Tost Ring Failure

On Tuesday, June 6, 2017 at 2:51:26 PM UTC-6, John Carlyle wrote:
Frank,

When there are "conical male/female shapes at the failure point" it generally indicates tensile overload failure (caused by exceeding the materials tensile strength). A giveaway would be necking on either side of these shapes, which might be what you're calling failure "at the weld taper".

Fatigue looks very different - the fracture surface shows a smaller smooth portion surrounding the origin, with the remainder of the fracture surface appearing granular (perhaps what you're calling calling "crystallization".. Fatigue failure is caused by thousands, perhaps tens of thousands, of load variation in the presence of a small defect in the part (usually on the surface).

These are two completely different failure modes, and have two completely different causes. It would be interesting to see pictures of the actual failed ring and the fracture surface.

-John

On Tuesday, June 6, 2017 at 4:26:34 PM UTC-4, Frank Whiteley wrote:
We had a TOST large ring failure while winch launching at a CAP Flight Academy a few years ago. It failed at the weld taper and the ring also broke opposite the weldment with the appearance of fatigue crystallization at the break. So, it's possible several launches were done with the failed weld before the ring failed at the second point. It was reported back to the vendor and also to TOST IIRC. Locally we discussed if perhaps some counterfeit supplies were getting into the channel. The academy leader passed away some time after the academy so I don't know the result of the report but perhaps the vendor will recall the event. I'll check.

Frank Whiteley

I'll amend my post to say that it was not evident that the failed ring was welded, but that separation had conical male/female shapes at the failure point. Looking for images in the archives, but nothing so far.

Frank Whiteley

John,

I think you've described it accurately. Still checking around for images. They may not exist. This happened around 2009 and the rings certainly had not seen that many cycles. Not aware that anyone attempted to load test them, but who knows?

Thanks for your comments.

Frank Whiteley

I have personally seen 3 tost ring failures at my gliding club this season,
(the
last one only about 3 hours ago!) these were all the large rings on the
strops,
not the ring pair that goes to the release, unfortunately I have not been
able
to recover any of the rings to see the failure mode, however I was
examining
the rings on the other strops and found a couple that were obviously of
welded construction, and one was clearly oval rather than round, I don't
know
the age of them but they get very heavy use.
Ben.

At 03:16 07 June 2017, Frank Whiteley wrote:
On Tuesday, June 6, 2017 at 2:51:26 PM UTC-6, John Carlyle wrote:
Frank,
=20
When there are "conical male/female shapes at the failure point" it
gener=
ally indicates tensile overload failure (caused by exceeding the
materials
=
tensile strength). A giveaway would be necking on either side of these
shap=
es, which might be what you're calling failure "at the weld taper".=20
=20
Fatigue looks very different - the fracture surface shows a smaller
smoot=
h portion surrounding the origin, with the remainder of the fracture
surfac=
e appearing granular (perhaps what you're calling calling
"crystallization"=
.. Fatigue failure is caused by thousands, perhaps tens of thousands, of
loa=
d variation in the presence of a small defect in the part (usually on the
s=
urface).=20
=20
These are two completely different failure modes, and have two
completely=
different causes. It would be interesting to see pictures of the actual
fa=
iled ring and the fracture surface.=20
=20
-John =20
=20
On Tuesday, June 6, 2017 at 4:26:34 PM UTC-4, Frank Whiteley wrote:
We had a TOST large ring failure while winch launching at a CAP
Fligh=
t Academy a few years ago. It failed at the weld taper and the ring also
b=
roke opposite the weldment with the appearance of fatigue crystallization
a=
t the break. So, it's possible several launches were done with the
failed
=
weld before the ring failed at the second point. It was reported back to
t=
he vendor and also to TOST IIRC. Locally we discussed if perhaps some
coun=
terfeit supplies were getting into the channel. The academy leader
passed
=
away some time after the academy so I don't know the result of the report
b=
ut perhaps the vendor will recall the event. I'll check.
=20
Frank Whiteley
=20
I'll amend my post to say that it was not evident that the failed
ring
=
was welded, but that separation had conical male/female shapes at the
failu=
re point. Looking for images in the archives, but nothing so far.
=20
Frank Whiteley

John,

I think you've described it accurately. Still checking around for images.

=
They may not exist. This happened around 2009 and the rings certainly
had
=
not seen that many cycles. Not aware that anyone attempted to load test
th=
em, but who knows?

Thanks for your comments.

Frank Whiteley

Would some kind soul who really knows please tell us whether genuine Tost rings are ever(a) welded or (b) oval? Sounds more like bits of chains such as for those safety chains on trailers to me. Hence their being called earlier Toast rings(sic)!!






