Bt50 shackles

Read this

www.tmr.qld.gov.au/~/media/Safety/.../Safe_towing_guide.pdf

I stated the rating incorrectly it should be WLL

And this

http://www.transport.nt.gov.au/__data/assets/pdf_file/0008/19646/vib13i-Light-Trailer-Safety-Chain-Shackles-Jan-2013.pdf

Yeh I've looked at the NT government document...it realy needs some revision.

There should be no mention of 6 times.

The legeslated safety margin is 4:1 and that is what we must work off to establish the nominal breaking strain for the purposes of selecting a shackle for trailers or recoveries or a variety of other things.


SO any shackle that complies with the standards and legeslation and is legally sold or has been legally sold in the past with a W.L.L. or S.W.L. marking on it, can be relaibly assumed to be good for 4 times its marked value.....mostly thought it will be a great deal more.


The word breaking load should not be used....because both the standards applying to the shackle and the standards and ADRs applying to the trailer imply that permanent distortion is not permitted.
so the breaking load may need to be be a great deal higher to be compliant.

We do not need to worry about grades of shackles or tracking test certificates.
we need to buy a reputable shackle marked with a W.L.L. or use a shackle purchased in the past marked with S.W.L.
( S.W.L. is an out of date term in relation to shakles)

The shackle matrix should not have been published, because it only serves to confuse the matter.

We are looking for a reputable shackle that is accordingly marked....that simple.

So we need a shackle that has a failure strain of one and a half times the Agrigate Trailer Mass.....this can be found my multiplying the marked value of any rated shackle by four.

ATM x 1.5 = required strength......required strenght/4 = required W.W.L.....buy the next size shackle



Now here is an interesting rub.

There IS NO REQUIREMENT in the ADRs that the shackle be an item of rated lifting equipment.

Nor is there are requirement that chain be high carbon steel rated in either the lifting industry or transport industry...it can in fact be mild steel.

ON most light trailers under 3.5 tonnes.

The problem is the proof.

The manufacturer of the trailer is responsible for proving that the chain they affix is appropraitly strong.

But there is no other means of establishing the credentials of a shackle that is not marked, on the road side..one way or the other.

So not specifically, but by implication the shackle must be rated.

Regardless you are crazy if you do not use an appropriately rated and marked shackle.


Now here is another thing..documents like the one above published by the NT governement are not law in any way shape or form..they are advisory only...and can only point to the law.

So if you get pinged and the document is not quite right..or it didn't mention something...its still your fault.

Check VSB01...( even that is not law..but it is a reliable summary)


What realy interests me..is the NT government are not sufficiently sure about this to recommend prosecution.

The Action recomended is to advise.

just some thaughts.

cheers

You need to get this straight.

equipment for industrial lifting is rated in working load limit (W.W.L.)or safe working load( S.W.L.)
Lifting equipment is rated with very generous safety margins.

This is not the case with towing equipment or recovery equipment, height safety equipment or mountaineering equipment....all these are in general rated at failure or breakage.

BUT we do interchange equipment across disciplines.

Because we are not we are not talking about a trailer being lifting equipment we in general resolve everything into minimum breaking strain or minimum failure load ( which may not mean breakage)

ALL shackles rated for industrial lifting purposes MUST by law and standard have at least a 4 to 1 safety factor...and that is minimum failure load..distortion is failure.

Where this 6:1 came from as something youcan rely on..I do not know.

SO a 1 tonne lifting industry shackle must by law and standard have a minimum falure loading of 4 tonnes.

Fact is most reputable lifting equipment manufacturers work on, at least 5 or 6 to one safety factors and the better ones 7 and 8 to one safety factors....a realy nice 1 tonne shackle may be good for 7 or 8 tonnes.

BUT not being able to know the brand for sure and thus the safety factor we must work on is 4:1.

The ADRs specify the minumim breaking strain of the safety chain and the attchment points..( not in those words)....not the SWL or WWL.

The ADRs do not specifically nominate the strength of the shackle

BUT
By inference it would be an "attachment point" or must be equal or greater than the attachment point on the drawbar.


quote VSB01

16.3 Drawbar Safety Chain Attachment Points

Safety chain attachment points are the means by which the safety chains are attached to the drawbar. These points must be located as near as practicable to the tow coupling. Where two points of attachment are required, they must be mounted one on either side of the centreline of the drawbar.
Each safety chain attachment point must be capable of withstanding the following minimum forces without incurring either any residual deformation that would interfere or degrade the function of the assembly, or any breaks, cracks or separation of components:

Longitudinal tension and compression (N) 1.5 x 9.81 x ATM (in kg)

Vertical tension and compression (N) 0.5 x 9.81 x ATM (in kg).

in the equasion the 9.81 is to convert Kg to Neutons

so the attachment point must be able to withstand 1.5 times the ATM of the trailer..

THUS
if it is a 2 tonne trailer ( 3 tonne requirement)....a 1 tonne shackle will be sufficient ( having at least a 4 tonne capacity)


There may be some that should know better and say other wise.
But you may not get a 2 tonne WWL shackle thru 3 tonne breaking strain chain......particulary if it is either transport or lifting grade chain



without any reference to regulations or tables....you should be using the largest shackle that will fit thu the chain fitted


If you are in doubt about anything trailer..start with VSB01 here http://www.infrastructure.gov.au/roads/vehicle_regulation/bulletin/vsb1/vsb_01_b.aspx#anc_16

cheers

Good post, Bantam.

To
"without any reference to regulations or tables....you should be using the largest shackle that will fit thu the chain fitted"

I would add

"or that will fit to the chain attachment points on the tow bar"

Reason being that the max size rated shackles the factory towbar on my Prado will accept is 1 tonne (for a 2.5 tonne rated towbar) and Barry seems to have the same problem on his BT50 for a 3.5 tonne towbar.

I would be very wary of enlarging the holes or slots of the attachment points to take larger shackles as has been mentioned by another poster. You could easily end up weakening the attachment points.

Cheers

If you use the largest shackle that fits you simply can't go wrong.

All the other components should be engineered adequately and sized correctly....and if they aren't ya cant do a damn thing about it.

you can not enlarge the hole in the tow bar...as the manufacturer would then wipe their hands of the whole thing.


This whole S.W.L./W.L.L. relationship with minimum rated breaking strain........is so poorly understood and trips so many people up...and many smart people who should know better.

At least the message it getting thru that quality rated shackles are a must.

If you buy in the right place they are cheaper than buying non rated rubbish at the local hardware.

I have seen some rediculous things used as connecting devices for safety chains.

Best place to buy your rated shackles is at you local specialist bolt shop.

AND buy BOW shackles rather than D shackles.....they perform better off line and they give more room to do stuff.

I use a half tonne rated bow shackle (2 tonne pluss strength) to connect my little 750kg box trailer...because that is as big as will fit in the chain......I would not get a 1/2 tonne D shackle into the toyota factory to bar.

cheers

Barry,

I was chasing up another matter today with NSW RMS (Roads and Maritime Services, the rego authority in NSW) and with this topic in mind asked about shackles.

The NSW requirement for a van of ATM 2500kg registered in NSW is rated chain 10mm dia links attached to the vehicle with 12.7mm rated shackles. NSW does not use WLL or BLL etc. However the 12.7mm bow shackles I have are stamped WLL 1.5

This link refers.

I would hazard a guess that the NSW requirement is likely to be the most stringent so if you followed it you probably wouldn't go wrong. (Subject to verification if you or anyone else has the time to do the research.)

Hope this helps.

Cheers