In a message dated 3/17/02 8:10:56 AM Pacific Standard Time,
djones449@cogeco.ca writes:
> First, my setup:
> - Self-support 48ft Delhi (Rohn BX-type equivilant).
> - Bearing on top plate
> - Rotor shelf 4ft below top
> - Hole in rotor plate slightly larger than 2" mast
> - Mast is 12ft (with small 2m/440 vert at top & Force 12 C-4e about 3ft
> above top plate)
>
> My initial plan is to brace the mast just above the rotor with angle iron
> running through the tower section and a 2" pipe clamp to hold the mast at a
> second point (instead of the rotor itself). I don't think the weight of
the
> assembly will be too much to ease the mast up slightly in the rotor clamp,
> then tighten the 2" clamp to hold it, resecure the bearing on top, allowing
> me to safely remove the rotor, still having the mast held in two places.
Is that what you're trying to do - remove the rotator? What kind of
bearing? What are the details on the mast - i.e. OD, wall, weight?
>
> But after that, unless I'm missing the obvious, the lingering problem would
> seem to be "lowering" the mast down through the hole in the rotor plate? I
> can envision the come-along concept, to that point.
>
> So, further questions, if you don't mind:
>
> a) Where to attach the come-along at tower end?
> - eye-hook bolted through bottom of top plate?
> - Sling around cross-brace on tower?
>
The middle of the X-brace seems a likely attachment point; you can put
the hook directly on it. Or use a webbing sling around two legs or across a
face.
> b) How to lower the cinched mast down through the rotor plate?
> - Unless you contemplate "removal" of rotor plate entirely?
>
It isn't necessary to remove the plate. Use a webbing sling as a choker
on the mast just above the rotator. All you have to do is pull the mast
barely above the contact point of the rotator; then the rotator will come out
when the weight's off.
If you want to lower the mast after the rotator is out, you need to lock
the thrust bearing down as you shift the sling up or down for lowering.
The mast will be a little top-heavy so first thing I'd do is get the
tribander right above the thrust bearing. I don't know how much slop you've
got in your bearing, but sometimes you can lower the mast onto the rotator
shelf at an angle so it's far enough away from the rotator so it'll just sit
there.
What's your concern - that the mast will be loose? Some sort of scheme to
hold the bottom of the mast will help. Angle iron and U-bolts is one way. You
can even use rope if you're confident in your knot tying.
Cheers,
Steve K7LXC
Tower Tech
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