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Tost Ring Failure



 
 
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  #1  
Old June 6th 17, 02:35 AM posted to rec.aviation.soaring
Jock Proudfoot
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Posts: 91
Default Tost Ring Failure

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

  #2  
Old June 6th 17, 04:44 AM posted to rec.aviation.soaring
Frank Whiteley
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Posts: 2,099
Default Tost Ring Failure

On Monday, June 5, 2017 at 7:45:05 PM UTC-6, 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


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
  #3  
Old June 6th 17, 06:34 AM posted to rec.aviation.soaring
CindyB[_2_]
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Posts: 157
Default Tost Ring Failure

On Monday, June 5, 2017 at 6:45:05 PM UTC-7, 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?


Yes.
Quite a long time ago, 15 years.
We subsequently retired the fractured Tost to the ground towing rig
for moving the gliders from tiedowns to launch and back. It is a very unusual occurence but was easily apparent from the loss of the clean 'ping' sound as they jingled around together. The sound was 'flat' and dramatically different, which is what led to discovery before complete failure.

So yes, preflight ALL the equipment. Don't settle for a line helper just waving a rope end or ring in front of the glider for your first daily launch.. How's the length of the back splice? How's the bulge of radius change at that point - frayed? Tape wrapped to be invisible? That transfers the wear point to the head of the tape. Look there, too.
Be thorough, be safe.

Cindy B
  #4  
Old June 6th 17, 11:54 AM posted to rec.aviation.soaring
Tango Eight
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Posts: 962
Default Tost Ring Failure

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
  #5  
Old June 6th 17, 12:29 PM posted to rec.aviation.soaring
Dan Daly[_2_]
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Posts: 718
Default Tost Ring Failure

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


The manual also says that the standard dimensions should be checked and they are available from the factory. Does anyone in ras-land have them?
  #6  
Old June 6th 17, 01:38 PM posted to rec.aviation.soaring
Tango Eight
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Posts: 962
Default Tost Ring Failure

On Monday, June 5, 2017 at 9:45:05 PM UTC-4, Jock Proudfoot wrote:
]
https://forum.sac.ca/download/file.php?id=254
https://forum.sac.ca/download/file.php?id=253


btw... these pics aren't publicly accessible.

T8
  #7  
Old June 6th 17, 02:44 PM posted to rec.aviation.soaring
Dan Daly[_2_]
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Posts: 718
Default Tost Ring Failure

On Tuesday, June 6, 2017 at 7:29:55 AM UTC-4, Dan Daly wrote:
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


The manual also says that the standard dimensions should be checked and they are available from the factory. Does anyone in ras-land have them?


Received a pdf by e-mail; thanks, Glen from Aboyne.
  #8  
Old June 6th 17, 03:13 PM posted to rec.aviation.soaring
Tom BravoMike
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Posts: 266
Default Tost Ring Failure

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  #9  
Old June 6th 17, 09:26 PM posted to rec.aviation.soaring
Frank Whiteley
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Posts: 2,099
Default Tost Ring Failure

On Monday, June 5, 2017 at 9:44:32 PM UTC-6, Frank Whiteley wrote:
On Monday, June 5, 2017 at 7:45:05 PM UTC-6, 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


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
  #10  
Old June 6th 17, 09:51 PM posted to rec.aviation.soaring
John Carlyle
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Posts: 324
Default Tost Ring Failure

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


 




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