Page 1 of 1

ARB Bull Bar Recovery Points ??

Posted: Mon 17 Aug, 2009 7:36 pm
by andrew_wale
G'day.

As most club members would know, the ARB bull bars come with recovery points.

I know every one who has an ARB bull bar has used them to winch off etc, but are they rated?

Re: ARB Bull Bar Recovery Points ??

Posted: Wed 19 Aug, 2009 6:20 pm
by gwagensteve
Short answer, no.

Long answer: Are you sure they are recovery points?

My understanding is that the holes provided on the vertical plates on an ARB bar aren't really designed for recovery, and they are certainly not "rated". ARB started putting reinforcing rings around them some time ago, but I still don't believe they are considered strong enough for a heavy recovery - the steel that they are made of is only 4mm (tops) thick. That's not enough for a snatch recovery and certainly not enough for a snatch blocked winch pull.

Things might have changed, maybe Callum could advise?

PS "rating" is an interesting term. I'm going to assume you mean "safe working load" or SWL. SWL is very hard to calculate for anything used for kinetic/dynamic recovery. (Like a snatch recovery) - the variables are too great. If you want to apply the same definition of SWL as for lifting equipment (which is the way shackles are rated) then you're talking 20% of the fail load, from memory

however, SWL is out of favour as a rigid working limit. It's been replaced by WLL or working load limit.

here's a good explanation why:

http://www.irata.org/uploads/healthandsafety/WLLSWL.pdf

and here's a simple explanation of how the ratings work.
DEFINITIONS

Information contained in this catalog is subject to change; all weights and dimensions are approximate. Ratings are stated in short tons (2,000lbs.) or pounds. All dimensions are in inches; all weights are in pounds, unless stated otherwise.

Working Load Limit (WLL)

The Working Load Limit is the maximum load which should ever be applied to the product, even when the product is new and when the load is uniformly applied - straight line pull only. Avoid side loading. All catalog ratings are based upon usual environmental conditions and consideration must be given to unusual conditions such as extreme high or low temperatures, chemical solutions or vapors, prolonged immersion in salt water, etc. Never exceed the Working Load Limit.

Proof Test Load (Proof Load)

The term "Proof Test" designates a quality control test applied to the product for the sole purpose of detecting defects in material or manufacture. The Proof Test Load (usually twice the Working Load Limit) is the load which the product withstood without deformation when new and under laboratory test conditions. A constantly increasing force is applied in direct line to the product at a uniform rate of speed on a standard pull testing machine. The Proof Test Load does not mean the Working Load Limit should ever be exceeded.

Breaking Strength/Ultimate Strength

Do not use breaking strength as a criterion for service or design purposes. Refer to the Working Load Limit instead. Breaking Strength is the average force at which the product, in the condition it would leave the factory, has been found by representative testing to break, when a constantly increasing force is applied in direct line to the product at a uniform rate of speed on a standard pull testing machine. Proof testing to twice the Working Load Limit does not apply to hand-spliced slings. Remember: Breaking Strengths, when published, were obtained under controlled laboratory conditions. Listing of the Breaking Strength does not mean the Working Load Limit should ever be exceeded.

Design Factor (sometimes referred to as safety factor)

An industry term usually computed by dividing the catalog Breaking Strength by the catalog Working Load Limit and generally expressed as a ratio. For example: 5 to 1.

Shock Load

A load resulting from rapid change of movement, such as impacting, jerking or swinging of a static load. Sudden release of tension is another form of shock loading. Shock loads are generally significantly greater than static loads. Any shock loading must be considered when selecting the item for use in a system.

Avoid shock loads as they may exceed the Working Load Limit.
under these circumstances, the "recovery" points on the front of an ARB bar would have to rated at about 3Kg. This is no reflection on the quality of ARB product, only a reflection of the way ratings are calculated. It's a massive liability issue for ARB to consider.

As an aside, notice how 9000kg rated snatch straps break often but 3.25 tonne rated shackles never do? - that's an example of the same problem. A snatch strap isn't rated as lifting equipment, so there's no real system of approval - it's indicative only, however, a shackle that's rated to 3.25 tonnes won't break until it's reached at least 16.25 tonnes, because it's rated for lifting.

It's a complicated area.

Steve.