Tail wheel cold weld

[gmpaul]

Has anyone had this to happen. I was pushing plane back into hanger and bumped a inch and a quarter door lip to roll into the hanger. The weld just snapped. I have been flying my RV for almost 400 hours.

[Mike S]

Wow, you are so lucky it did not happen on landing

[Ironflight]

First time I've seen that hapen! I've seen the bolts that hold the knuckle to the spring shear, but never that weld.

[6 Gun]

What brand is that tailwheel.
Bob

[gtmule]

Welds in tension...no bueno....

[Bob Kuykendall]

Originally Posted by gmpaul

...I was pushing plane back into hanger and bumped a inch and a quarter door lip to roll into the hanger...

If you were going backwards when you hit the 1.25" high lip, I think that it is possible that the loads on the weld were actually pretty high. As you go backwards, a load applied to the tailwheel by an obstruction will tend to pivot the tailwheel spring down, increasing the vertical force on the tailwheel and making it harder for it to roll over the obstruction.

[snoop9erdog]

Based on the photos/visual inspection it looks as if it was a lack of weld penetration. I'm assuming that the material is 4130 chromoly? Correct me if wrong, but it looks like a Bell.

With proper penetration, a tailwheel joint should withstand a tension load with no problem. I've tested firsthand a chromoly T joint in tension that didn't fail until @ 7200 psi. The tear occured in the heat affected weldzone and not in the weld joint itself.

It would be interested to know the weld process (TIG or MIG) and the filler rod used for these weldments.

[randyintejas]

"What brand is that tailwheel."
Looks like the Vans tail spring on an aftermarket tail wheel. the same thing I have.

[David Paule]

Originally Posted by snoop9erdog

I've tested firsthand a chromoly T joint in tension that didn't fail until @ 7200 psi.

A properly designed and fabricated weld in steel such as 4130 should have a strength much higher than that. Did you drop a zero -- that is, should it have been 72,000 psi?

According to MIL-HDBK-5H, page 8-137, in table 8.2.2.1.1(b), for 4130 that's been normalized after the weld (common practice with gas welding), the strength adjacent to the weld should be at least 80,000 psi.

If nothing is done to the region after welding, the tension strength should still be at least 51,000 psi, according to the same page.

Dave

[brad walton]

It does look like a Bell tail wheel fork. But the swivel is probably Van's. Bell builds the forks but suggests you install it on the Van's swivel, which it fits perfectly so there is no need to redrill the assembly to the tail spring.