SWLL & Breaking strength?

F

frans

Location
healdsburg, CA
This may sound like dumb question but I am curious.


I recently learned that the alum. rings on cambium savers such as what Buckingham makes, are rated at 350 pounds each. But the overall strength meets the 5 thousand pound requirement.

Can anyone explain this to me?
 
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Can anyone explain this to me?

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thinking.gif
I'm curious too...
 
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Can anyone explain this to me?

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I can't speak with authority since I have never actually seen an answer to this question in print, but for myself, I have always assumed the total SWL would be the total of each ring added since the rope would always run through both. I also believe that pulleys use a similar concept if that have sliding sideplates, i.e. the total SWL is the SWL of each side. I believe a few of my pulleys actually have this marked on them.

Again, this is just my thoughts.

I'm also curious what the official answer is.
 
Where did you get your info?

What is the safety factor used to rate the rings?

Since each ring, theoretically, supports half of the load the design may start with a breaking strength of 2,500#. Then, apply a 10:1 SF and 350# exceeds the SF.

I have NO clue if this is true or not though.

Why not write directly to B'ham?
 
[ QUOTE ]
Where did you get your info?

What is the safety factor used to rate the rings?

Since each ring, theoretically, supports half of the load the design may start with a breaking strength of 2,500#. Then, apply a 10:1 SF and 350# exceeds the SF.

I have NO clue if this is true or not though.

Why not write directly to B'ham?

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I agree that Buckingham will probably have the definitive answer, but I like the idea of walking through the problem to understand it.

If we take a sling with a 2500# breaking limit in a "straight" configuration, that would equate to near a 5000# breaking strength in a basket configuration. If the rings are rated at 350# SWL, (assuming a 10-1 SF) then I believe the whole system would still meet the 5000# breaking limit threshold, with the sling being the weakest link.

In looking at my previous post, I believe I should have stated that the total SWL of the system would be the SWL of each side, not necessarily the rings.

It would probably still be preferable for each component to meet the 5000# threshold for most people. (But on the other hand, even if the breaking limit of the system was 2500#, that still gives most climbers a 10-1 safety factor compared to their weight, but that is a different debate.. )
 
I did call buckingham yesterday, Tom. What they told me was that each component of the cambium savers meet the 5K requirement.

However, I also spoke with Bourdon Forge, who makes steel rings. They are a source for parachute components, rings and rigging hardware. The 'proof load' test of comparable steel rings is 2500 & 7500 lbs, respectively for the small & large rings in steel (items # 2058 & 2059).

http://www.bourdonforge.com/business/productsbusiness/products-orings.htm

It got me to thinking, because the two rings items 2058 & 2059 are similar in overall dimensions to the alum rings.
If a steel ring the same size as the alum ring used on a cambium saver is roughly around the 5 K limit, how can the alum. rings be just as strong?

Steel is stronger than alum. after all.

Part of my question is asking for a definition of 'Safe Working load', 'proof load' & 'Tensile load'.

The other part is, When I use a cambium saver with only one ring, I could very well be overloading that ring. ?

Also, I am curious about these alum rings. On many saddles one small alum. ring is used on the leg risers. Which means that that particular hardware component IS NOT at or above the 5K limit. Which is fine as a leg riser is not life support.

I always looked at the alum rings as EACH one meeting the 5 K limit. Maybe this is not true. Maybe they MUST be used together to meet the 5K limit.???

kevknep: I always figured that the webbing was one of the strongest parts of the cambium savers
 
Glad to hear that each component meets the minimum requirement. I also thought that the webbing was probably the strong point, it seems to be pretty thick, much thicker than my standard webbing I use for climbing.
 
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I did call buckingham yesterday...What they told me was that each component of the cambium savers meet the 5K requirement.

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This seems clear that each ring can hold 5K and the webbing alone can hold 5K.

Regarding the aluminum rings being "as strong" as steel. I know manufacturers sometimes way underly report the strengths of their goods...for liability, I guess.

Does anyone know where buckingham gets their rings? Maybe we can talk to the manufacturer directly. I asked them about 5 years ago and they wouldn't tell me.

love
nick
 
http://www.patrollersupply.com/gear/category_96.asp

Well, I guess this answers at least part of my question. If you look at the smaller alum. ring on this web site's very first page, it says that the small alum. ring is NOT rated. Hummm. perhaps buckingham gets their small ring somewhere else...
The description also says it is made out of 'tubular' alum. stock. I am assuming this does not mean a 'tube', but a 'rod' of alum.


Please tell me if I am correct:

tensile strength:
the resistance of a material to breaking under tension. (failure point? or likely-to-fail point?)

proof load: the specific item has been individually tested by loading it with the amount of weight which is stamped on the item. (so every 'proof loaded' item has already experienced a load?)

Breaking load: The exact point where the item WILL break.



A further thought; Climbers commonly use a micro-pulley (like the CMI) to climb on because it says on it that it is rated to 5 thousand pounds. Safe working load limits are set at 10%, so the micro-pulley is good for 500 pounds. Right?

But what is the breaking strength of a micro-pulley? Also 500 pounds can easily be achieved by a simple straightforward drop of only a foot or so by a climber loaded with gear coming in at or around 200 pounds, total weight...
 
Frans,

Those tubular rings are just that...hollow round rings.

Rap rings is another name,which I'm sure that you know.

They've b een used for years as leave-behinds when rapelling off of a climb.

The reason for SWL ratings is partially to take into account extreme use like drops or falls. Don Blair does a great job of explaining all of this in Arborist Equipment.
 
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the alum. rings on cambium savers such as what Buckingham makes, are rated at 350 pounds each. But the overall strength meets the 5 thousand pound requirement.

Can anyone explain this to me?

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It sounds like 350# is the SWL on a 5k tensile load device with a 15:1 safety factor ... almost. 5000/15 = 333, so conservatively, they should state 330# or 325# for a SWL to maintain their 15:1 SF.
 
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