Cobra Top Hinge Bolt Failure - Revisit

Any further information or new developments regarding the bolt failure
discussed last year? Discussion found he
http://groups.google.com/group/rec.a...b46ee572ef6bb6

Thanks,

WD

WD: The writeup I did on my solution seems to have passed muster at
the factory as I have learned that some folks have been referred to it
by Cobra. Here's the link again: http://www.box.net/shared/9dvnt7qgs8

Steve Koerner
www.wingrigger.com

On Apr 23, 2:09*pm, Steve Koerner wrote:
WD: *The writeup I did on my solution seems to have passed muster at
the factory as I have learned that some folks have been referred to it
by Cobra. *Here's the link again:http://www.box.net/shared/9dvnt7qgs8

Steve Koernerwww.wingrigger.com

Are you making these backing plates for sale or is the factory going
to create a modification kit, asking just in case?

On Monday, April 23, 2012 2:09:27 PM UTC-4, Steve Koerner wrote:
WD: The writeup I did on my solution seems to have passed muster at
the factory as I have learned that some folks have been referred to it
by Cobra. Here's the link again: http://www.box.net/shared/9dvnt7qgs8

Steve Koerner
www.wingrigger.com

The backing plate does not really help, as there are reinforcement
inserts in the top where the bolts go through, but not in the broader
area under the handle.

Distortion of the corners of the trailer is a separate problem from
the bolts. I sketched a solution that Alfred said he would build;
this reminded me I hadn't received the parts and I just sent Alfred
and Ralf an email. I've been a wee bit busy, sorry this hasn't
gotten completely sorted yet...

Hope this helps,
Best Regards, Dave "YO electric"

On Apr 23, 7:52*pm, Dave Nadler wrote:
On Monday, April 23, 2012 2:09:27 PM UTC-4, Steve Koerner wrote:
WD: *The writeup I did on my solution seems to have passed muster at
the factory as I have learned that some folks have been referred to it
by Cobra. *Here's the link again:http://www.box.net/shared/9dvnt7qgs8

Steve Koerner
www.wingrigger.com

The backing plate does not really help, as there are reinforcement
inserts in the top where the bolts go through, but not in the broader
area under the handle.

So a backing plate that distributes the load over an area that is
around ten times greater than the area under the original handle does
not really help. That's a pretty interesting conclusion, Dave. I'm
glad you have this all sorted out for them now.

On Tuesday, April 24, 2012 2:05:23 AM UTC-4, Steve Koerner wrote:
On Apr 23, 7:52*pm, Dave Nadler wrote:
On Monday, April 23, 2012 2:09:27 PM UTC-4, Steve Koerner wrote:
WD: *The writeup I did on my solution seems to have passed muster at
the factory as I have learned that some folks have been referred to it
by Cobra. *Here's the link again:http://www.box.net/shared/9dvnt7qgs8

Steve Koerner
www.wingrigger.com

The backing plate does not really help, as there are reinforcement
inserts in the top where the bolts go through, but not in the broader
area under the handle.

So a backing plate that distributes the load over an area that is
around ten times greater than the area under the original handle does
not really help. That's a pretty interesting conclusion, Dave. I'm
glad you have this all sorted out for them now.

The area where the bolts goes through has a solid material between
the inner and outer laminates; other than that its just the expanding
core material they use (no compressive strength). Spindelberger
told me it does not help to add a backing plate because of this...

Hope that is clear,
Best Regards, Dave

On Apr 24, 4:25*am, Dave Nadler wrote:

The area where the bolts goes through has a solid material between
the inner and outer laminates; other than that its just the expanding
core material they use (no compressive strength). Spindelberger
told me it does not help to add a backing plate because of this...

Hope that is clear,
Best Regards, Dave

Dave,

My trailer has not such reinforcing inserts. In fact I proposed
introducing such inserts as the permanent fix. Only the handles
themselves have hard inserts.

If there were inserts the outer shell would not have collapsed toward
the inner shell causing the bolt tension to be eliminated. I have
photos of the severe deformation of the outer shell under the handles
of my trailer.

In my opinion the insert fix would be far superior to the backing
plate solution but it fell on stony ground.

Andy

The structure immediately under the handles had clearly collapsed.
There is no such solid material between the inner and outer laminate
on mine.

The backing plate has resolved the problem quite well.

On Tuesday, April 24, 2012 11:26:45 AM UTC-4, Steve Koerner wrote:
The structure immediately under the handles had clearly collapsed.
There is no such solid material between the inner and outer laminate
on mine.

The backing plate has resolved the problem quite well.

I've looked at my hinge bolts a number of times, but can't detect any problems. Are there any symptoms that precede bolt failure, i.e. loose handles?

TIA,

Frank (TA)

At 22:21 25 April 2012, wrote:
On Tuesday, April 24, 2012 11:26:45 AM UTC-4, Steve Koerner wrote:
The structure immediately under the handles had clearly collapsed.
There is no such solid material between the inner and outer laminate
on mine.

The backing plate has resolved the problem quite well.

I've looked at my hinge bolts a number of times, but can't detect any
problems. Are there any symptoms that precede bolt failure, i.e. loose
handles?

TIA,

Frank (TA)


We checked all the Glass fibre top (twin skin) Cobra trailers at our site.
(over 10 older trailers ) None had so far suffered a hinge failure.
The most obvious sign of a potential problem is loose bolts which are
easily tightened. One older trailer had a couple of mm slack that could be
tightened out.
I changed the bolts on mine for longer stronger bolts (12.9 spec) that do
not have the thread section across a load bearing junction.
I noticed a lot of corrosion present on the bolts removed from my 13 year
old trailer stored in a English climate. It might be prudent to replace
them after about 10 years depending on local conditions.
I refitted with a aluminium backing plate for good measure but it probably
is not necessary as all the compression between the twin skins seems to
have taken place.