[Top] [All Lists]

Re: [TowerTalk] Crank-up mast mechanics.

To: towertalk reflector <>
Subject: Re: [TowerTalk] Crank-up mast mechanics.
From: Alan NV8A <>
Date: Sat, 24 May 2008 11:42:15 -0400
List-post: <">>
On 05/24/08 04:29 am 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. 
> If all else fails I can build a "rotating", fold over mast of the 
> desired height that would use the support for a raising fixture which 
> would be much simpler and far less expensive, but I'd really like to go 
> with the crank up.  However, right now the rotating, fold-over looks to 
> be much more practical and much faster to build at probably 1/3 to 1/4 
> of the price for the rotating, crank-up.
> I have lots of ideas and could eventually build one to easily get 60 
> feet, but I'd rather not go through all the design and experimentation 
> stages if the information is available.  That sort of experimenting is, 
> or can be expensive. I tend to err on the conservative side so if I do 
> the design it'll be far heavier than an existing design.  As it is the 
> price of steel is well over twice what I was paying just a couple years 
> ago and the local supplier told me to expect another 40% to 80% by the 
> end of summer I need to get busy.  I used to use a lot of steel for 
> building assembly jigs, tables, and other fixtures including masts and 
> telescoping masts.  Even the 60' fold over is going to be a bit pricey 
> just for the material.
> This would replace the 25G which is replacing an old 40' Aluminum tower 
> and will support the tri-bander that is now on top of the 45G which 
> hopefully will make room so something on 40.
>   At least that is the current thought.

 From what I have read, you need tube rather than pipe; and 
square-section tubing would eliminate the rotation problem.

But it seems to me that what you are trying to do is reinvent the US 
Tower Corp.'s MA-series, or something like it.


Alan NV8A

TowerTalk mailing list

<Prev in Thread] Current Thread [Next in Thread>