[TowerTalk] Ring Rotors and Swinging Gates

[Grant Saviers]

Since aftermarket clamps were unobtainium, I bored the stock Orion 2800 
clamp in my lathe to fit my 3" CM mast.  With a 3" mandrel test bar (I 
used some 3" 6061 boom scrap) it is not difficult to set up the clamps 
on a faceplate and take small boring passes until most of the grip 
points engage the test bar with about 3/16" spots.  Moving both castings 
in a bit for each pass.  This can be done in the common 12x36" lathes in 
many home shops.  This gets the casting pair bore perpendicular to the 
machined casting base (it wasn't).  Rotator to mast concentricity 
happens when the castings are mounted with the rotator positioned under 
the mast as it does with the unmodified stock clamps.

Then I replaced the grade 5 bolts with grade 8 UNF and torqued them to 
the max spec.

The Orion 2800 that I did this for was pretty heavily used/abused and 
the spline output was badly rusted.  That allowed excessive backlash 
which caused the hardened main drive gear to break a tooth in a major 
storm.  M2 said they had never seen that before. I bought the 
replacement gear and new design output shaft to rebuild it. Antenna is a 
375# JK 2L 80m beam at 157ft.

Both the K7LXC and K7NV mast clamps are good concepts, but I think a bit 
tricky to duplicate at least with my welding skills.  If somebody were 
to make them in production, good fixtures would be the way to go, but it 
is a tiny market.

Grant KZ1W

On 2/1/2023 09:20, Larry wrote:
> I am interested in what you might get in response to your downside 
> issue. I have a 4030 M2 antenna with an Orion2800 that tends to slip 
> when I get high winds. I had a Slipp-Nott (sp?) that I put up which I 
> hoped would eliminate the slip but alas no such luck. I had heard the 
> advice about not pinning through the rotor top years ago although I have 
> had rotors that were drilled for pinning from a manufacturer. I was 
> thinking of pinning maybe with something like the Slipp-Nott but have 
> not really thought it out yet. Someone had commented a month or two ago 
> about putting a grit in the rotor clamp to increase the grip to the mast 
> that I was also thinking about.
> 
> 73, Larry W6NWS
> 
> On 2/1/2023 11:15 AM, John Webster NN1SS wrote:
>> All:
>>
>> First, many thanks again for all of the great responses. As a result, my
>> way forward at this time is the swinging gate solution. The IDC 
>> Technology
>> "Sidewinder" is at the top of the list. It seems beefy enough and looks
>> like it will maintain a vertical position under a load which in New
>> Hampshire can mean more than just the weight of the antenna. Heavy wet 
>> snow
>> really piled up on the 404C a week or so ago. It also has an optional
>> thrust bearing shelf to make rotor replacement simple. I like that.
>>
>> So... Now on to rotor. I have a non-working Orion 2800 which has seen the
>> shop once but failed a second time with the same break release issue. 
>> It's
>> been sitting on the shelf for 7 years but perhaps could be made to work.
>> It's in otherwise good shape and I like the control box. The 
>> alternative is
>> an Orion 2300 which I used for a few years to turn a 6 ele mono 20. It's
>> even older (purchased used from K1ZM who I'm sure gave it a workout) 
>> but I
>> had it up on the bench a month ago and it still works. Direction 
>> indicator
>> needle jumps around a bit when it turns but I don't see that as a big 
>> issue
>> at the moment. I also have a spare Green Heron box that I think could be
>> made to work here as well. Best of all, it's free. And, given that the
>> Sidewinder has the thrust bearing shelf, I could replace it relatively
>> quickly if/when the time comes.
>>
>> The downside - and this I see as a real downside for this solution - 
>> is the
>> mast clamp assembly. Here I'm curious as to how those of you have 
>> addressed
>> the slippage issue. I really hated climbing 90' on a windy winter day the
>> Friday before ARRL CW to reposition the mono 20 yet another time. This 
>> will
>> be an issue if I use the Sidewinder as the inner mast has a 2" 
>> diameter. I
>> wish it had more for the rotor clamp to grab on to. Many years ago, I was
>> told once by one of my antenna Elmers to never ever pin the mast to the
>> rotor mast clamp. But in this case, I'm wondering what is the worst that
>> could happen if I do that.
>>
>> Again, advice here is very much appreciated.
>>
>> 73,
>> John
>> NN1SS
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