[TowerTalk] Crank-up mast mechanics.

[Jack/W6NF]

Roger (K8RI) wrote:
> Is there a good description of the mechanics for a crank up mast on the 
> web?  I'm looking at three sections or more.  I've found a couple of 
> basic designs, but I haven't be satisfied with the safety aspect and 
> they were basically just crank up poles.  Standard pipe (schedule 40) 
> might or might not be strong enough so some sections could be schedule 
> 80.  In addition to the raising cable(s) there need to be guides to 
> prevent each section from rotating inside the next larger size.  A 
> single cable, although easy to route has to support the entire weight so 
> it should have some sort of latching mechanism. (a single pulley in the 
> base of each section with a single on the outside at the top of the 
> section) It'd be even nicer if each section could be raised and lowered 
> independently of the rest which of course would mean a winch mounted at 
> the top of the previous section which would add overall weight and a 
> larger wind profile. Ideally the entire mast would rotate.  Also the 
> *innards* need to be accessible if the cable breaks or hangs up. 
>   
Hi, Roger:

I've never built one but we have quite a few 30-foot crankup masts at 
work that are made from thick-wall square aluminum material. The lower 
part of the mast is probably 6-inch outside dimension. I believe these 
are commercially available but there is nothing on the masts to identify 
the manufacturer. Neither have I ever paid any close attention to 
details of the way the cable and crank assembly are configured.

The square material obviously solves the rotation problem and may be a 
solution if the material is not cost prohibitive.

Have fun!

73,

Jack, W6NF