[TowerTalk] split locks vs star washers

[Michael Tope]

Comments below...........

----- Original Message ----- 
From: "Tom Rauch" <w8ji@contesting.com>
To: <towertalk@contesting.com>
Sent: Tuesday, September 26, 2000 11:53 AM
Subject: Re: [TowerTalk] split locks vs star washers


> 
> >  For the shield connections, I used split lockwashers under each nut.  I
> >  just tried replacing one of them with a star washer, and my impression is
> >  that it "grabbed" much more positively.  Is this generally the case, and
> >  are star washers preferred for conductive connections?
> > 
> >  73, Pete Smith N4ZR
> >   >>
> > I've found SS split washers virtually useless.  The bolts virtually all
> > loosened on my tower.  I now use Elastic Stop Nuts.  k7gco 
> 
> Split washers work well in lower tension applications where 
> materials are hard but have "give and take". They take up the slack 
> as required, and don't sink into the material (if it is the correct 
> harness).
> 
> Star washers have less compression, but apply more pressure. 
> They sink into the surface, and also collapse a bit. They are for 
> hard surfaces that don't expand or collapse much.
> 
> Conical washers are like high pressure split washers. They have 
> high pressure and don't dig in.
> 
> What most people miss about bolts is they only actually "lock" 
> when something elastic stretches and/or compresses. For 
> example, the lug nuts on your car stay in place because the nut 
> actually distorts and keeps tension on the wheel all the time.
> 
> Rod bolts on connecting rods are designed to "stretch", and that 
> keeps the connecting rod caps seated and the bolt under tension 
> despite loads that try to both tension and relax the bolts hundreds 
> or thousands of times a minute.
> 
> Your tower and rotator bolts are no different. Throwing the wrong 
> kind of locking hardware at the problem will just make things worse.
> 
> The tower leg is generally soft compared to the bolt. The hard bolt 
> can't stretch to maintain tension because it is working against a 
> soft leg that bends, the soft leg can't spring back because it takes 
> a set.

This is why for example the tower bolts that Rohn supplies use a fine
threads and no locking hardware. This confused me at first since fine
threads are easier to damage than coarse threads especially when you 
are on a tower trying to pound a bolt thru a slightly misaligned section joint
(I know - use a drift pin). After I gave it a little thought though, it started to 
make sense to me. For a given amount of leg compression and a fixed bolt 
diameter, the fine series maintains greater static friction between threads 
of the bolt and nut than the coarse series. 

Mike, W4EF........................................ 



> 
> The same applies to clamping hard masts against soft rotor plates, 
> or vice versa. The materials are poorly chosen, as are the bolts.
> 
> So we are left with the "glue it in place" or friction locking 
> alternatives. That's why this is always such a headache, while 
> things like connecting rods and lug nuts handle much more stress 
> and vibration without any locks at all. There are so many 
> combinations of bolts and materials what works for one person 
> probably won't work well for the next fellow.
> 
>       
> 73, Tom W8JI
> w8ji@contesting.com
> 
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> 


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