[TowerTalk] New to Group, WTB M2 OR2800PX and Rohn TB4

[Chuck Dietz]

Yaesu G-2800DXA is 180 ft lbs

Chuck W5PR


On Thu, Sep 21, 2017 at 9:42 AM, Jim Thomson <jim.thom at telus.net> wrote:

> Date: Thu, 21 Sep 2017 07:15:57 -0500
> From: Patrick Greenlee <patrick_g at windstream.net>
> To: towertalk at contesting.com
> Subject: Re: [TowerTalk] New to Group, WTB M2 OR2800PX and Rohn TB4
> Thrust
>
> <Many of us go bargain shopping and install marginal equipment. Those
> <choosing professionally re-purposed prop pitch motors such as those
> <provided by Kurt Andress complain less as they have little opportunity
> <to do so. Installations of equipment on your (below mentioned) list are
> <not the majority topics for a couple reasons: 1.? They don't fail as
> <often and 2. They constitute a small minority of installations.
>
> <The above is my personal opinion.? YMMV
>
> <Patrick??????? NJ5G
>
> On 9/21/2017 6:36 AM, Clay Autery wrote:
> > Curious why folks don't talk about the AlphaSpid RAK and BIG RAK
> > more....? These seem to be the answer to torque, braking, and mast
> > clamping...
> >
>
> ##  Rating rotors in....INCH lbs of torque  seems silly to me at best.
> Take the INCH lb tq rating.....then divide it by 12  to get reality...  IE:
> FOOT lbs of Torque.
>
> ##  IE:  ham-4   800 inch lbs =  67 ft lbs.
> T2X  1000 inch lbs =   83 ft lbs.
> OR-2800    2800 inch lbs =  233 ft lbs.
> K7NV  small prop pitch  =   14,400 inch lbs  =  1200  ft lbs.
>
> ##  Envision your boom as two torque wrenchs..back to back.   With any
> difference in the length of each side produces a huge tq imbalance.   Thats
> like dragging a parachute behind your car at 90 mph, then wondering why
> you require
> triple the HP to do the job.
>
> ##  The RAK and Big RAK have loads of TQ,  but at times they become tricky
> to install inside
> some tower tops.    If you have ever played with a 2 ft long TQ wrench,
> you will  rapidly come to the
> conclusion that  100-150 ft lbs of tq is not very much in the grand scheme
> of things.
>
> ##  Braking capability is another issue.   Although the worm gear is
> superb for this purpose, the
> worm gear is at the wrong end of the food chain.  The tq is all taken up
> initially by the complete
> gear train.   At least with the brake wedge, its at the output mast end.
>
> ## Most of these mast clamps are a joke.  The custom 2 inch mast clamp
> that came with my K7NV small prop
> pitch just barely takes a 2 inch OD mast.  Just pinch  the flanges  with
> vice grips..and it wont budge !  The surface area
> is immense... like 36 square inchs. K7NV will make the mast clamp for any
> mast diameter you want.  The 3 inch
> mast clamp will provide for 54 square inches of surface area.   His mast
> clamp consists  of a hollow steel tube, split
> down the middle, and welded flanges on either sidle of the slit.   5 x
> bolts used to pinch the 2 x flanges together.
> You barely have 1 square inch of actual contact area  with the m2  OR-2800
> mast clamp.  The K7NV version of a mast
> clamp for the OR-2800 is a real treat.  he will make em for any diameter
> mast you want.   BUT they will only work with
> that one exact size OD mast.   However,  you could use his  2 inch mast
> clamp on a 1.9 OD mast  by inserting a .050
> wall shim around the bottom 6 inchs of 1.9 OD mast.
>
> Jim   VE7RF
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