[TowerTalk] Slipp-Nott

[Roger (K8RI) on TT]

On 12/19/2013 8:50 PM, Richard Karlquist wrote:
> On 2013-12-19 13:07, dave arruzza wrote:
>> To all...
>> I have a Tennadyne T10 that recently has started to slip on the mast.
>> No matter how much I tighten the clamps slippage eventually returns
>> and then I am off the bearing the rotor displays.
>>
>> Tennadyne markets the Slipp-Nott. Does anyone on the reflector have
>> real world experience using this item. Does it really work?
>>
>> 73
>> Dave
>> W1CTN
>> Radio Ansonia
>
> The concept of Slipp-Nott seems good until you try to use it.
> So called "2 inch" masts actually vary somewhat in diameter
> depending on galvanizing, etc.  You might get a snug fit if
> you are lucky, but you might not be lucky.  OTOH, I have to
> hammer my Slipp-Nott onto the mast because it is too tight.

Why?  It's basically a split shim that should allow for mast size 
variations.

> Being too tight is just a bad as being loose in terms of
> gripping power.  Neither the mast nor the Slipp-Nott is
> machined to precision tolerances.

There are two approaches to the clamp, well, quite a number, but 
sticking with the Slipp-Nott approach.

NOTE: You can ruin a mount if not careful!

Don't think of the Slipp-Nott at the end, but rather the beginning. The 
design should easily fit most masts. I don't understand the comment 
about having to hammer one on as they are shown as a split spacer which 
should be easily adjustable. and they say right in the add that it can 
make up for differences in mast sizes.

I have not used a "Slipp Nott", but have used that approach shown in the 
link for years. http://www.tennadyne.com/slipp_nott.htm

I can take a standard 2 piece mount, clamp it together (with a 1/4" 
spacer between the halves) and bore the center hole about .005" under 
size to 0.005" over size.  If that's too tight or too loose, I can go 
0.002 or what ever is needed.  The Aluminum mount does spring, so the 
hole diameter depends somewhat on the alloy, or cast metal.  Typically, 
I've found 0.005" over size with a 1/4" space between halves will spring 
close (and tight) as the mount bolts are tightened.

Or I can bore out a mount and place a 1/8th or 1/16th split spacer 
around the mast.

If, OTOH the mount is too large, I can insert the split shim, I can 
mill, or just file off the face, or mating surfaces of the clamp to let 
it clamp a smaller mast

Don't think you are stuck with the mounts dimensions. Most mounts have 
"at least" a half inch space between the halves and use large serrations 
on the ID of the mount to grip the mast.  This give a minimal contact area.

There are many ways to increase the contact area and gripping force.  Be 
careful using drill presses as most are quite flimsy compared to a 
milling machine and can be dangerous. Hearing of someone using a fly 
cutter in a drill press scares me Which BTW, with a keyless chuck is the 
best drill press you'll ever find, although at a weight of a ton (give 
or take a 100#) they are certainly not portable.

Another approach is to rig up a foot or so of mast and using adhesive 
backed sand paper of various grades you can more or less custom fit the 
mount to the mast. a couple feet of mast with adhesive backed sandpaper 
and hand held, inserted through the mount which is clamped down will let 
you ream the mount to a custom fit. Tighten the mount bolts evenly so 
the bore will be symmetrical and use just enough tension to aid in the 
removal of excess metal. These mounts are typically cast Aluminum and 
the material comes off fast. Of course, if you have a ways to go, it may 
seem like forever.

Go slow and go careful Shift to a fine grade for the finished size and 
clean thoroughly when done. If you go too far, you can remove material 
from the mating surfaces of the mount and redo the bore to a slightly 
smaller diameter.

These mounts may appear rigid, but when the bolts are tightened the 
sides do spring in.  You are going fron a number of edges, to the same 
number of wider gripping surfaces.  Don't over do.  Taking off enough 
material to make the flats just 1/8th inch wide will multiply the 
gripping force by 2 to 3 times.

You really don't want to go so far as to have no space left between 
halves of the mount.

The point is, you are not stuck with the mount's current dimensions and 
they are "usually" easy to modify.

>
> Thus it might work well in some installations, and not in others.
> I know that it is not good enough to keep my MonstIR from slipping.
> It doesn't fit my Texas towers mast very well, because it has
> heavy galvanizing.  As the saying goes, YMMV.

This statement I don't understand, as the mount is designed to allow for 
these mast variations.

73

Roger, (K8RI)


>
>
> Rick N6RK
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk at contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk