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Old May 17th 11, 02:17 PM posted to rec.aviation.soaring
Andy[_1_]
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Default Cobra top hinge plate bolt failure

On May 16, 10:44*pm, db_sonic wrote:
On May 16, 5:23*pm, Steve Koerner wrote:

It looks like YO and I were both commenting at the same time to the
effect that it is more likely a tension failure. *However I don't
agree that the gas spring force has much to do with it. *The gas
spring force is small compared to the strength of two 5/16 cap
screws. *I suspect it has more to do with the inertia of the lid in
longitude with some combination of vibration and road bumping creating
the load. *Heaven knows my trailer has seen some bumpy roads.


GW


Examination of the failed bolt should tell you whether it was tensile
with necking or shear with a fairly clean break.
But, main concern I would have is having a failure while rolling down
the road and doesnt sound like something one could fix by themselves
even with a spare bolt on hand. *Maybe the solution is to pre-
emptively replace these bolts anyways at say 10 years?


Maybe the right solution would be for Cobra to redesign the hinge and
make a kit available to owners. The worst case failure is a nightmare
and YO was halfway there. Image what happens if all 4 bolts fail.
The front of the top could be lifted by the gas struts and at highway
speeds could tear off the trailer into the path of any vehicle
following.

There is no reason the handles have to share the same bolts as the
hinge plates. The hinge plate bolts could be made larger diameter and
the handles relocated.

Andy