On Monday, June 5, 2017 at 9:45:05 PM UTC-4, Jock Proudfoot wrote:
Larry Morrow posted
Yesterday we found a toast ring with a fracture in the big ring. It
appears to completely through the ring. Has anyone else had this
experience? I have attached two image flies showing both sides of the
ring.
https://forum.sac.ca/download/file.php?id=254
https://forum.sac.ca/download/file.php?id=253

On Sunday, June 11, 2017 at 11:34:20 AM UTC-4, howard banks wrote:
Would some kind soul who really knows please tell us whether genuine Tost rings are ever(a) welded or (b) oval?

The correct rings are stamped LN 65091 on the big ring. The most recent production also have TOST stamped on them. The big ring is oval, the little ring is round.

30+ years ago, there was a different Tost ring set in use. It is not stamped with the LN 65091 designation. It is obsolete and should not be used.

best,
Evan Ludeman / T8

The failures I have seen are not in the tost ring pair at the glider end of
the
strop but the ones further down that connect the strop to the drogue or on

either side of the weak link (a circular ring that the strop is spliced to
and is
coupled to the oval Tost link with the quick release flat), as these are an

integral part of the quick release link I assume that they should be a
genuine
Tost part, but several I have seen are welded construction and don't have
any
visible markings on them. (This is in the UK)


At 15:52 11 June 2017, Tango Eight wrote:
On Sunday, June 11, 2017 at 11:34:20 AM UTC-4, howard banks wrote:
Would some kind soul who really knows please tell us whether genuine
Tost
rings are ever(a) welded or (b) oval?

The correct rings are stamped LN 65091 on the big ring. The most recent
production also have TOST stamped on them. The big ring is oval, the
little ring is round.

30+ years ago, there was a different Tost ring set in use. It is not
stamped with the LN 65091 designation. It is obsolete and should not be
used.

best,
Evan Ludeman / T8

On Sunday, June 11, 2017 at 1:00:04 PM UTC-7, Benedict Smith wrote:
The failures I have seen are not in the tost ring pair at the glider end of
the
strop but the ones further down that connect the strop to the drogue or on

either side of the weak link (a circular ring that the strop is spliced to
and is
coupled to the oval Tost link with the quick release flat), as these are an

integral part of the quick release link I assume that they should be a
genuine
Tost part, but several I have seen are welded construction and don't have
any
visible markings on them. (This is in the UK)


At 15:52 11 June 2017, Tango Eight wrote:
On Sunday, June 11, 2017 at 11:34:20 AM UTC-4, howard banks wrote:
Would some kind soul who really knows please tell us whether genuine
Tost
rings are ever(a) welded or (b) oval?

The correct rings are stamped LN 65091 on the big ring. The most recent
production also have TOST stamped on them. The big ring is oval, the
little ring is round.

30+ years ago, there was a different Tost ring set in use. It is not
stamped with the LN 65091 designation. It is obsolete and should not be
used.

best,
Evan Ludeman / T8


Tost Connecting Rings do not have a weld. Tost states that type certification stipulates that every Tost tow release must be operated only with a ring pair meeting the LN 65091 aeronautical standard. Connecting ring pairs must be stamped with the manufacturer's name and the standard number.

WELDED RINGS ARE GENERALLY PROHIBITED. Use of welded rings voids tow release warranties. Welded rings cause damage to tow releases. Undersized rigs can lead to tow release jamming.

Connecting rings must be visually checked and measured at regular intervals.. Rings pairs that deviate from standard dimensions must be replaced.

See a ring pair picture he http://wingsandwheels.com/aircraft-p...tow-rings.html

Sean Franke

On Tuesday, June 6, 2017 at 6:54:52 AM UTC-4, Tango Eight wrote:
http://www.tost.de/PDF/Arbeitskatalog_engl.pdf

Page 19.

Welded rings are long obsolete (or possibly counterfeit).

The right rings to use are easily identified.

It's pretty important to be using the right rings.

best,
Evan / T8

That is true for the small ring! They are seamlessly rolled or forged but the large ring has to get through it somehow, so it starts its life as a piece or 'wire' which gets formed and its ends are then joined by electric resistance welding (look up 'chain making' on YouTube).
Today, I inspected all the large rings of the double ring pairs I have with our winch and all of them show the tell-tale signs of a weld opposite of the stamped name 'Tost'. At least a close visual did not show any cracks. Maybe a simple 'dye-pen test is in order.

