[TowerTalk] Mast slippage

[JP]

Exactly. Doesn’t take a lot of imagination to figure out a way to get a good working surface for the mag drill to do its thing. 

Better than perching up there for who knows how long with a handheld drill any day. 

J.P. W2XX/7

Sent from my iPhone

> On Jul 28, 2020, at 9:57 PM, Ron WV4P <wv4ptn at gmail.com> 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> 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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