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Superman32

Unwarranted Concern?

By Superman32, in Gear and Rigging

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Superman32    0

Superman32
Ever since I was shown a parachute works, I have been concerned about one point of failure.

I have always been afraid that the ball at the end of the reserve cable, within the d-ring, would come loose. So if it came time to pull silver, the handle would come out but the cable stay.

I have not read or heard of this happening, but how is that little ball attached to the cable? Could you make a litlte square not just above the ball, or would a knot damage the integrity of the cable?
Am I worried about an extremely unlikely failure point?
Inveniam Viam aut Faciam
I'm back biatches!

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ZigZagMarquis    9

ZigZagMarquis
Good question.

Take this with a grain... just passing on info... Years back, I believe, some reserve handles got out of the factory where the "ball" on the end of the reserve cable had just be "set" (lite hammer tap ?), but had not been swedged; thus a good "tug" would pull the ball off. However, if the ball on the end of a rip-cord cable is properly swedged... you're not strong enough to pull it off... but if by some freakish accident of gama radiation you were, that force required would be well above what it takes to extract the pin on the other end of the cable from the reserve closing loop... IMO.

I also believe that once put together, a reserve rip cord handle is supposed to go through a 100% proof test, which would have caught the problem I believe once happened and also would catch the problem you fear.

There are several riggers here on the forum that have worked or are working for manufacturers. Hopefully they'll chime in with info on how things are done at the factory and QA'ed.

As for tying a knot in the reserve cable... well, that may work, but my first few thoughts are:

-- It may "shorten" the useful length of reserve rip-cord cable to the point where the pin could be pulled by mistake.
-- It would certainly be bulky and attract attention from other skydivers.
-- Have you tried tying a knot in aircraft cable?

Anyway... just my thoughts...

* puts on flame suit *

;)

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AFFI    0

AFFI
Tell ya the truth - I used to have the same concern. then it went away, then I got pillows on each side and I bacame concerned about it again simply due to the fact the stopper was no longer visible, then it went away.

I actually heard a bondfire story where something caused to D-Ring to no longer be there and the jumper was able to take a wrap or the reserve cable and pull it hard enough on the first attempt to activate reserve deployment...

Make it a great day!
Mykel AFF-I10
Skydiving Priorities: 1) Open Canopy. 2) Land Safely. 3) Don’t hurt anyone. 4) Repeat…

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FrogNog    1

FrogNog
I was concerned about this as a student, myself. It's because I'm technical and anal about some things.

I believe Dan Poynter's parachute manual (vol 1) describes what swaging balls and pins to cables does, and what are the expected strengths for different kinds of balls.

Personally, I preferred to jump the student rigs where the swaged ripcord end was a ball with an extended tubular neck, because I knew the swaging strength on these was about double the strength of the ball-only style. :)
Later I noticed I could see deformation inside and outside some of the connectors to reassure me it was swaged. (It didn't look like someone whacked it with a hammer, it looks like a funky multi-fingered press had grabbed the ball and crushed it in stripes over 50% of its surface.)

If it's swaged, I'm not worried it's coming off. The reason is swaging causes the connector to flow like play-doh (tm) into the recesses in the braded steel cable, virtually (although not actually) welding them together.

Manufacturer proof loading (if actually conducted, and not missed) will prove it was swaged.

-=-=-=-=-
Pull.

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mjosparky    4

mjosparky
  Quote

The test requirement is 300 pounds, for 10/30/something like that seconds.



From AS8015-B

4.3.1 Primary Actuation Device/Ripcord Test: The ripcord, including all joints, shall not fail under a straight tension test load of 300 lbf (1337.7 N) applied for not less than 3 s. The reserve static line, if used,
must not fail under a straight tension test load of 600 lbf (2667.3 N) for not less than 3 s. If the ripcord
is to be static line operated, the test shall be 600 lbf (2667.3 N) for not less than 3 s. The pins, if used,
shall not yield under a 8 lbf (35.6 N) load applied to the cable (or equivalent) perpendicular to the axis
of the pin, for not less than 3 s. The pin shall be supported for 0.5 in (12.7 mm) maximum at the end
farthest from the cable attachment. The pin(s) shall be deemed to have passed this test if the primary
actuation device/ripcord which it (they) is (are) a part of then passes the tests specified in 4.3.2.4.

