[TowerTalk] Shorty Forty Hose Clamp thread

Tue Aug 11 10:50:19 EDT 2015

Good Morning All,

And despite a rather rude comment from Doug sent to directly to 
my email, here is a bit more information to HELP others perhaps.

Again, we are using clamp products in applications that may not 
represent their common usage. So your mileage may vary, WFWL.

Our website shows only the more popular common designs, not the 
special designs where the focus is on specific connection needs.

Doug's "simple" install method does not take into consideration
factors such as connection vibration nor repeated thermal cycling.

Let's say for example, you must hire a crane to lift and install
your new yagi. Once up there, you cannot reach the elements. If
something 'comes loose', it will be additional time and expense.

Now we have to make a critical decision:

A. Use the "simple" method outlined below that does not follow the 
manufacturers instructions. It might work well, or it might not.

B. Use the method and torque settings from the manufacturer and 
know you have followed the suggested install specifications.

Would that be over engineering, or simply using common sense given
risk of failure and related costs to repair the loose element(s)?

73 de Billy, AA4NU

----- Original Message -----
From: "Doug Renwick" <ve5ra at sasktel.net>

No one is pointing fingers.  I don't know where you got that idea.

Just what were the original design requirements for this gear clamp?

And just what are the performance limitations for my real world method?

Doug

I wasn't born in Saskatchewan, but I got here as soon as I could.

-----Original Message-----
Good Morning Doug,

Not at all my friend. "WE" are using products for applications
that were not part of the original design requirements here.

Your 'real world' method has some performance limitations, but 
then again you may do as you please, that's fine for you.

Just please don't go pointing fingers at manufacturers as to 
poor products or weak design when used or installed improperly.

Have a great week there!

73 de Billy, AA4NU

----- Original Message -----
From: "Doug Renwick" <ve5ra at sasktel.net>
To: "Billy Cox" <aa4nu at comcast.net>, "George Dubovsky" <n4ua.va at gmail.com>

Here we go again; over engineering something so simple.  Torque
specifications for a gear clamp used to secure one piece of tubing inside
another - really?

Here is how to do it in the real world.

Tighten the gear clamp only enough until the smaller tubing cannot be turned
inside the larger tubing.  Lubricate the clamp so that the band will slide
and not strip or distort the slots in the band.  Come back the next day and
test the joint.  If you can twist the smaller tubing then tighten the clamp
more or restart with less joint compound.  On small diameter tubing,
pre-form the clamp.  Simple - right.

Doug

I wasn't born in Saskatchewan, but I got here as soon as I could.

-----Original Message-----

Well done Geo ... per an often shared motto on this forum,
simply do what the manufacturer states to do ... B-)

The smaller standard 5/16" bandwidth clamps (also known as 
"micros" or SAE J1508 Type M) have low install torque values.

The common 1/2" and 9/16" bandwidths typically will have
install torque values which are much higher. 

Some use a nut with nylock (t-bolts) or Belleville washers
(CT clamps) as ways to maintain constant tension. 

Other clamp designs may have even higher values, but are not 
always offered in the diameters we use for yagi elements.

LINED design clamps are mainly for very soft tubing or hose
material such as silicon, not much advantage otherwise.

I would suggest using an all stainless clamp, something in
the all 300 SS materials class should work well. 

If you are in a more corrosive setting, say near salt water,
then the all 316 SS materials may provide better life.

Several years ago we added the install torque ratings to
help users properly tighten the various clamps designs:

http://idealtridon.com/aftermarket/

Perhaps a bit of general wide-stroke background might be 
useful here? Three torque values you might consider are:

Free torque ... this is simply stated as the minimum amount
of effort to turn the screw. Typically a very low value.

Install torque ... this value is normally stated to be at
50 to 70% of the ultimate torque value.

Ultimate torque ... consider this as a "never exceed" type
of value. Go much past this, you are likely on your own.

Also these values, as noted are inch-lbs, NOT foot-lbs!

Additional lubrication is typically NOT suggested, as that 
may distort the actual torque value being measured.

Size the clamp properly (band end should just be under the
screw cone area when tight) to help reduce snagging things.

One other suggestion, used by several OEMs is to slow down
the RPM rate as you approach getting the clamp "tight". 

Hope this helps, and have a great week!

73 de Billy, AA4NU 

(... also a Product Manager for Ideal-Tridon)

----- Original Message -----
From: "George Dubovsky" <n4ua.va at gmail.com>

I, too, have stripped hose clamps during installation, but it was my own
fault. Who knew the darn things had torque specs from the manufacturer...
;-)  Now I use a torque wrench (a small one, calibrated in inch-pounds as
well as some weird Klingon standard - Newton something or the other), and I
tighten the large ones to 35-40 in-lbs and the skinny ones to 15 in-lbs,
and they don't strip.

Then I add the rivet!

73,

geo - n4ua
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