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Metal tube joint basics

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BBerson

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That was just Ron Alexander's opinion about the 1/16" gap. I personally don't care if there is gap or not on .035". But aircraft do have thicker tubes and up to 1/8 or 1/4" thick fittings that may need a gap or V grind. It does depend on the thickness
 

Pops

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On welding the wall supply tubes on a large coal fired boiler ( 8" dia X 1" wall thickness) bezeled at about a 45 deg on each end. Use a 1/16" dia tig filler rod to measure the gap of 1/16". First pass is TIG and then 2 passes with 7018-- 3/32 stick, then fill with 7018--1/8" stick , then cover passes back to 3/32 rod.
 

TLAR

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that applies to gas welding, you want a slight gap because of the massive heat.TIG is completely the opposite. Very small concentration of heat and the filler is much more precise.

“Giving a darn” has nothing to do with creating a gap for heat expansion. You can still create a beautiful saddle joint and actually give a darn while simultaneously making a slightly lose fit.

A loose fit has nothing to do with perfection. A loose fit is created with intention, not giving a darn is a character trait, usual a undesirable trait anywhere around a airplane.

You should always want to do the best you can because it spills in to other areas of building. Again, if you read what was written it’s still a matter of a about 2 minutes on a joint which isn’t exactly demanding on a person. My joints are tight on TIG and slightly loose on Gas Welded fuselages. All my fuselages have been accurate anywhere you measure them to probably within a 1/32” of Inch front to back. Not because of trying hard but because I give a darn. It takes no more energy to care about quality.
1/32 front to back? Can you see a 32nd?
Really? LOL
 

TLAR

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A respectable aircraft designer once said that the filler metal that you use shouldn’t fit in the joint
Bob Barrows
 

proppastie

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How about if the tube is in tension overall between the two end holes?
I believe you would calculate the tear-out/bearing of the bolt of the hole of each tube, the tension failure of the x-section of area of the metal each tube, the (single or double) shear of the bolt.. The least value of the three calculations is the tension value.......depending on the span/length of the tube in compression this value may or may not be higher or lower than the compression calculation (Euler calculation) of the tube. Professional stress consultation for a more detailed answer, limit load test or test to destruction for real peace of mind.
 
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Vigilant1

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Sure it wasn't Joe Stalin?
No, but many attribute to Stalin a quote expressing a related sentiment:
"Quantity has a quality all its own."

This attribution is disputed. But during the Cold War it certainly seemed, to many, to be a key chracteristic of Soviet military materiel procurement.

"The F-4 is a better plane than the MiG-23."

"Noted. Does an F-4 have more capability than ten MiG-23s?"
 
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PTAirco

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Regarding the flattened tube end method: The DH Hornet Moth uses flattened tube ends as top and bottom crossmembers in the fuselage . The sides are welded in a jig and then set up vertically and the crossmember s were bolted in.
 

Mad MAC

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No, but many attribute to Stalin a quote expressing a related sentiment:
"Quantity has a quality all its own."

This attribution is disputed. But during the Cold War it certainly seemed, to many, to be a key chracteristic of Soviet military materiel procurement.

"The F-4 is a better plane than the MiG-23."

"Noted. Does an F-4 have more capability than ten MiG-23s?"
There is a quote from a Nazi General that goes something "a Tiger tank is worth 10 Sherman's, unfortunately the Americans always have 11".
 

120mm

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There is a quote from a Nazi General that goes something "a Tiger tank is worth 10 Sherman's, unfortunately the Americans always have 11".
Ironically the Sherman was a better tank, but mythology dies hard
 

Vigilant1

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Ironically the Sherman was a better tank, but mythology dies hard
I've never heard anyone say that. It was almost a match for very early Panzers, not the Tiger. Smaller gun with less velocity, much less armor, and slower to boot. In your estimation, what made the Sherman better, aside from numbers?
 

TFF

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Face to face, no. I think once the tactics of its relative agility were figured out, the Sherman got the job done. Running across an open field, no.
 
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