[TowerTalk] Mast slippage

[Grant Saviers]

Ron,

I shouldn't generalize, as it is possible to mag drill on a tower as you 
are doing.  But rigging my 60# mag drill on a tower with a custom 
fixture and using Rota-Broach drills is not in most ham skills and 
toolboxes.  Maybe the fact my mags get heavier every year is another 
factor ;) .

Grant KZ1W

On 7/28/2020 21:57, Ron WV4P wrote:
> I hate to disagree with Grant but I'm making a plate out of 1/4" steel 
> to clamp to mast with 2 u bolts, pop mag drill on with a HSS Annular 
> cutter and smoking a cig as I send it through making a perfect hole. I 
> have worked way to hard in the past to drill oval holes.
> 
> Ron, WV4P
> 
> 
> 
> 
> On Tue, Jul 28, 2020, 11:42 PM Grant Saviers <grants2 at pacbell.net 
> <mailto:grants2 at pacbell.net>> wrote:
> 
>     I looked at the 71D picture at Array Solutions.?? Not impressed with the
>     bent up clamps.?? Grade 8 bolts can apply 2x the force of the stock
>     SS if
>     torqued to spec, the easiest thing to try.?? Torque the bolts with a
>     torque wrench, wait a day and re-torque.?? I've had SS bolts take an
>     initial stretch, a known property. One project I worked on required
>     torquing the grade 9 bolts 3 times and temperature cycling the joint in
>     between.?? Quite amazing the change each cycle.
> 
>     Or the 71D ears may bend around more.?? Measure the separation top and
>     bottom to check for that with what you have done so far.
> 
>     A way to improve the existing bracket is bracing welded at least across
>     the top, say 5/16 thick x 3" with a V cutout.?? Even better if a second
>     one was cut to fit mid height and welded in.?? Or buy better one if it
>     exists.
> 
>     The problem with pins is it is very difficult to get a round straight
>     thru hole of correct diameter in both parts by hand, especially on
>     alloy
>     steel tube.?? ??So the mast will still work back and forth, elongating
>     the
>     hole and wearing the bolt.?? The back and forth is hard on the rotator.
>     Your mast will still be "slipping slightly".
> 
>     If the pin is your choice, I'd try a pilot point drill (Dewalt) of the
>     diameter that just fits the bracket hole.?? It has a center drill built
>     in and they are excellent quality steel. You might go thru with a
>     couple
>     of these. If they don't hack it a Co/M42 drill will have a good start
>     hole. You will need lots of thrust force and endurance and coolant.
>     Water in a spray bottle is better than oil, WD40 is easy and good
>     too, a
>     helper is necessary to have continuous application.?? The mast material
>     cert can tell you what you have and the possible hardness range is
>     greater than 2:1 Hrc. (there are 6 spec 4140 standards).?? Hand drilling
>     at the hardest level is doubtful.
> 
>     A punch might provide a drill start on round alloy steel tube for maybe
>     a 1/16" drill but how would you get it centered??? It is possible to
>     step
>     up in a few steps to reduce the thrust needed but by hand it's unlikely
>     to preserve the position.
> 
>     Drill from both sides, don't attempt to drill thru from one side.
> 
>     There is no way you want to mess with a MagDrill (I own 2) on a tower
>     and there is nothing for the magnet to clamp to.
> 
>     Good luck, be safe,
> 
>     Grant KZ1W
> 
> 
>     On 7/28/2020 16:00, Les Brown wrote:
>      > I have 2 large Yagis attached to a 3 inch OD ?? inch wall
>     thickness Chromoly
>      > mast running down the tower to a ProSisTel PST-71D. On a windy
>     day, I hear
>      > creaking sounds from the tower. The mast is slipping slightly in
>     the rotator
>      > mast bracket. I???ve already tried to tighten the 6 bolts, but it
>     still slips.
>      > I don???t want to tighten them to the point where they might
>     snap. I???m
>      > thinking that what I need to do is to go up the tower, drill a
>     hole through
>      > the mast (the rotator mast bracket already has holes), and pin
>     the mast and
>      > bracket. I understand that it???s not easy drilling through
>     Chromoly pipe, so
>      > before I try this, I thought I would ask if any of you have any other
>      > suggestions.
>      >
>      > 73, Les VE3NNT
>      >
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