Part of the tube cluster test after welding involves sawing the tubes
cluster along its center line. This alows a visual inspection of the root
for each side of the entire joint.
From this half cluster you can cut out bend test coupons.
Depending on how the bend test fails you can determine if you have adaquate
fusion on both sides of the joint; and if preheat may be required.

One method used to extend the life of welded aircraft structures was to pour
in a gallon or so of boiled linseed oil after all welding had taken place
and the structure passed a leak test. It is a time consuming task involving
rolling the structure as it is being tilted to ensure full coverage of the
interior of the tubes.

There is a publication out there that goes into great detail of fabricating
weldments for the tubular weld test just don't remember the name off hand.
I do have one reference I was able to find but it is the tentative code for
welding aircraft structures dated 1944.

They proposed the use of a piece of 1/4" x 6" flat bar 6" long. Three tubes
would be notched and coped to slide over the flat bar and form a Y type
connection with the third tube center on the two tubes forming the Y.
After the weld is completed the weldment was cut across the the flat bar
around the 2 1/2" mark exposing the ends of the tubes; allowing inspection
of the interior .

I had posted a pdf file many years back to a web site I forget the name of
but it was titled welding tubular structures or something along those lines.
It may still be out there.


John Noon


"John T" wrote in message
...
Another test is to put it in a vise and beat the crap out of it with a
hammer. If the tubes break before the welds, its a good weld.

John