Load testing new undercarriage bungees

[Smiffy]

Hello all

I'm about to replace the bungees on a MK2. I'm making them myself using crimp rings to form the loops.

I'd like to test one of the loops to failure just to make sure my method of assembly is good enough.

Anybody got an idea what sort of maximum load would be put on on a single loop?

I'm working on (MTOW) 950lb / (number of Undercarriage legs) 2, x (Hard landing factor) 2, divided by (number of loops) 6

((950 / 2) * 2) / 6 = 158lb

any thought chaps?

[David47]

Up the "hard landing factor" to 3 .... normal undercarriage ultimate loads are 1.5 times max anticipated service load. That way you give yourself a margin for a range of unknowns. That's typical for aircraft structures.

[HighWing]

I made bungees for a while and didn't get too scientific when testing. I used a hydraulic transmission Jack with fabricated devices top and bottom that mimicked the gear bungee geometry. I made up a set of bungees, wrapped them to desired length then pumped up the Jack to failure. When the bungee cord itself failed before my crimps, I called it good.

[HighWing]

Thinking about my test - I used certified bungee cord and felt that the weak point would be at the edges of the swadged fittings as they could possibly damage the elastic strands in the cords. That is why the breaks elsewhere in the cord made me comfortable about the swage design and overall serviceability.