Uli
'AS'

On Sunday, June 11, 2017 at 7:37:42 PM UTC-4, Sean Franke wrote:
On Sunday, June 11, 2017 at 1:00:04 PM UTC-7, Benedict Smith wrote:
The failures I have seen are not in the tost ring pair at the glider end of
the
strop but the ones further down that connect the strop to the drogue or on

either side of the weak link (a circular ring that the strop is spliced to
and is
coupled to the oval Tost link with the quick release flat), as these are an

integral part of the quick release link I assume that they should be a
genuine
Tost part, but several I have seen are welded construction and don't have
any
visible markings on them. (This is in the UK)


At 15:52 11 June 2017, Tango Eight wrote:
On Sunday, June 11, 2017 at 11:34:20 AM UTC-4, howard banks wrote:
Would some kind soul who really knows please tell us whether genuine
Tost
rings are ever(a) welded or (b) oval?

The correct rings are stamped LN 65091 on the big ring. The most recent
production also have TOST stamped on them. The big ring is oval, the
little ring is round.

30+ years ago, there was a different Tost ring set in use. It is not
stamped with the LN 65091 designation. It is obsolete and should not be
used.

best,
Evan Ludeman / T8


Tost Connecting Rings do not have a weld. Tost states that type certification stipulates that every Tost tow release must be operated only with a ring pair meeting the LN 65091 aeronautical standard. Connecting ring pairs must be stamped with the manufacturer's name and the standard number.

WELDED RINGS ARE GENERALLY PROHIBITED. Use of welded rings voids tow release warranties. Welded rings cause damage to tow releases. Undersized rigs can lead to tow release jamming.

Connecting rings must be visually checked and measured at regular intervals. Rings pairs that deviate from standard dimensions must be replaced.

See a ring pair picture he http://wingsandwheels.com/aircraft-p...tow-rings.html

Sean Franke

See my note above. The picture clearly shown the weld in the large ring....

On Tuesday, June 6, 2017 at 9:16:37 PM UTC-6, Frank Whiteley wrote:
On Tuesday, June 6, 2017 at 2:51:26 PM UTC-6, John Carlyle wrote:
Frank,

When there are "conical male/female shapes at the failure point" it generally indicates tensile overload failure (caused by exceeding the materials tensile strength). A giveaway would be necking on either side of these shapes, which might be what you're calling failure "at the weld taper".

Fatigue looks very different - the fracture surface shows a smaller smooth portion surrounding the origin, with the remainder of the fracture surface appearing granular (perhaps what you're calling calling "crystallization". Fatigue failure is caused by thousands, perhaps tens of thousands, of load variation in the presence of a small defect in the part (usually on the surface).

These are two completely different failure modes, and have two completely different causes. It would be interesting to see pictures of the actual failed ring and the fracture surface.

-John

On Tuesday, June 6, 2017 at 4:26:34 PM UTC-4, Frank Whiteley wrote:
We had a TOST large ring failure while winch launching at a CAP Flight Academy a few years ago. It failed at the weld taper and the ring also broke opposite the weldment with the appearance of fatigue crystallization at the break. So, it's possible several launches were done with the failed weld before the ring failed at the second point. It was reported back to the vendor and also to TOST IIRC. Locally we discussed if perhaps some counterfeit supplies were getting into the channel. The academy leader passed away some time after the academy so I don't know the result of the report but perhaps the vendor will recall the event. I'll check.

Frank Whiteley

I'll amend my post to say that it was not evident that the failed ring was welded, but that separation had conical male/female shapes at the failure point. Looking for images in the archives, but nothing so far.

Frank Whiteley

John,

I think you've described it accurately. Still checking around for images. They may not exist. This happened around 2009 and the rings certainly had not seen that many cycles. Not aware that anyone attempted to load test them, but who knows?

Thanks for your comments.

Frank Whiteley

On reflection, the person who acquired the rings in question was an interesting character. I would not be surprised to find that he might have found a way to load test this set and perhaps unknowingly damaged them prior to putting them in use with the K-21's. As no report is known to have been filed, this secret may have died with him.

Frank W

That is true for the small ring! They are seamlessly rolled or forged but the large ring has to get through it somehow, so it starts its life as a piece or 'wire' which gets formed and its ends are then joined by electric resistance welding (look up 'chain making' on YouTube).
Today, I inspected all the large rings of the double ring pairs I have with our winch and all of them show the tell-tale signs of a weld opposite of the stamped name 'Tost'. At least a close visual did not show any cracks. Maybe a simple 'dye-pen test is in order.

Uli
'AS'


I seem to remember having read that the rings are made that way without any form of welding now. I suppose you could get the exact method used if you agree to pay for the technical norm:

http://standards.globalspec.com/std/...7/din-ln-65091

It's cheaper than ordering from the original German institute: http://www.din.de/en/getting-involve...din21:84399512