Two rings? Three rings? *Five* rings?

[dgw 8]

I was wondering about the three ring system. I have recently acquired, for the craic, an old school harness/container with some form of Capewell release mechanism (I think). It looks like a real dogs-dinner of a release system compared to the three-ring release.

I was wondering if anybody has considered why three rings are used in the current release system, as opposed to two or four (or *five*)? It seems to me that the same mechanical advantage could be achieved with any number of rings (with the exception of a single ring), provided the sizing was appropriate.

Having had this thought, I further wondered if higher cut-away forces associated with mini-rings, compared to normal 'large' rings, could be mitigated with a mini-four-ring system? (More bling for your buck).

This post is not a slight on the three ring system. It is wonderful. I'm just interested in any views regarding 'flexing' the design parameters, and only for the sake of discussion.

Darren

[jheadley 0]

I've been wondering this myself. I *think* the reason 2 rings weren't used would be because the mechanical advantage would be too little, and more than 3 were not necessary, because when the 3 ring release was designed, people were jumping very large canopies that wouldn't spin very fast, which made the cutaway force low. In today's times, with very fast spinning canopies and high cutaway forces, I've often thought that a "4 ring release" may help. However with everyone using mini-risers, there'd really be no way to fit another ring onto the system unless you make all the rings bigger, which is not cool looking, so skydivers won't do it. Going back to just the large 3 rings would probably give you the same mechanical advantage.

Does anyone know, or know a way for me to calculate the true mechanical advantage (through a mathematical formula or a hands on test) of the 3 ring release? I read in the Poynter's manual that each ring is a 10:1 ratio, and then the white loop is 2:1, so a 200:1 total, but I'm assuming that's only true for the original large 3 rings.

Also apparently the Advance Tandem by Basik does use 4 rings.

[dgw 8]

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Going back to just the large 3 rings would probably give you the same mechanical advantage.

/reply

Agreed. I just thought that a four ring arrangement would allow the cool 'small' look, and satisfy the market demand, but offer the 'original three ring' advantage.
***

Does anyone know, or know a way for me to calculate the true mechanical advantage (through a mathematical formula or a hands on test) of the 3 ring release? I read in the Poynter's manual that each ring is a 10:1 ratio, and then the white loop is 2:1, so a 200:1 total, but I'm assuming that's only true for the original large 3 rings.

/reply

You can just measure the fulcrum points on your three-ring system on your rig, and invoke the law of the lever. (I suspect that this is probably trickier than it sounds)

**

Also apparently the Advance Tandem by Basik does use 4 rings.

[ZigZagMarquis 8]

Its more like pullys then a fulcrum lever problem, but kinda in-between really.

Anyway, search the forum on "Bill Booth" and "3-Rings" and you may find something which will answer your question... or maybe Bill will happen along and educate us... again.... hope he does, actually.

I've seen (pictures) and heard talk of going to 4-Rings on Tandems... especially a few years back when breaking risers on Tandems was a hot topic. Sounds like it may have gone into service on some Tandem system or another??? ... I've never seen one "live" in the field, doesn't mean it doesn't exist though.

[dgw 8]

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Its more like pullys then a fulcrum lever problem, but kinda in-between really.

I think (and I'm no expert) pullys pertain to mechanical advantage when the force is transmitted through a flexible mechanism (a rope or its ilk). In the three-ring system, the mechanical advantage is acquired through rigid (round rings) levers. Notwithstanding this, the fundamental parameter (for leverage) is the distance between the 'top' of the system, and the lowermost fulcrum.

Interesting info about the Tandem risers though. Thanks!

Darren

• Quote

[BIGUN 1,049]

If you email Dorothy at RWS; she'll send you the white paper on the 3-rings.

Nobody has time to listen; because they're desperately chasing the need of being heard.

[mjosparky 3]

Quote

Does anyone know, or know a way for me to calculate the true mechanical advantage (through a mathematical formula or a hands on test) of the 3 ring release? I read in the Poynter's manual that each ring is a 10:1 ratio, and then the white loop is 2:1, so a 200:1 total, but I'm assuming that's only true for the original large 3 rings.

See Attachment.

My idea of a fair fight is clubbing baby seals

[phoenixlpr 0]

3 ring was just optimal.

