Ring design and features?

[Downhill Trucker]

There's an entirely different application of clinching rings, which brings different seriousness to their quality: A pair of them to make a sling (or whatever it is called) in which to carry infants and babies.

(Edit: "Slingrings was easy enough to find)

The folks that market these--yes, another niche cottage industry -- go to a lot of trouble and expense to be sure the rings met quality and testing standards. (Just as with SMC descender rings.) No wonder, juries being sympathetic to babies and likely not too easy on easy-going, HYOH, parents and mfgs.

When I ran across these a year ago, the sizes or weight ratings were far below those of interest here. Babies aren't that fat......... yet. But the expected multiple of safe to tested BS strength of 11-15 was there.

I've used sling rings for years on several hammocks. They work great, are light, and come in colors!

They ship fast too!

[pulsemod]

Thanks everyone. It's appreciated. I have to move onto carabiners now. I'll eventually end up settling on a setup. I have to figure out what series of trade-offs yield a combination of durability, speed of set-up/tear-down, and ease of adjustability/reconfiguration without spending more than I have to.

[nothermark]

I have SMC's and have seen the others. SMC usually wins on price. All are stamped as a washer and rolled smooth round for rope work. No welds or bumps. I have not seen welded rings in climbing gear. Horse gear is another story. ;-)

[NCPatrick]

+1 to avoiding the Garda Hitch. It will pinch and damage rope under 4mm and has a suggested load limit of 220lb (100kg).

I agree on avoiding it. After doing a little more research I see that it fell out of favor a while ago, and for those reasons. Thanks.

[DemostiX]

Last week I dropped a note to the maker of Slingrings, asking what they were destructively tested to, on a sampling basis.

Here is the fantastic reply I just got, (after an apology for a delay.)

'scuse me. THIS is responsible service, not just to me as an (unlikely) potential customer, but to the customers he designs and gets the rings made for.

Thank you for your interest in our products. We were gone to the ASTM [American Society for the Testing of Materials] subcommittee meetings for baby carriers.

As you have noticed, our rings are marketed (and insured) specifically for baby carriers. For this usage we have determined that they need to be guaranteed to a maximum of 60 pounds. We test them to 250 pounds, giving a 4x safety factor. We do have some customers who purchase rings and use them for other purposes.

Periodically we have the rings tested at an outside facility. The large rings begin to deform around 350 pounds and break at 500 pounds. The medium rings break closer to 750 pounds and the small rings higher still, at around a thousand pounds. We have not tested a large enough sample to give a statistically significant or reliable answer. That's why we don't publish these results.

We have been asked to work on smaller (aluminum) rings for some additional applications. These rings could potentially be even stronger. They are 1.75 inch inner diameter.

If you have additional questions, please let me know, or you can call Paul, (owner and technical director) at 602-284-4158 to discuss your specific application.

Designed-in security is more valuable, imnsho, than replacement of products that have failed because they may not have been designed, made, and QC-inspected thoroughly before delivery.

Paul did not detail the engineering testing protocol, which is for me to find out about.

[NCPatrick]

Thanks for posting that. Here's some documentation I found on the SMC rings: http://www.rocknrescue.com/acatalog/...endingRing.pdf

[Simple Survival]

I made the ones I use my self from solid aircraft alum. pipe. Will hold over 250lbs. and were FREE!!

[kayak karl]

i've had the sling rings fail on me twice.
i use the SMC (large) rings with 12' of webbing. rings are 4+ years old. webbing i replace when i see damage (damage never from rings)

[Mouseskowitz]

Simple Survival, it appears you are using a Garda Hitch with your rings. If you haven't already I recommend you consider using a different system for your rigging. The reasons are three fold in your case. First is that it is not recommend for lines under 4mm due to line pinch and flattening. Second is that it is not recommended for loads over 220lb, which may or may not be a factor for you. Third is that your rings appear to be more squared off than most which could accentuate the first reason.

If anyone is interested in a more in depth discussion of the issue going on here.

[DemostiX]

i've had the sling rings fail on me twice.
i use the SMC (large) rings with 12' of webbing. rings are 4+ years old. webbing i replace when i see damage (damage never from rings)

I don't find the first statement immediately informative, especially when if follows a clear statement by the maker of what the expected use is, and then an approximation of load to bending and breaking failure for each of three sizes of ring.

I would doubt -- without seeing the ASTM testing protocol -- that Slingrings is paying for testing under fatigue conditions. How aluminum of particular kinds behaves is well known, and inferences are made from a single type of test, say with short term bending load, of how the rings will perfom under other conditions. IIRC, the heaviest ring is just 1/4" / 6mm thick.

Did slingrings fail to perform within their design parameters, or did you use them in such way as to confirm that they performed as might be predicted under the load and conditions?