Sparky
My idea of a fair fight is clubbing baby seals

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Zoter    0

Zoter
  Quote

Tell ya the truth - I used to have the same concern. then it went away, then I got pillows on each side and I bacame concerned about it again simply due to the fact the stopper was no longer visible, then it went away.



Hmmm just made me think....how are 'Pillow' type reserve handles constructed....?
How is the reserve cable ball secured....

Anyone have any pictures /diagrams.....?

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ZigZagMarquis    9

ZigZagMarquis
  Quote


Hmmm just made me think....how are 'Pillow' type reserve handles constructed....?



I had the same thoughts about how the pillow type cut-away handles were put togehter... so when I found a dropped one that had been out laying in the desert for awhile (the side of the pillow facing up was sun bleached white & the yellow cables cracked when flexed)... I took it apart carefully to see how they were put together... its one of those things that makes sense when seen, but hard to explain.

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diablopilot    2

diablopilot
  Quote

Hmmm just made me think....how are 'Pillow' type reserve handles constructed....?
How is the reserve cable ball secured....



There are several different designs on the market depending on manufacturer, and some are far better than others. The nicest IMO are the ones made using a slotted peice of aluminum pipe inside the pillow. They have a good "feel", are easy to get a grip on, securly hold the swedge when pulled, and most importantly allow the cable to "slip" when the harness is flexed like "D" ring handles do. VSE (Infinity) was the firt rig I encountered this handle with, I believe Mirage and RWS also use it too. I think Sunpath is using the "mini" d ring inside a pillow design that I saw them using a year or two ago. Perviously Sunpath had a design with a plastic stiffner in it which if not cut accurately could trap the swage at the bottom of the handle, risking extracting the pin when the harness was flexed (fortunately I'd only seen it hapen on the ground). They quickly re-engineered things when the problem was encountered.
----------------------------------------------
You're not as good as you think you are. Seriously.

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FrogNog    1

FrogNog
  Quote

Its a good argument for a Cypres/Vigil/Astra etc ;) if your concerned about the swaged ball coming off.



Very droll. I think it's a good argument for a trustworthy ripcord.

I get grumpy if a piece of equipment contains three parts and can't be made properly! :P

-=-=-=-=-
Pull.

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sunshine    2

sunshine
  Quote

Tell ya the truth - I used to have the same concern. then it went away, then I got pillows on each side and I bacame concerned about it again simply due to the fact the stopper was no longer visible, then it went away



I had the same feeling. Hehe, thats actually why i ordered a Dring on my first rig. I was too scared to have a pillow and not see the ball. Of course now i wish i had a pillow, but we all live and learn. :)

___________________________________________
meow

I get a Mike hug! I get a Mike hug!

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JerryBaumchen    1,451

JerryBaumchen
Hi Superman,

Any time anyone says "I have a concern about xxx..." is a good thing; it means you are thinking about your equipment.

Sparky has given you the line & verse from the TSO req'ments.

There is no TSO req'ment for any future testing once the TSO-authorization has been granted. I think that most, if not all, mfr's do additional testing on numerous parts that they put out. This is a good thing, in my opinion.

I have heard of some doing 100% testing of ripcords. If someone presented me (and please note, I say ME) with a ripcord that had been tested to 600 lbs for 3 seconds I would give it back to them. I would be concerned that it might have been a little too close to the failure point for future use. Now to do 100% testing at a lower value (a Proof Test is what this is usually called in the engineering world), say at 100 lbs I would be OK with that; some type of tollgate testing is what that would be. However, not wanting to use the 100% tested item, well, that is just me.

I am too lazy to go get my Loos & Co. catalog out but I think that ball without shank (that little tube that is attached to some ripcord balls) is rated at about 80% of cable strength (cable strength is 920 lbs I think; am I right on this value?). Ball with shank is rated at 100% of cable strength, as is the pin swage.

