Sq. ft of antenna's.

I'm having  a wee bit a' trouble with the phrasing, but I take it the 
rotator is off set (to the side) and 20 feet below the thrust bearing.  
Again, I'm not sure what you mean by "like the drive shaft in a car" as 
that is normally thought of as a straight line with universals and 
splined joints which allow a bit of angular movement or displacement. 
>  SC coastal location and could always 
> the chance it could see 100+ winds. The basic concept is like a driveshaft 
> in a car. Also the design is so we can change out the rotator without moving 
> the shaft ass. other than a inch upward to allow the rotor to slide out.
Are you saying you can move the shaft *up* an inch?
If you are set up like a drive shaft I'd eliminate the universals and 
use a shaft splined on the top end and you should have more than one 
inch engaged.  The spline needs to be precision with no noticeable play, 
particularly with 30^2 ft of antenna area.  Also the shaft needs to be 
held at each end to prevent any side to side movement.  Automotive 
splines are *hard*, steel and rust easily which means a good protective 
system and LOTS of grease. <:-))

OTOH you are asking what material to use, yet you say you are using a 
20' chrome molly shaft which sounds like you already have a good shaft 
material. 

I'm running about 40' of 2", structural steel tubing with about the same 
wind load.
I'd like to replace it with 40' of 2" chrome molly but I'm not quite 
ready to put over $800 just into a shaft.  That and I'd have to 
weld/couple two of them together
 
73

Roger (K8RI)
>  
> It's a big project and hope to get into service by summer's end. TX Gene 
> K2QWD 
>
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