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[Towertalk] BMW -- Mast Coupler

To: <>
Subject: [Towertalk] BMW -- Mast Coupler
From: (Lee Noonan)
Date: Wed, 11 Sep 2002 22:07:04 +1000
Good One Dennis,

I actually use a length [approx 10 ft long] of  2" grey PVC drainage pipe
between the rotator & the pipe from the antennas.. . and it does twist a bit
in strong winds...with a 10 element duobander 10+15m and a 10 element 2m
yagi at the top.
 I don't know if that is good or not....  Does it have a cushioning effect
on the rotator with strong gusty winds????
or the opposite ???   I do have a piece of steel pipe inside the lower end
of the PVC pipe to reinforce it...
Any Comments appreciated ....

Originally, I used a section [about 2ft long] of the PVC pipe to connect two
pieces of 2" ID pipe & also be flexible enough to keep the pipe in the
rotator aligned..  and  it twisted a bit in strong winds - with a 5 element
10-15m duobander yagi and an 8 element 2m Yagi at the top.
I kept checking all the bolts to see if any were loose... but never found
Lee Noonan VK2LEE

----- Original Message -----
From: "Dennis Mowers" <>
To: <>
Sent: Wednesday, September 11, 2002 8:34 PM
Subject: Re: [Towertalk] Mast Coupler

> Thanks everyone, for the many suggestions.
> I visited the BMW dealer, and had no trouble finding the part.
> When I mentioned flex disk, the parts man said "what size".  He said
> they come in small, med, and large.  He than walked about 5 ft, pulled
> out a couple of drawers, and brought a 4 inch disk, and a 7 inch disk
> for my inspection.
> I selected the small one.  The price was $63 with tax.  A little more
> than the $25 mentioned in the by Leeson.
> The actual size is 4.25 in X 1 inch thick, with 6, 1/16 inch wall
> inserts for 3/8 inch bolts.  Stamped with the BMW logo, which probably
> added $30 to the price.
> A couple of weeks ago, I spent a few hours looking for off the shelf
> couplers.
> Most of the flexible couplers I found by searching the internet are made
> for marine applications, and expensive.
> I spent a lot of time looking at couplers in the McMaster-Carr and
> Graniger catalogs.  There are several types available that might do the
> job and the ones for 2 inch shafts were also a little pricey.  You need
> to buy 3 pieces.  Two, 2 inch shaft couplers, and a rubber insert.  As I
> recall, Boston Gear has a nice one that would be about $150 for each
> coupler, and $40 for the insert.
> So, I saved a little money, and have the joy of trying something new,
> and making my own part.  The part will be a lot easier to make than the
> custom top plate and rotor shelf I just made, for the non Rohn tower I'm
> using.
> Now that I have the BMW part number, I will look for a cheaper
> substitute for the next one I need.

> 73,

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