[TowerTalk] More on Orion mast clamps

Al Williams alwilliams at olywa.net
Thu Mar 2 21:12:20 EST 2006

With one M2 2800p/Monstir combination and a second m2 2800p to have a large 
antenna I am very interested in this thread.
However, I wonder if these solutions are a "band aid"?

 As mentioned by others M2 specifically states in bold, capital letters in 
their Positioner instructions that pinning the mast will void the warranty. 
Secondly M2 states that the "Precision wormdrive-cannot be reversed by mast 
torque; NO BRAKE RQD".  but then also specifies a Braking Torque of 17000 

How did M2 come up with Braking Torque specification and what kinds of force 
(wind, inertia) is the rotator subjected to by the large beams?  How is it 

It seems to me that the "band aid" solutions may increase the holding 
strength of their mast clamp but ultimately would cause the rotator to 
break--whether pinned or the clamping just strengthened as the load is 

The real question is how capable is the is the rotator to withstand the 
forces applied by large beams.


PS I have thought of a solution similar to Steve's welding to the mast clamp 
but instead pinning a 3" mast collar to the smaller mast thinking that the 
mast clamp will hold better if more surface area is clamped but Marks 
posting seems to refute this idea?

----- Original Message ----- 
From: "Mark ." <n1lo at hotmail.com>
To: <towertalk at contesting.com>
Sent: Thursday, March 02, 2006 3:32 PM
Subject: Re: [TowerTalk] More on Orion mast clamps

> Howdy Steve et all;
> I think your proposed solution will work with any or all of the following
> mods:
> a) Use a locking compound between the inserts and the mast to mechanically
> bond them together. The extra contact surface area you are adding will 
> allow
> a *very* strong bond.
> b) Use an insert material that is scored or knurled and hard enough to 
> bite
> into the mast like vise jaws or vice-grip locking pliers.
> c) Replace the existing mast clamp bolts with larger diameter ones.
> Rick, N6RK, is spot-on when he pointed out that the *frictional force* 
> (not
> adhesive bonding) between two objects is largely *independent of contact
> area*:
> <<...snip...The physics of the slip-nott don't necessarily make sense.  If
> you have a certain coefficient of friction, and a certain amount
> of clamping force, in theory, it shouldn't matter if you distribute
> the force over a large area with a slip nott or a smaller area.
> The slip-nott is not engineered to have more total clamping force.
> Maybe it works for reasons I don't understand. Rick N6RK >>
> The bonding force of an adhesive is very dependent on the contact area.
> There are two ways to increase the friction force:
> 1) Increase the total force that pushes the objects together.
> 2) Increase the coefficient of friction between the contacting surfaces.
> On the other hand, using an adhesive, such as a locking compound, to
> mechanically bond the surfaces together, is largely independent of the
> clamping forces. In this case, extra contact area *will* increase the
> strength of the bond.
> Both methods can be applied together to help grip a mast.
> In the case of mast clamps:
> #1 above can be accomplished by:
>    a) Adding more total clamps or clamp bolts to push the surfaces 
> together
> (they all add up).
>    b) Replacing smaller bolts with larger ones that can hold more tension
> (if the clamp body/saddle
>       can take the extra stress).
> #2 above can be accomplished by:
>    a) Roughing up the contacting surfaces, or using different materials
> that have higher friction.
>    b) Adding knurling or longitudinal cut grooves into the harder of the
> two surfaces to allow it
>        to bite into the softer surface. Look at the jaws on your bench
> vise. These sharp edges force
>         material to be sheared off before the two surfaces will slip. Two
> examples of the extreme
>         extension of this process are woodruff/shaft keys and spline 
> joints
> in prop pitch devices.
>    c) Adding cemented grit (a la guy grips).
> Now, the reason the Slippnot works is by 1a above: The Slippnot adds more
> grip area but more importantly, *more clamping bolts*. The two tabs on it
> lock it to the rotator's existing clamp, effectively creating a composite
> clamp having more total clamping force.
> Hope this helps.
> --...MARK_N1LO...--
> Steve wrote:
> << Howdy, TowerTalkians --
>    Tnx to all for their input on the Orion and its  mast clamping 
> problems.
> While I've seen some bolt stretch that is probably a  contributing factor 
> to
> mast slippage, it seems that the main problem is that  there isn't much
> surface
> area on the clamps to really hold a big torsional load.  While the 
> SlippNott
> may help, it hasn't been verified that it'll actually fit  the Orion since
> it
> was designed for Hy-Gain rotators.
>    So it occurred to me that if we added more surface  area to the clamps,
> that would probably take care of the slippage problem. My  proposed 
> solution
> is
> to get some relatively thin pieces of 2" ID pipe or tubing  and weld a 
> piece
> onto each clamp since there's plenty of scope left in the  clamps for this
> sized mast. This should significantly add holding power to the  rotator 
> and
> inexpensively to boot...snip...Cheers, Steve  K7LXC >>
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