[TowerTalk] Saddle clamps (muffler clamps)

[Grant Saviers]

Steve,

Let us know your custom HDG u-bolt source.  Portland Bolt makes them but 
only 1/2" and up.

While I use the excellent DX Eng stainless u-bolts with the cast 
saddles, I also use hot dip galvanized u-bolts without saddles, but 
internally sleeve at the bolts.  Long sizes are available from McMaster 
when thicker plates are used.  (unfortunately, long are always too long 
(aesthetics not function)  and standard too short). SS always needs TLC 
to not gall which can be a real PITA when it happens.  As mentioned, 
taking them apart after a few years can be difficult.

An antenna I have in construction has all elements insulated with Stauff 
clamps to hold the elements to the boom plates.  Available from DXE, 
McM, ebay, and others.  For large diameters I make my own split 
insulators with 3/8 thru bolts out of 1" thick (or thicker) UV resistant 
nylon (or other UV resistant plastic).  These can be bored in a garage 
lathe 4 jaw chuck, small mill with a rotary table, or CNC, drilled and 
then and split on a bandsaw or table saw.  I use 3/8 thick 6061 plates 
on top.   I had to replace split ABS pipe used as an insulator on one 
commercial antenna.  ABS pipe is a very poor choice since it is foam 
core and compresses over time.  Most cast solid UV resistant plastics 
are ok at HF.  Center of element voltages are low and dissipation losses 
are minor.

Bent saddles (muffler clamps) get loose as the saddle splays out or 
deform the boom/element when tightened, so avoid them.

Another trick is to internally sleeve where a boom or element is 
clamped.  One size or two of telescoping tubing.  A damaged section can 
be cut out and two sleeves extended both sides plus the replacement 
center diameter.  Sometimes sleeves can be driven into lightly damaged 
sections with lots of Penetrox, a wood plate, and mallet.  Taper the edge.

Grant KZ1W

On 6/30/2017 6:40 AM, Steve NR4M wrote:
> Hello Gary,
>
> Good luck on finding something.
>
> Years ago, I was not happy with my choices.  I just can not see paying 
> ~$15 for a SS U-bolt and 'part-the-way-around' saddle. Don't know the 
> alloy of the SS material, but you can bet it's not the best stuff out 
> there.
> But, what really gripes me is because of the high coefficient of 
> adhesion, stainless galls and seizes sooo easily.  If I really NEED to 
> use SS, I consider it a 'one use' item..  I have not found a anti 
> seize compound that works well enough, or LONG ENOUGH, to alleviate 
> this problem.
> All may be fine now, but try and take the U-bolt apart in 5 years.
>
> Doesn't help you, but my solution was to have custom U-bolts made in 
> quantity, in several sizes, with a hot dipped galvanized coating.  
> Never had one fail; never had one gall.  I found a place in FL that 
> makes what I want.
>
> For saddles, I make my own from billet 6061-T6 aluminum 3/4 of an inch 
> thick, and just shy of a half circle.  These things hold super tight.
> Fortunate to be a retired machinist and have a Bridgeport milling 
> machine.  Wish I had a CNC machine, but not too bad doing 50 at a time.
>
> Good luck.
>
> 73 de Steve, NR4M
>
> On 6/29/2017 22:53, Gary Schafer wrote:
>> I am looking for some 2" and 3" saddle clamps (muffler clamps) to 
>> replace
>> all the boom to element plate clamps on the 40 meter beam.
>>
>> What is the best type, galvanized, zinc plated or just plain steel?
>> Also where do you guys buy them?
>>
>> Thanks
>> Gary  K4FMX
>>
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>