How reliably do CG hooks disconnect when the angle of the ropeexceeds the autorelease angle

On Monday, June 8, 2020 at 8:33:23 AM UTC-4, son_of_flubber wrote:
Does anyone have experience with non-Tost rings failing to release in Tost releases?

I've been warned about this possibility, and I know how to verify that a ring is genuine Tost. The explanation that I've been given is that 'hardware store rings' change shape with use and that at some point the elongation prevents the release.

That is correct - there is a good chance that a hardware store ring or a chain link can deform and kind of swage itself onto the beak inside the Tost hook, making it very difficult to release. That subject was discussed in great length in the 'winchdesign' forum.

Uli
'AS'

Also note that the small hookup ring can wear. If it gets deformed or reduced in size, it can jam or prematurely release. I looked for the specification on minimum thickness, but couldn't find it with a (very brief) search. Check with Wings & Wheels to see if they know the correct "go-no go" dimension.

On Monday, June 8, 2020 at 9:38:29 AM UTC-4, wrote:
Also note that the small hookup ring can wear. If it gets deformed or reduced in size, it can jam or prematurely release. I looked for the specification on minimum thickness, but couldn't find it with a (very brief) search. Check with Wings & Wheels to see if they know the correct "go-no go" dimension.

Mark - according the the DIN-LN65091, the oval ring has a wire diameter of 8mm, +0, -0.3mm. The round ring has a wire diameter of 7mm, +0, -0.3mm. The O.D. of the round ring is 35mm, +-0.3mm, which would give it a nominal I.D.. of 21mm. If you do a quick tolerance stack-up using just min.-max. material conditions while neglecting any ovality, the I.D. could range from 21.9mm to 20.7mm
The material specifications call for a high carbon Chrome-Vanadium alloy. No welding is permitted.

Uli
'AS'

On Monday, June 8, 2020 at 11:16:32 AM UTC-6, AS wrote:
On Monday, June 8, 2020 at 9:38:29 AM UTC-4, wrote:
Also note that the small hookup ring can wear. If it gets deformed or reduced in size, it can jam or prematurely release. I looked for the specification on minimum thickness, but couldn't find it with a (very brief) search. Check with Wings & Wheels to see if they know the correct "go-no go" dimension.

Mark - according the the DIN-LN65091, the oval ring has a wire diameter of 8mm, +0, -0.3mm. The round ring has a wire diameter of 7mm, +0, -0.3mm. The O.D. of the round ring is 35mm, +-0.3mm, which would give it a nominal I..D. of 21mm. If you do a quick tolerance stack-up using just min.-max. material conditions while neglecting any ovality, the I.D. could range from 21.9mm to 20.7mm
The material specifications call for a high carbon Chrome-Vanadium alloy. No welding is permitted.

Uli
'AS'

Thanks!

Soooo....."no welding allowed"......how do they make the ring? Just asking......usually round "wire/rod", bent, welded together.....
Shrug....

On Monday, June 8, 2020 at 1:14:41 PM UTC-6, Charlie M. (UH & 002 owner/pilot) wrote:
Soooo....."no welding allowed"......how do they make the ring? Just asking......usually round "wire/rod", bent, welded together.....
Shrug....

Forging a ring involves bending the stock in a circle with varying amounts of overlap- sometimes one or more full circles, but more often a lap of about 1/3 the circumference. Then it is heated to a bright, glowing temperature and beaten into the final shape. Hardening is sometimes done by quenching in oil. Linked rings are made by forging the first ring and looping the second though it and forging by the same method.

On Monday, June 8, 2020 at 3:30:08 PM UTC-4, wrote:
On Monday, June 8, 2020 at 1:14:41 PM UTC-6, Charlie M. (UH & 002 owner/pilot) wrote:
Soooo....."no welding allowed"......how do they make the ring? Just asking......usually round "wire/rod", bent, welded together.....
Shrug....

Forging a ring involves bending the stock in a circle with varying amounts of overlap- sometimes one or more full circles, but more often a lap of about 1/3 the circumference. Then it is heated to a bright, glowing temperature and beaten into the final shape. Hardening is sometimes done by quenching in oil. Linked rings are made by forging the first ring and looping the second though it and forging by the same method.

I am just speculating here but two interlocking rings could be easily made as an investment casting (lost wax casting). Given that it is a Cr-Va alloy, the raw cast product can be heat treated and quenched in oil, which would explain the blackened appearance when new.
I will see if I can get my hands on a discarded pair and have our metallurgists take a look at.

Uli
'AS'

On Monday, June 8, 2020 at 1:16:32 PM UTC-4, AS wrote:
...according the the DIN-LN65091, the oval ring has a wire diameter of 8mm, +0, -0.3mm. The round ring has a wire diameter of 7mm, +0, -0.3mm. The O.D. of the round ring is 35mm, +-0.3mm, which would give it a nominal I.D. of 21mm. If you do a quick tolerance stack-up using just min.-max. material conditions while neglecting any ovality, the I.D. could range from 21.9mm to 20.7mm

For those of us who know how to use a pair of calipers, and not much else, what is a quick way to determine that a ring is worn out?

A quick way is to only use a TOST ring set where you can still read (most) of the TOST part number stamped on the side of the small ring. With dimension change due to wear&tear, the part number will become unreadable.
This has the dual benefit of also ensuring you are being hooked up with a proper TOST ring set and not a home made or repaired set.
PS- Remind me to take a calipers out to the airfield next visit and validate a suspect worn ring’s dimensions. Thanks, whoever posted the spec dims.

On Tuesday, June 9, 2020 at 1:27:45 PM UTC-4, wrote:
A quick way is to only use a TOST ring set where you can still read (most) of the TOST part number stamped on the side of the small ring. With dimension change due to wear&tear, the part number will become unreadable.
This has the dual benefit of also ensuring you are being hooked up with a proper TOST ring set and not a home made or repaired set.
PS- Remind me to take a calipers out to the airfield next visit and validate a suspect worn ring’s dimensions. Thanks, whoever posted the spec dims.

It's on the oval ring on my ring pair... and TOST is stamped at the bottom of it.