Each ring acts as a lever.
Pulling force was too high using only 2 rings for cut-away.

Adding more rings will ease pulling but adds more complexity.

Check Aerodyne's risers! They are cheating. Their 2nd ring is not a ring, it's a kindda oval. Its virtually bigger.

[jheadley 0]

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Quote

Does anyone know, or know a way for me to calculate the true mechanical advantage (through a mathematical formula or a hands on test) of the 3 ring release? I read in the Poynter's manual that each ring is a 10:1 ratio, and then the white loop is 2:1, so a 200:1 total, but I'm assuming that's only true for the original large 3 rings.

See Attachment.

Hey thanks, those are interesting results. But those results make it sort of seem like either way, with the big rings or small, it's not that big a deal. Say I weigh 250 pounds and I have a spinning mal at 3Gs, which I imagine would be pretty quick, that'd make my weight 750 pounds right? So it'd be a difference of 5 pounds pull force with the mini rings versus 2.2 with the large. I guess less force is always better but with the reserve ripcord pull force being allowed to be up to 22 pounds, 5 pounds doesn't really seem that significant.

Maybe the hard pulls more likely come from the twisted risers trapping the cutaway cable if hard housings are not used, or people not peeling before pulling the cutaway handle?

[skydiverek 54]

Skydiving magazine wrote that there was a French company that was bulding rigs with FOUR rings.

[riggerrob 558]

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Skydiving magazine wrote that there was a French company that was bulding rigs with FOUR rings.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

Yes, Atom Tandem rigs - built by Parachutes de France use a 4-Ring system. P. de F. starts with a harness ring the same size as an RW-1. RW-2 and RW-3 rings are sewn to the bottom end of the riser, but the smallest ring is really a grommet set in a piece of tape.

[riggerrob 558]

Movie stunt men often use 2-Ring, 3-Ring, 4-Ring or even 5-Ring releases - depending upon the load - on their harnesses when ratcheting, jerking, lifting, swinging, flying, etc.
When sewing 2-Ring, etc. releases, stunt equipment technicians start with dimensions in RWS's 3-Ring Manual published in 1998.

[rigger_john 0]

[Reply]Yes, Atom Tandem rigs - built by Parachutes de France use a 4-Ring system. P. de F. starts with a harness ring the same size as an RW-1. RW-2 and RW-3 rings are sewn to the bottom end of the riser, but the smallest ring is really a grommet set in a piece of tape.

[riggerrob 558]

There are three ways to improve mechanical advantage in 3-Ring release systems: change the diameter of rings, change the length of rings, change the number of rings.

First a little history lesson: when (circa 1975) Bill Booth built the first (few hundred) 3-Rings with simple, round RW-0 rings that were sewn to the outside of harnesses. RW-0 is a simple standard to compare all other sizes of 3-Ring systems.

In 1981, Booth introduced the RW-1 harness ring. RW-1 has the same internal diameter as RW-0, but has a slot across the bottom. When harness webbing is inserted through the slot, the hardware acts like a confluence wrap, doubling the peel strength of the shoulder joint, preventing reserve risers form peeling off the harness, even when you deploy on your back..

The first attempt at changing the diameter of 3-Rings occurred in 1981, when Para-Flite introduced their Swift system with mini-3-Rings. The harness ring is the same diameter as the middle ring (RW-2) in a standard/original/large 3-Ring. Mini-rings are not as strong as RW-1 sized rings, but if manufacturing tolerances are kept really tight (1/16 of an inch) they are adequate for the skydiving environment.

A couple of years later, Parachutes de France introduced a slotted mini-ring that became the industry standard for mini-rings.

A few years later, RWS introduced their RW-7 slotted mini ring, that (had the same diameter as P. de F. mini-rings) but was only half as thick. RW-7 might have contributed to broken mini risers (one inch wide Type 17 webbing) and RWS quietly replaced it with RW-8 slotted mini-rings, which are the same thickness as P. de F. mini-rings.

In the late 1980s, the Canadian Army decided to move their freefallers out of the stoned age by developing a high-speed, heavy-weight version of Para-Flite's MC-4 military freefall system ( a really BIG version of the Swift skydiving rig) after bending a few RW-1 Rings, the Canadian government funded development of the huge/thick/bulky RW-9 slotted harness ring. RW-9 risers use RW-0 rings as middle rings and their smallest ring is RW-2. RW-9 risers are not compatible with any civilian skydiving system.