Now regarding the swaging method. Ron Dionne up in Canada has been making his own dies for swaging the pins & balls for many years. The ball, when swaged, looks a lot different than what outfits like Capewell put out, using rotary swagers. Al MacDonald of Flying High uses a set of Ron's dies for his ripcords, I believe. Me, I made my own dies (after a lot of R&D; way too much R&D, which = $$$) and for probably about 15-20 years now I have only built ripcords with two balls on the end, usually about 1 inch apart. For my cost of about $0.50, the customer gets 100% redundancy. Now again, that is just me.

As for your actual concern; a couple of things:

1. The lowest TSO rating of the ball is 300 lbs. Can you pull that amount (after all, you are Superman32 [just having some fun here])? Since virtually no one can, then you will be fine if everything is in good condition.

2. Always keep an eye on this part of your equipment (actually, all of your gear). If you see something that you do not like, ask your local rigger/call the mfr; but do not jump it. Look for things like frayed strands, kinks, rust (yes, s/s will rust, just in a different nature), damage (did you close the trunk on the cable), etc.

Back in the 60's we had a couple of local guys who designed and built their own piggyback rigs. For a ripcord, they got surplus B-5 ripcords (the reserve container was designed somewhat like a B-5 military rig), they cut off the ball (the ripcord was too long for their use) tied a knot in the cable and tucked the knot into a blast handle, which they used for a reserve ripcord handle. It was really crude but I would suppose it might haved worked OK; they never did have to use it under actual emergency conditions.

You've now got probably way more information that you thought you would get. I hope that this (way too long post) and the other posts have answered your 'concern.'

PS) I have often wondered if I could swage a ball that would pass the 300 lb test by using an anvil & a ball peen hammer and doing it very slowly, by hand. Maybe some day, hmmmmm?

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mjosparky    4

mjosparky
  Quote

am too lazy to go get my Loos & Co. catalog out but I think that ball without shank (that little tube that is attached to some ripcord balls) is rated at about 80% of cable strength (cable strength is 920 lbs I think; am I right on this value?). Ball with shank is rated at 100% of cable strength, as is the pin swage.



Right on the money Jerry, the cable is steel aircraft cable 3/32” (MIL-W-5424) and minimum tensile strenghtis920 lbs.

If the end of the ripcord had just a round ball on the end it is rated at 736 lbs. or 80% of the cable.

If the end has a round ball with a shank, it is rated at 100% of the cable.

(source: PPM Vol. I, page359)

Sparky
My idea of a fair fight is clubbing baby seals

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skytash    0

skytash
***I think Sunpath is using the "mini" d ring inside a pillow design that I saw them using a year or two ago.



that's what the reserve pillow on my Odyssey feels like, it was built in 2003.

tash
Don't ever save anything for a special occasion. Being alive is a special occasion. Avril Sloe

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alexey    6

alexey
Few weeks ago we found that problem with one of Ukrainian local manufacturers, that made exactly the same - just set the terminator, and didnt swaged it.

After a season, customer went to training stand, fastened his rig, cut away and pul the silver.

D-ring came off, the cable and the pin was on place.
He cant pul the pin by cable - not enouph grip for that...

Manufacturer uses standart cable, pin and terminator...

As for me - I much prefere, when end of the cable makes a loop - its much secure, and, cant make such problems:
http://www.skycentre.net/index.php?showtopic=343

Sorry, its in russian, but you can look at foto....
Lexa

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daniel_owen_uk    0

daniel_owen_uk
I did wonder about this, they taught me to check it as part of my gear check, make sure the ball doesn't come off the end of the cable.

If you think about the forces required to pull the pin from the reserve closing loop and the forces required to pull that little ball from the end of the cable, its makes sense that the pin is gonna give in first.

Yet another reason for RSL :P
__________________

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ZigZagMarquis    9

ZigZagMarquis
  Quote

Yet another reason for RSL :P



Ya know, I thought about that too... in the scenario where the ball comes off the end of the Reserve Rip Cord... an RSL may pull the reserve... but then I did a double take thinking it just may strip the cable through the housing and leave the pin in place... hmmmm... guess the only way to know would be to do some sort of test drops... MJO! You up for it???
;)

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