In the late 1990s, RWS developed the RW-10 slotted harness ring for tandems. RW-10 has the same internal dimensions as RW-1. but is slightly thicker/stronger.

Changing the length of rings was done by Aerodyne when they introduced their mini-force system (in the early 200s). Mini-force risers use standard mini-ring (RW-8 sized) components except for an oval (race track) shaped middle ring that increase the length of the lever.

Finally, a few tandem systems change the number of rings by adding a fourth ring. Parachutes de France and Advance (both in France) sew an extra ring on their tandem risers to produce a 4-Ring system. Their harness rings are the same size as RW-1, but their smallest ring (or grommet) is the same size as the smallest ring on a mini-riser.

[BKR 0]

Rob,

Just for your info, we used te 4 rings on Advance Tandem to reduce the force applied when pulling the breakaway handle in case of spinning malfunction with heavy loads. When testing the system, we load the rig at 540 kg and the pull force went from 3.6 to 6 kg max instead of 10.5 to 25 kg with the 3 rings.
This is the only reason of the use of this concept.

Jérôme Bunker
Basik Air Concept
www.basik.fr
http://www.facebook.com/pages/Le-Luc-France/BASIK-AIR-CONCEPT/172133350468

[dgw 8]

Thanks for the information Rob, and others. Very interesting stuff. I guess, like many design problems, there's a balance to be struck. Under 'normal' loading, you want sufficient pull force to ensure that the white loop has sufficent grip on the lolon cable so that the risers don't release if the cut-away handle is floating. On the other hand, under 'abnormal' conditions, you still want to have enough mechanical advantage to allow a release of the risers.

Whatever way you slice it up, when you line up a three ring release with the Capewell system (which I did), the three ring system makes me feel warm and fuzzy on the inside, whereas the Capewell system looks like a bad day out.

[jumper03 0]

I've been thinking about this all day and one possible disadvantage to more than three rings could be ring size. In a five ring system, each ring must fully fit through the next ring. You either will have a very tiny fifth ring, or very large first ring. Either way, I think three optimizes the ring size on both ends. no clue if that is correct - just another random thought I had today.

Jump

Scars remind us that the past is real

[mjosparky 3]

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you want sufficient pull force to ensure that the white loop has sufficent grip on the lolon cable so that the risers don't release if the cut-away handle is floating.

There is no load on the white loop to grip the cable until there is a load on the risers. If there was how would you hook up the risers? There is just the friction between the two components.

My idea of a fair fight is clubbing baby seals

[mjosparky 3]

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Whatever way you slice it up, when you line up a three ring release with the Capewell system (which I did), the three ring system makes me feel warm and fuzzy on the inside, whereas the Capewell system looks like a bad day out.

Take both harness and remove the risers. Now look at what is left attached to the harness.
The Capewell looks like a big grappling hook waiting to snag the first thing it can. One of the big advantages of the three ring system that gets overlooked.

My idea of a fair fight is clubbing baby seals

[billbooth 10]

We now use a 4 ring system for our military bundle systems with all up loads of over 850 lbs. A properly constructed 3 ring, starting with an RW 10, is more than enough for tandem jumps up to 500 lbs. I have made a 5 ring release for a 10,000 balloon gondola, and several other "secret" applications.

[riggerrob 558]

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I've been thinking about this all day and one possible disadvantage to more than three rings could be ring size. In a five ring system, each ring must fully fit through the next ring. You either will have a very tiny fifth ring, or very large first ring. Either way, I think three optimizes the ring size on both ends. no clue if that is correct - just another random thought I had today.

Jump

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

Yes, it is possible to build a 5-Ring release system using standard components.
Start with a RW-9 harness ring (extra-large for military freefallers) then sew an RW-0 ring on the bottom of the riser.
... then an RW-2 and an RW-3 then finish with the smallest ring (I forgot the number) from a mini-riser. Most of the dimensions were published - in 1998 - in the 3-Ring manual.

[dgw 8]

That is a good point. Thanks.